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Energy balance and evaporation loss of an agricultural reservoir in a semi‐arid climate (south‐eastern Spain)
Author(s) -
GallegoElvira B.,
Baille A.,
MartínGórriz B.,
MartínezÁlvarez V.
Publication year - 2009
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.7520
Subject(s) - advection , evaporation , arid , environmental science , energy balance , potential evaporation , flux (metallurgy) , atmospheric sciences , pan evaporation , hydrology (agriculture) , water cycle , annual cycle , climatology , meteorology , physics , geology , materials science , thermodynamics , ecology , paleontology , geotechnical engineering , biology , metallurgy
A typical agricultural water reservoir (AWR) of 2400 m 2 area and 5 m depth, located in a semi‐arid area (southern Spain), was surveyed on a daily basis for 1 year. The annual evaporation flux was 102·7 W m −2 , equivalent to an evaporated water depth of 1310 mm year −1 . The heat storage rate G exhibited a clear annual cycle with a peak gain in April ( G ∼ 45 W m −2 ) and a peak loss in November ( G ∼ 40 W m −2 ), leading to a marked annual hysteretic trend when evaporation (λ E ) was related to net radiation ( R n ). λ E was strongly correlated with the available energy A , representing 91% of the annual AWR energy loss. The sensible heat flux H accounted for the remaining 9%, leading to an annual Bowen ratio in the order of 0·10. The equilibrium and advective evaporation terms of the Penman formula represented 76 and 24%, respectively, of the total evaporation, corresponding to a annual value of the Priestley–Taylor (P–T) coefficient (α) of 1·32. The P–T coefficient presented a clear seasonal pattern, with a minimum of 1·23 (July) and a maximum of 1·65 (December), indicating that, during periods of limited available energy, AWR evaporation increased above the potential evaporation as a result of the advection process. Overall, the results stressed that accurate prediction of monthly evaporation by means of the P–T formula requires accounting for both the annual cycle of storage and the advective component. Some alternative approaches to estimating R n , G and α are proposed and discussed. Copyright © 2009 John Wiley & Sons, Ltd.