The exceptionally high spatial-temporal variability of the river runoff and the significance of its transboundary component considerably worsen the problem of the water supply of the republic. Due to the disadvantageous geographical location in the lower reaches of transboundary river basins, the Republic of Kazakhstan is largely dependent on water economy activities taking place in neighbouring countries. In the article the modern change of the resources of river runoff in Kazakhstan, taking into account climatic and anthropogenic influences is considered. For the assessment of the impact of economic activities on the river runoff and changes in climatic-related runoff, the complex of integral methods was used, and appropriate methodologies were developed. The obtained results of the modern influence of a complex of factors, as well as their significance for the future (till 2030), can be used for the development of scientifically based solutions for sustainable management and protection of water resources. An assessment of the anthropogenic activity of this study shows that the water resources of the river runoff of the Republic of Kazakhstan have decreased by 16.0 km 3∙y –1. According to our forecasts, there will be a further decrease in the water resources of the republic due to the expected decrease in transboundary flow to 87.1 km 3∙y –1 by 2030, in dry years less than 50.0 km 3∙y –1. We propose a set of measures to prevent the negative impact of possible reduction of river runoff resources in the future in the water basins of Kazakhstan.

Hydrological droughts occur due to a variety of hydrometeorological phenomena, such as lack of precipitation, reduced snow cover and high evaporation. The values of these factors vary depending on the climate and the severity of drought events. Droughts caused by a lack of precipitation and continuing in the warm season have a longer periodicity. This important statement raises the question of whether climate change may exacerbate the phenomenon of drought. Therefore, understanding changes in the formation of hydrological droughts is key to foreseeing possible changes in the future. This scientific study analyzes the spread of hydrometeorological droughts in the Ile-Balkash basin using standardized precipitation indices and the drought index of river runoff. Lake Balkash plays an important role in the hydrological cycle and is a valuable freshwater resource, especially in dry years. Prolonged droughts in the area have serious consequences, including deterioration of water quality and loss of wetlands, which are important to the ecological system and migratory birds. The analysis shows that during the period of instrumental observations, several extreme hydrological droughts were observed in this area, (1943–1946, 1973–1975 and 1983–1987), which emphasizes the relevance and importance of scientific research on the problem of drought.

The study presents a scenario analysis of the long-term dynamics of the water level of Lake Balkhash, one of the largest closed lakes in Central Asia, taking into account climate change according to CMIP6 scenarios (SSP2-4.5 and SSP5-8.5) and socio-economic factors of water use. Based on historical data (1947–2021) and a water balance model, the contribution of surface runoff, precipitation and evaporation to the formation of the lake’s hydrological regime was assessed. It was established that the main source of water resources for the lake is the flow of the Ile River, which feeds the western part of the reservoir. The eastern part is characterized by extremely limited water inflow, while evaporation remains the main element of water consumption, having increased significantly in recent decades due to rising air temperatures. Increasing intra-seasonal and interannual fluctuations in water levels have been recorded: The amplitude of short-term fluctuations reached 0.7–0.8 m, which exceeds previously characteristic values. The results of water balance modeling up to 2050 show a trend towards a 30% reduction in surface inflow and an increase in evaporation by 25% compared to the 1981–2010 climate norm, which highlights the high sensitivity of the lake’s hydrological regime to climatic and anthropogenic influences. The results obtained justify the need for the comprehensive and adaptive management of water resources in the Balkhash Lake basin, taking into account the transboundary nature of water use and changing climatic conditions.

In connection with the catastrophic floods in the spring of 2024 in the Western region of Kazakhstan, the goal was to conduct a critical analysis of the long-term dynamics of maximum water flow rates according to hydrological posts located along the main channel of the Zhaiyk River, for a retrospective assessment of the probabilistic recurrence of such values in 2024. The article discusses the main hydrological characteristics of floods on the Zhaiyk River for a long-term period up to 2021. Hydrological calculations, statistical analysis of long-term flow dynamics were carried out, and catastrophic years with high waters were identified in accordance with regulatory documents. The characteristic water levels in the years with correspondingly critical water consumption, as well as the area of flooding of territories, were studied, the time of the flood wave between hydrological posts, including the territory of Russia, was determined. In the future, it is planned to analyze the current situation for 2024, at the end of the flood and flood process in Western Kazakhstan.

The surface water resources of the West Kazakhstan Region (WKR) face escalating vulnerability due to the synergistic effects of a sharply continental climate, which intensifies climate change impacts, and rapidly increasing anthropogenic water demand. This study aims to quantify and project the future water stress on WKR’s surface waters, assessing the combined influence of climate change and socio-economic development over the critical period of 2030–2050. This study presents a comprehensive quantitative assessment and future projection of water stress on the region’s surface waters, integrating state-of-the-art CMIP6 climate scenarios (SSP2-4.5 and SSP5-8.5) with a novel model of water consumption growth accounting for regional demographic and economic developments. Employing advanced bias-corrected ensemble climate projections alongside physically interpretable water balance models, we estimate changes in river flows and lake volumes through mid-century. A newly developed Water Stress Index (WSI), supplemented by the Falkenmark Index, reveals an alarming increase in water stress, with projections indicating that over 70% of the WKR territory may face severe resource limitations by 2050. The analysis underscores significant spatial heterogeneity driven by climatic variability and socio-economic factors, emphasizing the urgent need for regionally tailored adaptation and water management strategies. These findings provide a robust scientific basis to guide policy decisions aimed at mitigating future water scarcity under evolving climate and development scenarios.

The article considers the key aspects of optimization of the composition and placement of the hydrological network of the Republic of Kazakhstan in the context of ensuring sustainable monitoring of water resources. The main attention is paid to the preservation of reference (long-row) observation points necessary for territorial generalizations, development of methods for hydrological calculations and forecasts, as well as assessment of long-term changes in the hydrological regime in the context of climate change. The scientific study emphasizes the importance of increasing the number of information posts to improve the reliability of hydrological forecasts and warnings of hazardous phenomena, equipping the hydrological network with modern equipment in strategically important areas, and restoring specialized observation points for experimental research. The implementation of the proposed measures will meet the current and future needs of the economy for hydrological information, as well as improve the accuracy and reliability of hydrological calculations and forecasts.