| Abstract: |
To help meet Federal and state mandates to regulate nutrient discharges, Maryland now requires that all Maryland municipalities prepare a non-point source discharge assessment as part of a Comprehensive Growth Plan. This mandate presents an ideal opportunity to integrate watershed science and management. State guidelines currently suggest using the Maryland Department of Planning (MDP) Non-Point Source Assessment Spreadsheet to downscale annual average predictions from the Chesapeake Bay Program’s HSPF Phase 4 model. The assessment tool is intended to help land managers minimize surface water quality impacts by providing nutrient load estimates under current and future land use scenarios. We implemented the MDP tool for a Maryland town, along with three watershed models, GWLF, SWAT, and the CBP-HSPF5, The differences in predicted water quality among alternative land use scenarios being considered by town planners (including a no change scenario) were small, especially compared to the variation among models in the predictions for any single scenario. In addition, all the models agreed that nutrient discharges originate primarily from outside the planning jurisdiction. Because of the dominance of external sources and the similarity among scenarios, the predicted impacts from non-point source pollution have had little influence on the Town’s land management decisions. |
