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.

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.

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.

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.

Location	12/01/16		01/13/17
Lake Tahoe water surface elevation	6222.74		6223.66	0.92 ft rise
Truckee River Flow at Reno (changes daily)	247 CFS		1,590 CFS
Truckee River Flow at Tracy (changes daily)	296 CFS		2,420 CFS
Truckee River Flow at Pyramid Lake (changes daily)	112 CFS		3,350 CFS
Ward Creek SNOTEL site (848) at 6745 ft: Snow water equivalent in snowpack	4.5 inches	136%	25.5 inches	189%
Ward Creek SNOTEL site (848) at 6745 ft: Snowpack depth	24 inches	–	93 inches	–
Ward Creek SNOTEL site (848) at 6745 ft: Total precipitation	25.8inches	194%	72.4	243%
Mt Rose Ski Area at 8801 ft: Snow water equivalent in snowpack	4.2 inches	81%	40.4 inches	246%
Mt Rose Ski Area at 8801 ft: Snowpack depth	22 inches	–	153 inches	–
Mt Rose Ski Area at 8801 ft: Total precipitation	17.6 inches	193%	49.3 inches	219%

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.

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