Versatility in Managing Large Scale Surface Irrigation Schems

The trends of global climate change as a result of the global warming phenomenon has affected local climate and micro-climate to such an extent that forecasting of rainfalls that traditionally have been taken for granted, is now difficult. In a recent study by the National Centre for Atmospheric Research in Boulder, Colorado, USA, it was found that the flow of water in the world s largest rivers has declined over the past half-century with significant changes in about a third of the big rivers such as the Yellow River and the Yangtze River in China, the Ganges in India, the Niger in west Africa and the Colorado in the US. An analysis of 925major rivers from1948 to2004 showed an overall decline in total discharge and this is not in any way due to human activities, but purely due to climate change. Freshwater resources will likely decline in the coming decades with annual freshwater discharge into the Pacific Ocean already down by 6%or 526cubic kilometers (roughly equivalent to the annual total volume delivered by the Mississippi River in the USA) of water only to be compensated in the Arctic where there is a significant increase due to snow and ice melt. The resulting consequence of climate change is, depending on locations, droughts, floods, inundation of low-lying areas, natural fires that wipe out large tract of forests etc. The consequences of such are that agriculture that relies significantly on abundant water resources may have to be managed differently, intelligently and with some degree of versatility. This could very well mean that crops that required lesser consumptive use may be an answer around the dwindling resources. Worldwide a substantial amount of a country s water resources are devoted to agriculture (with some as high as ). 75%of the total surface water resources ( 10billion cubic meters per year) in Malaysia is used for agriculture. Not only is rice irrigation the largest consumer of fresh water; it is also characterized by a comparatively low use efficiency (<50% ). Nevertheless, it is a national agenda in order to give some figure of security of at least 70%of the staple food of Malaysia. For the Southeast Asia s agriculture-dependent economies an Asian Development Bank study recommended that measures to mitigate the impact of climate change such as irrigation networks, flood control systems, early warning systems and protecting coastal mangroves be implemented to secure crop security. This paper covers aspects on including rainfall into rice irrigation scheduling, modeling water allocation in a run-of-the-river scheme, water allocation and delivery with a water management decision support system