Spring Fever? Climate Change And Water Quality In Our Local Lakes

Abstract

Eutrophication, a state in which a body of water becomes over-enriched with nutrients, remains one of the biggest water quality problems both in the United States and globally. Although nutrient pollution that causes eutrophication is regulated in the United States under the Clean Water Act (CWA), eutrophication remains a significant threat. Continued land-use change, internal regeneration of nutrients, and climate change all continue to contribute to nutrient loads that lead to eutrophication. This thesis is comprised of two chapters that aim to address the interplay between external and internal nutrient sources in lakes in the face of climate change. In the first chapter I examine how climate change impacts the internal nutrient cycling in two neighboring lakes in western Washington (USA). I found that climate variability can drive the internal regeneration of phosphorus in lakes that exhibit summer anoxia. This implies that climate change has the potential to increase nutrient loads in highly productive lakes, thereby increasing the risk of eutrophication in these systems in spite of control on external nutrient inputs. In the second chapter, I review the Clean Water Act and the policy tools implemented under it by which we manage external nutrient inputs. I found that the Clean Water Act is very good at addressing easy-to-identify point sources of nutrient pollution, but is much less effective at addressing diffuse, nonpoint sources. These results suggest that in order to maintain acceptable water quality in the future, we may need to be more aggressive with nonpoint source pollution that we currently are, particularly for productive lakes that exhibit summer anoxia. This information may also help managers allocate resources for nutrient control and identify lakes that are particularly at risk of eutrophication into the future.