Lake Tahoe Atmospheric Deposition Study (LTADS)

This page last reviewed September 13, 2006

LTADS - Overview

Project Overview

Between the mid-1960s and the mid-1990s, the water clarity of Lake Tahoe decreased from 100 feet to 65 feet. To address this deteriorating environmental quality indicator, California's Lahontan Regional Water Quality Board (LRWQCB) and the Nevada Division of Environmental Protection (NDEP) are developing the Lake Tahoe Nutrient and Sediment Total Maximum Daily Load (TMDL). A TMDL is a water quality restoration plan designed to determine the ability of a body of water to accept contaminants without resulting in a reduction in water quality. Contaminants adversely affecting water clarity enter the lake via runoff containing sediments and nutrients, seepage of groundwater containing nutrients, shoreline erosion and direct atmospheric deposition.
To update estimates of the impact of atmospheric deposition to the lake, the ARB conducted a comprehensive field study. The objective of this study was to better quantify the atmospheric deposition of nutrients and particulate matter directly to the lake. The study also provided insights into the relative contribution of local and regional sources of nutrients and PM to the declining water clarity of Lake Tahoe.
The study was primarily designed to answer specific informational needs of the TMDL and the Tahoe Regional Planning Agency. LTADS provided:
1) Improved estimates of the loading of nutrients and particulate matter from atmospheric deposition to Lake Tahoe.

2) Improved attribution of the in-basin and out-of-basin sources of these materials.

3) Assessment of the effect of ozone concentrations on forest health.

4) Confidence levels associated with these estimates and assessments.
The study provided data and information for developing the Technical TMDL. The implementation plan for the TMDL will identify means of achieving the necessary load reductions and a discussion of the effects of control programs already in place and potential future regulations to further reduce the inputs of materials adversely affecting the water clarity of Lake Tahoe.

For questions concerning the Lake Tahoe Atmospheric Deposition Study, please contact:

Mr. Leon Dolislager
Research Division
California Air Resources Board
P.O. Box 2815
Sacramento CA 95812
(916) 323-1533