Sustainable Development Goal (SDG). Water management is making a balance between water for livelihood and water as a resource. Environmental Flow Requirement (EFR) is water conservation, on the side of the water for livelihood, to sustain the river ecosystem. In Indonesia, the common quantification of EFR is dependable flow Q95%. However, there are alternative quantities: a) Guideline of irrigation states that 5% from the available water in the river is for environmental purposes; b) Adoption of the Tennant Method of using 10% of the mean flow; and recently Food and Agriculture Organization (FAO) in the framework of SDG proposed that in Java Island the EFR is from 40% to 50% of the mean annual flow. This paper discusses several ways of quantification of the EFR in Indonesia, and apply the different EFR quantities to Citarum, Cimanuk, and Cimandiri Rivers in West Java. It is concluded that EFR quantity according to FAO that might be suitable for the rivers in the pristine catchments in the southern part of West Java is too high for the rivers in the northern part of West Java which is heavily populated and maturely developed. Furthermore, the dependable flow of Q95% is found to be close to the quantity of FAO, but in the dry season, Q95% is more suitable. It is recommended using a modified FAO that combine with Q95% during the dry season.
Indonesia identifies as climate change hotspots and indicates to have increasing hydrological drought risk. The impact of hydrological drought is easier to analyze because only using river discharge directly affects by rain, which requires a long process and time. The impact of hydrological drought can be minimized using Disaster Risk Management (DRM) cycle. In this study, Standardized Runoff Index (SRI) was used as a quantitative index for the occurrence of hydrological drought and as a reference for phase change in DRM. This study consists of 3 parts: projecting monthly discharge until the year of 2045 using ensemble of seven Global Climate Models; projecting hydrological drought events using SRI; and suggesting six DRM stages for managing its impact. The study took case on Pawan River Basin, West Kalimantan. Kalimantan is predicted to be experienced more extreme dry climate in Indonesia. The potential for drought (Q80) is projected to be more severe in the range of January to July (-4% to -11%) and October (-3% to -5%) on the Pawan River Basin. DRM is divided into six phases: risk assessment, risk prevention, risk mitigation, preparedness for the occurrence, response to disaster and recovery.
Climate change affects temperature, rainfall and hydrological properties in the river basins. Projected rainfalls for several climate change models are widely available nowadays. However, in water resources planning and management, river discharges data is unfortunately more important. The information on climate change impact on river discharges is very limited. Conversion from the projected rainfall to the runoff in the rivers is needed. This study analyzes the performance of rainfall-runoff models: 1) Empirical Model that defines the discharge as a function of rainfall, evaporation, and temperature, widely applied by climate scientist; and 2) simple lump conceptual model of NRECA. These two rainfall-runoff models are applied during the control period in the year of 2006 to 2015 of the rainfall projections from the seven CMIP5 Global Circulation Models with the worst scenario, RCP 8.5. The ground station river discharge data selected is Nanjung river gauging station at Citarum River, situated just upstream of Saguling Reservoir, the uppermost of the cascade of three reservoirs Saguling-Cirata-Jatiluhur, with the catchment area of 1, 675 square kilometers. The results show that the simple conceptual model NRECA significantly gives better fitted to the observation data than the Empirical Model, especially during the dry season.
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