Indicator
Stream Habitat Condition
2019 Evaluation
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This indicator measures the amount of excellent, good, and marginal habitat in streams of the Tahoe Region. Stream habitat includes features such as gravel, boulders, large wood, pools, riffles, and riparian vegetation that provide habitat for a wide variety of organisms. Streams are critical to the Tahoe Region's water cycle by feeding freshwater to lakes and ponds, recharging groundwater, providing habitat for a wide variety of aquatic and terrestrial organisms, and corridors fish and wildlife migration. Past practices such as gravel mining, logging, and development along stream corridors negatively impacted fish habitat. Regional programs such as removing impassable culverts and stream habitat restoration projects aim to improve stream habitat. The health of Tahoe's streams is assessed by evaluating physical stream habitat (large woody debris, boulders, etc.) and benthic macroinvertebrates (mayflies, stoneflies, etc).

Miles Of Stream Habitat In Excellent Stream Condition.jpg
Status

Average California Stream Condition Index (CSCI) scores of all trend sites for each time period. Site scores are put into three different categories of excellent (CSCI >0.92), good (CSCI = 0.79-0.92), or marginal (CSCI <0.79). The California Stream Condition Index (CSCI) measures the biological health of streams by assessing the community of benthic macroinvertebrate in perennial streams.

2019 Evaluation
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Status
At or Somewhat Better Than Target
Trend
Moderate Improvement
Confidence
Moderate
Applicable Standard
F1-F3: As indicated by the Stream Habitat GIS data, amended May 1997, based upon the re-rated stream scores set forth in Appendix C-1, of the 1996 Evaluation Report, maintain: F1) 75 miles of excellent stream habitat, F2) 105 miles of good stream habitat, F3) 38 miles of marginal stream habitat.
Key Points
  • Over the last 30 years, stream restoration projects have been completed through the Environmental Improvement Program (EIP) that were identified in the 1982 Threshold Environmental Assessment such as removing fish passage barriers, improving in-stream physical habitat (large wood, pools, etc.), reducing bank erosion, increasing stream shading, and removing flow diversions.
  • These EIP projects have allowed the Tahoe Region to meet its goal for stream habitat for the first time in 2020, with recent projects such as the Upper Truckee River Reach 5 project and numerous projects on Blackwood Creek putting the Region over the top for meeting the goal.
  • Between 2016-2019 EIP partners restored 14,680 linear feet of streams and enhanced 24,140 linear feet of streams.
  • While the overall amount of stream habitat has met the goal set in 1982, there are still numerous stream segments identified for restoration that still need to be completed such as removing the fish passage barrier at the mouth of Meeks Creek and restoring several sections of the Upper Truckee River. These projects will help move the Region further into attainment for stream habitat.
Evaluation Map
Description

Stream ratings as of 2020 for the Tahoe Basin. Stream ratings incorporate stream health indicators such as fish passage, in-stream habitat, macroinvertebrate diversity, among others. 

About the Threshold
Streams are critical to the Lake Tahoe Region's water cycle by feeding freshwater to lakes and ponds, recharging groundwater, providing habitat for a wide variety of aquatic and terrestrial organisms, and corridors fish and wildlife migration.
Past practices such as gravel mining, logging, and development along stream corridors negatively impacted fish habitat. The regional plan and partner regulations prevent the disturbance of streams and riparian areas today. Regional programs such as removing impassable culverts and stream habitat restoration projects aim to improve stream habitat.
Delivering and Measuring Success

EIP Indicators

Example EIP Projects

Monitoring Programs

Rationale Details
Using the most up-to-date methods and data, the stream habitat threshold is in attainment as of 2020. As of 2020, there are currently 113 miles of excellent stream habitat, 44 miles of good stream habitat, and 27 miles of marginal habitat. This exceeds the threshold goal for stream habitat set in 1982. While there are fewer miles of streams in good habitat than called for in 1982, this is because these streams instead are in the improved "excellent category". The Basin is exceeding its goal for the number of stream miles in excellent condition while staying under the maximum allowable miles of streams in marginal condition.

The overall miles of stream habitat assessed in 2020 is lower than the number of miles assessed in 1982 because updates in mapping technologies have revealed that some of the areas mapped as streams in 1982 are not actually streams, rather headwater areas or meadows with no defined stream channel.

More detailed methods can be found in the 2020 "SEZ Baseline Condition Assessment" document produced by TRPA. Several indicators were assessed to determine stream habitat condition including:
- biotic integrity (macroinvertebrates)
- fish passage
- physical stream habitat (boulders, woody debris, pools, riffles, etc.)
- habitat fragmentation (development in riparian areas)
- headcuts
- bank erosion
- channel incision
Following the completion of large stream restoration projects over the past 10 years, such as projects like Third Creek and the Upper Truckee River, many miles of stream habitat have been improved. Therefore, the trend is considered to be "moderate improvement".
Confidence Details
High. The most up to date methods and data have been used to assess stream habitat.
Moderate. While it is clear than many stream miles have been improved over the past 10 years, 2020 is the first year the scientifically-defensible data has been used to assess this indicator. Therefore, there is not a good history of data to assess trends.
Moderate.
Additional Figures and Resources

No photos available.

No documents available.

References

SEZ Baseline Condition Assessment - An assessment of the current conditions of Stream Environment Zones (SEZ) throughout the Lake Tahoe Basin. Tahoe Regional Planning Agency - Funded through a United States E.P.A. Wetlands Development Grant. December 15, 2020.