Modeling the discharge of Kapuzbaşı spring for parameterization of the karst aquifer, Aladağ Mountains, Central Taurus, Türkiye

Kapuzbaşı karst spring is located between Kayseri and Adana, one of the most important and well-studied mountainous karst regions, Aladağlar, Central Taurus, Türkiye. Previous scientific studies revealed the hydrogeological setup, perceptual model including groundwater residence time and potential recharge-discharge relationship; however, there has not been any process-based conceptual modeling experiment on the karst spring aiming to parameterize the karst system hydrodynamics. In the present study, we aimed to develop a numerical model of the karst groundwater system to parameterize the system hydrodynamics, which was built based on the conceptual understanding of the karst hydrogeology. We selected the lumped-conceptual hydrological model of KarstMod to quantify the discharge of the Kapuzbaşı spring. The modeling experiment showed that the recharge area of the karst spring is covering approximately 350 km2, and the approximate annual discharge exceeds 250 hm3. The preferential flow mechanism triggered after the water level in epikarst exceeding 92 mm, and the melt factor is approximated as 9.91 mm/°C/day. The response time of conduit reservoir is approximately 1 day, and the loss flux triggered when the water level in conduit reservoir exceeding 4mm. The hydraulic conductivity of the matrix reservoir is found approx. 0.012 mm/day. The model performance based on the daily discharge was obtained as Nash Sutcliffe Efficiency (NSE) = 0.77, and Kling-Gupta Efficiency (KGE) = 0.87 in the calibration, and NSE = 0.76, and KGE = 0.77 for the validation periods, respectively. Eliminating the less sensitive model parameters in the calibration leads to more robust and less uncertain discharge simulations.