Reduction of Evaporation from Water Reservoirs Using Floating Covers in Isfahan

Document Type : Research Paper


1 . Former MSc Student of Irrigation and Drainage, Dept. of Water Eng., College of Agriculture, Isfahan. University. of Technology

2 Isfahan University of Technology


The aim of this study was to evaluate the influence of Floating Covers on the reducing evaporation from free water surface. In this study three types of covers (Polystyrene, Polystyrene with aluminum and polycarbonate) on the surface of 3 reservoirs (with three repetitions for each covers) were used. Changes in water depth of covered and uncovered reservoir were measured in one year from October 2014 until November 2015. Then the evaporation results of covered and uncovered trials were analyzed in form of a randomized complete block design with three replications using SAS software at confidence level 99% (P<0.01) and Duncan test. The rate of evaporation reduction using Polystyrene, Polystyrene with aluminum and Polycarbonate, are 85.60%, 83% and 76.5%, respectively. These amounts represent a good performance of three covers in reducing evaporation from reservoirs. Although Polycarbonate cover represents better and proper performance in relation to durability.


Main Subjects

Alizadeh, A. (2011) Principles of Applied Hydrology (28th ed.). Mashhad: Ferdowsi University of Mashhad.
Bengoechea, J.M., Perez, J., Perez-Parra, J.and Lopez, J. G. (1991). Evaluacion de las perdidas de agua de Riegoen el Campo de Dalias, Almerıa. In: Symposium sobre el agua en Andalucıa. Co rdoba, Spain.
Craig, I., Green, A., Scobie, M. and Schmidt, E. (2005). Controlling Evaporation Loss from Water Storages. Report 1000580/1, National Centre for Engineering in Agriculture, Toowoomba, 207 p.
Daneshkarasteh, P., Tajrishi, M., Mirlatifi, M. and Saghafian, B. (2006). The necessity of revision of evaporation estimation models from free water level in arid regions with regional oasis effect: a case study in Chahnimeh reservoir. Journal of Agricultural Engineering Research, 5, 37-58. (In Farsi)
Farzin, S. and Alizadeh Samani, F. (2015). Shadow Ball, measures to reduce water evaporation dam reservoirs. In: Proceedings of 3th International Congress on Civil Engineering, Architecture and Urban Development, 29-31 Dec., Shahid Beheshti University, Tehran, Iran. (In Farsi)
Gallego-Elvira, B., Baill. A., Martin-Gorriz, B., Maestre-Valero, J. F. and Martinez-Alvarez, V. (2011). Energy balance and evaporation loss of an irrigation reservoir equipped with a suspended cover in a semiarid climate in south eastern of Spain. Journal ofHydrological Processes, 25, 1694-1703.
Guerra, L.C., Watson, P. G. and Bhuiyan, S. I. (1990). Hydrological analysis of farm reservoirs in rained rice areas. Journal of Agricultural Water Management. 17, 351-366.
Hashemi Garm Dareh, E., and Eslamian, S.S. (2006). Using covers for reducing evaporation from reservoir. In: Presented at The 2th conference of Soil and Water Resources Management, 22-23 Feb., University of Kerman Bahonar Kerman, Iran. (In Farsi)
Helfer, F., Lemckert, Ch. and Zhang, H. (2012). Impacts of climate change on temperature and evaporation from a large reservoir in Australia. Journal of Hydrology, 475, 365-378.
Howard, B. C. (2015). Why Did L.A. Drop 96 Million ‘Shade Balls’ into Its Water? Retrieved August 12, 2015, National Geographic from
Hudson, N.W. (1987). Soil and Water Conservation in Semiarid Regions. FAO Land and Water Conservation Service, Rome, 256 pp.
Khan, M. A. and  V. C. Issac. (1990). Evaporation reduction in stock tanks for increasing water supplies. Journal of Hydrology, 119, 21–29.
Linsley, R.K., Kohler, M.A. and Paulhus, J.L., (1982). Hydrology for Engineers (3th ed.). McGraw-Hill, New York.
Martinez-Alvarez, V., Baille, A., Molina-Martinez, J. M. and Gonzalez-Real, M. M. (2006). Efficiency of shading materials in reducing evaporation from free water surfaces. Journal of Water Resources Management, 84(3), 229-239.
Martinez-Alvarez, V., Gonzales-Real, M.M., Baille, A., Valero, J.F.M., Elvira, B.G., (2008). Regional assessment of evaporation from agricultural irrigation reservoirs in a semiarid climate. Journal of Agricultural Water Management, 95, 1056–1066.
Martinez Alvarez, V., Calatrava Leyva, J., Maestre, J. F., and Martin Gorriz, B. (2009). Economic assessment of shade-cloth covers for agricultural irrigation reservoirs in a semi-arid climate. Journal of. Agricultural Water Management, 96, 1351- 1359
Martinez-Granados D., Maestre-Valero, J. F., Calatrava. J. and Martínez-Alvarez, V. (2011). The economic impact of water evaporation losses from water reservoirs in the Segura basin, SE Spain. 2011. Journal ofWater Resources Management, 25, 3153-75.
Moradi Mazraehno, H. R., Talebi, M, S. and Hasanzadeh, M. (2013). Assessment of evaporation reduction from agricultural water reservoirs using Ionolite cover (case study of Agda Region-Yazd). In: Proceedings of 1st National Conference on the Application of Modern Science and Technology in Agriculture and Natural Resources.,15 Mar., Islamic Azad University of Meybod, Yazd, Iran. (In Farsi)
Mugabe, F.T., Hodnett, M. G. and Senzanje, A. (2003). Opportunities for increasing productive water use from dam water: A case study from semi-arid Zimbabwe. Journal of Agricultural Water Management. 62, 149-163.
Piri, M., Hesam, M., Dehghani, M. M. and Meftah Halaghi, M. (2011). Experimental study on the effect of physical and chemical approach in reducing the evaporation from water surface. Journal of Water and Soil Conservation, 17(4). (In Farsi)
Stanhill, G. (2002). Is the Class-A evaporation pan still the most practical and accurate meteorological method for determining irrigation water requirements? Journal of Agricultural and Forest Meteorology, 112, 233–236
Wurbs, A. R. and Ayala, A.R. (2014). Reservoir evaporation in Texas, USA. Journal of Hydrology, 510, 1-9.
Yao X., Zhang, H. Lemckert, C., Brook, A., and Schouten, P. (2010). Evaporation Reduction by Suspended and Floating Covers: Overview, Modelling and Efficiency. Urban Water Security Research Alliance.Technical Report (No 28).