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Prospects for agricultural water management
Agricultural water is currently under threat by both climatic and non-climatic drivers. Changes in rainfall pattern will significantly disrupt cropping systems, particularly in rainfed areas. It will become more difficult and risky for farmers, in the face of climate change, to rely on rainfall for their planting calendar. Extreme climate events will likely impinge the hydrological system in most of the river basins and will mean water becoming either ‘too much’ or ‘too little’. When water becomes too much, the potential effects include flooding from overflowing rivers and excessive runoff from sloping lands, which damage water infrastructure, such as dams, and irrigation and drainage systems. At the other end, higher temperatures and decreased precipitation mean too little water, resulting in a decreased water supply and an increased water demand, which might cause deterioration in the quality of freshwater bodies. There will be possible alterations in the distribution of surface water and groundwater owing to changes in recharging (gaining) and discharging (losing) patterns. Stream flows will be significantly reduced and groundwater levels will decline, particularly shallow aquifers may dry up if water extraction is not properly regulated. Non-climatic drivers owing to human activities will continuously provide more pressure on water resources resulting in growing competition among water users.
In view of the above scenario, agricultural water management should incorporate the judicious use of water resources and engineering measures. To be able to deal with ‘too little water’, focus needs to be placed on both the demand and supply side of water management through water sources rehabilitation, water conservation, and augmentation of water supply, such as the optimum utilization of wastewater as an alternative to water sources for irrigation. To be able to deal with ‘ too much water’, drainage facilities that are used to immediately remove excess flood waters will need to be improved. The design of irrigation systems needs to be reviewed to include the effect of climate change and to incorporate properly designed drainage facilities to protect standing crops. The construction of rainwater harvesting structures (e.g. small water impounding project) to collect and store rainwater in the uplands could contribute to the mitigation of floods downstream and ensure available water during the dry season.