The storms that have hit northern California and Nevada during the last 6 weeks have changed the drought map dramatically from earlier in the winter. Rain in northern California has filled reservoirs and sent rivers flooding for the first time since 2005 in several areas in both northern California and Nevada – including the Truckee River here in Reno and Sparks.

Hunter Creek flooding into the Truckee River at Mayberry foot bridge.

The Reno Gazette-Journal reported today that the drought in northern California is officially over. The categories “severe”, “extreme”, and “exceptional” drought, however, persist in southern California according to the US Drought Monitor. Parts of western Nevada still have persistent drought but in the lower drought categories of “Abnormally Dry” and “Moderate”.  Storms categorized as “Atmospheric rivers” that bring sub-tropical moisture to the west coast appear responsible for the intense rain storms that have changed the outlook in northern California and Nevada.

Drought Monitor Map as of 1-13-2017 (drought_monitor-20170110_west_trd)

While the picture can change again at a moments notice, there is still a chance that additional storms will keep the region ahead in precipitation for the entire water year and bring a partial respite from the effect of a persistent drought pattern that began in 2000. [The water year runs from October 1 to September 30.]

On December 1, 2016 Lake Tahoe was below its rim by 3″ even after a wetter than average October. No water had flowed to the Truckee River from Lake Tahoe since September 13th. Today, Lake Tahoe has risen to 8″ above its rim with the Truckee River flowing at 26 CFS (cubic feet per second). Natural outflow from the Lake could be greater than 26 CFS since the Lake Tahoe dam at the outlet of Lake Tahoe controls the flow of the river according to the Truckee River Operating Agreement. Flows from the two rainstorms that pushed the Truckee River above flood stage in Reno and Sparks and all the way to Pyramid Lake will have a substantial benefit to the overall health of the river. The long warning period (at least 4 days ahead of the event) that residents and businesses received were responsible for minimizing the damage to buildings and homes.

Truckee River at Rock Park in Sparks (flow is around 1,100 CFS)

Comparing December 1, 2016 to January 13, 2017 for a few sites at Lake Tahoe shows just how quickly a few storms have changed the picture at this point in the winter.

The percentages shown in the above table are relative to the date of the reading.  The percentage of snow water equivalent, for example, is based on what the long-term average snow water equivalent measured on that date.  So even a small snowpack in early December may show above the long-term average, but as the winter progresses with little or no precipitation the percentage would drop.  The percentages that really count are those of the final April 1 measurements when the snowpack has traditionally reached its maximum water content prior to significant snow melt beginning.

Truckee River outlet with Lake Tahoe below its rim in 2015-02-16

Lake Tahoe Dam at the outlet to the Truckee River February 2015

Related articles across the web

• “Atmospheric river” pounding NorCal, flooding Nevada
• What is an “atmospheric river”?
• Flooded California residents rescued as major storms recede – FOX NEWS WEATHER CENTER
• California snowpack surveyed as indicator of drought
• Extraordinary storms blitz West with 100-plus inches of snow, flooding rains

Truckee River along the “crooked mile” west of Idlewild Park in Reno.

Flood waters in the Truckee River appear to have crested in downtown Reno earlier this morning (1-9-2017). The Vista Gauge¹ in east Truckee Meadows shows the river just reached its crest and is falling. Flood waters are continuing to rise, however, further downstream at Wadsworth and Nixon, right at Pyramid Lake.

The flood water crest is gradually moving downstream as the rain in the mountains lessens and temperatures drop. The three graphs show the Reno, Vista and Nixon Gauges. Nixon is more than 40 miles downstream of Vista.

Flood crest is past in downtown Reno. (click for full size)

Truckee River flood crest reached with decline beginning early morning of 1-9-2017. (click for full size)

Truckee River is still rising at Nixon on the Pyramid Lake Paiute Reservation early on 1-9-2017. (click for full size)

The storm did not appear to be quite as strong as forecast and the flood peaks in downtown Reno and Vista were slightly lower than forecast, but still the first significant flooding event in the Truckee Meadows since 2005.

¹[The Reno Gauge is located just downstream of the Sutro Street Bridge; the Vista Gauge is located at the Reno-Sparks Waste Water Treatment Plant. All Truckee River gauges are operated by the US Geological Survey and run continuously reporting river flow.]

Flooding due to the approach of a warm storm system forecast to bring rain to the Sierra and western Nevada is forecast for the upcoming weekend. The map below shows potential flood areas where the red indicates worse flooding and yellow moderate flooding. Flooding is expected in downtown Reno, but the greatest potential for loss will be in the Sparks industrial area east of McCarran Boulevard to Vista and southward to Rattlesnake Mountain. The SE Connector Road construction adds an unknown dynamic to the potential flooding so residents and businesses should take every precaution. The Cities of Reno and Sparks are urging people to stay away from the areas should flooding occur.

See the Truckee Meadows Flood Management Authority’s website for the latest information.

Flood potential for weekend storm (click for full size)