evaporation suppression
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2022 ◽  
Vol 27 (3) ◽  
Author(s):  
Mohammadreza Mohammadi ◽  
Ammar Safaie ◽  
Amir Nejatian ◽  
Azam Iraji zad ◽  
Massoud Tajrishy

2021 ◽  
Author(s):  
Maram M. Shalaby ◽  
Ibrahim N. Nassar ◽  
Ahmed M. Abdallah

<p>Global warming and population growth increase the need for better management of freshwater resources, in particular in arid and semi-arid regions. Due to increased rainfall variability,  reservoirs became a vital management tool that stores the water during rainfall, thus decrease flood risks and supply water during drought periods. However, large amounts of water are lost by evaporation, which markedly affects reservoirs’ function of ensuring water availability. In Egypt, about 20.0% of the country's Nile share (12.1 to 15.4 billion m<sup>3</sup>) are lost annually by evaporation from Lake Nasser. The floating covers, i.e. spheres, shade the water surface and act as a physical barrier that decreases energy flux into the water, thus decrease evaporation. Studies that compare the evaporation suppression efficiency of the floating covers, over different climatic conditions, while considering its impact on the water ecology are limited.</p><p>A field experiment in an outdoor setting (class A-pan) was conducted for nine months (March to November) in two locations that vary in their climatic conditions, i.e. Aswan and Damanhur, representing northern and southern Egypt, respectively. The water surface was covered by white, black, or multicolor spheres, in addition to the control. Daily evaporation rate (ER), water temperature (WT), evaporation suppression efficiency (ESE), were determined. Moreover, the microalgae growth was measured as an indicator of water ecology.  </p><p>Obtained results revealed massive evaporation losses from the uncovered water surface (control) in Aswan location, in which the nine-month average was 2.25 times higher than in Damanhour location. The floating spheres reduced ER in both locations, in particular the white spheres. The ESE in Aswan was less than in Damanhour location. The ESE in Damanhour was 63.38, 58.13, and 54.8%, while in Aswan was 48., 42.5, and 41.6% for white, multicolor and black spheres, respectively. Floating spheres decreased WT in the morning and mid-day, while in the evening the control treatment was the coldest, indicating partial isolation of covered water surface. Irrespective of the spheres’ color, the spheres had no detrimental effect on microalgae growth, indicating enough light penetration and gas exchange through the gaps between spheres.</p><p>In conclusion, the floating spheres is an effective mean for evaporation suppression and its efficiency is dependent on the climate and spheres’ color. The ESE of spheres is lower in environments with lower relative humidity. The white spheres are recommended for evaporation suppression without negative impacts on microalgae growth which could be a viable indicator for the ecology of the water ecosystem. Further studies on larger water reservoirs are needed while considering several aquatic organisms.</p>


2019 ◽  
Vol 33 (10) ◽  
pp. 3513-3522
Author(s):  
Ali Mozafari ◽  
Bozorgmehr Mansouri ◽  
S. Farshid Chini

2018 ◽  
Vol 22 (7) ◽  
pp. 4015-4032 ◽  
Author(s):  
Milad Aminzadeh ◽  
Peter Lehmann ◽  
Dani Or

Abstract. The growing pressure on natural freshwater resources and the projected climate variability are expected to increase the need for water storage during rainy periods. Evaporative losses present a challenge for the efficiency of water storage in reservoirs, especially in arid regions with chronic water shortages. Among the available methods for suppressing evaporative losses, self-assembling floating elements offer a simple and scalable solution, especially for small reservoirs. The use of floating elements has often been empirically based; we thus seek a framework for systematic consideration of floating element properties, local climate and reservoir conditions to better predict evaporative loss, energy balance and heat fluxes from covered water reservoirs. We linked the energy balance of the water column with energy considerations of the floating elements. Results suggest significant suppression of evaporative losses from covered reservoirs in which incoming radiative energy is partitioned to sensible and long wave fluxes that reduce latent heat flux and thus increase the Bowen ratio over covered water reservoirs. Model findings were consistent with laboratory-scale observations using an uncovered and covered small basin. The study offers a physically based framework for testing design scenarios in terms of evaporation suppression efficiency for various climatic conditions; it hence strengthens the science in the basis of this important water resource conservation strategy.


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