Assessment of the impacts of climate change in the 21st century on the groundwater balance of the south-western Crimea

A regional groundwater flow model of southwestern Crimea within the Alma artesian basin and the adjacent area of fissure-karst groundwater in Mountain Crimea was developed and calibrated for the modern period. On the basis of numerical experiments with this model, changes in groundwater resources under the influence of expected climatic changes in the 21st century were estimated. For this purpose, predictive maps of infiltration recharge were constructed for the selected study area. The predictive maps of groundwater recharge were developed for the plain part of the study area using infiltration water exchange modeling. For the mountainous part, precipitation accumulation by surface karst forms was considered in the prediction of recharge. The extreme climate change scenario SSP5-8.5 from the GSM models of the CMPI 5 family, which assumes maximum warming, was used as the prediction scenario. As a result of ensemble forecasting, the most contrasting scenarios of aridity index change were selected and three projected maps of groundwarer recharge change in the 21st century were obtained, which were then used in numerical experiments. The predicted infiltration recharge values significantly differ from the current figure of 366400 m³/day: under the «dry» climate, the recharge is 187900 m³/day, under the «average» climate, 283600 m³/day, and under the «wet» climate, 403300 m³/day. The results of the predictive groundwater balance modeling for the 21st century, using these recharge maps, demonstrated the high adaptive capacity of groundwater reserves and the reduction of minimum river runoff over the study period of about a hundred years, assuming the continuation of the current groundwater extraction rates.