Land Use Change and Its Impact on the Water Balance in Sumitro Sub-Watershed

Kulonprogo Regency is projected to experience population growth, increasing basic needs such as food, raw materials, settlements, and development activities. The Sumitro Sub-Watershed is upstream of the Serang Watershed, which is a critical watershed. It has a high level of damage due to changes in land cover, resulting in high erosion, flooding, and drought. This study aimed to determine the land use change, the water balance and their relationships. This research also formulated the optimal form of land use to improve water storage capacity and reduce runoff in the Sumitro Sub-Watershed area. This study uses the Thornthwaite-Mather method. The calculation of the water balance analysis is based on 12 land-use changes from 2011 to 2022. The land use directive adopts the concept of agroforestry by considering the spatial plans of the Kulon Progo Regency. The study results showed that land use in the Sumitro SubWatershed had changed, causing the condition of the water balance also to change. A land use change of 8.08% has led to a change in water storage capacity (WHC). Land use direction with the agroforestry concept can increase water storage capacity by 60.04 mm and reduce runoff value.