Climate change has driven multidecadal declines in lake levels in central Alberta, Canada

Abstract

Timoney, KP. 2024. Climate change has driven multidecadal declines in lake levels in central Alberta, Canada. Lake Reserv Manage. 40:205–220. This study examined water level data from 5 lakes in central Alberta to determine the timing and rates of change and to identify the causes for those changes. Over the past century, the estimated average levels of Beaverhill and Cooking lakes declined ∼3 m. Highest lake levels were observed ca. 1902–1904. Lake levels varied widely over the decades, punctuated by periods of high or low water conditions embedded within the longer term declines. Over the past 50 yr, average rates of lake drawdown were as follows: Miquelon −6.8 cm/yr, Cooking −4.4 cm/yr, Beaverhill −4.4 cm/yr, Hastings −0.9 cm/yr, and Ministik −0.7 cm/yr. Over time, annual temperature, evaporation, and net evaporation increased while annual precipitation, runoff, and Palmer Drought Severity Index (PDSI) decreased. Annual precipitation was significantly correlated with the levels of all 5 lakes, and with annual runoff and PDSI. Net evaporation was significantly correlated with temperature, runoff, PDSI, and the levels of all lakes but Ministik. Annual runoff was significantly correlated with the levels of all 5 lakes and PDSI. Conversely, neither annual temperature nor evaporation was correlated significantly with the annual lake levels. Annual levels of all 5 lakes were significantly correlated with each other. The lake level declines are part of a larger pattern of declining levels observed in other lakes in western North America over many decades. In central Alberta, data from several sources indicate accelerated rates of drawdown since the late 1970s to early 1980s at some lakes and accelerated declines since the mid to late 1990s at other lakes.