Analysis of the Genetic Components of Groundwater (Spring) Discharge in a Fracture–Karst Massif

Fissure-karst groundwater in the southwestern part of the Crimean Peninsula serves as a resource base for the formation of groundwater and surface water in Crimea and plays an extremely important role in the water supply of the population. The genetic components of groundwater (spring) runoff in a fracture–karst massif were assessed for the case of a large spring draining the Ai-Petri karst plateau in the southwestern Crimean Peninsula. A conceptual model of karst massif runoff formation is proposed taking into account water percolation through karst sinkholes and infiltration water exchange between groundwater and surface water. Two approaches were used to identify the genetic components of runoff: the analysis of its formation using the lumped-parameter precipitation–runoff model and hydrograph separation based on digital filtering of daily flow data. Based on the results of water exchange modeling on the ground surface and in the vadose zone, the genetic components of the runoff of fracture–karst groundwater in the upper reaches of the Chernaya River were estimated: the surface runoff is 58 mm/year, percolation through karst sinkholes and infiltration groundwater recharge are 394 and 157 mm/year, respectively. Using the method of two-pass digital filtering for hydrograph separation, the average value of groundwater discharge from the zone of constant full saturation (0.35 m³/s) was obtained, and the genetic components of the averaged intra-annual hydrograph of the Rodnikovskoye village gage were estimated: the discharge of fissure–karst groundwater from the variable saturation zone is 67%, from the zone of constant full saturation—25%, and 8% is surface runoff.