and

CHEHALIS RIVER COUNCIL
417 N. Pearl St., Centralia, WA 9853

 

 

 

 

 

Stream Ecology

of the

South Fork Chehalis River Watershed

 

 

 

By

Abigail Leigh Brown

 

 

December 9, 2005

 

 

 

 

 

 

 

 

 

 

 

 

SUMMARY

 

            Declining water quality is occurring in the South Fork Chehalis River and its tributaries. This study evaluated near-stream and in-stream conditions in the watershed. There are major stream habitat and water quality problems occurring. Defined in the tables below are the specified issues. The situation presented in the South Fork watershed is a common one found near waterways in heavy agricultural and residential areas. The problems could be assumed to be linked to the land use, except the high pH, which is possibly an isolated occurrence. These issues, while common, still threaten the biological health and diversity of the South Fork Chehalis River and its tributaries. Human health, drinking water availability, wild salmon runs, wild animal presence, and future land use within the watershed could be threatened, if further restoration does not occur. Restoration efforts are occurring in the South Fork Chehalis Watershed by the Lewis County Conservation District. They are restoring riparian areas and creating Best Management Practices Plans for several agricultural operations.  The question still occurs: Why is the water quality still declining with all the agricultural restoration that is occurring in the watershed? It is possible, that other factors could be influencing the high amount of fecal coliform found in the stream, perhaps failing septic tanks or increased wildlife usage of the waterway.

 

 

Table 3. Stream Habitat Problems in the South Fork Chehalis Watershed

 

STREAM HABITAT PROBLEMS

POSSIBLE CAUSE

1

Lack of in-stream woody debris

Debris torrents, Historical splash dams, Historical removal of log jams, Lack of trees along the stream bank

2

Increased erosion

Lack of riparian zone, High road density, Heavy agricultural use, Agricultural animals in the waterway

3

Fish passage impediments

Culverts, Dams, Lack of pool and riffle habitat, Low in-stream flows

4

Lack of riparian cover

Forestry, Agriculture, Human influence

 

Table 4. Water Quality Problems in the South Fork Chehalis Watershed

 

WATER QUALITY PROBLEMS

POSSIBLE CAUSE

1

High temperature

Lack of trees along the stream bank,

Excessive sedimentation

2

Low dissolved oxygen

High temperature, Lack of trees along the stream bank, Excessive sedimentation

3

High fecal coliform counts

Agricultural animals in the waterway

4

Low pH

Acidic conditions in the waterway

5

Low pollution intolerant benthic macro invertebrate counts

Declining water quality

6

Excessive sedimentation

Agricultural animals in the waterway, High road density, Lack of trees along the stream bank

7

Low Stream Flows during the Summer Months

High water use within the basin

8

Closure to additional Water Rights

Lack of sufficient in-stream flows during summer months to sustain wild salmon runs.

 

 

RECOMENDATIONS

 

            There is a large amount of stream ecology data that has been collected in the Chehalis River watershed, yet it is uncommon for some of the smaller sub-basin to have summaries completed on the micro-ecology of one stream or river. This report compiles existing data of the South Fork Chehalis River and Stillman Creek area that pertains to water quality and stream habitat. It is the first step in a multi-step development process of creating a stewardship program for the community members of the South Fork Chehalis Watershed. Information in this report can be used as baseline data for the community. The community can then creates and implement (with the assistance of CRC) a prioritized restoration program. Eventually, the stewardship program can be used a model to implement in other sub-basins. The following is a step-by-step recommendation list for that process.

 

  1. Compile all existing data on water quality and stream habitat issues into a research report format. Identify major ecological problems.
  2. Develop outreach materials for the general public, including a pamphlet and power point presentation.
  3. Hold public workshops to present findings and brainstorm on priority issues and potential solutions
  4. Organize a stewardship group.
  5. Meet with stewardship group to begin developing prioritized projects.
  6. Seek out funding and resources to complete prioritized projects.
  7. Implement prioritized projects.
  8. Use model in other watersheds.

 

 

ADDITIONAL RESEARCH NEEDS

 

There are also many future research need for the South Fork Chehalis River and Stillman Creek watersheds. Additional research would allow for many questions to be answered, and accent any restoration processes that may occur.

 

1. Additional pH monitoring in the South Fork Chehalis River and Stillman Creek.

2. Research identifying invasive vegetation in the watershed.

3. Historical mapping of the watershed.

4. Identifications of sources of fecal coliform in the watershed.

5. Identification of wetland classification in the watershed.

6. Evaluation of current forest practices used in the headwaters of the watershed.

7. Detailed stream flow study during the summer months.

8. Application of TMDL suggestions for improvement in the sub-basin.

 

 

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