Non-Degradation Standard for Instream Flow
This indicator measures whether streamflows have been altered by diversions. Alteration of streamflow regimes, such as water diversions, can result in adverse impacts to stream habitat diversity, function, and productivity of aquatic ecosystems and organisms. Past streamflow diversions exist in the Tahoe Region for a variety of reasons including providing water for agriculture and sending water to communities outside the Tahoe Region. Regional policies are aimed at removing existing streamflow diversions and prohibiting new diversions. There is no active monitoring of streamflow diversions but new streamflow diversions are not permitted.
2023 Evaluation
- Status
- Implemented
Applicable Standard
F5: Until instream flow standards are established in the Regional Plan to protect fishery values, a non-degradation standard shall apply to instream flows.
Key Points
- No projects have been approved that allow diversions or reduce in-stream flow.
About the Threshold
- There are 63 tributaries that drain into Lake Tahoe, and one tributary that drains from the basin. The amount of water flowing through a stream is primarily dependent on the size of its watershed and the amount of precipitation within a given year. Streams provide critical habitat to a diversity of native and non-native fish populations and other riverine-dependent organisms. Historic logging, grazing, and land use interrupted the hydrologic integrity of many of the streams and tributaries draining into Lake Tahoe, and the results of these legacy activities are evident today. Alteration of stream flow regimes, such as water diversions, can result in adverse impacts to stream habitat diversity, function, and productivity of aquatic ecosystems and organisms. A component of the TRPA Regional Plan is to maintain a healthy functioning fishery through the conservation and restoration of natural flow regimes.
- Weather, climate patterns, geology, elevation, and topography all significantly affect stream flow characteristics. Historic channel modifications associated with logging activities and land use (e.g., dams, water extraction, and within-watershed diversions, urban development and infrastructure, flumes, stream channelization, and flood control impoundments) that preceded the 1987 Regional Plan altered stream channel structure and watershed-specific hydrology.
Rationale Details
- Implemented. Permits were reviewed to determine if any stream diversions were permitted and no new diversions were allowed. No permits have been issued that permitted new diversions.
Additional Figures and Resources
No photos available.
No documents available.