Using HSPF to evaluate stormwater Best Management Practices in the Charles River Watershed

Abstract

This thesis describes how the hydrologic computer model HSPF was used to model hydrologic and sediment transport in the Charles River Watershed and subsequently to evaluate stormwater management practices in the watershed. The thesis briefly describes the problem of stormwater pollution. It discusses U.S. federal laws, regulations and programs that are intended to address the issue, and then focuses on the state of Massachusetts. The Massachusetts Department of Envi­ronmental Protection (DEP) has recently issued Stormwater Management Standards, which are used as guidelines by Conservation Commissions throughout the state, and which will soon become part of the Code of Massachusetts Regulations, DEP's Stormwater Management Standards require the use of any number of Best Management Practices (BMPs) that will reduce the average annual load of total suspended solids (TSS) in stormwater by 80%. This thesis briefly describes some common BMPs and discusses the validity of using TSS as a target pollutant. The thesis then describes in detail how the HSPF computer model was calibrated to predict sediment washoff and transport in the Charles River Watershed. It, then shows how the model was used to test the effectiveness of DEP's Stormwater Management Standards. The Standards were applied to the town of Franklin in the lower part of the watershed by changing the land use in the town in order to simulate development. The solids load from this new development was then reduced by 80%. According to the model predictions, if the Standards are applied only to the part of the watershed that falls under the jurisdiction of the law, then there might be little improvement seen in the river, However, if the standards arc applied wherever development occurs in the town, there may be noticeable improvement in tho levels of TSS concentration in the Charles River.