Water balance analysis of Talau-Loes Watershed, a cross border watershed of Indonesia and East Timor

Abstract. Riwu-Kaho M, Mella WII, Mau YS, Riwu-Kaho NPLB, Nur MSM. 2020. Water balance analysis of Talau-Loes Watershed, a cross border watershed of Indonesia and East Timor. Trop Drylands 21: 17-24. The Talau-Loes watershed is a cross-border watershed in Indonesia and Timor Leste (East Timor) which has traditionally been a natural resource for living, cultivation and conservation areas for communities in several districts of Belu Regency, Indonesia, and several areas in the Timor Leste territory. Water shortages in the land system are thought to play a significant role in the low productivity of agricultural crops. This study aimed to predict water balance in the Talau watershed, and to estimate river discharge in Malibaka Sub-watershed of Talau-Loes watershed. The study results showed that the amount of annual precipitation of 1679 mm was smaller than the total amount of water lost, amounting to 1914.79 mm per year, originating from evapotranspiration (ET) of 1650.91 mm and runoff water of 263.85 mm. Thus, theoretically, there would be an annual deficit of 235.79 mm in the Talau watershed. However, at the peak of the groundwater deficit, it turned out that the Malibaka River in the Malibaka sub-watershed and the Talau watershed had a discharge of 18 mm3/sec. This gives a clue about the ability of the groundwater level to gradually release its water reservoir as a source of base flow. Soil and water conservation actions that combine integrated systems such as agroforestry systems with mechanical conservation actions are proposed as solutions that need to be studied and developed in the future.