Assessing freshwater water balance in Cimanuk River Basin

Indramayu Estuary plays a vital role in the sufficiency of food crop production in Indonesia. Managing freshwater inflows is essential due to the complex interaction between river flow and water extraction for multiple users. This study aimed to evaluate the freshwater water balance in the lower Cimanuk River Basin, West Java, Indonesia. The hydrological, meteorological, and statistical data were analyzed the water availability and demand. The Water Evaluation and Planning System model was used to evaluate water demand and supply, taking into account changes in river flow. The model was calibrated using the streamflow and the water requirement for irrigation, fishery, domestic, and industries. The study showed that the Lower Cimanuk River Basin's current water shortages were relatively high, indicated by flow discharge of only 2.7 to 48.04 CMS from August to December 2020. This shortage would become a critical constraint in which coverage of water demand does not satisfied water users for irrigating food crop cultivation in the areas and it is threatening the sustainability of food need nationally. Therefore, it is necessary to store freshwater inflow in the study area for the relevant decision-makers by rubber dam restoration at the lower Cimanuk River Basin.