Evaporation from a temperate closed-basin lake and its impact on present, past, and future water level

Authors: XIAO, KE - University Of Minnesota; GRIFFIS, TIMOTHY - University Of Minnesota; Baker, John; BOLSTAD, PAUL - University Of Minnesota; ERICKSON, MATT - University Of Minnesota; LEE, XUHUI - Yale University; WOOD, JEFFREY - University Of Missouri; HU, CHENG - Yale University; NIEBER, JOHN - University Of Minnesota

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2018
Publication Date: 3/22/2018
Citation: Xiao, K., Griffis, T.J., Baker, J.M., Bolstad, P.V., Erickson, M.D., Lee, X., Wood, J.D., Hu, C., Nieber, J.L. 2018. Evaporation from a temperate closed-basin lake and its impact on present, past, and future water level. Journal of Hydrology. 561:59-75. https://doi.org/10.1016/j.jhydrol.2018.03.059.
DOI: https://doi.org/10.1016/j.jhydrol.2018.03.059

Interpretive Summary: Lakes provide many environmental, economic, recreational, and aesthetic benefits to society that can be adversely affected by climate change. One such lake is White Bear Lake in Minnesota, where water levels decined precipitously duringthe decade from 2003-2013, for reasons that were not well understood. The two major components of the water balance of a lake are precipitation and evaporation. The first is well-measured, the second is not. We set up two eddy covariance towers on the lake to measure evaporation over a three year period. We found that annual evaporation varied substantially from year to year, surprisingly due primarily to differences in the severity of winter. Specifically, the length of the ice-free period was the primary determinant of annual evaporation losses. The data that were colected were used to test a mdoel of lake evaporation that was then used to predict long-term changes in lake evaporation, both retrospectively using recorded climate data, and into the furutre, using predicted changes in climate due to greenhouse gas forcing. The results suggest that annual evaporation will increase at an average rate of 1.4 mm per yr over the remainder of this century, primarily due to shorter winters. By the end of the century this would mean annual evaporative losses neraly 17% greater than current average annual rates, which could have a serious negative impact on lake level and lake health.

Technical Abstract: Lakes provide enormous economic, recreational, and aesthetic benefits to citizens. These ecosystem services may be adversely impacted by climate change. In the Twin Cities Metropolitan Area of Minnesota, USA, many lakes have been at historic low levels and water augmentation strategies have been proposed to alleviate the problem. For example, the water level of White Bear Lake (WBL) declined 1.5 m during 2003–2013 for reasons that are not fully understood. This study examined current, past, and future lake evaporation to better understand how climate will impact the water balance of lakes within this region. Evaporation from WBL was measured from July 2014 to February 2017 using two eddy covariance (EC) systems to provide better constraints on the water budget and to investigate the impact of evaporation on lake level. The annual evaporation for years 2014 through 2016 were 559±22 mm, 779±81 mm, and 766±11 mm, respectively. The larger evaporation in 2015 and 2016 was caused by the combined effects of larger average daily evaporation and a longer ice-free season. The EC measurements were used to tune the Community Land Model 4 – Lake, Ice, Snow and Sediment Simulator (CLM4-LISSS) to estimate lake evaporation over the period 1979–2016. Retrospective analyses indicated that WBL evaporation increased by about 3.8 mm yr-1. Using a business-as-usual greenhouse gas emission scenario (RCP8.5), lake evaporation was modeled forward in time from 2017 to 2100. Annual evaporation is expected to increase by 1.4 mm yr-1 over this century, which is largely driven by lengthening ice-free periods. These changes in ice phenology and evaporation will have important implications for the regional water balance, and water management and water augmentation strategies that are being proposed for these Metropolitan lakes.