Experimental Study On Inhibiting Water Surface Evaporation Of Reservior In Arid Region

In Northwest China, water shortage is very serious due to lower precipitation and higher evaporation, and water resources have become the "bottleneck" of regional sustainable social economic development. Those studies related to water saving techniques had been focal point for long time. Among those, most studies were focused on techniques of water utilization and transportation. However, in recent time, studies on how to inhibit water surface evaporation of reservoirs became a new direction in water saving technology. Based on former studies, new method for inhibiting water surface evaporation by Expanded Polystyrene, Polyethylene and Paraffin was proposed, and water saving efficiency and the economic benefits of the three materials were analyzed. Following conclusions can be drawn:(1)Analyzing calculation accuracy of different methods for inhibition of water surface evaporation on daily, ten-daily, monthly scales. Three water surface evaporation models, including Vapor transfer model, Penman model and CRLE model, were applied to simulate the daily, ten-daily, monthly water surface evaporation from 2004 to 2006 in Jingtai. And results showed that with the increase of time scale, calculation precisions were greatly improved, and results on month scale was the best one among the three scales. Results by Vapor transfer model was better than other two models in calculating daily water suiface evaporation, while the Penman model was better for the ten-daily, monthly calculations.(2) Finding piecewise relation for calculation of water surface evaporation. Contrastive analysis of the calculation results from Vapor transfer model, Penman model and CRLE model indicated that all simulating results fitted well except for the months with higher evaporation. Aiming at this, piecewise relation for calculation of water surface evaporation was found. Results by this method showed higher accuracy, and reflected the changing trends of water surface evaporation.(3) Contrastive analyzing the effect of inhibiting water surface evaporation by three materials. Results indicated that inhibiting efficiency of water surface evaporation varied a lot due to the difference of material properties, such as density, reflectivity, adiabaticty. And the inhibiting efficiency of the three materials was in the order of Expanded Polystyrene> Polyethylene>Paraffin. Using data in water surface evaporation calculation, new model for inhibiting water surface evaporation was put forward, and tested by observed data in experiment.(4) Analyzing the inhibiting water surface evaporation efficiency under the cover of the three materials. Using grey topological prediction method, annual water surface evaporation from 2005 to 2015 in Jingtai was calculated. Analysis to the inhibiting water surface evaporation efficiency of the three materials indicated that the inhibiting-water surface evaporation efficiency of Expanded Polystyrene, Polyethylene and Paraffin was 51.99%, 44.37% and 20.83% respectively.(5) Analyzing the economic benefit of three different water surface covered materials. Considering crop yield only, economic benefit of the three materials was in the order of Polystyrene> Polyethylene>Paraffin, Polyethylene's economic benefit was the highest of all, and its cost can be recovered in current year. Thus Polyethylene measure was suggested in practice.