Abstract
Changes in climate and land use land cover (LULC) are important factors that affect water yield (WY). This study explores which factors have more significant impact on changes in WY, spatially and temporally, within the Citarum River Basin Unit (RBU), West Java Province, Indonesia with an area of ±11.317 km2. The climate in the area of Citarum RBU belongs to the Am climate type, which is characterized by the presence of one or more dry months. The objectives of the study were: (1) To estimate a water yield model using integrated valuation of ecosystem services and tradeoffs (InVEST), and (2) to test the sensitivity of water yield (WY) to changes in climate variables (rainfall and evapotranspiration) and in LULC. The integration of remote sensing (RS), geographic information system (GIS), and the integrated valuation of ecosystem services and tradeoffs (InVEST) approach were used in this study. InVEST is a suite of models used to map and value the goods and services from nature that sustain and fulfill human life. The parameters used for determining the WY are LULC, precipitation, average annual potential evapotranspiration, soil depth, and plant available water content (PAWC). The results showed that the WY within the territory of Citarum RBU was 12.17 billion m3/year, with mean WY (MWY) of 935.26 mm/year. The results also show that the magnitude of MWY in Citarum RBU is lower than the results obtained in Lake Rawa Pening Catchment Areas, Semarang Regency and Salatiga City, Central Java (1.137 mm/year) and in the Patuha Mountain region, Bandung Regency, West Java (2.163 mm/year), which have the same climatic conditions. The WY volume decreased from 2006, to 2012, and 2018. Based on the results of the simulation, climatic parameters played a major role affecting WY compared to changes in LULC in the Citarum RBU. This model also shows that the effect of changes in rainfall (14.06–27.53%) is more dominant followed by the effect of evapotranspiration (10.97–23.86%) and LULC (10.29–12.96%). The InVEST model is very effective and robust for estimating WY in Citarum RBU, which was indicated by high coefficient of determination (R2) 0.9942 and the RSME value of 0.70.
Highlights
The climate in the area of Citarum River Basin Unit (RBU) belongs to the Am climate type, which is characterized by the presence of one or more dry months
Based on the results of the analysis of the integrated valuation of ecosystem services and tradeoffs (InVEST) model, the volume of water yield (WY) at RBU Citarum is around 12.17 × 109 m3 /year, where this value is obtained from the average thickness of water 935.26 mm/year multiplied by the total area of the entire RBU
Based on the validation of the InVEST model, these results indicate that the InVEST model can be used in estimating WY in the Citarum RBU as well as rule model for the application of the InVEST Model in developing countries with tropical climates
Summary
Water yield (WY) is an indicator of the health of a watershed. Water fluctuations between the rainy and dry seasons tends to be small [1]. The guaranteed quantity, quality, and continuity of water in a watershed is essential to the concept of water security, which directly or indirectly supports national food and energy security [2]. Quantitative evaluation and visualization of WY is valuable for understanding trends in the function of water supply in an ecosystem. Understanding WY is very useful for water resource managers to determine the effect of human activities on water resources [3]
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