Evaporation Suppression from Water Reservoirs using Floating Covers - Insights and Surprises from a Field Study
Abstract
Water storage in arid regions has been continually practiced for millennia, and it is expected to increase with projected climate variability and expansion of agricultural lands. Evaporative losses may account for non-negligible fraction of the water stored in reservoirs in arid regions. A cost effective and scalable method for reducing such losses is to use floating covers. We report a field study aimed to examine evaporation suppression characteristics under natural conditions using eight identical ponds (14 m2 and 1.5 m deep at EAWAG near Zurich, Switzerland). We used white and black 200 mm disks of PEVA foam (15 mm thick) to cover six ponds leaving two uncovered for control. We monitored energy balance, water losses, radiation and temperature in each of the ponds during the fall of 2017 and summer of 2018. Results indicate different thermal regimes and evaporation rates from the different covers and uncovered with evaporation suppression of 40% in fall (low rates) and 85% in summer. The modified energy balance resulted in having highest surface water temperatures for black covered ponds during all the seasons, but overall higher vertical temperature profiles at the uncovered ponds during hot season (temperature differences up to five degrees at the bottom). Surprisingly, the difference in evaporation rates between the black and white covers was not very large despite differences in energy balance components. Presence or absence of algae had an additional effect on energy balance and evaporation and indicates the relevance of ecological aspects on choice of optimal floating covers.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.H11S1712M
- Keywords:
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- 1803 Anthropogenic effects;
- HYDROLOGYDE: 1807 Climate impacts;
- HYDROLOGYDE: 1845 Limnology;
- HYDROLOGYDE: 1878 Water/energy interactions;
- HYDROLOGY