Climate change influences over years clearly can affect a catchment area in terms of
quantity and quality of water. High annual rainfall in Malaysia does not solve water
scarcity problems during the El Nino phenomenon and can cause severe flooding
during La Nina. A simulation from year 1980 to 2006 has been done at Sg. Ketil
streamflow station at Kuala Pegang, Kedah in the North region of Malaysia according
to availability of data. The monthly streamflow later has been calibrated and validated
using SWAT-CUP. Water level data was obtained from an inventory water level station
recorded at the station. Land-use, soil type and slope are taken account to produce a
number of hydrologic response units (HRU). This study used developed gridded daily
hydrometeorological data set for Peninsular from 1980-2006using interpolation
technique. The results shown that the calibrated model is able to simulate the flow for
the river basin successfully with the R2
= 0.65 and NSE=0.52 and validated value of
R
2=0.5 and NSE=0.43. A recommendation is purposed to simulate the catchment using
hydrometeorological data set in the stations located in the area to compare the results
for further study.
A GIS-based user-interface programme was developed to compute the geospatial Water ProductivityIndex (WPI) of a river-fed rice irrigation scheme in Northwest Selangor, Malaysia. The spatial analysisincludes irrigation blocks with sizes ranging from 20 to 300 ha. The amount of daily water use for eachirrigation block was determined using irrigation delivery model and stored in the database for both mainseason (August to December) and off season (February to May). After cut-off of the irrigation supply,a sub-module was used to compute the total water use including rainfall for each irrigation block. Therice yield data for both seasons were obtained from DOA (Department of Agriculture, Malaysia) of thescheme. Then, the Water Productivity Index (WPI) was computed for each irrigation block and spatialthematic map was also generated. ArcObjects and Visual Basic Application (VBA) programminglanguages were used to structure user-interface in the ArcGIS software. The WPI, expressed in termsof crop yield per unit amount of water used (irrigation and effective rainfall), ranged from 0.02 to 0.57kg/m3 in the main season and 0.02 to 0.40 in off season among irrigation blocks, respectively. Thedevelopment of the overall system and the procedure are illustrated using the data obtained from thestudy area. The approach could be used to depict the gaps between the existing and appropriate watermanagement practices. Suitable interventions could be made to fill the gaps and enhance water useefficiency at the field level and also help in saving irrigation water through remedial measures in theseason. The approach could be useful for irrigation managers to rectify and enhance decision-makingin both the management and operation of the next irrigation season.
Hydrological models are reliable tools that have been extensively used for hydrological studies. However, the complexity of some of these models has been a major setback, which affects their performance. This study compared Hydrologic Engineering Corps Hydrologic Modeling System (HEC-HMS) with most widely applied Soil Water Assessment Tool (ArcSWAT) model and used to assess impacts of climate change on streamflow at Bernam Basin, Malaysia for 2010-2039, 2040-2069 and 2070-2099 to the baseline period (1976- 2005) using an ensemble of ten GCMs under three RCP scenarios (RCPs 4.5, 6.0 and 8.5). The models performed satisfactorily. However, HEC-HMS performed better compared to ArcSWAT with 0.74, 0.71, 4.21 and 0.37; and 0.71, 0.69, 5.32 and 0.31 for R2 , NSE, PBIAS and RSR, respectively, during the calibration and validation periods. Future periods suggest a decreasing pattern in streamflow, with a higher percentage (−5.94%) expected for the RCP 8.5 scenario in the late century (2080s) during dry season period. In the wet season, streamflow decreases in all future periods except for RCP4.5 where it is expected to increase (0.36%). Therefore, the Basin may likely experience tremendous pressure in the late century due to low streamflow, particularly in dry season months.