SUBSURFACE DRAINAGE DESIGN AND COST ANALYSIS AT HADEJIA VALLEY RIVER BASIN JIGAWA STATE, NIGERIA.
Publication Date : 01/02/2019
The twin problem of waterlogging and salinization in irrigated lands remains a serious challenge around the world. This study was conducted to provide a solution in combating the effect of waterlogging and salinization along the command area of Hadejia valley river basin. Soil samples were collected from the study area using stratified random sampling techniques to identify the extent of salinity or sodicity in the study area. Nineteen observations wells were drilled randomly in the study area to measure the water table depth and the depth of impervious layer. The result obtained from the soil test indicates that Calcium was generally the dominant base in the exchange complex. However, the levels of exchangeable sodium was high in some areas and increase with soil depth ranging from 0.2 to 8.1 cmol (+) kg-1 and 0.3 to 12.4 cmol (+) kg-1 for topsoil and subsoil respectively. The ESP mean values ranged from 14.8% and 17.5% for the top soil and subsoil, respectively. Soil pH varied from 5.6 to 9.9 in the top soil and 4.8 to 9.8 in the subsoil. Values for Electrical Conductivity (EC) of the soil saturation extract were generally very low, indicating that the soils are generally non-saline. Strong evidence shows that Soil sodicity was the most serious problem in the area. Results from observation wells indicated that the study area has a shallow impervious layer of 2.6m. Seepage from adjacent River Hadejia contributes to the high water table (WT) and subsequent waterlogging. For optimum use of the land, a subsurface drainage was designed and the drain depth was calculated as 1.6m, drain diameter of 20cm and drain spacing of 14m and 10m using Hooghoudt’s and Glover Dumm’s conditions respectively. However, the WT was lowered to 1.1m suitable for most agricultural activities in the area. The overall pre-construction and construction cost was calculated as ₦635,000 and ₦1,520,000 respectively for a hectare of land.
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