Water availability identification of underground river in the Gunung Sewu karst area using inverse model

Abstract The karst area is identified in the Gunung Kidul Regency, so-called Sewu area, as one of Geopark areas Indonesia. Gunungkidul Regency has had moderate to high yearly rainfall for last ten years. However, this region a problem with surface water shortage. It due characteristics karst, which allows rainwater penetrate geological layers accumulating certain noose yielding abundant underground reserves. purpose study assess river availability and hydrological using Inverse Modeling. Modeling method identify features by adjusting variables an input output discharge control. FJ Mock Model model used characterize Karst region’s river. There were five models total be simulated. conditions under show consistent results compared stepwise terms low conditions; Coefficient Correlation, RMSE, R 2 values obtain 0.637, 17.29, 0.407, respectively. In case, estimating flow more accurate than high-rate conditions. are closer without infiltration variable involved.