Herdianto, Revalin and Istijono , Bambang Istijono and Darlino, Darlino and Rizaldi, Adek
(2013)
The Use of Satellite-Derived Rainfall Data and Digital Elevation Model for Estimation of Rainfall over Scantily Gauged Basins.
In: Seminar Nasional Komite Nasional Indonesia-ICID, 29-30 November 2013, Semarang, Indonesia.
Abstract
In areas where rainfall gauge are sparse such as in West Sumatera, estimation of irrigation water may be problematic. The computation of irrigation water uses data either from stations that may be far from design areas or from a single station. Area averaging schemes can be of erroneous if the stations and the irrigated areas vary in topographic and wind. 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. It has an advantage in that the data are available in 3 hour interval, which minimizes the effect of wind in data acquisition. However, the TRMM radar presents off-the surface information that is subject to distortion. In addition, its fairly large pixel size may override topographic variations within a pixel. Therefore, before used for practical purposes, a validation is essential. We use TRMM data over a catchment in Kuranji watershed in City of Padang from year 2000 to 2012. The Kuranji catchment is located at 0.92 S and 100.47 E with Batang Kuranji being the main river flowing to the West in the Indian Ocean. This catchment is selected due to available rainfall stations for validation. In addition, rapid land use change in the upper catchment since year 1985 has altered irrigation requirement and stream flow. These conditions need an updated irrigation scheme for future water allocation and a watershed land use management. We use TRMM in 0.5o x 0.5o grid size in daily temporal resolution from TRMM PR, in order to match ground measured rainfall. Digital Elevation Model (DEM) of the catchment and its surroundings is downloaded from SRTM (Survey Radar Topographic Mission) CGIAR-CSI in 90-m resolution. The Kuranji catchment is extracted from its surroundings using ArcGIS(TM). The TRMM pixels are mosaicked with the catchment DEM to build layers of topographic and rainfall information. Then the TRMM mosaic is used to extract daily rainfall data to make time series of rainfall. Ground measured data are gathered from on-catchment stations (Batu Busuk, Gunung Nago), and off-catchment station (Tabing). These stations are suitable to study the orographic effect on rainfall in the upper catchment. We develop a model based on rainfall changes along topographic transects using the TRMM data. The data are then validated using ground measured rainfall data from the three stations. 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 that confirms the previous findings.
Keywords: TRMM, DEM, rainfall, topographic
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