WATER BALANCE ANALYSIS AND WATER ALLOCATION USING WATER EVALUATION AND PLANNING (WEAP) PROGRAM (CASE STUDY: CIUJUNG DAS, CIUJUNG WS – CIDANAU – CIDURIAN, BANTEN PROVINCE)

• Main Author: Kusdarningrum Kusuma, Nabiela
• Format: Final Project
• Language: Indonesia
• Subjects: Teknik saniter dan perkotaan; teknik perlindungan lingkungan
• Online Access: https://digilib.itb.ac.id/gdl/view/82844
• Institution: Institut Teknologi Bandung

Water needs are one of the vital aspects that must be met to support daily life, agriculture, and industrial activities. Water needs in Lebak, Pandeglang, and Serang Regencies are served by the Ciujung River Basin (DAS). Along with increasing population, industrial development, and decreasing forest land cover, the three regencies have experienced a significant increase in water needs. However, the availability of water in the Ciujung Watershed is unable to keep up with the increasing needs. Therefore, this study aims to calculate the water balance, identify water availability and needs, and simulate water allocation using the WEAP (Water Evaluation and Planning) program in the Ciujung Watershed area. The discharge calculation in the WEAP modeling is similar to the actual discharge measured by the AWLR (Air Water Level Recorder) with an R-value of 0.93 and r² of 0.87. Based on the results of the study, water availability in the Ciujung Watershed comes from thirteen sub-DAS, with the largest discharge contribution from the Rangkasbitung Bridge sub-DAS reaching 32.54 m³/s. Water needs in the Ciujung Watershed are divided into four sectors, namely domestic (30.96 m³/s), irrigation (374.78 m³/s), industry (29.89 m³/s), and river maintenance and water loss (57.19 m³/s). Water balance analysis shows that the Ciujung Watershed experiences an overall water deficit, but there is a surplus in January, May, and December. Various scenarios are analyzed to estimate the future water balance. The first to third scenarios use variations in water availability (Q10, Q20, Q50), which indicate a water surplus. The fourth scenario uses variations in water availability with a probability of Q90, which indicates that the majority of periods experience a water deficit, and several periods experience a water surplus. The fifth scenario shows an increase in water consumption (return flow) in the industrial sector by 90% and an increase in intake by industry by 10%, which results in a water deficit from the end of June to early November and early April with a surplus in other months. The sixth scenario involves a decrease in the irrigation area by 14.94% due to land conversion. This scenario shows a water deficit in early April and late June to early November, with surplus conditions in other months. The seventh scenario shows an increase in the coverage of PDAM Lebak by 25% and PDAM Tirta Albantani by 45%. This scenario results in a water deficit from late March to early April and from June to November, with surplus conditions in other months. The eighth scenario is a combination of a decrease in the irrigation area by 14.94%, an increase in water consumption (return flow) to 90% and an increase in water intake in the industrial sector by 10%, an increase in the coverage of PDAM Lebak and PDAM Tirta Albantani by 25% and 45% respectively, and water availability using the Q80 debit. This scenario shows a water deficit from late March to early April, and a deficit occurs again from June to November, with surplus conditions in other months.