TRPA began monitoring perennial streams in 2009 to determine if TRPA thresholds for stream habitat are being met, and to detect changes in the overall condition of the Tahoe Basin's streams. Bioassessment, which uses benthic macroinvertebrates (BMI) and physical stream habitat to assess overall stream health, is used to monitor the Basin's streams. To obtain a stream health "score", the California Stream Condition Index (CSCI) is used. The CSCI is a model that compares the BMI found in sampled streams against the BMI expected to be found in pristine streams in the Sierra Nevada.

  • CSCI stream score greater than 0.92 = excellent health
  • CSCI stream score of 0.79 to 0.92 = good health
  • CSCI stream score of less than 0.79 = degraded health
Program Overview
Water Quality

TRPA's stream monitoring program uses the Surface Water Ambient Monitoring Program bioassessment protocol, which measures Benthic Macroinvertebrate (BMI) composition and physical stream habitat to assess overall stream health. BMI composition and habitat is compared against pristine streams using the California Stream Condition Index to determine the biotic integrity of streams. Probabilistic and targeted sampling is used to assess the overall health of Tahoe streams, changes in stream health over time, and to assess large scale restoration and BMP implementation projects. 20 probabilistic, one-time "status" sites are sampled per year, as well as 73 "trend" sites re-visited every four years. Only trend sites are displayed on this page. Status site information can be found at

To download all of the stream data on this page please see Tahoe Open Data.

Monitoring Sites

Select a Monitoring Site from the list or click a location marker on the map to explore.

TRPA is the lead implementer of the stream monitoring program. Lahontan Water Quality Control Board and Nevada Department of Environmental Protection help fund the program, while the California Department of Fish & Wildlife help train TRPA staff in protocols.

California Stream Condition Index manual
This document outlines what the California Stream Condition Index is and how it scores stream health.

Surface Water Ambient Monitoring Program - Bioassessment protocol
This document describes the protocol TRPA uses for collecting physical stream habitat data and macroinvertebrates.

TRPA Stream Monitoring Plan
This plan outlines why bioassessment was chosen as the indicator for stream health, sampling design, protocols used, etc.

Monitoring Site List
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