Optimizing irrigation efficiency: a case study of the Bakbakti Rice System in Akdala Massif

Introduction: Water scarcity increasingly limits irrigated agriculture in arid and semi-arid regions, particularly in Kazakhstan's northernmost rice-growing zone, the Akdala irrigation massif of the Ile River basin. This study examines the feasibility of reusing collector-drainage water, together with groundwater and surface water, to reduce freshwater deficits in the Tasmurun section of the Bakbakty system.

Methods: Field experiments were conducted from 2022 to 2024 on two rice fields (311 ha) to evaluate water and salt balances, soil and groundwater dynamics, and water-saving irrigation technologies. The irrigation regime incorporated 25–30% collector-drainage water and was compared to a 2022 freshwater control.

Results: The mixed-source irrigation approach reduced freshwater withdrawals by 14% (1.674 million m3 annually) and lowered the irrigation norm from 26,082 to 22,900 m3/ha. Soil and groundwater quality indicators remained stable, and rice yields increased by 6.8–9.2%. Economic efficiency rose by 25%, with farm profitability reaching 35%.

Discussion: The findings confirm that on-farm reuse of collector-drainage water is a viable, environmentally safe strategy for offsetting irrigation deficits and reducing anthropogenic pressure on transboundary water resources. As the first field-validated study of its kind in Kazakhstan, this research presents a novel technology that avoids the negative impacts of diverting drainage water into river channels and provides practical balance parameters for adapting irrigation systems under water scarcity. The rational reuse of collector-drainage water offers a sustainable pathway to strengthen water security, support rice cultivation, and enhance economic resilience in Kazakhstan's vulnerable semi-desert regions.

1 Introduction

Water scarcity is an increasingly critical issue in irrigated agriculture worldwide, especially in arid regions like southeastern Kazakhstan. The Akdala irrigation system in the Ili River Basin exemplifies these challenges, where inefficient water use and deteriorating irrigation infrastructure have led to declining productivity and land degradation. Reusing collector-drainage and groundwater resources for irrigation represents a promising water-saving strategy.

This study aims to develop and evaluate a field-scale irrigation technology that integrates surface water with reused drainage and shallow groundwater for sustainable rice cultivation in the Akdala irrigation massif.

Drainage water, a by-product of irrigation, can be viewed either as a valuable resource for reuse or as a form of wastewater requiring management (Qadir et al., 2010). The judicious management of water reuse is imperative, considering both immediate local impacts and broader external effects, alongside the needs of present and future generations. In arid and semi-arid regions, irrigated agriculture dominates global water demand, accounting for over 70–80% of the total, particularly during periods of extreme drought.

As one study indicates, the reuse of treated wastewater in irrigation has proven to be one of the best ways to recycle nutrients and water and thus protect the environment and public health (Al-Anzi et al., 2012). Additionally, it can directly contribute to environmental sustainability by increasing crop production (Al-Anzi et al., 2012). However, it's crucial to prohibit reclaimed water irrigation in areas with a high risk of groundwater pollution (Wu P. et al., 2023).

Assessments of collector-drainage water quality can indicate its suitability for irrigation and soil reclamation through land washing, provided appropriate hydrogeological conditions are present.

The suitability of agricultural drainage water quality for irrigation purposes is usually assessed by various water quality parameters: sodium percentage (SP; % Na), residual sodium carbonate, residual alkalinity, Kelly index, permeability index, chlor-alkali indices (CAI1 and CAI2), potential salinity, magnesium adsorption ratio and total hardness (Rejesus et al., 2011; Laze and Rizani, 2016; Temesgen et al., 2023; Prasad et al., 2001; Al-Aizari et al., 2024; Nagaiah et al., 2017). In existing works, much attention is paid to setting acceptable limits for total dissolved solids in the water used (Rawat et al., 2018; Singh et al., 2020; FAO, 1994).

Limits on water salinity for irrigation are typically based on the need to prevent salinization of non-saline soils, the effect of saline water on plant productivity (Dotaniya et al., 2023; Murtazin et al., 2025), or the risk of soil alkalization under irrigation (Fereres and Soriano, 2007; Hejase et al., 2022).

In the long term, given the depletion of available high-quality water resources, it is clear that we will need to utilize drainage water with higher salinity for irrigation, diluting it with higher quality water before reuse. Reused drainage water is widely used as a method of supplementing water supply, for example in surface and subsurface rice farming systems.

A study of an irrigation network in western Greece suggests optimizing drainage water use by incorporating crop-water production functions to simulate crop performance under saline conditions, considering different prices of fresh water and salinity values of drainage water (Gotsis et al., 2011).

The most practical immediate step for reducing water supply degradation appears to be improved on-farm irrigation management to reduce the volume of drainage water. Also, with increasing demand for irrigation water, alternative sources are being sought, so seawater (saline water) was previously considered unusable for irrigation, but this water can be used successfully to grow crops under certain conditions (Sadak et al., 2015).

For an irrigation system in Niigata Prefecture, Japan, a region known for its rice production, the effects of water reuse on the rice land ecosystem, its effects on total phosphorus, total nitrogen, suspended solids and chemical oxygen demand were evaluated. It has been found that water reuse not only helps to meet irrigation water requirements but also helps to treat agricultural drainage water and preserve the rice land ecosystem (Ouyang et al., 2024).

The suitability of drainage water from the Mwea irrigation scheme in Kenya for reuse was evaluated in new rice areas downstream. The results showed that blending drainage water with fresh water for reuse in Mwea scheme is suitable for irrigated rice production as all nutrient parameters are within the critical limits recommended by FAO standard for water quality in irrigation (Kudoyarova et al., 2015).

The benefits of reusing water in irrigation systems extend beyond the conservation of groundwater resources. These systems can also reduce the amount of pollutants released from agricultural watersheds. For example, a rice and soybean field rotation project on Christian Richard's farm in Louisiana utilized a supplemental filtration system with reused irrigation water, which improved the overall water quality. Similar positive outcomes for irrigation using reused drainage water have been documented in other studies (Temesgen et al., 2023; van Asten et al., 2003; Zulu et al., 1996).

The suitability of drainage water for reuse in irrigation varies significantly depending on the specific irrigation area, climatic zone, and soil conditions, even when the chemical quality of the irrigation water is similar. Therefore, the use of collector-drainage water in rice irrigation systems at the on-farm level requires careful consideration. This highlights the need for field studies and diligent monitoring of soil-water parameters when implementing on-site water recycling systems.

One of the main challenges faced by rural communities engaged in rice production within the Akdala irrigation massif is the scarcity of irrigation water, compounded by the inefficient operation of the irrigation and drainage network, secondary soil salinization, and degradation of irrigated lands, as discussed in the introduction of this paper. Therefore, a key objective is to develop technological guidelines for rice irrigation using drainage water reuse. This approach aims to facilitate the cultivation of unproductive and meliorative unfavorable lands within the irrigated area, specifically at the on-farm network level (rice field).

A review and analysis of domestic and international publications and scholarly works clearly demonstrates heightened attention toward water-salt balance studies and specific issues concerning the ameliorative state of rice irrigation systems. In recent years, these systems have been the focus as a primary means of actively and purposefully influencing the water-salt regime of reclaimed areas and shaping the groundwater level regime, both during the growing season and the non-irrigated period for rice and associated crops. Given the increasing scarcity of water resources, there is a clear need and demand to identify potential sources for replenishing them, including through the reuse of collector-drainage water generated in rice irrigation systems.

In their 2020 study, Okuda et al. (2022) investigated the water-salt balance on irrigated agricultural lands in Uzbekistan, where leaching was conducted using shallow subsurface drainage combined with cut-drains. This research is particularly relevant to arid regions, where secondary salinization frequently leads to rising groundwater tables.

In the work of R. Singh, J. C. van Dam, and R. K. Jhorar (Wu Z. et al., 2023; Verma et al., 2012), a calibrated SWAP agro-hydrological model is used to analyze and derive the water and salt balance in measured farmer fields. The key unknowns were the soil hydraulic functions, which are valid at the field scale. SWAP model can also be used with saline water for irrigation (Jiang et al., 2010; Kumar and Verma, 2012).

In the article by S. Kasymbetova and D. Ergashova, the results of the water-salt balance of floodplain massifs, the aeration zone, the balance of the root layer of agricultural crops, and the overall water-salt balance of the Shuruzyak massif in the Syrdarya region are presented. The inflow and outflow components of the water-salt balance were determined, based on which an assessment of the ameliorative state of irrigated lands was carried out.

In published materials, Zaitsev and Semenenko (1962), and Reshetnyak (1973) outline, and present practical interest in, respectively, the characteristics of the groundwater regime in flooded rice fields and the influence of groundwater on the dynamics of water-soluble salts in the soil of rice crop rotations(Averyanov, 1978).

Thus, the discussion and analysis of numerous domestic and international publications and scholarly works clearly demonstrates increased attention to water-salt balance studies. It also proves that substantiating predictive real-world characteristics, the quantitative and qualitative potential, and the intensity of collector-drainage water use should be based on the study of the water and salt balance of the area (Imanudin et al., 2021).

Previous studies have emphasized the challenges of inefficient on-farm water management. Akhtar et al. (2013) identified critical problems such as improper irrigation timing and uneven water distribution across fields, which persist despite being solvable without significant costs. Farmers often resort to applying excessive irrigation to mitigate the risk of future crop stress. A further cause of low irrigation efficiency is the high level of operational water losses, which can be reduced through the institutionalization of farmer participation in irrigation water allocation planning. In this context, Akhtar et al. developed optimal and deficit irrigation regimes for cotton under shallow groundwater conditions in the Khorezm region of Uzbekistan. The novelty of their study was the explicit consideration of capillary rise from shallow groundwater when scheduling surface irrigation. This demonstrated that in areas with shallow groundwater tables, the contribution of groundwater to crop evapotranspiration cannot be neglected.

Jalil et al. (2020) applied the AquaCrop model to winter wheat in the Kabul River Basin (KRB), with calibration and validation based on field data. Their results highlighted the importance of optimizing irrigation methods to improve water use efficiency and crop yield. Specifically, four irrigation scheduling scenarios were modeled: (i) business-as-usual (S-A), (ii) refilling the soil profile to field capacity at 50% depletion (S-B), (iii) refilling at 100% depletion (S-C), and (iv) refilling at 130% depletion (S-D). The study evaluated these scenarios in terms of yield response, water productivity (WP), and biomass production, offering valuable insights for subsequent research on water-saving strategies under water-scarce conditions.

A comprehensive review of pertinent published sources was conducted through a statistical analysis, yielding the following conclusions. For several decades, the global research community has been actively developing and justifying water-saving methods and technologies for irrigating agricultural crops. However, the majority of previous and ongoing studies have focused on the process of redirecting drainage water back into river channels for subsequent reuse, with the primary objective being to enhance the irrigation potential of river runoff (available water resources).

A salient issue that remains unresolved pertains to the management of return flows and their subsequent discharge into rivers, lakes, and wetlands. This is of particular concern given the recognized role of collector–drainage runoff as a substantial contributor of salts and pollutants to surface water bodies. A promising direction for the further development of the agricultural sector is the elaboration of measures aimed at reducing collector–drainage discharges through their reuse at the points of formation. This approach is particularly pertinent in light of the substantial volumes of mineralized drainage and groundwater, with concentrations ranging from 1.0 to 1.8 g/L, that are present in the region.

At present, the reuse of collector–drainage water is limited to mechanical diversion from low-lying areas of rice irrigation systems into the canal network, with no reuse at the on-farm level (e.g., the Tasmurun irrigation system). Moreover, the recent years of low-flow conditions have exposed detrimental practices, such as the obstruction of collectors with earth dams, leading to the formation of backwater and a reduction in the aeration zone. While this may temporarily reduce groundwater drawdown during harvesting, it also prevents the flushing of saline soils and exacerbates alkalinity in rice fields.

A research hypothesis was formulated and subsequently verified through experimental analysis. This hypothesis posits that the reduction of collector–drainage discharges can be achieved by reusing them at the points of formation. The viability of this methodology is substantiated by the presence of drainage and groundwater with minimal mineralization levels (1.2–1.5 g/L). The representativeness of the selected territory was confirmed through a combination of hydrogeological, hydrological, and soil–reclamation studies, as well as long-term assessments of water and salt balances under rice irrigation.

The objective of the present research was to demonstrate, under real-world conditions of global warming and severe shortages of traditional irrigation sources, the advantages and prospects of an innovative water-saving technology for the reuse of collector–drainage waters at the field level. A primary objective was to determine environmentally safe volumes of collector–drainage flow, taking into account soil characteristics, hydrogeological conditions, and the technical feasibility of water intake from the existing drainage network.

The proposed technology facilitates the reuse of up to 14% of collector–drainage flow within the Tasmurun–Bakbakty irrigation system. This not only reduces water abstraction from the Ili River but also enhances the leaching function of rice irrigation, thereby contributing to the desalination of topsoil and ultimately improving the productivity of degraded irrigated lands by 10–15%. Significantly, this study signifies the inaugural endeavor in Kazakhstan to implement such technology at the field level, specifically in the northernmost rice-growing region of the country—the Akdala irrigation massif—utilizing the most water-vulnerable system, Tasmurun.

Field experiments were conducted under conditions of climate warming and increasing water scarcity, with the primary focus on water conservation through the application of a recommended irrigation regime, minimizing unproductive water losses, and reducing specific drainage discharge per irrigated hectare. As part of an information and training campaign to promote these results, on-site workshops were organized for local farming communities. Participants were trained to use modern rapid-measurement devices, including the PH300 electronic soil tester (pH, moisture, temperature, and light), soil moisture and pH meters with light sensors, and the COM-80 conductivity meter for water salinity assessment.

Furthermore, practical demonstrations were conducted using an innovative, cost-effective pumping unit—equipped with a power take-off drive from a tractor and a multiplier—which was employed to transfer drainage water from collector K-2 into the Tasmurun main canal. This pump, capable of achieving outputs of 300 L/s or more, proved to be a technically efficient and economically feasible solution for enhancing on-farm reuse of drainage water.

2 Materials and methods

2.1 Study area

The field study region is situated in the Balkash district of the Almaty region, Republic of Kazakhstan, within the Tasmurun section of the Bakbakty system in the Akdala irrigation massif, which lies in the Ile River basin (Figure 1).

Figure 1

Figure 1. Outline map of the Akdala Irrigation Massif (study area) in the semi-desert zone of Balkash region, Kazakhstan.

The territory's arid climate, typical of a desert zone, combined with a shallow groundwater table, promotes significant salt accumulation in the soil profile.

The irrigated lands in the study area are situated within the ancient delta of the Ile River. The surface topography results from alternating erosion and deposition processes influenced by aeolian activity. The average surface slope is 0.0002.

Prior to the development of irrigated agriculture, the area exhibited numerous micro-relief features, which were largely leveled during construction and land preparation.

The soils developed on Quaternary alluvial, lacustrine-alluvial, and aeolian sediments, characterized by alternating layers of sands, sandy loams, and loams. This heterogeneous lithological structure contributes to significant variability in soil cover, particularly in terms of salinity and mechanical composition.

The extent of groundwater influence on soil formation depends on its depth, salinity, and the mechanical composition of the soil profile.

The irrigation system and collector-drainage network (collector K-2) serving the irrigated lands of SPK ‘Miyaly Agro', PC “Dinara,” and LLP ‘EDD' were chosen as a representative site for investigating collector-drainage water reuse technology within the Tasmurun area of the Bakbakti irrigation system in the Akdala irrigation massif (Figure 2).

Figure 2

Figure 2. Collector-drainage water reuse development scheme for the Tasmurun area of the Bakbakti irrigation system. 1—pumping unit for transferring collector-drainage water; 2—suction hose V-1-200, 7 meters long, with a check valve; 3 −8-inch (200 mm) flexible hose, rated for 3 bar pressure, 50 m long, for supplying water from collector K-2 to the Tasmurun main canal; 4—dynamic levels in the collector and irrigation canal during the transfer of the optimal volume of collector-drainage water; 5—embankment dams on the collector and irrigation canal.

The irrigated area of six-field crop rotation III (rice-alfalfa) totals 890 ha, with an experimental plot of 607 ha. This plot is divided as follows: Field 2 (173 ha, comprising 81 ha of SPK ‘Miyaly-agro' farm ‘Alga' and 92 ha of PC ‘Dinara'), Field 3 (187 ha, PC ‘Dinara'), Field 4 (138 ha, PC “Dinara”), and Field 5 (109 ha, LLP ‘EDD').

During the 2022–2024 period, the cropping structure was: rice in Fields 2 (173 ha) and 4 (136 ha), and alfalfa in Fields 3 (187 ha) and 5 (109 ha).

The recommended rice irrigation technology, which reuses drainage-discharge water, begins with irrigating rice with river water during the initial flooding of rice paddies and maintenance of the water layer (the first three stages, see Figure 3). Afterwards (stages four through six), irrigation uses a mixture of water containing up to 25% drainage-discharge water and 75% river water.

Figure 3

Figure 3. Recommended irrigation regime and technologies for rice, with collector-drainage water reuse, in Tasmurun pilot plots, Bakbakti system.

In 2022, a comprehensive monitoring program was conducted on the irrigated lands of the third rice–alfalfa crop rotation system within the Tasmurun section of the Bakbakty irrigation network of the Akdala irrigation massif. This area was utilized as a control site under real conditions of the traditional irrigation regime, without the reuse of collector–drainage waters. The objective was to establish a foundation for subsequent comparison with the experimental scenarios conducted in 2023–2024, during which the implementation of a recirculating water-use system with the reuse of environmentally safe volumes of collector–drainage flow was tested.

The conceptual workflow applied in the experimental studies on the Tasmurun irrigation system included the following: The installation of monitoring and sampling equipment is imperative for the study. In addition, the controlled mixing of drainage and irrigation water is necessary, as is the measurement of rice productivity under these conditions. Pursuant to the chemical analysis of water samples and ancillary field measurements, corresponding evaluations were performed (Figure 4).

Figure 4

Figure 4. Conceptual scheme of the working process applied in the experimental research.

The experimental research on the reuse of collector-drainage waters in the Tasmurun sector of the Bakbakty irrigation system was conducted in accordance with a conceptual workflow guiding data collection, processing, and interpretation. Statistical analyses were performed using mathematical statistics, including graphical methods, statistical population analysis, and econometric approaches. Water quality data (TDS, major ion concentrations, pH, SAR, ESP, residual sodium carbonate, and related indices) were processed in HydroGeoAnalyst (Waterloo Hydrogeologic, Canada). Geochemical results were presented using Kurlov's formula and analyzed with Piper and Durov diagrams in Grapher (Golden Software, USA). Spatial visualization and mapping of hydrogeochemical data were carried out in ArcGIS (Esri, USA).

Prior to the growing season, equipment was installed on representative plots to comprehensively assess the processes and components of the water-salt balance in the irrigated lands.

Within the central part of the rice irrigation map checks, phenological sites were established to monitor water-air, salt, and biochemical regimes of soils; surface and groundwater levels and mineralization; crop weediness; and rice biomass accumulation. At the experimental plots, a network of stationary posts was established for periodic monitoring of surface water, collector-drainage water, and groundwater regimes (Figure 5). Specially made and calibrated water gauges were installed in flooded rice paddies to measure water layer depth, and in irrigation canals and catchment drains to monitor water discharge during the growing season (Figure 6).

Figure 5

Figure 5. Map of the irrigation and collector-drainage network in the representative study area, showing the locations of monitoring and observation points (hydrometric, hydrological, and hydrogeological). Map Key: 1—Pumping unit: pumps collector-drainage water from collector K-2 to the Tasmurun main irrigation canal; 2—Hydrological post; 3—Irrigation water sampling location; 4—Collector-drainage water sampling location; 5—Monitoring hydrogeological well (with inventory number); 6—Rice-lucerne crop rotation area (with rotation number); 7—Field within rice-lucerne crop rotation (with field number); 8—Irrigation canals (irrigators); 9—Collector drains (collectors).

Figure 6

Figure 6. Water measuring laths. (a) For installation in flooded rice paddies to monitor water layer depth. (b) For installation and subsequent hydrological observation of water discharge in irrigation and drainage canals during the growing season.

2.2 Methodology of research

Irrigation water supply volumes in fixed sections of irrigation canals and collector-drainage runoff volumes in collectors were measured monthly during the growing season at certified hydrological posts.

Measurements were taken:

1. At the TMK pumping unit site, before and after collector-drainage water from collector K-2 was pumped into the irrigation canal.

2. At collector K-2, before and after pumping unit transfer of collector-drainage water.

3. In the group distribution channel R-10, before and after mixing with water from K-2.

4. In the group distribution channel R-15, before and after mixing with water from K-2.

5. In the district distribution canal supplying irrigation water to the 2nd field with rice crops, before and after mixing with water from K-2.

6. In the district distribution canal supplying irrigation water to the 4th field with rice crops, before and after mixing with water from K-2.

7. In the district distribution canal supplying irrigation water to the 5th field with alfalfa crops, before and after mixing with water from K-2.

Groundwater level measurements were conducted monthly during the non-growing season and every 10 days (decade) during the growing season. Water samples were collected once in a month before the growing season and after the completion of irrigation. Measurements were taken in monitoring wells 308, 184, and 306, located on irrigated lands with rice crops; in wells 336 and 370, located on alfalfa crops; and in well 309, located at the switchyard. Acoustic and electric level gauges were used for these measurements.

Irrigation water was sampled monthly during the growing season at the following locations within the Bakbakti Rice System, Akdala Massif:

1. TMC before and after mixing from K-2;

2. R-15 before and after mixing from K-2;

3. R-10 before and after mixing from K-2;

4. District distribution canal for water supply to irrigated lands of the 2nd field with rice crops before and after mixing from K-2;

5. District distribution canal for water supply to irrigated lands of the 4th field with rice crops before and after mixing from K-2;

6. District distribution canal for water supply to irrigated lands of the 5th field with alfalfa crops before and after mixing from K-2.

Collector-drainage water was sampled monthly during the growing season at the following locations within the Bakbakti Rice System, Akdala Massif:

1. K-2 at the station for pumping collector-drainage water from the collector to TMK, before and after mixing from K-2.

2. Cart collector K-3-2-1 in the end part of the 2nd field with rice crops, before and after mixing from K-2.

3. Group collector K-3-2 in the end part of the 4th field with rice crops, before and after mixing from K-2.

4. Collector K-3 in the end part of the 5th field with alfalfa crops, before and after mixing from K-2.

5. United collector at the confluence with the map drainage-discharge channel from irrigated lands of irrigation system R-15 of the 3rd field with alfalfa crops, before and after mixing from K-2.

6. UC in the section after the confluence with the end-map drainage-discharge canal from irrigated lands of irrigation system R-15 of the 5th field with alfalfa crops, before and after mixing from K-2.

Water and soil sampling was conducted in accordance with standard methods of the Republic of Kazakhstan for monitoring and assessment of irrigated reclaimed lands. Field procedures included preparing water intake points for sampling, collecting and preserving samples, and visually assessing suspended and emulsified substances, as well as insoluble sediments directly in the water source. To evaluate the impact of irrigation water (surface water from the Ile River and reused collector-drainage water mixed with surface water) on soil salinization, alkalization, and sodification, the following water quality indicators were analyzed: total dissolved solids; concentrations of major ions (Ca, Mg, Na, SO4, Cl, CO3, and HCO3); pH; soil salinity hazard based on the Cl/SO4 ratio; soil alkalization hazard based on the exchangeable sodium percentage, sodium adsorption ratio, and calcium/magnesium ratio (Ca/Mg); and sodification hazard based on residual sodium carbonate [(CO3 + HCO3) – (Ca + Mg)]. Standard chemical analyses of the six major chemical components (Ca, Mg, Na, Cl, SO4, and HCO3), as well as TDS and the type of salinization based on the predominant anion and granulometric composition of soils, were performed on soil samples.

Chemical-analytical studies of water and soil samples were carried out by the laboratory of the U.M. Akhmedsafin Institute of Hydrogeology and Geoecology LLP (Accreditation Certificate No. KZ.T.02.0782, valid until 27.11.2025).

Methods of analyzing soil samples and equipment used to determine individual water parameters are given in Tables 1, 2.

Table 1

Table 1. Methods of laboratory testing of water samples.

Table 2

Table 2. Methods and equipment for the determination of chemical parameters in water samples.

Electrolytes were prepared using the following reagents: potassium tetrachlorochromate, diethylamino, tartaric acid, hydrochloric acid, and sodium hydroxide. Calibration results are expressed in mg/L.

Boron (B) and silicon concentrations were measured using a KFK-2 photocolorimeter. Metals were analyzed using an ICPE-9820 emission spectrometer (International Organization for Standardization, 2003). The samples were treated with nitric acid and filtered before analysis. The methods used to analyze soil samples and the equipment used to determine individual soil parameters, as well as the error levels, are given in Table 3.

Table 3

Table 3. Methods of laboratory testing of soil samples and equipment.

Laboratory tests were conducted in accordance with the National Standard (Lumex, 2010).

Chemical analysis of water samples was performed using a MettlerToledo liquid analyzer to measure pH, conductivity, and dry residue. Sodium and potassium contents were determined using a PFP-7 flame photometer. Dissolved calcium, magnesium, nitrite, sulfate, chloride, and fluoride were determined using Capel 105 M capillary electrophoresis (Committee for Standardization, 2003).

Laboratory self- and systematic quality control was carried out to check the validity of the chemical analysis results and technology and to prevent possible laboratory errors. In the mechanical analysis of soils, self-control was 100% of the analyzed samples. The control of the water extract analysis was carried out by comparing the sum of anions and cations. For comparison with previously obtained results (systematic control), 20% of soil samples were reanalyzed for chemical analysis.

The integrated assessment of irrigation water quality was based on the following criteria: agronomic, groundwater suitability for irrigation, technical, and environmental.

Agronomic criteria for determining irrigation water quality are based on:

• Crop yield in terms of gross yield and cultivation intensity.

• Quality of agricultural products in terms of their value and safety.

• Maintenance of soil viability and fertility, and prevention of salinization.

Technical criteria define water quality in relation to its impact on the safety and efficiency of irrigation and drainage systems. Ecological criteria determine the quality of irrigation water in terms of environmental protection.

The criteria of groundwater suitability for irrigation took into account chemical analysis using irrigation coefficients, which, in the absence of unified approved requirements, were calculated by different methods.

The risk assessment of irrigation water alkalinization was based on the sodium adsorption ratio, which represents the relative amount of sodium ions to the total amount of calcium and magnesium ions:

$\begin{array}{ll}SAR=\frac{\text{rN}{\text{a}}^{+}}{\sqrt{\frac{\text{rC}{\text{a}}^{2+}rM{g}^{2+}}{2}}}& (1)\end{array}$

This means that if sodium concentration exceeds divalent cations, there is a risk of calcium displacement from the absorption complex and its replacement by sodium. In this case, the soil may become alkalized with a rapid deterioration of its water-physical properties.

The calculations of the Sodium Adsorption Ratio (SAR) in this study were carried out using the most widely applied formula (1) adopted by the United States Department of Agriculture (USDA). The evaluation of irrigation water in terms of sodicity hazard was performed according to the commonly accepted classification proposed by L. A. Richards (Richards et al., 1954) shown in Table 4.

Table 4

Table 4. Risk of soil alkalinization by irrigation water (Bezborodov et al., 2022).

The suitability of water for irrigation was determined based on its chemical analysis using irrigation coefficients, which were calculated using the Stebler and Antipov-Karataev-Kader methods (Antipov-Karataev and Kader, 1959).

Ka by the Stebler method was calculated according to the following Equations 2–4.

$\begin{array}{ll}{\text{K}}_{\text{a}}=\frac{288}{5rC{l}^{\prime }}\text{, for }\text{rN}{\text{a}}^{+}<\text{rC}{\text{l}}^{-}& (2)\end{array}$

$\begin{array}{ll}{\text{K}}_{\text{a}}=\frac{288}{r{Na}^{+}+4r\text{C}{\text{l}}^{\prime }}\text{,for }\text{rC}{\text{l}}^{-}+\text{rS}{\text{O}}_4^2>\text{rN}{\text{a}}^{-}>\text{rC}{\text{l}}^{-}& (3)\end{array}$

$\begin{array}{ll}{\text{K}}_{\text{a}}=\frac{288}{10r{Na}^{+}-5r{Cl}^{-}-9r{SO}_4^2},\text{for }\text{rN}{\text{a}}^{+}>\text{rC}{\text{l}}^{-}+\text{rS}{\text{O}}_4^2& (4)\end{array}$

The suitability of water for irrigation based on the value of Stebler irrigation coefficient was evaluated according to the following criteria (Table 5).

Table 5

Table 5. Assessment of water suitability for irrigation based on the value of the Stebler irrigation coefficient.

Ka assesses the suitability of water for irrigation

• More than 18 points “Good”: Water is suitable for irrigation.

• 6–18 points “Satisfactory”: Water may accumulate alkalis in the soil, but this is not a significant problem.

• 1.2–5.9 “Unsatisfactory”: artificial drainage is required for irrigation.

• Less than 1.2 “Unsatisfactory”: water is unsuitable for irrigation.

Ka according to the Antipov-Karataev-Kader method was calculated according to equation:

$\begin{array}{ll}\text{Ka=}\frac{\text{rC}{\text{a}}^{\text{2+}}\text{+rM}{\text{g}}^{\text{2+}}}{\text{rN}{\text{a}}^{+}+0.238\sum \text{u}}& (5)\end{array}$

where: r—content of corresponding ions in irrigation water, mg-eq/L;

$\sum ^u$–sum of ion content in the irrigation water, mg/L;

According to the methodology of Antipov-Karataev and Kader (1959) water is suitable for irrigation if the condition is fulfilled:

$\begin{array}{ll}\frac{\left[\text{C}{\text{a}}^{2+}\right]+\left[\text{M}{\text{g}}^{2+}\right]}{\left[\text{N}{\text{a}}^{+}\right]}\le 0.23C& (6)\end{array}$

where [Na⁺]; [Ca²⁺]; [Mg²⁺]—concentration of ions in irrigation water, mEq/L; C—mineralization of irrigation water, g/L.

In addition, irrigation water quality was classified according to the degree of negative impact of water on soils (see Table 6) Antipov-Karataev and Kader, (1959): chloride salinization, sodium salinization, magnesium salinization, sodic processes Cl⁻, mg-eq/L; Ca⁺⁺/Na⁻, mg-eq/L; Ca⁺⁺/Na⁺, mg-eq/L; Ca²⁺/Mg²⁺ , mg-eq/L; (${\text{CO}}_3^2$ + HCO₃) – (Ca²⁺ +Mg²⁺), mg-eq/L.

Table 6

Table 6. Assessment of quality by danger of negative processes development and degree of suitability of irrigation water for irrigation (Bezborodov et al., 2022).

To determine the degree and type of possible salinization of irrigated lands after the end of the experiment, the results of analysis of water extract of soil samples were used. The degree of soil salinization reflects the percentage content of water-soluble salts in the dry residue as follows:

• non-saline—less than 0.30%,

• slightly saline—less than 0.5%,

• moderately saline—less than 1.0%,

• highly saline—less than 2.0%,

• very highly saline—>2%.

Soil salinity types were determined depending on the prevalence of anions and cations. Type and degree of soil salinization were regulated on the basis of the Republican Instruction ‘Procedure for determination of chemical type and degree of soil salinization', which stipulates the following sequence:

• weighted average content of all ions (in 0–100 cm layer) was estimated. If this value was less than 0.1 %, then salinization in the 0–100 cm layer was absent for all types of salinization. In this case the type of salinity chemistry was not determined and soils were classified as non-saline. If more than 0.1 % and if the sum of CO₃ + HCO₃ exceeded the Ca content, the chemistry type was defined as sodic;

• in the absence of sodic salinization, the ratio of chloride ions and sulfate ions was taken into account. If sulfate ions predominated, the salinity chemistry was defined as sulfate or chloride-sulfate. If the content of chloride ions exceeded the content of sulfate ions, the type of salinization was determined as chloride or sulfate-chloride.

Justification of forecast real characteristics, quantitative and qualitative possibility and intensity of collector-drainage water use was based on water and salt balance study as a summary of results and outcomes of three-year full-scale scientific-experimental research on development of collector-drainage water reuse technology in years of certain water availability on Tasmurun part of Bakbakti irrigation system.

Calculations of water and salt balance are based on actual materials of stationary hydrogeological observations, observations of collector-drainage water flow, meteorological data, as well as information on agricultural and water management conditions, which were carried out separately for two sites of experimental studies on the area of irrigated lands within field No. 2 and field No. 4 with rice crops in 2022 using existing irrigation regimes and technical conditions of operation at Tasmurun part of the irrigation system.

The calculated equation of the total water balance of the irrigated experimental plots has the following form:

$\begin{array}{cc}(\text{P}+\text{I}+\text{U})-(\text{ET}+\text{R}+\text{D}+\text{L})=\pm \Delta \text{S}& (7)\end{array}$

where, P—precipitation; I—irrigation additions; U—upward groundwater inflow; ET—evapotranspiration; R—runoff; D—vertical drainage ; L—lateral drainage; ΔS—change in soil water storage.

The total amount of atmospheric precipitation falling on the irrigated area within field No. 2 and field No. 4 with rice crops during the hydrological year is referred to the inflow items of the water balance; the water supply volume is determined from the accepted conditions using the existing irrigation regimes and technical parameters of operation in the first year of the experiment, and in the following 2 years—under the application of the recommended irrigation regime and technology of rice irrigation with the introduction of a recycling system of reuse of collector-drainage water and inflow under the irrigation system.

Water balance expenditure items include: volume of drainage-discharge runoff, total evaporation, volume of water supplied to aeration zone due to infiltration of irrigation and mixed irrigation-collector-drainage waters and value of lateral filtration outflow of groundwater outside the experimental study sites.

Salt balance is calculated by the formula:

$\begin{array}{ll}{\text{±ΔM = M}}_{\text{gw}}{\text{ s + M}}_{\text{I}}{\text{+M}}_{\text{P}}{\text{ - M}}_{\text{gw}}{\text{e - M}}_{\text{D}}{\text{ - M}}_{\text{R}}\text{,}& (8)\end{array}$

where: ±ΔM – balance mismatch;

${\text{M}}_{\text{gw}}^{\text{s}}$–the salt content of the groundwater in the balance layer at the start of the calculation period;

${\text{M}}_{\text{gw}}^{\text{e}}$–the same at the end of the period;

M_I И M_P–the volume of salts brought with the irrigation water and the precipitation, respectively;

M_D И M_R–the volume of salts carried outside the massif by drainage and groundwater outflow, respectively.

3 Results and discussion

According to the results of the monitoring of agrometeorological conditions conducted in the research region (Figure 7), it can be concluded that the total amount of precipitation that fell on the irrigated land in fields 2 and 4 (according to the Bakanas district meteorological station for 2022–2024) was 257.6 and 205.5 thousand m3 in 2022; 214.7 and 171.3 thousand m3 in 2023; and 321.8 and 256.7 thousand m3 in 2024. These figures are consistent with the existing arid and low-water conditions (4.5–7.4% of the water balance inflow items).

Figure 7

Figure 7. Dynamics of average monthly air temperature and precipitation at the Akdala irrigation massif for 2022—2024 hydrological years.

In 2022, the volume of water supply using existing irrigation regimes and technical conditions of operation on the Tasmurun part of the Bakbakti massif is accepted according to the data of the State Municipal Water Management Enterprise ‘Balkhashirrigatsi-ya', which was 4,131 and 3,599 million m³ for rice irrigation on fields Nos. 2, 4 respectively, with irrigation norm (netto) at the field level of 23,879 and 26,082 m³/ha.

During the 2023–2024 growing seasons, the recommended irrigation regime and rice irrigation technology incorporating a collector-drainage water reuse system were implemented on experimental fields No. 2 and No. 4. With a net irrigation rate of 22,900 m3/ha, the total irrigation water supplied amounted to 3.962 million m3 on field No. 2 and 3.16 million m3 on field No. 4. Of these volumes, 3.031 million m3 and 2.417 million m3, respectively, were sourced from surface runoff of the Ile River. Additionally, 0.931 million m3 in 2023 and 0.743 million m3 in 2024 were provided by pumping collector-drainage water from collector K-2 into the Tasmurun main canal. As a result, collector-drainage water accounted for 23.5% of the total irrigation water used on both experimental fields in each year.

Calculations indicate that irrigation is the primary component shaping the water balance, with irrigation water accounting for 91–93.4% of the total inflow in the balance structure.

The results of chemical analyses and processing of irrigation and collector-drainage water samples from the irrigated lands of the experimental site and adjacent areas—conducted both before (2020–2022) and during the study period (2023–2024)—are presented in the form of Kurlov's formula.

Comprehensive analysis of the hydrochemical regime of irrigation water during the reuse of collector-drainage water as an additional source to compensate for water deficits during the dry phases of the rice growing season revealed that the irrigation water of the Tasmurun irrigation system is fresh and falls into the first class based on salinity level, which ranged from 0.52 to 0.84 g/L (Table 7).

Table 7

Table 7. Chemical composition of irrigation and collector-drainage water on the irrigated lands of the experimental site and adjacent areas before (2020–2022) and during (2023–2024) the research period, based on Kurlov's formula.

According to the value of total hardness from soft to medium hardness (0.95–5.9 mg-eq/l), water reaction is slightly alkaline before and after mixing with collector-drainage water and practically does not change (pH 7.2–7.9). Water composition is predominantly sulfate-hydrocabonate sodium. Water content of nitrates less than 0.1 mg/L; nitrites less than 0.002 mg/L; ammonium 0.39–0.49 mg/L; silicon 5.4–6.1 mg/L; total iron up to 1.0 mg/L; petroleum products < 005–0.0125 mg/L; heavy metals, mg/L: Pb 0.005–0.013; Cu 0.02–0.0018 and Zn,0018–0.009 is within the maximum permissible concentrations of MAC (Table 8).

Table 8

Table 8. Content of microcomponents in irrigation, collector-drainage and groundwater in experimental plots before the start of the research (2022) and during the scientific research (2023–2024) on the reuse of collector-drainage waters, mg/L.

The results of analyzed irrigation water samples from the primary irrigation canals R-10 and R-15, as well as the check irrigation canal (Field 4), indicate that before the study period (2022), the waters were classified as fresh (Class I), with salinity levels ranging from 0.44 to 0.59 g/L. During the research period (2023–2024), the waters were characterized as slightly brackish, but still close to Class I, with salinity ranging from 0.65 to 0.74 g/L (Figures 8, 9). The water composition is predominantly sulfate–hydrocarbonate with calcium–magnesium–sodium cations. The waters are neutral in reaction, with pH values between 6.9 and 7.9, and total hardness ranging from soft to moderately hard (2.0–5.1 mg-eq/L). The concentrations of key microcomponents were as follows: nitrates < 0.13 mg/L, nitrites < 0.001 mg/L, ammonium 5.4–13.1 mg/L, silica 1.0–3.4 mg/L, total iron up to 1.8 mg/L, petroleum hydrocarbons 0.02–0.08 mg/L. Heavy metal concentrations (mg/L) were: Pb 0.01–0.05, Cu 0.002–0.005, and Zn 0.001–0.006.

Figure 8

Figure 8. Dynamics of mineralization of irrigation and collector-drainage water on the irrigated lands of the experimental plot and adjacent areas before (2022–2023) the research period.

Figure 9

Figure 9. Dynamics of mineralization of irrigation and collector-drainage water on the irrigated lands of the experimental plot and adjacent areas during (2023–2024) the research period.

Assessment of water quality by total mineralization, water reaction (pH), Stebler and SAR, as well as by Antipov-Karataev sedimentation hazard, give grounds to conclude that irrigation surface waters are highly suitable for use as the main source of irrigation.

The corrected class of water groups according to the danger of negative processes development, depending on the decrease of one or more of the group indices leading to the corresponding total decrease, characterizes irrigation waters as of good quality (Annex A–E, Tables 9–13).

Mineralization of collector-drainage water in collector K-2 during the whole vegetation period before and during its reuse by mixing with irrigation runoff of Tasmurun main canal tended to increase slightly from 0.55 to 0.64 g/L in 2022, from 0.74 to 0.84 g/L in 2023 and from 0.84 to 1.01 g/L in 2024 (Figures 7, 8), which gives full reason to attribute them to fresh water and to class II, suitable for irrigation of all crops, not worsening physical properties of soil and not reducing crop yields. Collector-drainage waters of K-2 system have sulfate-hydrocarbonate sodium-calcium or sodium-magnesium chemical composition (Table 9).

Table 9

Table 9. The chemical composition of the groundwater in the monitoring wells on the irrigated land of the experimental site, before the start of the scientific and applied research (2022) and during the research (2023–2024), in g/L.

Water content of nitrate less than 0.2 mg/L; nitrite less than 0.001 mg/L; ammonium up to 5.5 mg/L; silicon 0.46–1.14 mg/L; total iron up to 0.8; heavy metals, mg/L: Pb 0.01–0.02; Cu 0.005–0.01; petroleum products 0.016–0.097.

Quality assessment by Stebler—irrigation coefficient, good; assessment of quality and danger of salinization by SAR—closer to average, and assessment of quality and danger of salinization by I. N. Antipov-Karataev—suitable as an additional source of irrigation for any agricultural crops by mixing with irrigation water of the Ile River in recommended proportions (Annex A–E, Table 9).

According to the results of performed analyses, mineralization of water in the main collector (MC) within the boundaries of perspective sites and during the period of collector-drainage water reuse varied from 0.70 to 0.61 g/L, which refers it to the II - class as fresh. Chemical composition is sodium-calcium hydrocarbonate-sulfate. Water content of nitrates less than 0.2 mg/L; nitrites less than 0.001 mg/L; ammonium up to 5.5 mg/L; silicon 0.46–1.14 mg/L; total iron up to 0.8; heavy metals, mg/L: Pb 0.012–0.0069; Cu 0.0021–0.011; Zn 0.09–0.0024; petroleum products 0.05–0.015 (Table 8).

Rice and groundwater are inseparable concepts. Based on frequent measurements of the groundwater table, it was established that on irrigated lands of the experimental plots—regardless of the initial conditions and throughout the scientific-applied research period (2023–2024)—a quasi-stationary irrigation-type groundwater regime was formed. This regime is characterized by cyclic groundwater table fluctuations.

A general pattern of this regime is the widespread rise of the groundwater table during the growing season due to irrigation, followed by the formation of an irrigation-groundwater dome. This dome gradually dissipates during the non-vegetation period as a result of drainage system operations and the natural drainability of the area (Figure 10).

Figure 10

Figure 10. Graphs of groundwater level fluctuations in monitoring wells on irrigated lands of the experimental research site and adjacent territories for the observation period from 2021 to 2024 years. Year 2021: Wells No. 184, 306, 308, 336, and 370—alfalfa; well 309—out of operation. Years 2022–2024: Wells No. 184, 306, and 308—rice; wells 336 and 370—alfalfa; well 309—out of operation.

During water supply to the fields, a widespread rise in the groundwater table was observed, with the highest rate of increase occurring in May and the first ten-day period of June (in wells No. 184, 306, and 308 on rice fields and wells No. 336 and 370 on alfalfa fields). The groundwater table reached its highest level in July–August, with the amplitude of the rise reaching 2.5–3.0 m in rice fields (wells No. 184, 306, and 308), prior to the convergence of irrigation water and groundwater, and 1.5–2.0 m in alfalfa fields (wells No. 336 and 370).

After the end of irrigation season and water discharge from rice checks there was observed a widespread decrease of groundwater level with different intensity, mainly reaching marks below 2 m from the ground surface, and thus creating favorable conditions for harvesting operations. Restoration of groundwater position after the irrigation season continued during the non-growing season.

In fields with dryland crops, groundwater table fluctuations during the irrigation season were less intensive.

The results of chemical analysis and treatment of groundwater samples in the irrigated lands of the experimental site and adjacent areas before (2020–2022) and during the study (2023–2024), presented as Kurlov formula are summarized in Table 9.

On the irrigated lands of the experimental plot, both before the beginning of the research in 2022 and during the scientific investigations in 2023–2024, fresh and slightly saline groundwater is common. In April, groundwater mineralization varied from 0.35 g/L to 0.99 g/L across almost the entire area. Only in the adjacent non-irrigated areas did the salt content of the groundwater reach 1.19–1.45 g/L. The chemical composition is primarily hydrocarbonate-sulfate or sulfate-hydrocarbonate, sodium-magnesium or sodium-calcium. At the end of the growing season, desalination of the groundwater occurred due to moisture accumulation in the aeration zone, causing a slight decrease in salinity from 0.86 g/L to 0.56 g/L. SAR in groundwater fluctuated within the range of 0.3–8.1 during the growing season, indicating the absence of soil salinization in contact with these waters.

Change of mineralization and chemical composition on the irrigated massif has seasonal character. On the fields with rice crops there is a decrease in groundwater salinity due to dilution with more fresh irrigation water. At the end of the irrigation season there is a return of salinity to the initial value, associated with a decrease in groundwater table and intra-soil processes (Figure 11).

Figure 11

Figure 11. Graph of dynamics of groundwater salinity in monitoring wells on irrigated lands of the experimental site before the beginning (2022) and during scientific and applied research (2023-2024), g/L. Wells No. 184, 306, 308—rice; 336 and 370—alfalfa; well 309—out of operation.

On fields with dryland crops, salts in the aeration zone soils dissolve, leading to salinization or desalinization. The direction depends on factors like soil salinity, territory drainability, water supply, and the condition of the collector-drainage network. Generally, groundwater salinity returns to its initial state during the non-growing season.

Positive results of complex analysis and assessment of irrigation water, collector-drainage and groundwater influence degree during 2-year experiment on collector-drainage water reuse at field level in six-field rice and alfalfa crop rotation of Tasmurun part of Akdala massif testify to satisfactory ameliorative condition of irrigated lands, on which introduction of water-saving technologies for rice and accompanying crops irrigation is very effective, both in terms of water saving and water supply. At the same time, ameliorative condition of lands will improve due to reduction of water supply volume and decrease of salt intake with irrigation water.

To support our conclusions regarding the meliorative processes on the irrigated lands at our experimental rice system research site, we present the calculated inflow and outflow components of water and salt balances. These calculations, along with analytical conclusions, are compared to baseline data from 2022 provided by the RGU ‘Zonal Hydrogeological and Meliorative Centre' of the Ministry of Water Resources and Irrigation of Kazakhstan. The positive results from our two-year experiment on collector-drainage water reuse in a six-field rice and alfalfa crop rotation indicate a satisfactory ameliorative condition of the irrigated lands. This demonstrates that the introduction of water-saving technologies for rice and associated crops is effective in both water saving and water conservation. Furthermore, reducing water supply volume and decreasing water intake should further improve the meliorative condition of the lands.

A key characteristic of the water balance in these rice crop rotations is the significant contribution of infiltration to the water supply. This is influenced by flow and water discharges from the checks, as well as substantial water losses due to reed consumption. Calculations of actual groundwater inflow to the experimental plots revealed very low values, indicating a negligible impact on the overall inflow components of the water balance (see Annex A).

The total evaporation was estimated at 10,930 thousand m3/ha for all 3 years of the study, accounting for over 40% of the total water balance expenditures. This finding supports the widely accepted view that rice, being cultivated on water-saturated soils and partially submerged in water, is classified as a hydrophyte. Hydrophytic plants exhibit high transpiration rates due to their continuously open stomata. In rice, evaporation losses are comparable to free water surface evaporation.

The results of the water balance calculations for irrigated lands revealed a small but negative non-closure value, ranging from 0.4% to 0.6% in 2022 and from 0.001% to 0.02% in 2023–2024. When recalculated, this corresponds to an average decline in the groundwater table across the experimental sites—from 0.04 m in 2022 to 0.015 m in 2023–2024. These results are confirmed by data from long-term groundwater level monitoring and supporting mapping materials (Annex A). The findings indicate that the inflow components of the balance remained relatively stable and were largely offset by the outflow components.

The slight positive salt balance on experimental plots (fields 2 and 4) in the rice-alfalfa crop rotation of the Tasmurun irrigation system, both before and during the research (2023–2024), remained minimal despite the reuse of collector-drainage water. Values ranged from +0.016 to +0.29 tons/ha in rice field No. 2 and from +0.049 to +0.089 tons/ha in rice field No. 4. This suggests a negligible accumulation of salt reserves in the active salt exchange zone during the growing season (see Annex K). This seasonal increase in salt, due to the rice leaching regime and the predominance of easily soluble salts in the groundwater's chemical composition, is unlikely to cause a regional deterioration of the irrigated lands' meliorative condition.

In terms of spatial distribution, the most prevalent soil types within the experimental site are alluvial meadow soils and light-textured meadow soils. These soils are characterized by stratification of the profile, which is caused by the alternation of horizons with different granulometric compositions. These soils consist of sands and silty sandy loams with a light texture and an absorption capacity of less than 15 meq per 100 g of soil.

These soils form under conditions of surface wetting, predominant downward water flow, and groundwater outflow, which ensures the leaching of salts. Salinization is sporadic and generally secondary, resulting from design flaws or improper operation of irrigation systems. The content of readily soluble salts in the top one-meter layer of non-saline soils does not exceed 0.2%.

Non-saline irrigated lands classified as Class I have a low-hazard rating of irrigation water quality when irrigated with water of mineralization up to 1.0 g/L, according to permissible mineralization levels for such soils. The aqueous suspension reaction is slightly alkaline in the upper horizons and alkaline in the lower horizons. Depending on the content of fine mineral particles and organic colloids, the cation exchange capacity varies from 12 to 23 meq per 100 g of soil. Calcium dominates the composition of exchangeable cations, and the proportion of exchangeable sodium is less than 5% of the total absorbed bases.

These soils are characterized by low nutrient reserves. While the humus content in regularly irrigated areas used for rice cultivation and associated crops may reach 3–5% or higher, the soils are generally deficient in nutrients such as nitrogen, phosphorus, and potassium. Long-term use of the soil for rice cultivation leads to significant changes in its properties, particularly the deterioration of its hydro-physical characteristics. This includes increased density, profile stratification, and reduced permeability. Therefore, the optimal management practice is a six-field crop rotation of rice and alfalfa, with rice occupying no more than 50% of the rotation and being replaced by restorative crops after 3 years (Figure 12).

Figure 12

Figure 12. Schematic map of soil salinity in the upper meter of the Tasmurun area, Akdala irrigation massif. Key: 1—Non-saline, 2—Weakly saline, 3—Salinization contours, 4—Irrigation canals, 5—Collectors, 6—River, 7—Settlements.

According to the results of the conducted salt survey and the preliminary schematic map of the degree and type of salinization of irrigated lands (0–100 cm soil layer), the soils across all plots, following the experimental studies, were predominantly classified as non-saline, accounting for 85% of the surveyed area. Slight salinity was observed in narrow strips of land adjacent to the collector-drainage network, with the salinization type identified as sulfate–sodium–calcium. In the alfalfa fields, soils were also slightly saline, with the salinity type characterized as sulfate–hydrocarbonate–calcium. The salt content in the soil profile ranged from 0.185% in the upper soil layer to 0.091% at a depth of 60 cm and below.

Significant improvements were achieved through the introduction of experimental water-saving measures and the reuse of collector-drainage waters, compared to the traditional irrigation regime applied in 2022. During the vegetation period, a total of 608,000 m3 of water was conserved by adhering to controlled irrigation parameters, including 169,000 m3 in Field 2 and 439,000 m3 in Field 4. Additionally, reusing collector-drainage waters provided an extra 1.674 million m3 of savings. Consequently, the irrigation norm decreased by 14%, from 26,082 m3/ha to 22,900 m3/ha, and drainage return flows from rice systems decreased by the same percentage.

There were positive effects on crop performance: rice yields increased by 6.8% in 2023 and 9.2% in 2024, reaching 40.6–42.6 quintals per hectare. Water use efficiency improved as well, with the amount of irrigation water used per quintal of rice decreasing by 18%. For instance, the indicator reached 564.04 m3/ha in SPK Miyaly-Agro and ranged from 537.56 to 549.16 m3/ha in PK Dinara across 66–92 ha fields.

The economic outcomes were equally substantial. Rice production efficiency increased by 1,605,000 KZT/ha (equivalent to USD 3,800 at the 2024 average exchange rate), representing a 25% improvement. Profitability rose by 25%, reaching 35%.

All field instruments and installed equipment were certified with documented error margins and calibration intervals. To ensure accuracy, measurements were repeated ten times and weighted averages were calculated to minimize random error and prevent exceeding the manufacturer's stated tolerance.

Laboratory quality control was performed to validate the reliability of the chemical analyses and prevent methodological errors. One hundred percent of the tested samples were included in self-control during mechanical analyses, while water extract analyses were verified by comparing the ionic balance (sum of cations and anions) and cross-checking calculated values with measurements obtained using precision instruments. Systematic control was achieved by incorporating 20% coded soil samples into the analytical program and comparing the results to standard references or those of independent laboratories.

The reliability of the laboratory results was confirmed by participating in interlaboratory comparison tests annually, which were organized by a certified provider.

In line with the stated objectives, the study demonstrated:

- the feasibility of collector-drainage water reuse in rice irrigation;

- environmental safety confirmed through water and salt balance assessments;

- specific technological guidelines (25–30% reuse proportion) that can be directly applied in practice.

Together, these outcomes provide a validated framework for sustainable water management in the Akdala rice irrigation system.

During the vegetation period, a total of 608,000 m3 of water was saved by maintaining and monitoring established irrigation parameters −169,000 m3 on Field 2 and 439,000 m3 on Field 4. An additional 1.674 million m3 was conserved through the reuse of collector-drainage waters. Consequently, the irrigation norm decreased from 26,082 m3/ha to 22,900 m3/ha, representing a 14% reduction, accompanied by a 14% decrease in drainage return flow from rice systems.

Crop performance improved significantly: rice yields increased by 6.8% in 2023 and by 9.2% in 2024, reaching 40.6–42.6 quintals per hectare. Water use efficiency also improved, with specific irrigation water consumption per quintal of rice reduced by 18%. For example, in SPK Miyaly-Agro (Alga) the indicator reached 564.04 m3/ha over an area of 81 ha, while in PK Dinara it ranged between 537.56 and 549.16 m3/ha across fields of 66–92 ha. Economic outcomes were equally notable. The efficiency of rice production increased by 1,605,000 KZT/ha (equivalent to USD 3,800 at the 2024 average exchange rate), representing a 25% gain. Profitability of rice cultivation also rose by 25%, reaching 35%.

4 Conclusions

Currently, and increasingly in the future, irrigated agriculture is developing under conditions of water scarcity. The study region is no exception, as forecasts indicate a worsening ecological situation in the Ile-Balkash natural-economic complex. This is primarily due to the gradual decline in the Ile River's flow, resulting from increased water withdrawals by the People's Republic of China and high water demand for rice cultivation in the Akdala rice field.

The water shortage negatively affects the ecological landscape of the region, leading to reduced income and deteriorating socio-economic conditions for local rural communities.

In response to these challenges, the main objective of the field studies was to demonstrate the advantages of innovative, water-saving technologies—specifically, the reuse of collector-drainage water. This task is highly relevant and of significant economic, social, and environmental importance. The study aimed to assess the ecologically safe volumes of collector-drainage return flow that can be reused, considering the local soil, hydrogeological, and reclamation conditions, as well as the technical feasibility of water intake from the existing drainage-discharge network.

The main objective of the field studies was to develop the technological parameters for rice irrigation using the reuse of collector-drainage water at selected recommended sites, while determining environmentally safe volumes of collector-drainage flow.

As representative sites for developing the reuse technology, irrigated lands served by the Tasmurun Main Canal and the collector-drainage network (Collector K-2) were selected. These sites included Fields 2, 3, 4, and 5—part of the III-rd rice and alfalfa crop rotation—with a total area of 607 ha, managed by SPK ‘Miyaly Agro', PC ‘Dinara', and LLP ‘EDD'. The cropping pattern for 2022–2024 was as follows: Fields 2 (173 ha) and 4 (138 ha) were planted with rice, while Fields 3 (187 ha) and 5 (109 ha) were sown with alfalfa.

During 2023–2024, detailed monitoring was conducted at the level of the on-farm rice irrigation network, covering all key parameters required for experimental research. The aim was to develop a recycling water-use system and establish the technological conditions for rice irrigation using environmentally safe volumes of collector-drainage water. This was based on the existing soil-reclamation and hydrogeological-reclamation conditions, as well as the technical feasibility of mechanical water intake from the existing collector-drainage system.

Analyses indicate that collector-drainage waters, transported and partially reused during the dry season, are highly suitable for rice irrigation. This conclusion is based on a corrected classification of water groups, considering the risk of negative processes arising from a decline in group indicators. The reuse of this water is assessed positively for its environmental impact.

The justification of the projected real characteristics, as well as the quantitative, qualitative feasibility, and intensity of collector-drainage water reuse in this study, was based on an analysis of the water and salt balance in the Tasmurun section of the Bakbakti irrigation system. This system serves the irrigated lands of SPK ‘Miyaly Agro', PC ‘Dinara', and LLP ‘EDD' over a three-year period, characterized as dry and low-water in terms of water availability in water-intensive rice fields.

Importantly, the calculation of all components of the water and salt balances was not based on literature sources or previously reported data, but on original field research conducted with the direct participation of project beneficiaries (local farms), ensuring the reliability and validity of the initial data.

Water balance studies, conducted as part of a comprehensive investigation into the formation of the hydrochemical regime of groundwater, were carried out at a representative site with the following objectives.

To study the dynamics of the irrigation–groundwater dome formation during the growing season, including the degree and intensity of soil desalinization due to irrigation water infiltration; the amplitude and rate of groundwater level rise; and the potential for interaction between groundwater and surface irrigation water. These processes were observed on rice paddies and associated crops in Field 6 of the third rice–alfalfa seven-field crop rotation system within the Bakanas irrigation network of the Akdala irrigation area.

To investigate the specific features of sub-irrigation regimes on alfalfa fields, focusing on changes in soil salinity profiles resulting from capillary rise of groundwater.

To examine the characteristics of groundwater hydrochemical regime formation after the rice fields are drained, continuing through the following spring. This includes monitoring the amplitude and rate of groundwater table decline, as well as the degree and extent of secondary soil salinization caused by in-soil evaporation and the effect of the capillary fringe.

Groundwater salinity and chemical composition fluctuate seasonally. In rice fields, salinity decreases due to dilution with fresh irrigation water. As the irrigation season ends, salinity returns to its initial level, influenced by the declining water table and intra-soil processes such as capillary action and evaporation.

In fields with dryland crops, salts from the aeration zone dissolve, leading to either salinization or desalinization. The specific outcome depends on initial soil salinity, drainage, water supply, and the condition of the collector-drainage network. Generally, groundwater salinity reverts to its initial state during the non-growing season.

A six-field crop rotation (1 year—reclamation field, 2 years—alfalfa, 3 years—rice) improves soil organic matter and contributes to good yields. Alfalfa acts as biological drainage, consuming groundwater and preventing salt rise through water uptake and transpiration, while also providing soil coverage. Irrigating alfalfa in this rotation, maintaining soil moisture at 75% of field capacity, increases alfalfa hay yield by 25–30% and further reduces salt accumulation on the soil surface.

Recycled water use in rice fields reduces irrigation water consumption, mitigates land degradation, increases rice yields, and improves local community welfare through increased agricultural productivity.

Compared to 2022, the application of the recommended irrigation regime—along with adherence to the established and controlled operational parameters within the recommended hydromodule ordinates during the vegetation period—resulted in annual savings of 608 thousand m3 of scarce surface water from the transboundary flow of the Ile River. This included 169 thousand m3 for Field 2 and 439 thousand m3 for Field 4.

In addition, the reuse of collector-drainage water led to further savings of 1.674 million m3 of transboundary surface water, with 0.931 million m3 and 0.743 million m3 used for rice irrigation in Fields 2 and 4, respectively.

Thus, the total annual volume of saved surface water from the transboundary Ile River flow amounted to 2.282 million m3.

A reduction in the irrigation norm—from 26,082 m3/ha to 22,900 m3/ha—was achieved, with the shortfall compensated by an additional 5,382 m3/ha provided through the reuse of collector-drainage water over the 3-month growing season. Furthermore, drainage return flow from the rice irrigation system was reduced by 14%.

The specific water consumption for rice production ranged from 537.56 to 564.04 cubic meters per hectare across different farms: 564.04 m³/ha in SPK ‘Miyaly-agro' farm “Alga” (81 ha area), 537.56 m³/ha (92 ha), 547.85 m³/ha (66 ha), and 549.16 m³/ha in PC ‘Dinara' (92 ha).

Gross rice yield increased by 3–6 centner/ha. Based on calculations (Annex L, N), the biological yield on phenological sites of representative plots reached 40.6–42.6 c/ha, compared to a previous yield of 35–40 c/ha. This 9% increase is attributed to a 10–15% improvement in water availability within the rice systems.

The gross income from the increased rice yield amounted to 165,704 thousand tenge (approximately 3,452 USD), based on a consolidated production cost of 184.296 thousand tenge per ton of rice and a market price of 350.0 thousand tenge per ton (calculated using 2024 prices and exchange rates).

Income generated from the savings of 1.674 million m3 of surface water from the Ile River was 117,180 thousand tenge, calculated at the established tariff of 0.07 tenge per cubic meter.

Direct economic benefits were received by the local farms: Peasant Farm ‘Alga' of SPK ‘Miyaly Agro' (81 hectares) and PC ‘Dinara' (240 hectares). A detailed breakdown of costs is provided in Appendix P, using the example of the local community—Peasant Farm ‘Alga' of SPK ‘Miyaly Agro'—in the development of collector-drainage water reuse technology at the representative site in Field 2 of the third crop rotation within the Tasmurun irrigation system of the Akdala irrigation massif.

Given increasing water scarcity in the Akdala Massif, the introduction of innovative water-saving technologies, such as the rational reuse (water recycling) of collector-drainage water, is an urgent task with significant economic, social, and ecological importance for the region.

Detailed studies on the safe development of collector-drainage water reuse technologies at the on-farm rice field network level have demonstrated the prospects and real possibilities of sustainable and innovative approaches to water consumption reduction. These studies address safety considerations such as monitoring water quality and preventing soil salinization.

In the long term, with the depletion of available high-quality water resources, utilizing drainage water with increased mineralization for irrigation will become necessary, requiring dilution with freshwater for safe and effective reuse.

Data availability statement

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Author contributions

MA: Conceptualization, Writing – review & editing, Software. DU: Writing – review & editing, Investigation, Data curation. VK: Project administration, Methodology, Writing – original draft. TR: Conceptualization, Methodology, Supervision, Writing – original draft. VM: Supervision, Writing – original draft, Visualization. AI: Formal analysis, Writing – review & editing. VR: Writing – review & editing, Writing – original draft, Conceptualization.

Funding

The author(s) declare that financial support was received for the research and/or publication of this article. This study was funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Groundwater Resources as the Main Reserve for Sustainable Irrigated Agriculture in Kazakhstan No. BR 21882211).

Conflict of interest

MA, VK, TR, and VR were employed by Ahmedsafin Institute of Hydrogeology and Environmental Geoscience LLP.

The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Generative AI statement

The author(s) declare that no Gen AI was used in the creation of this manuscript.

Any alternative text (alt text) provided alongside figures in this article has been generated by Frontiers with the support of artificial intelligence and reasonable efforts have been made to ensure accuracy, including review by the authors wherever possible. If you identify any issues, please contact us.

Publisher's note

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Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/frwa.2025.1650089/full#supplementary-material

References

Akhtar, F., Tischbein, B., and Awan, U. (2013). Optimizing deficit irrigation scheduling under shallow groundwater conditions in lower reaches of Amu Darya River Basin. Water Resour. Manag. 27, 3165–3178. doi: 10.1007/s11269-013-0341-0

Crossref Full Text | Google Scholar

Al-Aizari, H. S., Aslaou, F., Mohsen, O., Al-Aizari, A. R., Al-Odayni, A-. B., Abduh, N. A. Y., et al. (2024). Assessment of groundwater quality for irrigation purpose using irrigation water quality index (IWQI). J. Environ. Eng. Landsc. Manag. 32, 1–11. doi: 10.3846/jeelm.2024.20598

Crossref Full Text | Google Scholar

Al-Anzi, B., Abusam, A., and Shahalam, A. (2012). Assessment of waste water reuse in kuwait and its impact on amounts of pollutants discharged into the sea. J. Environ. Prot. 3, 935–939. doi: 10.4236/jep.2012.328108

Crossref Full Text | Google Scholar

Antipov-Karataev, N. I., and Kader, G. M. (1959). ‘Methods for assessing the quality of irrigation water'. Soil Sci. 2, 96–100.

Google Scholar

Averyanov, S. F. (1978). Combating Salinization of Irrigated Lands (Kolos: Moscow), 288.

Google Scholar

Bezborodov, Y., Khozhanov, N., Mirdadayev, M., and Ustabaev, T. (2022). Methodology of recycling of drainage and waste water in Kazakhstan. Agrar. Scientif. J. 11, 96–99. doi: 10.28983/asj.y2022i11pp96-99

Crossref Full Text | Google Scholar

Committee for Standardization (2003). ST RK GOST R 51232; National Standard. Drinking Water General Requirements for the Organization and Methods of Quality Control. Astana, Kazakhstan: Committee for Standardization

Google Scholar

Dotaniya, M. L., Meena, V. D., Saha, J. K., Dotaniya, C. K., Mahmoud, A. E. D., Meena, B. L., et al. (2023). Reuse of poor-quality water for sustainable crop production in the changing scenario of climate. Environ. Dev. Sustain. 25, 7345–7376. doi: 10.1007/s10668-022-02365-9

PubMed Abstract | Crossref Full Text | Google Scholar

FAO (1994). Water Quality for Agriculture. Irrigation and Drainage. Rome, Italy: Food and Agriculture Organisation.

Google Scholar

Fereres, E., and Soriano, M. A. (2007). Deficit irrigation for reducing agricultural water use, J. Exp. Bot. 58, 147–159. doi: 10.1093/jxb/erl165

Crossref Full Text | Google Scholar

Gotsis, D., Spiliotis, M., and Giakoumakis, S. (2011). Reuse of drainage water in irrigation with the aid of 0-1 linear programming. Irrig. Drain. Syst. 25, 385–394. doi: 10.1007/s10795-012-9131-8

Crossref Full Text | Google Scholar

Hejase, C. A., Weitzel, K. A., Stokes, S. C., Grauberger, B. M., Young, R. B., Arias-Paic, M. S., et al. (2022). Opportunities for treatment and reuse of agricultural drainage in the United States. ACS ESandT Eng. 2, 292–305. doi: 10.1021/acsestengg.1c00277

Crossref Full Text | Google Scholar

Imanudin, M. S., Sulistiyani, Armanto, M. E., Madjid, A., and Saputra, A. (2021). Land suitability and agricultural technology for rice cultivation on tidal lowland reclamation in South Sumatra. Jurnal Lahan Suboptimal: Journal of Suboptimal Lands 10, 91–103. doi: 10.36706/JLSO.10.1.2021.527

Crossref Full Text | Google Scholar

International Organization for Standardization (2003). ISO 17294-2; International Standard. Water Quality—Application of Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Part 2: Determination of 62 Elements. Geneva, Switzerland: ISO

Google Scholar

Jalil, A., Akhtar, F., and Awan, U. (2020). Evaluation of the AquaCrop model for winter wheat under different irrigation optimization strategies at the downstream Kabul River Basin of Afghanistan. Agricult. Water Manag. 240:106321. doi: 10.1016/j.agwat.2020.106321

Crossref Full Text | Google Scholar

Jiang, W., He, Z. Y., and Bo, Z. Q. (2010). “The overview of research on microgrid protection development,” in Proceedings of International Conference on Intelligent System Design and Engineering Application, Beijing, 692–697. doi: 10.1109/ISDEA.2010.69

Crossref Full Text | Google Scholar

Kudoyarova, G., Dodd, I., and Veselov, D. Rothwell S. A.. (2015). Common and specific responses to availability of mineral nutrients and water. J. Exp. Bot. 66, 2133–2144. doi: 10.1093/jxb/erv017

PubMed Abstract | Crossref Full Text | Google Scholar

Kumar, R., and Verma, R. (2012). Classification algorithms for data mining: a survey. Int. J. Innov. Eng. Technol. (IJIET), 1, 7–14.

Google Scholar

Laze, P., and Rizani, S. (2016). Assessment of irrigation water quality of Dukagjin basin in Kosovo. Agricult. Food J. Int. Sci. Public. 4, 544–551. doi: 10.7251/AGREN1603243R

Crossref Full Text | Google Scholar

Lumex (2010). PND F 16.1: 2: 2.3: 2.2.69-10: National Standard. Determination of Water-Soluble Forms of Inorganic and Organic Anions in Soils, Greenhouse Soils, Clays, Peat, Sewage Sludge, Activated Sludge, and Bottom Sediments. Methodology M 03-06-2010. Moscow, Russia: Lumex.

Google Scholar

Murtazin, Y., Kulagin, V., Mirlas, V., Anker, Y., Rakhimov, T., Onglassynov, Z., et al. (2025). Integrated Assessment of Groundwater Quality for Water-Saving Irrigation Technology (Western Kazakhstan). Water 17:1232. doi: 10.3390/w17081232

Crossref Full Text | Google Scholar

Nagaiah, E., Sonkamble, S., Mondal, N. C., and Ahmed, S. (2017). Natural zeolites enhance groundwater quality: evidences from Deccan basalts in India. Environ. Earth Sci. 76:536. doi: 10.1007/s12665-017-6873-5

Crossref Full Text | Google Scholar

Okuda, Y., Onishi, J., Omori, K., Oya, T., Fukuo, A., Kurvantaev, R., et al. (2022). Current status and problems of the drainage system in Uzbekistan. J. Arid Land Stud. 25, 81–84. doi: 10.14976/jals.25.3_81

Crossref Full Text | Google Scholar

Ouyang, Z., Tian, J., and Yan, X. (2024). Effects of mineralization degree of irrigation water on yield, fruit quality, and soil microbial and enzyme activities of cucumbers in greenhouse drip irrigation. Horticulturae 10:113. doi: 10.3390/horticulturae10020113

Crossref Full Text | Google Scholar

Prasad, A., Kumar, D., and Singh, D. V. (2001). Effect of residual sodium carbonate in irrigation water on the soil sodication and yield of palmarosa (Cymbopogon martinni) and lemongrass (Cymbopogon flexuosus). Agricult. Water Manag. 50, 161–172. doi: 10.1016/S0378-3774(01)00103-2

Crossref Full Text | Google Scholar

Qadir, M., Wichelns, D., Raschid-Sally, L., McCornick, P. G., Drechsel, P., Bahri, A., et al. (2010). The challenges of wastewater irrigation in developing countries. Agricult. Water Manag. 97, 561–568. doi: 10.1016/j.agwat.2008.11.004

Crossref Full Text | Google Scholar

Rawat, K. S., Singh, S. K., and Gautam, S. K. (2018). Assessment of groundwater quality for irrigation use: a peninsular case study. Appl. Water Sci. 8:233. doi: 10.1007/s13201-018-0866-8

Crossref Full Text | Google Scholar

Rejesus, R. M., Palis, F. G., Rodriguez, D. G. P., Lampayan, R. M., and Bouman, B. A. M. (2011). Impact of the alternate wetting and drying (AWD) water-saving irrigation technique: evidence from rice producers in the Philippines. Food Policy 36, 280–288. doi: 10.1016/j.foodpol.2010.11.026

Crossref Full Text | Google Scholar

Reshetnyak, N. F. (1973). Influence of groundwater on dynamics of water-soluble salts in soils of rice crop rotations. Soil Sci. 2, 111–121.

Google Scholar

Richards, L. A., Ellison, L., Bernstein, C. A., Bauer, J. W., Brown, M., Fireman, J. T., et al. (1954). Diagnosis and improvement of saline and alkaline soils. Soil Sci. Soc. Am. J. 18:348. doi: 10.2136/sssaj1954.03615995001800030032x

Crossref Full Text | Google Scholar

Sadak, M., Abdelhamid, M., and Schmidhalter, U. (2015). Effect of foliar application of aminoacids on plant yield and physiological parameters in bean plants irrigated with seawater. Acta Biologica Colombiana 20, 141–152. doi: 10.15446/abc.v20n1.42865

Crossref Full Text | Google Scholar

Singh, K. K., Tewari, G., and Kumar, S. (2020). Evaluation of groundwater quality for suitability of irrigation purposes: a case study in the Udham Singh Nagar, Uttarakhand. J. Chem. 2020:6924026. doi: 10.1155/2020/6924026

Crossref Full Text | Google Scholar

Temesgen, E., Gulie, G., and Akili, D. (2023). Evaluation of drainage water quality for irrigation reuse in Kulfo and Hare irrigation command areas, southern Ethiopia. Water Pract. Technol. 18, 2329–2340. doi: 10.2166/wpt.2023.146

Crossref Full Text | Google Scholar

van Asten, P. J. A., Barbiéro, L., Wopereis, M. C. S., Maeght, J. L., and van der Zee, S. E. A. T. M. (2003). Actual and potential salt-related soil degradation in an irrigated rice scheme in the Sahelian zone of Mauritania. Agricult. Water Manag. 60, 13–32. doi: 10.1016/S0378-3774(02)00155-5

Crossref Full Text | Google Scholar

Verma, P., Solanki, H., Chandawat, D., and Gupta, U. (2012). Water quality analysis of an organically polluted lake by investigating different physical and chemical parameters. Int. J. Res. Chem. Environ. 2, 105–111.

Google Scholar

Wu, P., Wang, Y., Li, Y., Yu, H., Shao, J., Zhao, Z., et al. (2023). Optimizing irrigation strategies for sustainable crop productivity and reduced groundwater consumption in a winter wheat-maize rotation system. J. Environ. Manag. 348:119469. doi: 10.1016/j.jenvman.2023.119469

PubMed Abstract | Crossref Full Text | Google Scholar

Wu, Z., Li, Y., Wang, R., Xu, X., Ren, D., Huang, Q., et al. (2023). Evaluation of irrigation water saving and salinity control practices of maize and sunflower in the upper Yellow River basin with an agro-hydrological model based method. Agricult. Water Manag. 278:108157. doi: 10.1016/j.agwat.2023.108157

Crossref Full Text | Google Scholar

Zaitsev, V. B., and Semenenko, A. N. N. (1962). “Peculiarities of groundwater regime of flooded rice field,” in Book: Summary Results of Scientific-Research Work for 1959-1960 (Krasnodar: Kuban Rice Experimental Station), 12–32.

Google Scholar

Zulu, G., Toyota, M., and Misawa, S. (1996). Characteristics of water reuse and its effects on paddy irrigation system water balance and the riceland ecosystem. Agricult. Water Manag. 31, 269–283. doi: 10.1016/0378-3774(95)01233-8

Crossref Full Text | Google Scholar