Analysis of return flows in a tank cascade system in Sri Lanka |
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Authors: | Matsuno Yutaka Tasumi Masahiro van der Hoek Wim Sakthivadivel Ramaswamy Otsuki Kyoichi |
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Affiliation: | (1) Department of International Resources Management, School of Agriculture, Kinki University, 3327-204 Nakamachi, 631-8505 Nara, Japan;(2) R and E Center, University of Idaho Kimberly, 3793N 3600E, Kimberly, ID 83341, USA;(3) International Water Management Institute, PO Box 2075, Colombo, Sri Lanka;(4) Faculty of Agriculture, Kyushu University, 394 Tsubakuro, 811-2415 Fukuoka, Japan |
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Abstract: | In Sri Lanka, irrigation reservoirs (tanks) are usually connected sequentially and form cascades along the landscape. A study was carried out in the Anuradhapura District in the dry zone of Sri Lanka to understand the role of return flows in such tank cascade systems. The water balance of a tank cascade system was estimated using hydrological data collected over a one-year period. The system was extended about 25 km along a river composed of three small reservoirs having the command area of 31, 55, and 55 ha, respectively. In this system, about 46% of seepage water from tanks entered the paddy fields of the command area. The crop consumed part of the water and the rest returned to the downstream tank through the drainage canals. Percolation loss in the command areas was low (3.6 mm/day) since a considerable portion of the percolation returned to the downstream tank. These results showed that return flows, which are generally disregarded in the water budget, contributed considerably to the water supply of the tank cascade system. |
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Keywords: | Irrigation reservoir Paddy rice Water balance Water management |
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