In hot water: Climate change, water level, and the future of water quality in lakes

Climate change is the dominant global environmental problem of our time, and lakes are sensitive sentinels of change (Williams et al. 2009). Nevertheless, 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 and variation in evapotranspiration and precipitation, however, are predicted to disproportionately affect lakes and as a result, lake water levels will change substantially across the world. The impact of changes to lake water levels and how this affects the lake ecosystem is still poorly understood. This lack of understanding and evidence undermines our ability to manage effectively our lakes in the future.

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. 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, are rarely 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 PhD will combine fieldwork, high resolution automated monitoring, and numerical modelling to study the impacts of changing water level on vertically resolved temperature and oxygen dynamics of lakes. As such, the project offers an exceptional training and development opportunity in a full range of techniques used in modern lake science. Automated sensors for temperature, oxygen, and

depth will be deployed in two beautiful study sites, Airthrey Loch on the University of Stirling campus and Elterwater, a small productive lake in the English Lake District. The student will additionally carry out a placement at the UK Centre for Ecology & Hydrology (Lancaster), one of the largest groups of lake scientists in the UK, to conduct a summer field campaign at Elterwater, collecting weekly samples of water quality data. These data will supplement existing historic datasets for Elterwater. The high-resolution monitoring data will be used to calibrate and validate lake physics and lake oxygen models (for example, Burchard et al. 1999; Livingstone & Imboden, 1996). Modelling studies will explore the impacts of a wide range of water level change and air temperature change scenarios on stratification and bottom water deoxygenation in both lakes. Further modelling will then focus on the role of lake shape and depth. The impact of geographical region – indicative of the background climate – will also be investigated to determine which types of lakes in which parts of the world will be most susceptible to reductions in water quality driven by changes in water level.

Further information on the project, skills and training opportunities can be found here: https://iapetus2.ac.uk/how-to-apply/.

In order to address historical imbalances in the higher education sector, Iapetus is committed to recruiting a diverse, representative community of researchers in Environmental Science. The DTP has developed an Equality, Diversity and Inclusion policy to further this. This includes the Widening Participation Scheme, which identifies Home applicants from underrepresented groups. Also, we are pleased to introduce the IAPETUS2 Diversifying Talent Scholarship Scheme, a separate competition designed for those from underrepresented groups. For more, please see the Iapetus website.