SUMMARY
Population growth, urbanization, industrial development, and agricultural activities increase water demand on the watershed. An increase in water demand will propagate the excessive exploitation of surface water and groundwater resources. This will probably influence the water balance of the watershed. Therefore, understanding the water balance is a necessity. Continuous imbalance between water supply and demand will generate many serious environmental problems. A study of agricultural water balance is needed to answer the question whether the available water resources can meet the needs of sufficient water for irrigation. The study was conducted in Rawatamtu sub-watershed which was part of Bedadung Watershed. The Water Evaluation and Planning (WEAP) model was used to analyze agricultural water balance. The procedure included inventory data, installing WEAP on the system, running the WEAP, and using WEAP for simulating future water balance conditions. The simulation results showed that agricultural water balance for the next 10 years will be more frequently in surplus condition rather than in deficit condition. The water surplus was estimated to occur in the year of 2020, 2021, 2023, 2025, 2027 and 2028. The highest surplus occurred in the year of 2028 which reached 56.59 million m3. Furthermore, the potential water balance deficit was projected to occur in 2019, 2022, 2024 and 2026.