ESTIMATING SEEPAGE LOSSES IN DIFFERENT SIZE OF EARTHEN WATERCOURSES AT FARM LEVEL
Keywords:bed width, empirical equations, flow depth, inflow-outflow method, seepage losses, soil factor
AbstractThe research work evaluates the effect of different size of field channels on seepage losses and its comparison with empirical equations developed for seepage estimation. Inflow-Outflow method was used as bench mark method for seepage losses which estimated seepage losses as 0.0342 and 0.024 cusec per 30ft reach which equals to 4.86% and 3.3% under bed-width greater than and equal to flow depth, respectively. The significant differences were observed between Inflow-Outflow and empirical methods. Formula used under Indian conditions under estimated seepage losses for two cases i.e. bed-width greater than and equal to flow depth. However, values of soil factor (C) could be adjusted for tangible estimates. The values of C = 1.71 and C = 3.33 might provide better estimates that will match the measured data. Lower soil factor limits could be used for watercourses with bed width equal to flow depth while, upper soil factor limits could be useful in water courses with bed-width greater than flow depth. Formula used under Pakistan conditions over estimated seepage losses under both cases. Formula does not consider any other hydraulic or soil parameters except discharge for seepage computations that is not enough to estimate actual seepage losses. The hydraulic parameters and soil characteristics for a range of soils need to be considered. Otherwise, this equation cannot be used to estimate seepage losses for clay loam soil. The results of this study can be referred by the engineer and decision makers who are actively involved in seepage estimation.
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