ASSESSING THE ROLE OF BASEFLOW IN WATERSHED DISCHARGE UNDER SEMI-ANNUAL RAINFALL: A CASE STUDY OF THE CIKAPUNDUNG SUB-WATERSHED
Alecio Yusran Rizqullah (a), Edi Riawan (b), Fadhillah Nurzaki Waliyatullah (c), Fattah Ghiffari (c), Faza Haniyah Firstrizanda (c), Safinka Putri Minanda (a)

a) Meteorology Departement, Faculty of Earth Science and Technology, Institut Teknologi Bandung, 40132, Indonesia

b) Atmospheric Science Research Group, Faculty of Earth Sciences and Technology, Institut Teknologi Bandung, 40132, Indonesia

c) Groundwater Engineering Departement, Faculty of Earth Science and Technology, Institut Teknologi Bandung, 40132, Indonesia

Abstract

Cikapundung River is one of tributaries of the Citarum River, serves as a vital water source for residents in the Bandung Basin while also contributing to frequent flooding in the southern Bandung region. This study aims to identify the hydrometeorological characteristics of the Cikapundung Sub-watershed, focusing on baseflow and discharge responses to rainfall, which is suspected to follow a semi-annual pattern. Using rainfall, runoff, elevation, land use, and soil type data, the GSSHA model was employed to simulate soil moisture scenarios and represent baseflow. The model was calibrated by comparing simulated and observed runoff, adjusting surface roughness and infiltration parameters until a match was achieved. Results show that the annual runoff pattern resemble the rainfall pattern, but the peak runoff lags by a month, likely due to rainfall infiltration in the upstream areas during the first peak, causing increased runoff downstream during the second peak. GSSHA modeling also highlights the critical role of soil moisture in influencing discharge, particularly during extreme events

Keywords: Runoff, infiltration, Soil Moisture

Topic: Atmospheric Sciences