Mahsa Hasanpour Nodehi; Maryam Navabian; Mehdi Esmaeili Varaki
Abstract
The purpose of this study was to evaluate WASP7.3 model in simulation of drainage water quality of paddy fields in Nodeh and Nopashan villages of Someh Sara township located in F4 unit of Sefidrood irrigation and drainage network. To evaluate the model, drainage discharge and drain water quality at nine ...
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The purpose of this study was to evaluate WASP7.3 model in simulation of drainage water quality of paddy fields in Nodeh and Nopashan villages of Someh Sara township located in F4 unit of Sefidrood irrigation and drainage network. To evaluate the model, drainage discharge and drain water quality at nine sections of drainage and nine drainage inlets and outlets were measured and introduced to the model. Model sensitivity analysis showed that in simulation of salinity and nitrate, drainage discharge was effective, while in simulation of orthophosphate and ammonium, in addition to drainage discharge and diffusion coefficient, phosphate dissociation coefficients in water column (orthophosphate), nitrification rate, and temperature coefficient of nitrification (ammonium) were more sensitive. Results showed that discharge, nitrate, orthophosphate, ammonium, biological oxygen demand, dissolved oxygen, and salinity were simulated with normalized root-mean-square error of, respectively, 0.166, 0.176, 0.143, 0.283, 0.148, 0.179 and 0.156. According to the results, the accuracy of the model simulation in the study area was classified as acceptable for all parameters, except for ammonium, and is recommended for simulating drain water quality. Due to the limitation of the model to obtain the number of discharge functions of the input and output sources to the drainage channel, application of the model in the main paddy field drainage canals that have fewer inputs than field drainage, can improve the simulation results.
Mahboubeh Aghajani; Maryam Navabian; Majid Vazifehdost; Mojtaba Rezaee
Abstract
In recent years, discharge of Sefidroud River, which is the main source of agricultural water in Guilan province, has been decreasing because of construction of several dams in the upstream of Sefidroud basin. The future of rice production will depend on appropriate management strategy for optimization ...
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In recent years, discharge of Sefidroud River, which is the main source of agricultural water in Guilan province, has been decreasing because of construction of several dams in the upstream of Sefidroud basin. The future of rice production will depend on appropriate management strategy for optimization of water consumption in the paddy fields. In this research, to maximize water productivity in paddy fields, two optimal models were selected for irrigation management as fixed interval irrigation in the entire growing season and variable interval irrigation in different physiological growth stages of Hashemi variety, using SWAP model and Genetic Algorithm (GA). After validation of SWAP model, the chosen values were optimized by GA. In the optimal models, irrigation water depths and rice irrigation intervals were selected as the decision variables in different crop growth stages. Periodic irrigation management with fixed interval i.e. 7.33 days during the growing season, showed the maximum efficiency of irrigation water. However, the optimal variable intervals were 6.53, 4.60, 4.31 and 7.74 days during establishment, tillering stage, maturity, and harvest respectively. Finally, for saving of water, improvement of irrigation water productivity, reduction of evapotranspiration, proper irrigation interval in Sefidroud irrigation network, and ease of measurement of inflow water volume, a fixed irrigation interval of 8 days and irrigation depth of 52, 30, 40 and 12 mm in, respectively, establishment stage, tillering, maturity, and harvest stages was recommended. The highest water productivity obtained was 1.59 kg/ m3.