Aplikasi teknik remote sensing bagi terbitan maklumat hasilan air di Semenanjung Malaysia

Abstract

Satellite remote sensing techniques have found wide applications in hydrology including water-yield determination. This however requires the localization to area-of-interest that are influenced by the local climate and biophysical factors. This study focussed to develop a method for determining the water-yield information through full satellite-based data for Peninsular Malaysia from the public domain sources, for a period of 10 years (July 2000 - June 2010). The specific objectives were to investigate on: (i) derivation of information on monthly rainfall from Tropical Rainfall Measuring Mission Multisatellite Precipitation Analysis (TMPA) satellite data; (ii) derivation of monthly Actual- Evapotranspiration (AET) from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite with Normalized Differential Vegetation Index (NDVI) data product; (iii) derivation of water yield from fully satellite-based information using water balance analysis; and (iv) water yield variation, with respect to changes of corresponding land cover and land use. Results, indicated good correlation between monthly rainfall TMPA with the corresponding rain gauge records (r2=0.71: p<0.001, n=1337) with accuracy (RMSE) of +83 mm (n=2308). The TMPAcalibrated annual averaged rainfall for the entire study area is 2357mm, which is - 5.3% compared with independent studies undertaken by an international consultant appointed by the government. The bio-physical parameters based on MODIS used NDVI as an indicator of AET to represent the land use, reported good match-up (r2=0.55: p<0.001, n=1664) with accuracy (RMSE) of +15 mm (n=864). The NDVIcalibrated annual averaged AET throughout the study area was determined at 1153mm, which is -9.9% compared with the same independent research report. Annual averaged water-yield for the entire study area is 1204mm, with -0.5% and 1.6% variations when compared to the two independent studies, the same independent research report and, Drainage and Irrigation Department respectively. But at state level, the estimated rainfall, AET and water-yield varies with larger magnitudes. Analysis at selected basin level, the annual water-yield is determined at 1393mm, in access of 9.5% compared to the independent studies water flowrate, with a standard deviation of 22%. The regression analysis between water-yield and land use cover changes, clearly indicated strong relationship (r2=0:51, p<0.0001; n=151), and independent accuracy (RMSE) of 8.3% (n=154). The main findings in this study, especially the devised techniques indeed have contributed significantly as an alternative method for the determination of water-yield in Peninsular Malaysia based on fully satellite-driven data. The devised method could be accustomized to other areas through localised calibration approach thus, could serve as a guideline for the relevant authorities to have accurate and comprehensive water-yield information.