Date of Award

1-1-2011

Document Type

Campus Access Thesis

Department

Geography

First Advisor

Kirstin Dow

Abstract

Responding to climate change entails potential trade-offs between adaptation and mitigation options available to cities. It is important to understand the implications of different water management efforts on these options, especially within the context of a changing climate, because of the potential interactions among various efforts. In particular, it is imperative to understand these implications because of the rapid growth of urban populations. In 2008, the number of Americans living in urban areas topped 80% (CIA World Factbook 2010). Urban areas have multiple options for adaptation and mitigation but with consequences for water quantity and quality.

I modeled the impact of two urban development scenarios--an urban densification scenario and an increased perviousness scenario-to understand the impacts of potential climate changes and urban population growth on land use, and therefore on water quantity and quality in the Florence, South Carolina watershed. A BASINS/HSPF model of the Great Pee Dee River, South Carolina was calibrated for water quantity and quality, specifically flow, water temperature, dissolved oxygen, biochemical oxygen demand, and total ammonia-nitrogen. This model was used to represent the effects of various urban growth patterns and climate change scenarios on indicators of watershed health. Analysis of multiple downscaled GCMs for the southeastern United States indicates that climate change could have a wide range of impacts on precipitation:

from 15% less to 10% more precipitation by the end of the 21st century than is currently experienced (Maurer et al. 2007). I used downscaled climate data to model these different urban growth scenarios under three different climate change scenarios, representing a range of possible future climate conditions, to understand the combined impacts of these scenarios. I statistically evaluated the implications of these scenarios on the water quantity and quality, as well as analyzing the adaptation and mitigation options and the resulting tradeoffs associated with adjusting to climate change in urban areas.

Findings indicate that the combined impacts of urbanization and climate changes on urban water quantity and quality in Florence, South Carolina are greater than the impacts of either of these changes alone. Although increased pervious area within urban regions helps to counteract these impacts, it does not fully compensate for the impacts of climate changes. The contributions of urban change are sometimes larger than the contributions of climate change to these impacts and vice versa.

The impacts of these changes on water quality constituents are negative: causing increases in water temperature, BOD and TAN and decreases in dissolved oxygen, with few exceptions. However, there is some seasonal variation in the statistical significance of these impacts. Total ammonia-nitrogen in particular shows significant increases during the summer months under all scenarios. BOD values were very low during the summer months, resulting in statistical values that were not significant across this season. Although the scenarios resulted in increases in water temperature, these changes were slight, with percent changes less than one percent. This was also true for TAN: percent changes were less than two percent. Tradeoffs between densification and increased perviousness, and therefore mitigation and adaptation, vary under different scenarios.

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