Date of Award
Doctor of Philosophy
Agricultural and Biosystems Engineering
The objectives of this study are related to the determination of the optimal use of water for a run-of-the-river irrigation system for rice production. A simulation model was developed based on the concept of rotation irrigation and was used in the irrigation water management study to estimate the optimal irrigation time interval that will maximize the yield of rice, determine the effects of subdividing the irrigable area into rotation areas on the yield of rice and water supply, and estimate the maximum area that would give the highest yield and the optimal area that could be put under rice production for a river water source;The input data were rainfall, pan evaporation and stream flow. The depth of water applied and the potential evapotranspiration were computed. Water depletion was calculated by adding the potential evapotranspiration and soil percolation. The number of moisture-stress days was determined, based on the depth of water in the field; the yield of rice was calculated by use of a yield function based on the number of moisture-stress days developed from the data obtained in the Philippines;The combination of the number of rotation areas and the rotation interval that produced the highest yield was selected as the optimal water management for a given area. Since the simulation was done for several irrigable areas, the largest area that gave the potential yield of 2.43 tons/acre was selected as the irrigable area that can be supplied with irrigation water without moisture stress, and the area that obtained the highest profit was selected as the optimal irrigable area;It was not necessary to subdivide the irrigable area into rotation areas when the water supply was adequate. The rotation interval varied from 1 to 8 days and did not affect significantly the yield of rice. However, an interval of more than 8 days considerably decreased the yield. For the irrigable area of highest profit, it was necessary to divide the area into 4 rotation areas which were irrigated at 4-day intervals;There was no significant difference between the rotation irrigation scheme and continuous irrigation for small irrigable areas when the water supply was adequate. However, rotation irrigation provided for a significantly greater optimal irrigable area. It also gave significantly higher production for large irrigable areas when the water supply became inadequate;Since the results of this study are realistic and comparable with all research findings and field observations that are available in the literature, it can be concluded that the model is acceptable, rice production can be optimized by rotation irrigation, and selection of the area and interval is required for a given quantity of diverted water.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Margarito Coballes Escalante
Escalante, Margarito Coballes, "Irrigation water management by simulation for a diversion irrigation system and saturated soil conditions " (1982). Retrospective Theses and Dissertations. 7037.