Dry Creek Watershed Assessment and Indicator Report

The Dry Creek watershed spans the communities of Roseville, Rocklin, Loomis, Granite Bay, and many parts of unincorporated Placer County northeast of Sacramento. The watershed has historically provided spawning grounds for fall- run chinook salmon as well as steelhead. In the past 15 years, salmon counts have decreased drastically. Changes in marine conditions and food supply have played an important role in this decline. But changes within the Dry Creek watershed have also contributed. In response to these changes, the Dry Creek Conservancy (DCC), a local non-profit organization, has obtained funds from various state agencies to collect a large amount of physical and biological data on the watershed. OEHHA was asked to help the DCC and the regional watershed stakeholder organization, the American Basin Council of Watersheds, with the analysis of this data. We took on this project both to assist the local organizations in gaining a better understanding of the stressors in the watershed as well as to test a relatively new methodology for analyzing watershed data, the Stressor Identification (ID) method developed by the US Environmental Protection Agency. The Stressor ID approach was developed to assess conditions in the waterways and identify cause(s) of impairment. The results of the assessment and associated watershed indicator report are posted in this section of OEHHA’s website.

Background Information

The history of the Dry Creek watershed reflects the changes over the years within California as a whole. The region was heavily influenced by mining back to the Gold Rush. Placer and hard rock mining occurred throughout the watershed. Placer mine tailings can still be seen as small mounds alongside the tributaries, especially in the upper reaches of the watershed. Hard rock mines are found near Newcastle and Penryn. Large slabs of granite were mined in Rocklin (formerly known as Rockland) and used to build many historic buildings in San Francisco. Subsequent to the intense mining activity, farms within the watershed were among the most productive sources of stone fruits in the nation. Apricots, peaches, and plums were grown and shipped from the packing houses in Loomis to locations around the U.S. The last packing house in Loomis closed in 2002. Roseville began to urbanize more rapidly in the early 1990s, and earned national recognition at that time as one of the nation’s fastest growing cities. Today, much of the lower watershed is composed of densely populated suburbs. The upper portions, above Rocklin Road, still retain some of the historic rural character, being comprised primarily of rural residential areas. Some agriculture production including irrigated agriculture and livestock still remain in the upper watershed as well as the floodplain areas of the lower watershed.


The Dry Creek watershed


Stories from elderly watershed residents as well as local records indicate that fall-run salmon were historically abundant in Dry Creek tributaries. Dry Creek used to be ‘dry’ in the summertime but the life history of fall run Chinook salmon is well adapted to the intermittent nature of foothill waterways. A number of non-profit organizations, primarily the Dry Creek Conservancy (DCC), but also others, recognized the valuable aquatic resources that were threatened by the impacts of urbanization. They began counting salmon carcasses and redds (nests) in the 1990s. Over time, they received a number of grants to study in greater detail the conditions in the waterways that might be contributing to the apparent decline in the salmon population.

The data used in the OEHHA assessment comes primarily from the DCC, but also from other sources, as shown in Table 1 below. The Dry Creek Conservancy collected multiple types of data, including instream physical habitat, water quality parameters (conventional and contaminants), benthic macroinvertebrate data, and chinook salmon carcass, fish, and redd counts. In addition, OEHHA collected additional data on land use, sediment quality, sediment toxicity, pyrethroid pesticides, and geomorphologic characteristics. Data on such factors as precipitation and stream flow have been gathered from various public agencies at the local, state, and national levels. Lastly, to help substantiate the analysis of the data collected, previous published reports on the Dry Creek watershed were reviewed. The reports varied from habitat assessments to hydrology/geomorphology analyses of the watershed. Table 2 provides a list of reports that were used.

Table 1. Selected Stressors in the Dry Creek Watershed and Number of Years of Data Collection


Metrics Type

Metrics Measured


Dry Creek Conservancy

Biological measurements

Fall-run chinook salmon fish counts


Benthic macroinvertebrate measures

Water quality

Conventional water quality constituents


Metals, nutrients, pesticides, organic contaminants

Total suspended solids

Physical habitat

Physical habitat characteristics



Landscape influences

Impervious cover


Land uses

Sediment Quality




Physical Habitat

% Silt, Sand, Fine Gravel


City of Roseville

Physical Habitat




Physical Habitat



Selected List of Reports used in the Dry Creek Watershed Assessment.

  • Ayres, E., Knapp, E., Lieberman, S., Love, J., Vodopals, K. 2003. Assessment of Stressors on Fall-Run Chinook Salmon in Secret Ravine (Placer County, CA). MS Thesis, Donald Bren School of Environmental Science and Management, UC Santa Barbara.
  • Bishop, D. 1997. An Evaluation of Dry Creek and its Major Tributaries in Placer Couty, California. M.S. Thesis. California State University, Sacramento.
  • Li, S. and W. Fields. 1999. Assessments of Stream Habitat in Secret Ravine. Report to the Dry Creek Conservancy.
  • Swanson, M. 2000. Reconnaissance Hydrology and Geomorphology, Study of Secret Ravine, Placer County, California, with Emphasis on Habitat Conditions for Fisheries. Report to the City of Roseville, Swanson Hydrology & Geomorphology. Santa Cruz, CA
  • Titus, Rob. 2001. Memorandum on Perennial Rearing Habitat for Juvenile Steelhead in the Dry Creek Drainage(Placer County), California Department of Fish and Wildlife.
  • Vanicek, David C. 1993. Fisheries Habitat Evaluation, Dry Creek, Antelope Creek, Secret Ravine, and Miners Ravine, EIP Associates.

Watershed Indicator Report

The results of the Stressor ID effort are being organized into a watershed indicator report. The report will include chapters on the background and history of the watershed, biological indicators (fall-run chinook salmon and benthic macroinvertebrates), physical habitat stressors, water quality stressors, landscape sources of stress, as well as chapters on possible administrative responses. Each indicator will describe an important stressor or piece of the puzzle, what the data for this stressor revealed, why it is important, and technical details related to the analysis of the stressor. The indicator report is being written for a broad audience, but will also contain technical information to answer the questions of scientists and engineers.

The Indicators:



Benthic Macroinvertebrates

Benthic organisms, such as bugs and snails, are widely used as an indicator of the overall health of the aquatic ecosystem.

Dissolved Oxygen

Sufficient DO is one of the primary challenges of living in an aquatic environment and is particularly important for salmonids and sensitive BMIs.

Fall Run Salmon

Anadramous fish are important commercially and culturally. They are very sensitive to disturbance of their habitat and poor water quality.

Fine Sediments in Streambed

Large amounts of fine sediment in the streambed, also known as bedded sediment, reduces useable habitat for many aquatic organisms, most notably interfering with reproduction of salmonids.


High frequency and rapidity of short term changes in stream flow in response to storm events is known as flashiness. Highly flashy streams are affected by the erosive forces of water during storm events.

Instream Cover

Boulders, logs, and other natural features that can be used by fish and benthic macroinvertebrates to hide, rest, or hunt for prey. Often referred to as epifaunal substrate.

Instream Flow Diversity

The combinations of slow and fast moving water, as well as shallow and deep water, which provides BMIs and fish with different habitat types.


Metals are a common pollutant in urban waterways that can cause adverse effects at concentrations in the low parts per billion ranges.


Pesticides and pyrethroids in particular can be lethal to aquatic organisms at very low concentrations.


Aquatic organisms have a temperature window in which they can survive. Changes in stream corridor and watershed land use can alter water temperature.

Total Suspended Solids

Suspended solids cause water to become cloudy; impairing photosynthesis needed to support algae and plant growth, scarring the gills of aquatic organisms, and reducing the ability of young salmon to find food.

Urban Development

Urban land uses, and impervious cover in particular, alters the hydrologic cycle within the watershed and can adversely affect aquatic life.

Draft indicator chapters will be posted here as they become available. We welcome feedback from stakeholders within the watershed, scientists involved in the use of watershed indicators, those using the Stressor ID methodology, and all other interested parties. You can offer comments and suggestions by contacting Barbara Washburn, Ecotoxicology Program, OEHHA.