Estimation of Water Balance for Maninjau Hydropower in West Sumatera using TRMM and Discharge Data

Istijono , Bambang Istijono and Hardianto, Revalin and Darlino, Darlino and Rizaldi, Adek (2014) Estimation of Water Balance for Maninjau Hydropower in West Sumatera using TRMM and Discharge Data. In: International Symposium of The 82nd Annual Meeting of International Commission on Large Dams (ICOLD), 2-6 Juni 2014, Denpasar, Bali.

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Abstract

Flow from Lake Maninjau in Agam Regency, is used to generate a 68 megawatt hydropower and to irrigate 4200 ha paddy field. There are 19 rivers flowing into the lake, its outflow from hydropower station flows to Batang Antokan which ends in the Indian Ocean. Water balance for both inflow and outflow from 2009 to 2012 show an increase from an average of 5.8 m3/second to 23.53 m3/second. This condition raised a concern that rainfall input cannot maintain sustainable water level. In addition, an instant discharge measurement on 25 and 26 March 2013 shows that input to the lake was smaller than the output. An initial study suggested that the discrepancy is due to an effect of ground water. However, this study did not confirm this through a field or model study. The Tropical Rainfall Monitoring Mission (TRMM) has long been used as an auxiliary data for both prediction of rainfall in ungauged basins and for simulation in hydrological models that require spatially distributed rainfall input. When coupled with discharge and topographic information, the TRMM may be used to estimate input discharge to the lake. We use daily TRMM data over the Lake Maninjau catchment from year 2000 to 2010 TRMM in 0.5o x 0.5o grid resolution in order to match ground measured rainfall. Data are converted into time series with a Matlab program. Digital Elevation Model of Survey Radar Topographic Mission CGIAR-CSI in 90-m resolution. Ground measured data are gathered from on-catchment stations. We estimate water balance based on rainfall and discharge data from the TRMM data. Preceding studies show that high rainfall is over estimated and low rainfall is under estimated. In our study, we find that orographic effect is more prominent during high rainfall and subsurface flow is predominant during rainy season that confirms the previous findings. Keywords: TRMM, DEM, rainfall, topographic .

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