Under conditions of increasing climatic uncertainty, this scientific study analyzes multi-year trends of seasonal distribution of river flow in the Zhaiyk–Caspian water basin. In specific natural conditions of the territory under consideration, under scarce water resources availability in the vast territory, and exceptional variability of river flow in time, the problem of water supply is especially important. The paper considers multi-year dynamics of runoff-forming factors and flow parameters taking into account phases of different water availability. River flow estimation methods include analyses of average monthly maximum and minimum values of river flow. The assessment of homogeneity of river flow series was carried out on the basis of genetic analysis and statistical analysis, application of Mann–Kendall test, Student's t test, and Fisher criterion. The identified results indicate significant transformations in the river flow in the basin: the share of spring flow has decreased, while the share of low-water flow, especially in winter, has increased. These changes are associated with higher winter temperatures and an increase in the frequency of winter thaws. In the River Elek Basin, the share of spring flow decreased to 40% of the annual value, and in the River Or Basin, to 15%.

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.

This study presents a scenario-based assessment of the future sensitivity of minimal low-water runoff to climate change in Western Kazakhstan. An ensemble of global climate models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), combined with dynamically downscaled projections for Central Asia, was applied to estimate minimal monthly runoff during the summer–autumn and winter low-water periods for the rivers of the Zhaiyk–Caspian water management basin. The analysis covers three future time horizons: 2040 (2031–2050), 2060 (2051–2070), and 2080 (2071–2090), under two greenhouse gas concentration scenarios: SSP3-7.0 (moderately high emissions) and SSP5-8.5 (high emissions). The results reveal a pronounced seasonal contrast in the projected hydrological response. During the winter low-water period, a steady increase in minimal runoff is projected for all rivers, with the most significant changes observed for the Or, Zhem, Temir, and Shagan rivers. This increase is primarily driven by higher winter precipitation, increased thaw frequency, and enhanced infiltration recharge. Conversely, despite modest increases in summer–autumn precipitation, minimal runoff during the summer–autumn low-water period is projected to decline significantly, particularly in the southern basins, due to elevated evapotranspiration rates and soil moisture deficits associated with rising air temperatures. These findings emphasize the importance of developing seasonally differentiated, climate-resilient water management strategies to mitigate low-flow risks and ensure water security under future climate conditions in arid and semi-arid regions.

The global water crisis, which intensifies each year, underscores the urgent need for accurate assessment and sustainable management of freshwater resources. Lakes, as significant components of surface water systems, are particularly vulnerable to human activities and climate change due to their slow renewal rates. Western Kazakhstan, a region affected by economic development and intensive mining activities, faces acute water scarcity. A reliable water supply is crucial to meeting the requirements of industrial operations and the needs of the region’s population. Understanding the dynamics of lake systems and implementing effective conservation and restoration strategies are essential to addressing this challenge. This study, employing cartographic and remote sensing techniques, identified 323 lakes in Western Kazakhstan, covering a total area of 1944 km². Comparative analysis with historical data from the 1960s and 1970s revealed a 23% decrease in the number of lakes exceeding 1 km². The most significant decline was observed in the Atyrau and Mangystau Regions, where the number of such lakes diminished by a factor of three. These findings highlight the pressing need for an integrated, interdisciplinary approach to water resource management in Western Kazakhstan.

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.