Sensitivity analysis of hydraulic parameters in simulation of unsaturated soil water dynamics
2007
Ghanbarian, B. | Parsinejad, M.
Soil water content is one of the most important parameters for estimating the irrigation frequency and providing the plant water requirement. Since measurement of soil water content is both expensive and time consuming so water movement models are used to estimate these values. In this study, LEACHW model was used to estimate the soil water content for two "dry"(20-29 Aug) and "wet" (1-6 Jul) periods during the 1995 growing season. Different values of hydraulic parameters were applied to investigate the sensivity analysis of these parameters in estimation of soil water content. Thus the values of b (pore distribution coefficient in Campbell`s equation, 1974) were selected from 2 to 24 and k(theta)/ks ratios of 0.1, 1, 10 and 100 were used. Finally 32 treatments were investigated for each period. Results showed that despite large variation for the hydraulic parameters, similar trends of results were obtained for all soil water content estimations. Comparison between estimated and measured results showed results showed a systematic difference which can be adjusted using a few measured values of soil moistures. As an example simulated results using b=24 and k(theta)/ks =0.1 were calibrated to adjust the simulated results. The results of this study showed that a simple calibration methods can be used for estimation of soil moisture content without the use of extensive data required to present hydraulic characteristics of soils.
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