Tahoe Sierra snowpack well below average – March a critical month

The Truckee River near the California and Nevada state line - image - CC BY-NC-SA 4.0 Bob Tregilus Photography

According to the March 1 United State Department of Agriculture Nevada Water Supply Outlook Report, the current Tahoe Sierra snowpack is roughly 50 percent of average. Winter 2019/2020 snowpack in the Tahoe and Truckee basins ranks the sixth lowest in more than 40 years of Snow Telemetry or SNOTEL record keeping. In years that had less snow, strong precipitation during March was key to fending off drought.

Based on SNOTEL records, February 2020 was the driest on record at most of the sites in the eastern Sierra and the second driest at a handful of monitoring sites across northern Nevada. Nevada’s overall snowpack is a mix of good to abysmal.

Snowpack 2020 – Image – United State Department of Agriculture. From the Nevada Water Supply Outlook Report released on March 1.

The end of March is historically when Tahoe Sierra monitoring stations see peak snow levels, but the March 1 survey shows that some sites are literally bare.

Sites without snow include Tahoe City Cross and Fallen Leaf Lake (Tahoe Basin) and Spratt Creek (Carson Basin).

Leavitt Meadows (Walker Basin) “is holding onto a little snow, but also near melt out.”

The above sites were nearing record snow amounts at the same time last year.

An abandoned fishing boat far from the water line on the east shore of Walker Lake – image – CC BY-NC-SA 4.0 Bob Tregilus Photography

According to the Nevada Water Supply Outlook Report, strong precipitation during March in the Tahoe Sierra could yet raise snowpack levels near median values, but as of March 8, only one storm has hit the Sierra and long-range forecasts show a high potential for continued dry weather for the rest of March.

Water storage enables the timed release of water when needed to maintain healthy river flows. If the 2020 snowpack does not improve, the amount of stored water will be a critical factor for citizens and the environment, especially sensitive fisheries.

Image – US Department of Agriculture.

The Truckee River

The Truckee River is a 125 mile-long system of reservoirs and diversions. Provisions set forth in the Truckee River Operating Agreement govern operation of the vast system. Federal Water Master Chad Blanchard is based in Reno and manages diversions and reservoirs. On the Truckee, there are five bodies of water that help sustain river flow during dry periods.

These reservoirs and lakes are intended to mitigate the effects of flooding and provide recreational opportunities. The water master decides how much water to release and divert and when. Winter and spring are the seasons for water banking.

Five reservoirs are part of the Truckee River system. A closed river that runs 125 miles from Lake Tahoe to its terminus in Pyramid Lake – image – US Dept. of Agriculture.

Truckee River Diversions

The Truckee Meadows Water Authority appropriates more water from the river than any other entity. Eighty-five percent of the water consumed in the Reno/Sparks metroplex comes from the Truckee River.

Twenty miles east of Reno, since 1906, the Derby Dam has diverted water from the river just before it flows into Pyramid Lake. Since the diversion began, Pyramid Lake level has dropped roughly 70 feet. The appropriated water flows east through an earthen ditch or the Truckee Canal to Fernely and ultimately the Lahontan Reservoir. The Reclamation Act of 1902 stipulates the water be used for agriculture, but as residential development east of Reno and Sparks continues to grow, concerns have been raised that the diverted water will be used to support larger communities rather than crops.

The Truckee Canal (c. 1906) originates at the Derby Diversion Dam approximately 20 miles east of Reno-Sparks. The 31-mile long canal feeds water to agricultural areas east of the Dam in Fernley and the Lahontan Valley terminating at the Lahontan Reservoir. Part of the Newlands Project (Reclamation Act of 1902) the canal was designed to “irrigate more than 400,000 acres of land in western Nevada using the combined waters of the Truckee and Carson Rivers.” Historically, the
canal operates at a flow rate of between 300 to 1,000 cubic feet per second. Since its construction Pyramid Lake has lost roughly 70 feet of elevation and Winnemucca Lake (formerly Mud Lake) dried up – image – CC BY-NC-SA 4.0 Bob Tregilus Photography

Near Mogul, west of Reno on the south side of the river, the Steamboat Ditch diverts water that winds through the Truckee Meadows picking up pollutants and non-point source runoff as it flows though neighborhoods and golf course ponds. The ditch joins Steamboat Creek on the east side of the Truckee Meadows and reenters the river in Sparks after effluent from the regional sewage treatment facility discharges into it. The treated effluent improves the water quality in Steamboat Creek.

On the north side of the river, the Highland Ditch diverts water in Verdi, west of Reno. The ditch twists through the city and flows through several golf courses, a reverse siphon at the University of Nevada Reno and ultimately reenters the river after mingling with water in the Sparks Marina. The ditch discharges a water laden with sediments and pollutants back into the river in Sparks.

Stampede, Boca and Prosser Reservoirs

A dam on the Little Truckee River created Stampede Reservoir in 1970. The US Bureau of Reclamation manages the dam and the outflow that winds its way to Boca Reservoir before being released into the Truckee.

Recent concern over the potential for a large flood event to overflow the dam on Stampede Reservoir prompted the federal government to raise the dam by 11.5 feet. Construction took 2 years and was completed in 2018.

The US Bureau of Reclamation constructed the Prosser Creek Dam in 1959, which created Prosser Reservoir, a regulated feeder to the Truckee River.

Ten Years of Stampede Reservoir Water Level History

Ten years of Stampede Reservoir water level data – image – US Department of Agriculture

Below, you can see the wide-ranging variability of when the reservoir fills and empties. Each graph represent one water year that starts on November 1.

Stampede Reservoir taken on August 9, 2014 when the water level was 60 feet below where it is today – image – Brian Bahouth