Experimental Study On Anti-evaporation Water-saving With Partially Covering Floating Ball In The Plain Reservoirs Of Arid Area

Due to the special geographical location and geomorphologic features,the inland northwest of China is in the arid area,with little rainfall and uneven distribution.The evaporation loss of fresh water resources is large,especially in the plain reservoir,and the utilization rate of surface water resources is low.By summarizing the previous research results,the floating ball was selected to cover the water surface of the reservoir in the test,and the feasibility of restraining the evaporation of the water surface was explored,aiming at improving the effective utilization rate of the reservoir.The meteorological conditions and wet area of floating ball were observed and recorded during the test period,the water-saving efficiency under different working conditions of floating ball was calculated,and various experimental conditions were compared and analyzed.The main conclusions of this paper are as follows:(1)According to the meteorological data observed during the test period,the calculation model of water surface evaporation was established with wind speed,temperature,relative humidity,saturation water vapor pressure and water vapor temperature as the main influencing factors using Dalton’s theory and the variation of water surface evaporation under the influence of single factor was analyzed.Through the applicability test of the established surface evaporation model,it is concluded that the accuracy of the evaporation model satisfies the evaluation criteria,and the calculated surface evaporation is reasonable.(2)Black PE hard floating ball was used to cover the hydrostatic surface to study the effect of floating ball on the water surface evaporation.The test results showed that the PE hard floating ball covering the water surface had a good effect of preventing evaporation.The higher the coverage,the better anti-evaporation.When the coverage rate is 75%,the average evaporation inhibition rate of the test period can reach 59%.(3)Four kinds of floating balls of different densities were selected to cover the water surface of plain reservoir in arid area,and the meteorological conditions and wet area of floating balls were observed and recorded.In this paper,the influence of different density and different arrangement of floating ball on water saving efficiency of floating ball was studied.The result showed that The anti-evaporation effect of floating ball was related to the density of floating ball and its arrangement.The higher the density of floating ball was,the closer the arrangement was,the better the anti-evaporation effect was.(4)Because of the defect of poor stability and insufficient wind resistance of circular net girder structure,the floating ball was arranged on the reservoir with triangular net girder structure to explore its wind resistance and water saving effect,and to fit the relation curve between the anti-evaporation coefficient and the covered area.The analysis showed that by improving the network structure and using the highly stable polar floating ball,the anti-evaporation efficiency was increased by 4.6%.When the anti-evaporation coefficient was close to 0.91,the coverage area of circular net was 17.08m~2,while that of triangular net was only 4.48m~2,which was good for stability.