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PENDEKATAN SUPPLY-DEMAND UNTUK IDENTIFIKASI INDEKS KEKRITISAN AIR DI PULAU JAWA, INDONESIA Santikayasa, I Putu; Okhy Wiranta, Dimas
JURNAL SUMBER DAYA AIR Vol 18, No 1 (2022)
Publisher : Direktorat Bina Teknik Sumber Daya Air, Kementerian Pekerjaan Umum dan Perumahan Rakyat

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32679/jsda.v18i1.735

Abstract

Water supply and demand are the most discussed issue in the world including in Indonesia. Java with the largest population and center for industrial and agricultural activities in Indonesia faces problems in water availability and water demand. This condition illustrates the potential of Java to experience water scarcity. This study analyzes water status in Java using the water balance approach and Water Scarcity Index. The analysis was carried out to evaluate changes in the annual water balance during a period of the 10-year average (1981-1990, 1991-2000, and 2001-2010). The rainfall data from CHIRPS and air temperature from CRU were used to calculate water availability. Water demand is calculated for the domestic, industrial, agricultural, and environmental sectors based on Indonesia water use standards. The results indicate that the average water availability in Java varies in each period. The highest water availability occurred in 1981-1990 (160 billion m3/year), while the lowest was in 1991-2000 (149 billion m3/year}. The water availability decreased from 1981 to 2010, on a per capita basis. The water scarcity index also changes every period. The area experiencing a water deficit as described by their water scarcity index as a very critical class. Moreover, DKI Jakarta and East Java Provinces are in very critical condition with more than 50% area. Based on the study results, evaluation of water balance and water scarcity index can be used to describe the water status in a certain area as the reference for decision-makers in determining programs in water resources management.Keyword: Water status, water balance, water resources management, water scarcity, spatial analysis
RESPON MODEL HBV DAN MODEL TANGKI TERHADAP ESTIMASI DEBIT ALIRAN DI DAS BOGOWONTO, JAWA TENGAH Andini, Fitri Yusti; Dasanto, Bambang Dwi; Santikayasa, I Putu
JURNAL SUMBER DAYA AIR Vol 19, No 2 (2023)
Publisher : Direktorat Bina Teknik Sumber Daya Air, Kementerian Pekerjaan Umum dan Perumahan Rakyat

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.32679/jsda.v19i2.830

Abstract

 The scarcity of discharge data compared to rainfall data have driven the development of the rainfall-runoff model, such as the HBV and Tank models. This research aims to apply the rainfall-runoff model in the Bogowonto watershed and to assess the model outputs. The research consisted of two main stages: 1) model calibration and validation; 2) model evaluation which assesses the model performance based on the Nash-Sutcliffe Efficiency (NSE) index and the coefficient of determination (R2). The results showed that the pattern of the simulation discharge was in accordance with the observed discharge pattern; indicating performance of both models was good (NSE > 0.7 and R2 > 0.65). However, the performance of both models in the daily simulation, particularly at the beginning of the simulation period, is still not satisfactory as the simulated discharge does not match the observed discharge. In the next simulation period, the discharge of the model results were in accordance with the observed discharge; this means the performance of the model was better. In the monthly simulation, the performance of both models is not yet satisfactory during the wet season, but it is good during the dry season. Based on the results of the daily and monthly simulations, both models demonstrate good performance under low precipitation conditions, but their performance declines under high precipitation conditionsKeywords:       Bogowonto watershed, HBV, rainfall-runoff model, simulation, tank 
ECMWF SEAS5 Seasonal Rainfall Assessment: A Study Case in Papua Andika, Steven; Santikayasa, I Putu; Donaldi Sukma, Permana
Agromet Vol. 39 No. 2 (2025): DECEMBER 2025
Publisher : PERHIMPI (Indonesian Association of Agricultural Meteorology)

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.29244/j.agromet.39.2.%p

Abstract

Papua, Indonesia’s easternmost island, is prone to seasonal hydrometeorological disasters, necessitating high-quality climate forecasts for effective risk management. This study evaluates the performance of the European Centre for Medium-Range Weather Forecasts (ECMWF) Seasonal Forecast System 5 (SEAS5) in predicting seasonal (3-monthly) rainfall across Papua from 1982 to 2016, using the blended Climate Hazards group InfraRed Precipitation with in-situ rainfall data (CHIRP+Pos) as the observational reference. SEAS5 forecasts at 1 to 3 month lead times were assessed across seasons which defined as July-August-September (JAS), August-September-October (ASO), September-October-November (SON), and December-January-February (DJF), and El Niño-Southern Oscillation (ENSO) phases (El Niño, La Niña, Neutral), using Pearson correlation coefficient (Corr), root mean square error (RMSE), and Kling-Gupta Efficiency (KGE) metrics. Results show stronger SEAS5 skill in JAS–SON (Corr up to 0.939) compared to DJF-JFM (Corr as low as -0.208), with a robust ENSO-rainfall relationship in JJA-SON. SEAS5 performed best during El Niño, particularly in lowlands and exhibited greater variability skill during La Niña and Neutral phases. Benchmarking against a linear regression baseline showed SEAS5’s superior Corr in 76.2% of grids but higher RMSE in 60.6%. Despite limitations in mountainous regions and at longer lead times, SEAS5 offers reliable forecasts for lowland areas during JAS-SON under El Niño, supporting operational applications like drought preparedness and agricultural planning in the regions.