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Effect of submerged, freshwater aquatic macrophytes and littoral sediments on pan evaporation in the Lake Balaton region, Hungary

Author:
Anda, A., Simon, B., Soos, G., Teixeira da Silva, J.A., Kucserka, T.
Source:
Journal of hydrology 2016 v.542 pp. 615-626
ISSN:
0022-1694
Subject:
Myriophyllum spicatum, Najas marina, Potamogeton perfoliatus, air, evaporation, evapotranspiration, freshwater, growing season, lakes, littoral zone, macrophytes, sediments, solar radiation, water temperature, Hungary, United States
Abstract:
The evaporation (Ep) of a US Class A pan (C) with submerged, freshwater aquatic macrophytes (Potamogeton perfoliatus, Myriophyllum spicatum and Najas marina), hereafter macrophytes (Ps) and a sediment-covered bottom (S) was measured in Hungary during 2014–2015 using reference E of Shuttleworth (Eo) and Penman-Monteith crop reference evapotranspiration (crop ETo). There were two main climatic controls affecting variation in E: direct (air and water temperature) and indirect (wind-mediated change affecting the penetration of sunlight; precipitation inflow, impacting plant emergence). Lower seasonal mean Ep rates of 2.75±0.89, 2.83±0.91and3.06±1.14mmday−1 were observed in C, S and Ps, respectively, during the wet 2014. In the 2015 season, higher overall daily mean Ep rates for C, S and Ps were 3.76±1.3, 4.19±1.34and4.65±1.52mmday−1, respectively. A comparison of US Class A pan Ep containing macrophytes/sediments with that of a standard US Class A pan showed that pan coefficients (Kap and Kas) might allow for more accurate on-site lake E estimates. In 2014, seasonal mean Kas and Kap were 1.04±0.14and1.09±0.18, respectively. Slightly higher Ka values were observed during the warm and dry 2015 (Kas: 1.15±0.22; Kap: 1.26±0.23). A Ka value greater than 1 indicates that the Ep of a US Class A pan containing macrophytes and sediment is always higher than that of C. The calculated Eo overestimated measured Ep of Ps during the course of this study. During the warm-dry growing season, crop ETo was closest to Ep of Ps. Empirical coefficients can be useful for estimating E of lakes with submerged macrophytes more precisely. The accuracy of the estimate of Keszthely Bay’s E improved by 9.85% when Ka was determined on site.
Agid:
5564941