| Abstract: |
The Mass Department of Environmental Protection's GIS Program is using the digital terrain data from MassGIS' 1:5000 OrthoPhoto project with the ESRI ArcHydro toolset to accurately delineate public water supply watersheds and protection zones. High quality digital elevation models are created using mass elevation points, hard and soft breaklines, and detailed drainage networks that are extracted from the MassDEP 1:12000 Wetlands datalayer. The delineated basins are then mapped and compared to the existing contours and elevation data, problem areas are flagged for field checking, additional streams and ponds are extracted from the wetlands data and added to the 1:2500 Hydrography datalayer and protection zones are modified to match the new watersheds and hydrography. Field checking is needed because of issues relating to manmade modifications to the landscape or natural featuers that have no outputs. About 35% of the active water supply watersheds have been mapped, work is ongoing. |