The risk of flood or waterlogging in irrigation districts has increased due to global climate change and intensive human activities. A Model of Optimal Operation of Drainage Works (MOODW) for flat irrigation district was established by incorporating the hydrological model of waterlogging process and waterlogging loss estimation, which was solved by an optimization method of genetic algorithm. The model of waterlogging process was built based on a modified Tank model and hydrodynamic model for the ditch-river system. The waterlogging loss is calculated under the condition of inconstant inundated depth by linear interpolation. The adaptive genetic algorithm with the global optimization function was selected to solve the model. With an extreme rainfall events in Gaoyou irrigation district as cases, results showed that operation time and numbers of pumps increased; thus, operating costs were 1.4 times higher than before, but the yield loss of rice decreased by 35.4% observably. Finally, the total waterlogging loss was reduced by 33.8% compared with the traditional operation of waterlogging work. The most significant improvement was found in units with high waterlogging vulnerability. The MOODW can provide the waterlogging information visually and assist the district manager in making a reasonable decision.
Global warming induced by increasing greenhouse gas concentrations in the atmosphere is a matter of great environmental concern. Nitrous oxide (N 2 O) is an important long-living greenhouse gas that has attracted considerable attention during the past few decades because of its contribution to global warming and ozone depletion [1][2][3] Water management has been recognized as one of the most important practices affecting N 2 O emissions [6][7]. Many researchers have found that peak N 2 O emissions were observed during the drying period after soil watering, caused either by precipitation or irrigation. For instance, Ding [8] found that rainfall and irrigation typically enhance soil N 2 O peak emissions from maize-wheat rotation soils. Yao et al. [9] showed that pulse emissions of N 2 O occurred during repeated drying and wetting cycles in rice-wheat rotation systems. Peng et al. [10] reported that maximum N 2 O emissions were measured eight days after irrigation and applying base fertilizer in winter wheat croplands.In addition, some previous studies have confirmed that the peak N 2 O emissions can be observed in a specific water-filled pore space (WFPS) range. In a field trial, Pol. J. Environ. Stud. Vol. 25, No. 6 (2016), 2623-2631 AbstractTo reveal the impact of vertical non-uniform distribution of soil moisture on nitrous oxide (N 2 O) emissions, incubated experiments were conducted from April to August 2013 on silty clay and sandy loam with four watering regimes [surface watering (SW) and subsurface watering application to levels 12, 15, and 18 cm below soil surface (SUW12, SUW15, SUW18)]. Short-term pulse emissions of N 2 O from both soils during the drying process were observed. The soil water-filled pore space (WFPS) at 0-12 cm depths for peak N 2 O fluxes in SW and SUW soils fell within 34-66%, 22-72%, 25-35%, and 19-39% for silty clay and sandy loam, respectively. Our results also suggest that the N 2 O fluxes from soil of sily clay with higher N content are much higher than that from sandy loam, and N 2 O were more easily influenced by soil moisture in SW soils than in SUW soils. However, more research is needed to identify an ideal soil-wetting pattern and the way to realize the ideal soil-wetting pattern, especially on soil with plant growth and fertilization.
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