Tuolumne Meadows Temporary Turbidimeter Installation

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This project will install a temporary water quality sonde at the outlet of Tuolumne Meadows to measure turbidity. It is part of the larger Restore Tuolumne Riverbanks project which includes investigations and restoration actions to assess and address development impacts and visitor use on the Tuolumne Meadows system. The installation will add an Aqua TROLL 600 multiparameter sonde with a turbidimeter probe to complement the existing turbidimeter at the Tioga Road gage to identify and isolate any turbidity sourced from within the meadow system. It will also measure temperature and conductivity. The sonde will be deployed on the river bottom and anchored to a boulder in the location of an existing stage logger. The sonde will not be visible from the riverbank. No ground disturbance will occur for the deployment.

The site is located in designated wilderness.

The installation would be installed onsite for five years.

Justification: This project would aid understanding of water quality impacts on the Tuolumne River. These include those outlined in the Tuolumne River Plan such as river widening, failure of riparian willow recruitment, extensive areas of bare soil, head cuts in the river, and incision of the meadow surface. Many of these are suspected to be a direct result from human related impacts like social trails, old roads, and drainage features. These features result in large amounts of meadow soil deposition into the river, typically impacting water quality parameters including turbidity. This project would quantify these impacts with the purpose of protecting water quality, and assist in identifying necessary meadow hydrology restoration.

Additionally, roadwork on the Tioga Road along the Tuolumne Meadow corridor will commence during summer 2021 and continue through 2022, and will include new parking areas, closure and restoration of old parking areas, and updates to the road drainage infrastructure. This work will include the use of heavy machinery along the road corridor for tree cutting, excavating, paving, and alteration to culvert size and location. Installation of a turbidimeter will help monitor impacts of this construction on sediment and contaminant contributions to the Tuolumne River.


June 2021: Aqua TROLL 600 multiparameter sonde.

Ongoing: Site visit approximately every 6-months to download the data and replace batteries.