Water Savings Efficiency of Counterweighted Spheres Covering a Plain Reservoir in an Arid Area

Abstract

Plain reservoirs in arid areas typically have long dams, large water areas and shallow water depths. Considerable evaporation loss occurs from these reservoirs. To suppress evaporation, this work adopts counterweighted HDPE spheres with diameters of 100 mm as plain reservoir anti-evaporation materials. The main purpose of this work is to study the factors that influence evaporative loss from a water surface covered by spheres and the annual water savings efficiency of the spheres. In this work, pans A and B, with areas of 1 m2 (pan A was completely covered by spheres, and pan B was uncovered), were selected to study the effects of microclimate changes on evaporation from openings among the spheres. The water temperature difference at different depths in pan A was significant, and there were significant differences in the temperature of the water surface, the air temperature near the water surface, and the relative humidity in the two pans. The factors affecting the wetted area of spheres were studied using spheres of different areas covering the reservoir. In this study, the annual water savings efficiency of the counterweighted spheres per unit area coverage was obtained by developing an evaporation calculation model. The results showed that when the coverage area of the counterweighted spheres increased from 1 m2 to 4 m2, the annual water savings efficiency per unit area increased from 69.71% to 75.42%. An economic analysis was performed to assess the viability of spheres under the current conditions of water pricing and in the given ecological context in Xinjiang.