Chesapeake Bay River Input Monitoring Program

The USGS Chesapeake Bay River Input Monitoring (RIM) Program was established to
quantify loads and long-term trends in concentrations of nutrients and
suspended material entering the tidal part of the Chesapeake Bay Basin from its
nine major tributaries. These nine rivers account for approximately 93% of the
stream flow entering Chesapeake Bay from the non-tidal part of its watershed.
Results of the RIM program are being used by resource managers, policy makers,
and concerned citizens to help evaluate the effectiveness of strategies aimed
at reducing nutrients and sediment entering Chesapeake Bay from its
tributaries.

Water samples are collected upstream of the transition area between the tidal
and non-tidal regions of the nine rivers (Figure 1). This transition zone
historically has been referred to as the "Fall Line" for the many sets of falls
and rapids that are found at this point on the rivers. Below the Fall Line in
the tidal areas of these rivers, tides can transport water, nutrients, and
suspended material from downstream, making it difficult to determine the cause
of any observed changes. Because water-quality samples are collected above the
influence of tides, any observed changes in nutrients or suspended material can
be attributed to upstream causes.

[Summary provided by the USGS.]