SIMULATING HYDROLOGIC AND WATER QUALITY IMPACTS IN AN URBANIZING WATERSHED¹

Abstract

The Hydrologic Simulation Program‐Fortran (HSPF) was calibrated and used to assess the future effects of various land development scenarios on water quality in the Polecat Creek watershed in Caroline County, Virginia. Model parameters related to hydrology and water quality were calibrated and validated using observed stream flow and water quality data collected at the watershed outlet and the outlets of two sub water sheds. Using the county's Comprehensive Plan, land use scenarios were developed by taking into account the trends and spatial distributions of future development. The simulation results for the various land use scenarios indicate that runoff volume and peak rate increased as urban areas increased. Urbanization also increased sediment loads mainly due to increases in channel erosion. Constituent loads of total Kjeldal nitrogen, orthophosphorus, and total phosphorous for Polecat Creek watershed slightly decreased under future development scenarios. These reductions are due to increases in urban areas that typically contribute smaller quantities of nitrogen and phosphorous, as compared to agricultural areas. However, nitrate loads increased for the future land use scenarios, as compared to the existing land use. The increases in nitrate loads may result from increases in residential land and associated fertilizer use and concurrent decreases in forested land. The procedures used in this paper could assist local, state, and regional policy makers in developing land management strategies that minimize environmental impacts while allowing for future development.

Impact Assessment of Climate and Land-Use Changes on Flooding Behavior in the Upper Ciliwung River, Jakarta, Indonesia

“…Rising urbanization would lead to an increase in the extent of impervious lands, resulting in more severe flood events. These results are comparable with those from Im et al [39] in the Polecat Creek watershed in Caroline County, Virginia, and Hejazi and Markus [40] in Northeastern Illinois. The increase in flood peaks due to urban expansion is also discussed by Du et al [11], wherein they revealed that impervious land in the Qinhuai River basin, China, will increase from 3% to 31% by 2018, resulting in an increase in daily peak discharge of approximately 14%.…”

Hydrologic impacts of climate and land-use change on Namnam Stream in Koycegiz Watershed, Turkey

“…HSPF has been widely applied in watersheds with diverse geographic characteristics and is commonly used to characterize watershed processes and stream hydrology (Im et al 2003;Ribarova et al 2008) to evaluate the hydrologic and water quality impacts of land-use changes (Hunter and Walton 2008), and to explore effects of climate change (Albek et al 2004). …”

“…Similarly, livestock grazing and dairies may increase the presence of fecal bacteria (Bach et al 2002), provoke erosion problems, and increase stream turbidity (Strunk 2003). Conversion of agricultural areas, forests, grass, and wetlands to urban areas leads to large proportional increases in land imperviousness in the form of roofs, sidewalks, roads, parking lots, and turf grass that can dramatically alter the natural hydrologic condition within a watershed (Im et al 2003). The outcome of this alteration is typically reflected in increases in the volume and rate of surface runoff and decreases in groundwater recharge and base flow.…”

Managing the Effects of the Climate Change on Water Resources and Watershed Ecology

“…The bibliography provided by developers contains more than 300 entries. The performance of SWAT and HSPF were compared by several authors (Im et al, 2003;Nasr et al, 2004;Saleh and Du, 2004;Sigh, et al, 2004), where both models were applied to the same watersheds. In these studies, both models produced comparable results; however HSPF produced slightly more accurate results in river discharges, whereas SWAT was better in reproducing the nutrient loads.…”