Abstract:A simulation and optimization model was developed and applied to an irrigated area in Delta, Utah to optimize the economic benefit, simulate the water demand, and search the related crop area percentages with specified water supply and planted area constraints. The user interface model begins with the weather generation submodel, which produces daily weather data, which is based on long-term monthly average and standard deviation data from Delta, Utah. To simulate the daily crop water demand and relative crop yield for seven crops in two command areas, the information provided by this submodel was applied to the on-farm irrigation scheduling submodel. Furthermore, to optimize the project benefit by searching for the best allocation of planted crop areas given the constraints of projected water supply, the results were employed in the genetic algorithm submodel. Optimal planning for the 394Ð6-ha area of the Delta irrigation project is projected to produce the maximum economic benefit. That is, projected profit equals US$113 826 and projected water demand equals 3Ð03 ð 10 6 m 3 . Also, area percentages of crops within UCA#2 command area are 70Ð1%, 19% and 10Ð9% for alfalfa, barley and corn, respectively, and within UCA#4 command area are 41Ð5%, 38Ð9%, 14Ð4% and 5Ð2% for alfalfa, barley, corn and wheat, respectively. As this model can plan irrigation application depths and allocate crop areas for optimal economic benefit, it can thus be applied to many irrigation projects.
Paddy field storage of rainfall by bunds is like a rainwater cistern system during the rainy season. Deepwater management practice in paddy fields might be good for rice production and water storage capacity at the same time. The study was conducted in an experiment testing two water management treatments with six rice variety treatments using two lysimeter experiments.The results revealed that deepwater management significantly affected rice production. On the other hand, deepwater management increased the effective rainfall (70 mm) and percolation (225 mm). The runoff coefficient under deepwater management decreased from 0.67 to 0.53. It was reasonable to conclude that the deepwater management provided more water storage capacity during the growing season. Finally, water productivity results point out that even though the volume of input water under deepwater management had increased, deepwater management still can generate higher water productivity.It looks as if it is pointless to save water during the rainy season. On the contrary, if excess water is available in rivers, it should be delivered in timely fashion to the wetland rice fields to increase effective rainfall and the excess saved by maintaining adequate percolation to replenish groundwater, without having to follow strict water conservation measures. Copyright # 2007 John Wiley & Sons, Ltd. RÉ SUMÉ Le stockage des précipitations dans les rizières au moyen de diguettes est analogue à la récupération de l'eau de pluie par citerne. La pratique de la gestion de plan d'eau dans les rizières pourrait être une bonne chose à la fois pour la production de riz et la capacité de stockage de l'eau. L'étude porte sur une expérience combinant deux types de gestion de l'eau, six variétés de riz et deux sortes de lysimètre.Les résultats montrent que la gestion de plan d'eau a affecté de manière significative la production de riz. Par ailleurs elle a augmenté les précipitations efficaces (70 millimètres) et la percolation (225 millimètres). Le coefficient d'écoulement a diminué de 0,67 à 0,53. Il était donc raisonnable de conclure que la gestion de plan d'eau a augmenté la capacité de stockage de l'eau pendant la saison de croissance. Et finalement, les résultats de productivité de l'eau montrent que, en dépit de l'augmentation du volume d'eau entré dans la rizière grâce à la gestion de plan d'eau, cette dernière permet une productivité de l'eau plus élevée.
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