Optimal water use strategies for mitigating high urban temperatures

Abstract

Urban irrigation and road sprinkling are methods for mitigating high urban temperatures which are expected to enhance evapotranspiration and affect the urban weather, climate, and environment. Optimizing limited water supplies is necessary in regions with water shortages. In this study, we implemented urban water usage schemes, including urban irrigation and road sprinkling in the Weather Research and Forecasting (WRF) model, and assessed their effects with different amounts of water in city centers, suburbs, and rural areas by using the WRF model at a resolution of 1 km in Beijing, China. In addition, we developed an optimization scheme with a cooling effect as the optimal objective and the total water supply as the constraint condition. Nonlinear relationships were identified between the cooling effect and water consumption for both road sprinkling and urban irrigation, and the cooling effect due to urban irrigation was more effective than that attributed to road sprinkling. Based on the optimal water management scheme, and according to Beijing's 13th 5 Year Plan, about 90 % of the total water supply should be used for urban irrigation and 10 % for road sprinkling as the most effective approach for decreasing urban temperatures by about 1.9 ∘C.