Lake Tahoe Tributary Monitoring

Science Center Objects

The Lake Tahoe Interagency Monitoring Program (LTIMP) is an essential part of integrated science in the Lake Tahoe Basin and has provided long-term, consistent, reliable, and accessible tributary monitoring data for decades.

Map of Lake Tahoe with Lake Tahoe Interagency Monitoring Program Sites
Lake Tahoe with Lake Tahoe Interagency Monitoring Program sites and monitored basins. (Public domain.)

Deteriorating water quality and clarity in Lake Tahoe prompted the initiation of environmental programs in the Lake Tahoe basin. Water-quality data, especially nutrient and sediment data, for streams and ground-water aquifers that discharge to Lake Tahoe are needed to document the local and regional effectiveness of environmental programs and to assure compliance with California and Nevada water-quality management programs.  The Lake Tahoe Interagency Monitoring Program (LTIMP) was started in 1979 to help understand why clarity was declining in Lake Tahoe. Currently, LTIMP stream monitoring is a partnership between USGS, UC Davis, the Tahoe Regional Planning Agency, Lahontan Regional Water-Quality Control Board, and the California Tahoe Conservancy. 

Currently, water managers in Lake Tahoe are concerned about

  1. current tributary nutrient and suspended sediment concentrations and loads (status),
  2. assessing trends in nutrient and sediment concentrations and loads (trends), and
  3. what factors influence the observed status and trends.

USGS Nevada Water Science Center scientists are collecting streamflow and water-quality data at pertinent Lake Tahoe tributaries to estimate nutrient and sediment loads to the lake and assess trends in stream water quality. Within the Lake Tahoe watershed:

Streamflow and stage are measured at 9 gages in 8 basins 
Site names below are linked to available data.

Water quality is monitored at 8 sites in 7 basins 
Site names below are linked to available data.

Water-quality samples are collected during routine visits, storm events, and snow-melt runoff. As samples are collected, they are analyzed for 

Water-quality sample from Incline Creek near Crystal Bay, Nevada during a storm event
Water-quality sample from Incline Creek, Nev., during storm event (Public domain.)
  • temperature,
  • specific conductance,
  • pH (quarterly),
  • dissolved oxygen (quarterly),

Samples collected are analyzed at the laboratory for

  • fine sediment,
  • turbidity,
  • nitrogen,
  • phosphorus, and
  • suspended sediment.

Turbidity and temperature are monitored continuously at 5 of the water-quality sites. 
Site names below are linked to available data.

    General Creek, CA with graph of discharge and turbidity
    Left: Water-quality sonde at General Creek, CA. Right: Discharge and turbidity at General Creek, CA. (Public domain.)