Publication Summary

This report presents results of an analysis of water quality monitoring data from the Nooksack River at Brennan and at North Cedarville. Fecal coliform bacteria, the biggest contributor to poor water quality in the lower Nooksack River among the constituents we monitor, have declined dramatically during the past 20 years. There were indications that major sediment contributions to the lower river have also declined. However, nitrogen concentrations were much higher at the lower station than at the upper and concentrations may be increasing. Sediment additions from smaller sources in the reach may also be increasing.

Among the 62 long-term stations monitored by the Washington State Department of Ecology Freshwater Monitoring Unit are 16 sets of upstream and downstream stations that delineate stream reaches. Stations at the Nooksack River at Brennan and at North Cedarville comprise one of these sets. This report is the first in a series that presents results of an analysis of water quality monitoring data from these 16 stream reaches.

The lower Nooksack River is a success story for water quality management. Fecal coliform bacteria (FC), the biggest contributor to poor water quality in the lower Nooksack River among the constituents we monitor, have declined dramatically during the past 20 years. There were indications that major sediment contributions to the lower river have also declined. However, nitrogen concentrations were much higher at the lower station than at the upper, and concentrations may be increasing. Sediment additions from smaller sources in the reach may also be increasing.

The successful reductions in FC concentrations are particularly commendable given the increases in human and dairy cow populations in the reach since 1980. Vigilance will be necessary to ensure concentrations stay low and eutrophication does not increase in the face of continuing population pressures.