Sediment and Nutrient Assessment Program (SNAP)

SRBC's Sediment and Nutrient Assessment Program sampling network is an integral part of the Chesapeake Bay Program’s Non-tidal Water Quality Monitoring Network. The SNAP network consists of 26 sites monitored for various nitrogen and phosphorus species and suspended sediment. Data are used to quantify the amount of nitrogen, phosphorus, and suspended sediment transported at each site and to calculate trends in loads and concentrations. The Chesapeake Bay Program Quality Assurance: Nontidal Water Quality Monitoring Program web page provides a means to explore the network and the results of a variety of data analyses.

Sampling Sites

Begun in 1984, the initial Sediment and Nutrient Monitoring Program (SNAP) network consisted of two mainstem sites on the Susquehanna River and 10 tributary sites. Since 1989, several modifications to the network were made including adding 20 sites as part of the CBPO non-tidal water quality monitoring network. The current SNAP network consists of six sites on the mainstem of the Susquehanna River and 20 tributary sites. The 26-site network contains five sites in New York, 20 in Pennsylvania, and one in Maryland.


  • Concentration: amount of a constituent per volume water typically milligrams per liter
  • Load (aka Flux): actual mass of the constituent being transported in the water column past a given point over a specific duration of time, expressed in units of mass/time
  • Yield: the load divided by the acres within the watershed above the monitoring sites, expressed as pounds or kilograms per acre
  • Trend: measure of the change in load or concentration over a given time period
  • Weighted Regressions on Time, Discharge, and Season (WRTDS): USGS model used to calculate concentrations, loads, and trends
  • Flow Normalization: a method utilized by WRTDS to remove the effects of stream flow on constituent loads and concentrations

Monitoring Sites in the Susquehanna River Basin