Preparing the Rinko oxygen sensor for deployment off Glenbrook, NV (Photo credit: Brant Allen; Hand model: Katie Webb).

Deep Lake Oxygen

Close to the deepest part of Lake Tahoe, a set of temperature sensors and a dissolved oxygen sensor are quietly gathering data that will give us vital information on how the water quality in Lake Tahoe will change in the coming decades. The 20 temperature sensors are spaced out from the bottom of the lake to within a few meters of the surface, while the dissolved oxygen sensor sits immediately above the lake bottom. Every 30 minutes a measurement is taken and recorded internally. Every 6 months TERC’s boat crew returns to the site, retrieves the instruments, downloads the almost 1 million data points, recalibrates the instruments and then returns them to the lake.

Dissolved oxygen is the most critical water quality variable. The rate at which the deepest parts of the lake loses dissolved oxygen will determine how many years it may take for a dead zone to form in the bottom of the lake. With sufficient mixing, this may never occur, but the extent of mixing may change with a changing climate. Using these data, our models can be refined to better predict the types of processes responsible for mixing, the amount of oxygen that they can transfer, and the rate at which microbial processes in the lake are consuming oxygen.    

This project is funded through philanthropic gifts.

Temperature and dissolved oxygen at the bottom of Lake Tahoe at 444 m depth. Increase in water temperature is due to geothermal heating. Decline of oxygen is due to microbial activity. Fluctuations in both are believed due to internal wave motions and bottom currents.