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Evaporation from partially covered water surfaces
Author(s) -
Assouline S.,
Narkis K.,
Or D.
Publication year - 2010
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/2010wr009121
Subject(s) - evaporation , materials science , potential evaporation , diffusion , range (aeronautics) , mechanics , flux (metallurgy) , environmental science , evaporative cooler , thermodynamics , composite material , physics , metallurgy
Evaporative losses from large water bodies may exceed 20% of water used in irrigated agriculture, with losses from reservoirs estimated at 50% of storage capacity. Prominent among proposed methods to curtail these evaporative losses are various forms of partial covers placed over water surfaces. Studies show that evaporation through perforated covers and from partially covered water surfaces exhibit nonlinear behavior, where rates of water loss are not proportional to uncovered surface fraction and are significantly affected by opening size and relative spacing. We studied evaporation from small water bodies under various perforated covers, extending the so‐called diameter law to opening sizes in the range of 10 −5 to 10 −1 m. Contradicting claims concerning effects of openings and their arrangement on performance of evaporation barriers are analyzed on per opening and on per area mass losses. Our results help reconcile some classical findings invoking detailed pore‐scale diffusion and simple temperature‐based energetic behaviors. For fixed relative spacing, area‐averaged evaporative flux density remains nearly constant across several orders of magnitude variations in opening size. For the scale of the experimental setup, we predict relative evaporation reduction efficiency for various configurations of perforated evaporation barriers.