Optimized Allocation Of Water Resources Under Low Impact Development

This paper is about the optimization of water resources planning in the greenecological district, which is seldom researched in the former optimal allocation ofregional water resources. Analyzed the condition of water resources development andutilization in the district, it is found that there are many problems like overexploitationof deep groundwater, low guarantee rate of water supply, unavailable surface waterresources. To alleviate these problems, on one hand, the utilization of unconventionalwater resources should be strengthened, on the other hand, the rainwater utilizationshould be focused on infiltration to supply groundwater. Based on these two pointsand the existing research results at home and abroad, with the application of theprinciples and methods in environmental engineering and mathematical programming,the concept of low impact development was introduced into the optimized allocationof water resources for the first time, and the reclaimed water and rainwater werebrought into the district’s water supply system. A water resources optimal allocationmodel of the green ecological district was established.First of all, the applicability of the water demand forecasting methods and theactual situation of the district(under construction) were comprehensively considered,the index method was uesd to predict the water demand in2020, and the availabilityof water resources in the district in2020was known by consulting information andsurvey.Afterwards, a regional rainwater system model was established by InfoWorksCollection System. After calculating the designed rainfall under recurrence interval of1year,2years and5years using Chicago rain style formula, the rainfall flood controleffects before and after the implementation of the low impact development wereanalyzed, the runoff coefficient (about0.3) after implementation of the low impactdevelopment was determined, and the relationship between the storage and infiltrationof rainfall and the area of green roof and sunken lawn was obtained, then thisarea-rainfall relational expression was applied to the water resources optimalallocation model as one of the constraints, which realized the quantification ofecological benefit. Finally, the allocation ratio of diversion water, drinking water, reclaimed water,rainwater and area of green roof and sunken lawn were selected as independentvariables, least cost of water supply, minimum amount of fresh water, minimumpollution discharge, maximum rainwater infiltration were selected as the objectivefunctions. The model was established with the constraints of the low impactdevelopment techniques, COD discharging, reuse rate of reclaimed water and pipelineleakage. The linear weighted technique was used to transfer the multi-objectivefunction into single objective, and the LINGO software was used to solve the function,then the reasonable water allocation in the ecological environment and socialeconomic system and the appropriate area of green roof and sunken lawn was found.The evaluation of the optimization results shows that the allocation has high economic,social and ecological benefit, achieving the balance of comprehensive benefit.