Abstract
Assessing climate change (CC) impacts on urban watersheds is difficult due to differences in model spatial and temporal scales, making prediction of hydrologic restoration a challenge. A methodology was developed using an autocalibration tool to calibrate a previously developed Storm Water Management Model (SWMM) of Difficult Run in Fairfax, Virginia. Calibration was assisted by use of multi-objective optimization. Results showed a good agreement between simulated and observed data. Simulations of CC for the 2041–2068 period were developed using dynamically downscaled North American Regional CC Assessment Program models. Washoff loads were used to simulate water quality, and a method was developed to estimate treatment performed in stormwater control measures (SCMs) to assess water quality impacts from CC. CC simulations indicated that annual runoff volume would increase by 6.5%, while total suspended solids, total nitrogen, and total phosphorus would increase by 7.6%, 7.1%, and 8.1%, respectively. The simulations also indicated that within season variability would increase by a larger percentage. Treatment practices (e.g., bioswale) that were intended to mitigate the negative effects of urban development will need to deal with additional runoff volumes and nutrient loads from CC to achieve the required water quality goals.
Highlights
Historical evaluations of the U.S climate (1950–2009) revealed significant temperature increases for most US cities, which was attributed to climate change (CC) as opposed to “heat island” effects caused by urban development [1]
The objective of this study is to evaluate the impacts of CC on an urban watershed including the impact on runoff volume, peak flow, and water quality (Total Suspended Solids, TSS; Total Nitrogen, TN; and Total Phosphorous, Total Phosphorus (TP)), using a Storm Water Management Model (SWMM) calibrated with a robust autocalibration tool, R
TP values were significantly different at 95% confidence interval, which implies that TP may be more sensitive to CC
Summary
Historical evaluations of the U.S climate (1950–2009) revealed significant temperature increases for most US cities, which was attributed to climate change (CC) as opposed to “heat island” effects caused by urban development [1]. 30% of the urban areas exhibited a significant increase in extreme precipitation. Najjar et al [3] found that, in the mid-Atlantic region, precipitation magnitude and intensity, CO2 concentrations, sea level, and water temperatures are likely to increase by the end of the 21st century. These predicted increases in rainfall magnitude and intensity could cause infrastructure failures due to increased runoff volumes and rates [4,5,6,7], overwhelming systems designed for much less. Madsen and Figdor [8] found that CC in the
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