Mountain Lake Evaporation: A Comparative Study between Hourly Estimations Models and In Situ Measurements

The quantification of evaporation is very important for water resource management, determination of water availability and environmental modeling. Evaporation (E) is a key component of the hydrological cycle, which becomes more relevant under a changing climate scenario, where increases in temperature and E are projected on a regional scale. This study evaluated the hourly applicability of 21 methods to estimate E in a mountain lake. Models were grouped as combination, solar radiation-temperature and mass transfer methods. Estimated E by all models were compared to three measurement campaigns with an eddy covariance system in Lake Laja during the month of January (22 to 28), March (17 to 23) and November (09 to 15) of 2016. The average evaporated water during the measurement sessions were 3.40, 3.38 and 1.89 mm d(-1), respectively. Best model performance was obtained with models whose main E principles are heat flow and water vapor flow. The best performance in this group was the Penman model using a calibrated wind function with a determination coefficient (R-2) of 0.91, Nash-Sutcliffe coefficient (NS) of 0.9, and index of agreement (W) of 0.98. Comparing daytime and nighttime hours, it was found that the daytime E in the lake is best explained by the product of the vapor pressure deficit and wind speed, while the nighttime E was explained by the flow of heat in the water. The results highlight the importance of the analysis of diurnal dynamics of water flux and energy stored in water to better understand the E in water bodies.