Development of sustainability assessment model for climate change adaptation on water availability

The humid tropical basin of Upper Bernam River Basin (UBRB) in Malaysia is considered as the most important irrigation water supply source for a 20,000 ha rice granary. An irrigation scheme is located adjacent to the Tanjung Karang peat swamp at the east. It is designed based on the water drained from UBRB. Therefore, the basin importance as irrigation water source due to the unavailability of dam to store water and the irrigation scheme is a run-of-river system. Two Regional Climate Models (RCMs) data were used to evaluate the climate changes impact on water availability on local scale using RCM data with a distributed hydrologic model. First, RCM data was downscaled using a RCM known as Providing Regional Climates for Impacts Studies (PRECIS). Second, RCM data was Regional hydrologic- atmospheric model of Peninsular Malaysia, (RegHCM-PM). The comparison results revealed that RCMs temperature data for specific grids were closer to the actual temperature data compared to the rainfall data. The actual data and RCMs data were then used with SWAT model to simulate stream flow. For average monthly flows using weather station data, Nash and Sutcliffe Efficiency (ENS) and coefficient of determination (R2) were found to be 0.79 and 0.80 respectively while ENS and R2 for average monthly flows using RCMs data were found to be -4.297, 0.05 for PRECIS and -0.548, 0.12 RegHCM-PM respectively. The average monthly flows with data from weather station, PRECIS and RegHCM-PM were 43.2, 72.3 and 39 m3/s respectively. The Mann–Kendall test was then used to examine the trend presence for temperature, rainfall and flow time series of actual data and RCM. In all cases, Mann–Kendall test results showed an increasing trend for temperature. However, in all cases, there is no trend detected for rainfall and the flow trend analysis using weather station inputs resulted in increasing trend with more than 90% probability level of significance, whereas no flow trend was detected using RCM data. A paired t-test was used to compare two RCMs means with observed data means for rainfall, temperature and flow. The t- test results of P value with 95% confidence for PRECIS and RegHCM-PM were 0.0000 and 0.0750 for rainfall, 0.00 and 0.00 for temperature and 0.00 and 0.0840 for flow. Based on the research findings, it can be stated that the PRECIS model has better performance than RegHCM-PM in downscaling the temperature, while RegHCM-PM performed better than PRECIS in downscaling rainfall. In the study area, the increasing trend of temperature was projected with the global increasing temperature trend. The rice cultivation is sensitive to climate change as the its production is decreased with temperature increase. In addition to temperature impacts on rice production, is also correlated with water availability. According to the research findings, there is a real need to find out the possible alternatives to mitigate the impacts of climate changes. Consequently, Sustainability Assessment Analysis for Available Water Resource (SAAM-AWR) model was developed to find out the most sustainable management intervention alternative to mitigate the impacts of climate change. Two management intervention alternatives were identified. The chosen alternatives were constructing Bernam Dam and ponds. Then, four main criteria were selected including technical, economic, environmental and social aspects for the analysis purpose. Each criterion has a number of indicators. In most of the criteria, the dam performance was found to have higher sustainability index compared to the ponds. The dam sustainability index of 68% which is considered as medium while the ponds showed low sustainability index of only 32% revealing the importance of constructing dam for more sustainability. The methods and processes developed by this research can be applied in other watersheds as it has proven the usefulness of Sustainability Analysis in Water Resources Management.

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