WATER HARVESTING METHODS IN ARID REGION
• In arid regions water is harvested by different methods like runoff farming, water spreading, microcatchments, inter row water harvesting systems and traditional water harvesting systems like tanka, nadi, khadin.
• In water spreading method flood waters are deliberately diverted from their natural courses and spread over adjacent plains.
• In microcatchment method rainwater catchment basin is built around the plant.
• In inter-row water harvesting systems water collected from ridge is stored in furrow and the crop is benefited by high moisture.
• Ridge and furrow system is better for getting higher yield of pearl millet than flat bed method.
• Ridge provides partial shading of the furrow for 6 to 7 hours a day and reduces evaporation.
• Tanka, nadi, khadin are the important traditional water harvesting systems of Rajasthan.
• Tanka is an underground tank or cistern constructed for collection and storage of runoff water from natural catchment or artificially prepared catchment or from a roof top.
• Nadi or village pond is constructed for storing water from natural catchments.
• Khadin is unique land use system wherein runoff water from rocky catchments are collected in valley plains during rainy season.
• In Khadin method crops are grown in the winter season after water is receded in shallow pond on the residual moisture.
WATER HARVESTING METHODS IN SEMIARID REGIONS
• In semiarid regions water harvesting techniques include dug wells, tanks, percolation tanks, farm ponds, inter-row water harvesting, broad bed and furrows.
• Quality of water is generally poor in dug wells due to dissolved salts.
• To avoid the breaching of tank bund, spillways are provided at one or both the ends of the tank bund to dispose of excess water.
• Sluice is provided in the central area of the tank bund to allow controlled flow of water into the command area.
• Unlike wells, quality of water is good in tanks.
• Flowing rivulets are obstructed and water is ponded in percolation tanks, which percolates into the soil and raises the water table of the region.
• Problem associated with farm ponds in red soils is high seepage loss.
• Seepage loss controlled by the use of bentonite, soil dispersants and soil-cement mixture.
• In alfisols mixture of red soil and black soil in the ratio of 1:2 is used for lining farmponds to reduce seepage losses.
• In high rainfall areas, there is possibility for occasional waterlogging and yield of maize is affected.
• In inter-row water harvesting maize is grown on beds and rice in furrows helps in increasing the yields of both the crops. Excess water collected on beds is stored in furrows which is beneficial for rice.
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