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 as a result of various hydrometeorological conditions, such as precipitation deficits, reduced snow cover, and high evapotranspiration. Droughts caused by precipitation deficits and occurring during warm seasons are usually longer in duration. This important observation raises the question that climate change associated with global warming may increase drought conditions. Consequently, it is important to understand changes in the processes leading to dry periods in order to predict potential changes in the future. This study is a scientific analysis of the impact of climate change on drought conditions in the Zhaiyk–Caspian, Tobyl–Torgai, Yesil, and Nura–Sarysu water management basins using the standardized precipitation index (SPI) and streamflow drought index (SDI). The analysis methods include the collection of hydrometeorological data for the entire observation period up to and including 2021 and the calculation of drought indices to assess their intensity and duration. The results of this study indicate an increase in the intensity and frequency of drought periods in the areas under consideration, which is associated with changes in climatic conditions. The identified trends have serious implications for agriculture, ecological balance, and water resources. The conclusions of this scientific study can be useful for the development of climate change adaptation strategies and the sustainable management of natural resources in the regions under consideration.

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.

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%.

This study analyzes long-term changes in minimal streamflow in the Zhaiyk-Caspian Water Management Basin (WMB), Western Kazakhstan, under climate variability. Using extensive hydrometeorological datasets (monthly discharge and daily meteorological records) from 1940 to 2021, the research assesses trends in low-flow characteristics across 18 hydrological posts. The analysis distinguishes two climatic periods: climate stabilization (pre-1973) and climate change (1974–2021). The methodology integrates hydrological and statistical analyses, including minimal monthly discharges, low-flow durations, soil freezing depths, and thaw frequencies. Findings reveal a widespread increase in winter low flows—up to 5.2 times—due to reduced frost depths and more frequent thaw events, enhancing groundwater contributions. Conversely, summer-autumn flows declined in several rivers, with drying trends linked to rising air temperatures and precipitation deficits. This study offers a novel, regionally adapted methodology for characterizing minimal streamflow under climate change, providing critical insights for hydrological drought assessment and water resource planning in arid and semi-arid environments.