This web site was copied prior to January 20, 2005. It is now a Federal record managed by the National Archives and Records Administration. External links, forms, and search boxes may not function within this collection. Learn more.   [hide]
Link to USGS Homepage
Water Data
Maryland Flag
Delaware Flag
D.C. Flag
U.S. Flag
Real-Time Streamflow
Real-Time Ground-Water
Real-Time Water Quality
Real-Time Streamflow
Real-Time Ground-Water
Real-Time Water Quality
Washington, D.C.
Real-Time Streamflow
Real-Time Ground-Water
Real-Time Water Quality
Real-Time Streamflow
Real-Time Ground-Water
Real-Time Water Quality

News Release  

Featuring the latest information on ground-water and surface-water in the MD-DE-DC district.

National District Sites

Major Cooperators
Maryland Department of the Environment
Delaware Department of Natural Resources and Environmental Control
Maryland Department of the Environment
Delaware Geological Survey
Maryland Geological Survey
Chesapeake Bay Foundation
Aberdeen Proving Ground
Environmental Protection Agency
Dover Air Force Base
Maryland Department of Transportation
Washington Metropolitan Area Transit Authority
City of Baltimore
National Park Service
Interstate Commission on the Potomac River Basin
Air Force Research Labratory
Baltimore County
Patuxent Naval Air Station
U.S. Fish and Wildlife Service
 Online Publication - WRIR-00-4232
 Home >> District Publications >> Online Publication - WRIR-00-4232
Statistical Identification of Hydrochemical Response Units for Hydrologic Monitoring and Modeling in Maryland
By Stephen D. Preston 

>> View as HTML
>> Download WRIR-00-4232
     (1.5 Mb PDF Document)


In support of Maryland's efforts to develop statewide water-quality management plans, a statistical analysis was performed to identify a set of representative and relatively homogeneous areas referred to as Hydrochemical Response Units (HRUs). The State intends to select representative areas within each hydrochemical response unit for monitoring and model development, and then apply the model to the entire unit. To identify hydrochemical response units, cluster analysis was applied to 1,136 digitally defined watershed units. Basin characteristics including land cover, soil type, slope, and geology were determined for each watershed unit and a clustering algorithm was applied to the data sets. A total of 11 hydrochemical response units were identified by the analysis. Major features that were important in distinguishing different areas of the state include: 1) upland and lowland Coastal Plain settings, 2) igneous, shale, and carbonate geology; and 3) urban land cover. The hydrochemical response units described in this report are considered to be an initial classification of watersheds in Maryland that can be refined as geographic data sets are improved and additional hydrologic data are collected.


   National Sites   
USGS Water Resources Division MD-DE-DC
8987 Yellow Brick Road, Baltimore, MD 21237
Tel: 410-238-4200 | Fax: 410-238-4210
Last Modified Wednesday, October 6, 2004 by LL
USGS Privacy | Disclaimer | FOIA | DOI | 508