Field staff collecting data during Upper Patuxent Watershed assessment


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Upper Patuxent River Watershed Field Studies

The Upper Patuxent River watershed is one of close to a dozen watersheds in Anne Arundel County, Maryland, that ultimately flows into the Chesapeake Bay.  The Upper Patuxent basin drains approximately 22,500 acres, is subdivided into 19 subwatersheds, and contains approximately 130 miles of perennial stream reaches.


As part of its National Pollutant Discharge Elimination System (NPDES) municipal separate storm sewer system (MS4) permit, Anne Arundel County was required to perform an assessment of land-use conditions within the Upper Patuxent watershed.  This assessment was intended to help the County determine where to focus resources, to maintain healthy waterbodies and to determine where changes are needed to improve overall watershed health and quality.


LimnoTech’s role in this process was to provide the County with seamless, accurate, up-to-date data and information for the 19 subwatersheds within the Upper Patuxent River basin. The County then incorporated these data into a suite of models to perform an in-depth assessment of the watershed.  The major data elements that LimnoTech collected for the County were:

Physical Habitat Condition Assessments:  LimnoTech staff utilized Maryland Physical Habitat Index (MPHI) protocols to characterize over 130 miles of perennial streams within the watershed. All field data were collected using handheld computers with GIS/GPS capabilities.

Base Flow Sampling:  LimnoTech performed dry weather base flow sampling from perennial reaches within all 19 subwatersheds to characterize water quality. Sampled parameters included nutrients, metals, field parameters, and bacteria.

Stormwater Facility Mapping: LimnoTech developed an inventory of all urban stormwater facilities and agricultural best management practices (BMPs) within the watershed.  These data were combined with other existing data to create a geodatabase of all urban stormwater facilities and agricultural BMPs.

Rosgen Level I and II Classifications: From the field assessments performed, LimnoTech assisted the County in developing broad Rosgen Level I classifications for all stream reaches.


Upon project completion, LimnoTech will provide the County with final GIS and database deliverables that will be used for additional modeling, ranking and decision-making. LimnoTech streamlined several elements in the data collection approach, enabling a more efficient and accurate data collection and assessment process.  LimnoTech is providing guidance on watershed management planning, assessment, modeling, and BMP implementation. 

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