Modelling Lake Titicaca's daily and monthly evaporation

• Published in: Hydrology and earth system sciences 2019-02, Vol.23 (2), p.657-668
• Main Authors: Pillco Zola, Ramiro, Bengtsson, Lars, Berndtsson, Ronny, Marti-Cardona, Belen, Satge, Frederic, Timouk, Franck, Bonnet, Marie-Paule, Mollericon, Luis, Gamarra, Cesar, Pasapera, Jose
• Format: Article
• Language: English
• Subjects: Adaptation; Climate change; Convection; Daily; Earth and Related Environmental Sciences; Earth Sciences; Energy management; Estimates; Evaporation; Evaporation estimation; Forecasts and trends; Geovetenskap och miljövetenskap; Global temperature changes; Global warming; Heat; Heat balance; Heat balance method; Heat storage; Hydrological research; Hydrology; Hydrometeorology; Lake evaporation; Lakes; Mass transfer; Meteorological measurements; Meteorological parameters; Modelling; Monthly; Natural Sciences; Naturvetenskap; Oceanografi, hydrologi och vattenresurser; Oceanography, Hydrology, Water Resources; Sciences of the Universe; Surface temperature; Temporal resolution; Water balance; Water balance (Hydrology); Water resources; Water resources planning; Weather
• ISSN: 1607-7938; 1027-5606; 1607-7938
• DOI: 10.5194/hess-23-657-2019

Lake Titicaca is a crucial water resource in the central part of the Andean mountain range, and it is one of the lakes most affected by climate warming. Since surface evaporation explains most of the lake's water losses, reliable estimates are paramount to the prediction of global warming impacts on Lake Titicaca and to the region's water resource planning and adaptation to climate change. Evaporation estimates were done in the past at monthly time steps and using the four methods as follows: water balance, heat balance, and the mass transfer and Penman's equations. The obtained annual evaporation values showed significant dispersion. This study used new, daily frequency hydro-meteorological measurements. Evaporation losses were calculated following the mentioned methods using both daily records and their monthly averages to assess the impact of higher temporal resolution data in the evaporation estimates. Changes in the lake heat storage needed for the heat balance method were estimated based on the morning water surface temperature, because convection during nights results in a well-mixed top layer every morning over a constant temperature depth. We found that the most reliable method for determining the annual lake evaporation was the heat balance approach, although the Penman equation allows for an easier implementation based on generally available meteorological parameters. The mean annual lake evaporation was found to be 1700 mm year−1. This value is considered an upper limit of the annual evaporation, since the main study period was abnormally warm. The obtained upper limit lowers by 200 mm year−1, the highest evaporation estimation obtained previously, thus reducing the uncertainty in the actual value. Regarding the evaporation estimates using daily and monthly averages, these resulted in minor differences for all methodologies.