Conservation Strategy of Landuse Change Model in Tropical Springwater Recharge Area. Case of: Umbulan Springwater, Pasuruan Regency

The dynamics of land change due to human activities have a negative impact on hydrological components. Intervention of population increased along with dependence on water resources which affect on the decline of watershed conditions (DAS). As the largest water sources in East Java Province, Umbulan Spring, experienced a decrease in flow rate to 3,278 l/s from the original 4,051 l/s in 2008. The purpose of this research is to formulate conservation strategy of landuse change to preserve and sustain the Umbulan's flow rate over spring conservation area. The method used in this research consist of identification of land use land cover (LULC) changes and the proposed optimal spatial LULC using the Land Change Modeler (LCM) with LULC in the 2012-2019 as a baseline year, hydrological modeling by reviewing climatic conditions and observations on runoff water using the Soil and Water Assessment Tool (SWAT), and Typology analysis to calculate the impact of each typology of land use change on the decrease in flow rate. The result of this study is the LULC playing a significant role in flow rate degression especially in watershed area. By considering soil type data, rainfall and LULC, the results of hydrological modeling create flow rate model with a r² coefficient value of 0.89. The results of the optimal spatial pattern recommendations with strict spatial regulations can reduce the discharge to 75.27% in the core utilization zone; 66% in the 80% recharge zone; and 88.32% in the 20% recharge zone.