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| DOI： |
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| Optimizing Irrigation Schedule for Rice Based on Stochastically Generated Precipitation |
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LEI Caixiu, XIONG Weihong, JIANG Zhong, ZHANG Jifang
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Hubei Provincial Water Resources and Hydropower Planning Survey and Design Institute, Wuhan 430064, China
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| Abstract: |
| A new method based on stochastically generated precipitation series was presented in this paper to determine rational irrigation schedule for rice with the water required by the crop in each ten days as the decision variables; the objective was to maximize the relative yield. A long series of precipitations were first generate dusing the Monte Carlo method based onmeasured rainfall data. The genetic algorithm was then used to solve the model in which the generated precipitations were taken as input parameter. The optimal irrigation schedule for rice was obtained by statistical analysis. The model was applied to the Zhang River Irrigation District (ZID). The results showed that 30-year precipitation series in ZID could be described by the gamma distribution. Irrigating 120 mm of water to the middle-season rice was sufficient to avoid wilting. It was also found that irrigating 180 mm of water could keep the rice grow normally. If the overall irrigation was 180 mm and the amount of each irrigation is 30 mm, the rice would need two irrigations in early June and early August respectively, each with an amount of 30 mm, and further two irrigations in mid-June and late July respectively each with 60 mm of water. It is relatively dry in ZID from mid-June to early August, and an optimal irrigation is hence the only way to meet the demands of rice for water. |
| Key words: irrigation schedule; Monte Carlo method; rice; stochastic precipitation; genetic algorithm |
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