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The Nam Suai river a tributary of the Mekong river has drainage area of 1,250 sq.km. It
is located in Nong Khai and Udon Thani provinces is northeast Thailand. Flooding and
drought conditions are majority problems in the basin. The development plan from the
feasibility study are regulator construction at the river mouth and irrigation development
on both banks of the river. The objectives of this study are to investigate the potential
of water resources development in the basin and the effect of flood damage reduction from
the project.
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The data such as hydro-meteorology and physical characteristic of basin are collected.
NAM Model, a rainfall-runoff model is used to generate the runoff of the basin. Computer
models namely Effective Rainfall Model, Irrigation Demand Model and System Simulation
Model are used to study of water use in the basin. By assuming the water requirement for
land preparation of 200 millimeters with 3-week period for an area of 1 rai, and using
minimum, medium and maximum levels of storage in field at 45, 90 and 120 millimeters
respectively for Effective Rainfall Model. The calculated irrigation efficiency is about
67 % and 70 % for wet and dry seasons respectively. The reservoir operation are studied
for both cases namely with and without pumping form the Mekong river.
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Bi-dimension Flood Flow Model is a selected model to be used for flood study in the
basin with modified flow equation through regulation for submerged flow condition. The
result of flood study shows that regulator can reduce flood damage caused by high water
level of Mekong river, but flood from heavy rainfall in river basin still be existed.
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From the result of the study, its is recommended that cropping pattern in wet season
should be shifted to begin at the end of June. The maximum reservoir water level operated
in wet season is +161.00 m. MSL an dry season area reduction curve can be applied when
water level in reservoir is above +159.00MSL In case of without pumping water from the
Mekong river, wet season rice and dry season crop (vegetables and mung bean) areas are
almost the same at 142,040 rais. By pumping water form the Mekong river with 3.0 cms.
capacity, the average dry season rive area is about 33,160 rais.
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