Estimation of Run-off Using Simple Tank Model in Dez River Basin

Run-offs are considered as important hydrological factors in feasibility studies of river engineering and irrigation-related projects under arid and semi-arid condition. Flood control is one of the crucial factor, the management of which while mitigates its destructive consequences, abstracts considerable volume of renewable water resources. The methodology applied here was based on Mizumura, which applied a mathematical model for simple tank to simulate the rainfall-run-off process in a particular water basin using the data from the observational hydrograph. The model was applied in the Dez River water basin to simulate and estimate the floods. The water tank has a horizontal cross-sectional area, which is a function of the water depth and which may be determined from the recession curves of flood hydrographs. The total vertical depth of the water tank and the infiltration velocity, which govern the time lag between rainfall and runoff, are computed from the rising limbs of the flow hydrograph. Results indicated that the calculated hydrographs using the simple tank method and the observation hydrographs had a close proximity. Results also showed a linear relation between the rainfall and run-off. It was found that the recession curve slope is constant for the subsurface and underground flows under different conditions, quite similar to the results arrive at by. There was however a considerable variation in the surface run-off from one flooding to the other.