Variations of Runoff Entering the Sea Estuaries of Southwestern Crimea Rivers

The impact of runoff on the river mouths of southwestern Crimea depends on natural and anthropogenic basin factors that determine its transformation. Information from Roshydromet gages (2 on each river), located 7–38 km from the headwaters of sea river mouths, is insufficient to obtain reliable runoff estimates, to perform balance calculations, and to forecast hazardous phenomena and processes downstream of stationary observation points. The purpose of the work is to identify patterns of runoff variability in the Chernaya, Belbek, Kacha, and Alma rivers. To do this, the data of hydrometeorological observations of the network divisions of the Crimean UGMS in river basins for 1931–2020 and the results of special studies by MHI RAS in 2017–2024 in the lower reaches of the rivers were summarized, and mathematical modeling was also used. In the modern climatic period 1991–2020, the regulated river runoff did not have significant trends. The flow module decreased by 40–85% with an increase in the basin area due to karstification, a deficit of lateral inflow, global warming, and an increase in anthropogenic load. It was found that in recent years, the flow discrepancies between the lower hydrometric gages of Roshydromet and the gages at the headwaters of the sea mouths of the rivers in question varied from 25 to –90%. The results obtained will improve the quality of balance and forecast assessments of the state of river mouths and the adjacent part of the sea with an increase in water intake, flow variations, and climate change, and will facilitate the initiation of similar studies in other regions.