Sediment and Turbidity Monitoring

The following streams in the Nooksack River were Clean Water Act 303(d) listed as Category 5 during 2008 for fine sediment (DOE 2008): North Fork Nooksack River (NFN), South Fork Nooksack River (SFN), Racehorse Creek (NFN tributary), Howard Creek (SFN tributary), and Anderson Creek (mainstem tributary). In addition to these listings, habitat modeling indicates that sediment load is limiting population productivity for ESA-listed spring chinook in Glacier Creek, in Racehorse and Bar Creeks (North Fork tributaries), and in the North Fork downstream from the confluence with the Middle Fork. More recent data suggests that many other river segments and tributaries exhibit substantial fine sediment exceedances including the Middle Fork Nooksack River. 

The hydrology and sediment dynamics of the Nooksack River basin is of great interest to many users and interest groups including members of the Nooksack Indian Tribe, Lummi Nation, agricultural, residential, and industrial users, and those agencies responsible for managing water resources within the Nooksack River basin including Whatcom County, the City of Bellingham, Washington Department of Ecology, City of Lynden, City of Ferndale, and Public Utility District No. 1. Recent climate trends and future climate change scenarios suggest that altered streamflow and sediment dynamics will adversely impact all of these users. Not only will changed sediment dynamics impact fish habitat and survival, increased sediment loads will adversely impact water withdrawal for irrigation, industrial, and municipal uses. These impacts will exacerbate existing and future legacy impacts caused by land management.  Of particular interest to the Nooksack Indian Tribe is how changes in streamflow and sediment dynamics will affect survival of salmonids in the Nooksack River as well as what tools we can implement now to address these impacts.

What contributes to high turbidity and SSC levels?

High fine sediment (sand, silt and clay fractions) loads can be attributed to both natural and management related (i.e., land use) sources. Both the NFN and MFN are glacially fed and have abundant natural sources of sediment that are readily available to streams, particularly during snow melt and glacier melt periods. The SFN is also lined with structurally weak glacial deposits that frequently fail and slide into the channel, usually during the rainy season. Many of these are deep seated landslide features.  Some of the human-caused and natural sources that contribute to high levels of suspended sediment include:  

  • Agricultural runoff
  • Urban and residential development and runoff
  • Landslides
  • Glaciers
  • Loss of riparian vegetation
  • Disconnection of the channel from its floodplain
  • Timber harvesting
  • Forest roads

The goals of the sediment monitoring project are to:

  •  Develop annual and seasonal sediment discharge estimates and budgets for the three forks (South Fork, Middle Fork, and North Fork Nooksack Rivers) and mainstem Nooksack River;
  •  Assess existing conditions and monitor changes in turbidity and sediment through time. 
  • Identify sediment sources and compare relative to location, land management, mass wasting, and degree of active glaciation;
  •  Inform adaptive management of the WRIA 1 Watershed Management Project and WRIA 1 Salmon Recovery efforts;
  • Characterize the effects of turbidity and sediment on aquatic life;
  •  Evaluate the effectiveness of watershed restoration actions, such as forest road maintenance, abandonment and decommissioning, riparian planting and engineered logjam projects;
  •   Inform watershed restoration of areas for potential restoration projects.

Field Methods

Turbidity is the measure of clarity of a water column and suspended sediment concentration (SSC) is the weight of fine sediment (sand, clay, or silt) in milligrams that is in a 1 liter bottle of water (mg/L). Turbidity is measured continuously at four sites throughout the Nooksack watershed.  Water samples are then collected at each location to measure the SSC and calculate sediment loads. Two locations with bridge access allow for a cross-section of samples to be collected across the channel. An ISCO automated sampler was installed at the Cedarville Bridge that automatically collects water samples from the river when turbidity levels reach a certain threshold. During a flood event, the sampler can collect many samples over the course of the event in order to create a relationship between streamflow, turbidity, and suspended sediment. In addition, water samples are collected at 12 other locations throughout the watershed to assess sediment contribution of major tributaries, both glaciated and non-glaciated.  Water samples collected from the ISCO are then sent to the Cascade Volcano Observatory for analysis. 

Data collected through this project is shared with stakeholders in hopes of finding solutions to reducing sediment loads in the river (Curran et al., 2018).  Data is also shared in order to help calibrate and validate hydrological models that forecast the effect of climate change on sediment dynamics (Knapp, 2018). 

Turbidity and sediment monitoring sites

Tom Cline and Rich Auguston install the DTS-12 turbidimeter at Cedarville Bridge in Deming.


Curran, C.A., Anderson, S.W., Foreman, J.R., and Beaulieu, J., 2018, Suspended sediment concentration and loads in the Nooksack River Basin, northwest Washington: U.S. Geological Survey data release,

Knapp, Kevin, “The Effects of Forecasted Climate Change on Mass Wasting Susceptibility in the Nooksack River Basin” (2018). WWU Graduate School Collection. 807.