Drinking water reservoir resiliency in a changing climate

: (Alternative Format Thesis)

Abstract

Reservoirs are a vital part of water infrastructure; however, they face worsening water quality due to anthropogenic climate change. Management and mitigation methods exist to resolve current water quality problems, but there is a lack of research on their future viability. This PhD research explores how reservoirs will respond to climate change, if artificial destratification systems will be effective in the future, and what tools reservoir managers can use to identify at-risk reservoirs. A monomictic (i.e., mixed once annually), drinking-water-supply reservoir that experiences hypoxia and manganese release from sediment was modelled. This reservoir was forced with future climates to see how these problems will develop. Under future projections with greater emissions, the modelled reservoir stratification experienced significant increases in duration and strength. This indicates that reservoirs will face issues in the future from changes to stratification including increased anoxic periods. Many reservoirs make use of artificial destratification systems to improve water quality; these interventions could improve resilience. Two such aerated reservoir systems were modelled under future climates. Neither was found to fully mix (i.e., destratify) the reservoirs though at least one system reduced the stratification strength. As these interventions are not always successful, better planning is required for their long-term viability. Different methods were explored that allowed reservoir managers to identify and/or design for reservoirs at-risk from stratification and changes to water clarity. These shifts in water quality and related risk were quantified by Lake Number and Osgood Index. Deeper reservoirs with larger mean depths and smaller surface areas were shown to be stratified for longer and more intensely. Results can help manage and plan for intervention and land management practices to improve resilience to climate change. This doctoral research is innovative in its 1) exploration of certain reservoir stratification implications for water quality 2) predictive assessment of implications of future climates and corresponding management tools using 3) a novel combined approach of field investigation and modelling. Multiple avenues about how reservoirs will respond to climate change and how these issues may be predicted and prevented were explored. In conclusion better planning and more extensive observations will be needed to ensure adequate future water quality, ecosystem health and sustainable water resources.

Date of Award	4 Dec 2023
Original language	English
Awarding Institution	University of Bath
Supervisor	Jun Zang (Supervisor), Lee Bryant (Supervisor), Danielle Wain (Supervisor) & Rupert Perkins (Supervisor)