This project will use a combined monitoring and numerical modelling approach to investigate how changes in water level will impact temperature and oxygen dynamics, two critical components of lake ecosystems, in standing water bodies across the globe.
Our current understanding of climate change impacts on lakes is largely based on how atmospheric warming will lead to increased water temperatures and thermal stratification, and the consequences these changes will impose on the chemistry and biology in standing waters. Future changes in evapotranspiration and precipitation, however, are predicted to be much larger than those in air temperature and be more variable across the globe. As a result, lake water levels will change substantially across the world. Changing water extraction practices will also severely impact lake water levels, exacerbating climate-induced changes. The combined impact of these pressures on lake water levels and how this affects the lake ecosystem is poorly understood, yet we need this information for the effective management of our lakes in the future.
Water temperature has a huge influence on lake ecosystems as it is an important control on most biological and chemical rates and reactions. Similarly, the variation in temperature with depth – stratification – is of fundamental importance to the ecosystem, because it impacts rates of vertical mixing, particularly of oxygen, and hence influences whether bottom waters will become anoxic. The impacts of water level change on lake temperatures, stratification, and depth of surface mixing, have, though, been little investigated. This is despite the possible synergistic or antagonistic effects of a change in water level and a simultaneous increase in air temperature. Recent work has shown that even small, shallow lakes can experience complicated temperature and stratification changes on a daily basis (Anderson et al. 2017). Changes in water level could therefore affect temperature and stratification in a wide variety of standing water bodies. Ultimately, future variation in water level could have a profound influence on water quality worldwide. The impacts need to be understood in order to ascertain which lakes and regions are most at risk of a deterioration in water quality so that appropriate remediation measures can be employed. This project will use a number of different approaches to develop understanding of this global issue. It will investigate the influence of lake shape and depth as well as the overlying climate region on the fundamental physical processes, and use this understanding to predict how oxygen dynamics will be affected.