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1st Int. Transborder Conf. of the Timor Island: Timor %u2013 Science without borderDili, 7-8 May 2025169Runoff Estimation For The Loes Watershed In Timor-Leste Using Soil Conservation Service-Curve Number (SCS-CN)Delfim da Costa1*, Maria Victoria O. Espaldon2, Decibel V. Faustino-Eslava2, Patricia Ann J. Sanchez2and Cristino L. Tiburan Jr2.1Department of Agronomy, Faculty of Agriculture, Universidade Nacional Timor Lorosa%u2019e2School of Environmental Science and Management, University of the Philippines Los Ba%u00f1os*Corresponding author: delfimdacosta915@gmail.com.AbstractMeasuring runoff is crucial for watershed management in Timor-Leste, as it plays a critical role not only in forecasting floods but also in water resource management. Scholars have widely used numerous methods to measure runoff; however, each method has its own advantages and disadvantages regarding data availability, resources, time, and equipment use. In Timor-Leste, runoff estimation is rarely conducted due to a lack of equipment for direct measurement, limited human resources, and a low national budget allocated for the responsible departments%u2014the Watershed Management Department at the Ministry of Agriculture, Fisheries, Livestock, and Forestry, and the National Directorate of Water and Sanitation (DNAS) at the Ministry of Infrastructure.Thus, the Soil Conservation Service-Curve Number (SCS-CN) is seen as a costeffective, low-budget, and widely accepted method used to estimate runoff, and is assumed to be a model for future application in other watersheds in Timor-Leste. Therefore, this study used the SCS-CN method to estimate runoff in the Loes watershed. The study area lies between 9%u00b012'49.78\to 125%u00b06'19.82%used for determining the Antecedent Moisture Condition (AMC). The weighted Curve Number was obtained from land use/land cover (LULC) data generated by the University of Maryland for ASEAN, and the Hydrological Soil Group (HSG) was determined according to the soil texture obtained from the ISRIC Soil Data Hub. The results of the study revealed that the SCS-CN method can be used to estimate runoff in a watershed in Timor-Leste. Runoff in the Loes watershed has steadily increased from 2018 to 2022. In addition, the increasing annual rainfall intensity%u2014from 1,564 mm to 3,307 mm in 2018 and 2022%u2014influenced the runoff. Moreover, the conversion of approximately 25,000 hectares of forest to other land uses has contributed to this increase. Thus, this study concludes that runoff has occurred and is continuously increasing. Therefore, this study recommends intensifying land management through integrated strategies to ensure the sustainability of the watershed and the livelihoods of water resource users.Keywords: Runoff, SCS-CN, Watershed, Land Use Change, Timor-Leste.