ESTIMATION OF LAKE EVAPORATION FROM A SHALLOW LAKE IN CENTRAL SWEDEN BY OXYGEN-18

✍ Scribed by R. K. SAXENA

• Publisher: John Wiley and Sons
• Year: 1996
• Tongue: English
• Weight: 556 KB
• Volume: 10
• Category: Article
• ISSN: 0885-6087
• DOI: 10.1002/(sici)1099-1085(199610)10:10<1273::aid-hyp459>3.0.co;2-y

✦ Synopsis

Lake evaporation has been estimated for a shallow lake using a combination of water and isotope mass balance, accounting for the isotopic non-steady state of lake water. The main feature of the isotope method is that inflows need not be measured. Knowledge of their isotopic content is sufficient. Oxygen-18 content, i.e. (d80), of lake water, inflows and outflow was measured on a weekly basis, whereas for precipitation it was monitored daily. The discharge from the lake was also recorded daily. Lake water level, relative humidity, air, and lake water surface temperatures were recorded by a logger. The weather data were recorded on a small island in the lake. It was observed that the lake is isotopically well mixed. Furthermore, the atmospheric moisture was not always in isotopic equilibrium with the precipitation. Daily lake evaporation was estimated as an average of six to eight days depending upon the field logistics. Lake evaporation varied from 0.6 to about 54mm day during the experimental period. It was found that evaporation estimates are very sensitive to small variations in 6 0 of lake evaporate. Induced changes of 10% in d80 of lake evaporate caused errors in evaporation estimates of 9-31%, while similar induced changes in S " 0 of inflows caused errors of 8-18%. Thus, an accurate experimental determination of 6'*0 of lake evaporate is relatively more important.