Precipitation and drought effects are not evenly distributed in Nevada

Precipitation and drought effects are not evenly distributed in Nevada

Precipitation and drought effects are not evenly distributed in Nevada.  The graph below (from the Natural Resources Conservation Service's SNOTeL sites in northeastern Nevada, for the upper Humboldt River Basin) shows that as we reach the end of February, the amount of water estimated to be in the snowpack is approximately two inches less than what we observed last year at this time.  A few definitions:  first, the water year begins on October 1st and ends on September 30th of the following year.  This corresponds with theoretical completion of a hydrologic cycle that spans a single year period, after evaporation and plants have depleted the maximum expected amount of water from the soil and deeper in the soil profile.  The water year designation always corresponds with the calendar year in which it ends (for example, we are in water year (WY) 2014, which began on October 1, 2013 and will end on September 30, 2014).   Another aspect of this that is important is the concept of snow water equivalent.  Snow is not 100% water--it contains air pockets and the crystals themselves don't allow for even packing. This means that 12" of snow is not the equivalent of 12" of water.  If we had a column of snow that was, for example, 12 inches deep and we melted it, the amount of water released would not rise to 12" above the measuring surface.  As you can see from the graph below, the Upper Humboldt River Basin appears to have more water in the snowpack this year than we saw in WY 2012 at this time and for the remainder of that year.   

Snow pack water equivalents for water year 2011 through current year. 

Currently nine counties in Nevada have been declared to be in a state of drought emergency (see previous posts and http://1.usa.gov/1fs5Dkx.   

Nevada's Emergency Conservation Cost-Share Program

Nevada's Emergency Conservation Cost-Share Program

The U.S. Department of Agriculture's Farm Services Agency is preparing a drought relief program to help farmers and ranchers who anticipate having so little water available that livestock, orchards and vineyards are likely to fail.  The program is available in Nevada counties classified as being in a drought emergency, including Churchill, Douglas, Elko, Eureka, Humboldt, Lander, Lyon, Mineral, Nye, Pershing, Storey, Washoe and Carson City.  This program supports up to 50% of costs associated with installing temporary measures to bring water to livestock and crops.  It supports up to 75% of costs for permanent improvements, such as deepening wells and installing pipelines. The program began accepting applications on February 23rd and will be open until April 25th.  For more information contact Annie Rossi at the Farm Services Agency (775-857-8500, or annie.rossi@nv.usda.gov).  Also, see http://1.usa.gov/1fs5Dkx. 

Definitions of drought

Definitions of drought:

We define drought in four general ways--hydrologic drought, meteorological drought, agricultural drought,  and socioeconomic drought.  Why the different categories?  Each represents a different effect.  For example, hydrologic drought represents the effects of drought on water availability from groundwater and surface water, including reservoirs.  Agricultural drought considers water availability in the soil to support crop growth.  Meteorological considers duration of periods from the last amount of precipitation that equaled or exceeded a specific threshold.  Finally, socio-economic drought focuses on the economic effects of water shortage.  When you look at a drought report issued by the U.S. Department of Agriculture, you see a combination of meteorological, hydrological and agricultural drought assessments.  Drought maps indicate the severity of water shortages in terms of last received significant precipitation, soil moisture and surface and groundwater storage. 

Drought Intensity for February 18, (from United States Drought Monitor, http://droughtmonitor.unl.edu/Home/StateDroughtMonitor.aspx?NV):

• D0 - Abnormally Dry
• D1 - Moderate Drought
• D2 - Severe Drought

• D3 - Extreme Drought
• D4 - Exceptional Drought

Sierra snowpack very low

Drought conditions for Northern Nevada, February 20, 2014


Northern Nevada depends upon snowpack to sustain water supplies.  Snow accumulates during the winter months until the beginning of April, and the slow release of melt water during the spring and summer months fills reservoirs, recharges groundwater and sustains streamflow.  As of February 20th the snowpack accumulations for the major river systems in northwest Nevada (the Truckee, Walker, and Carson Rivers) are approximately half of the average (http://www.wcc.nrcs.usda.gov/cgibin/precup-graph.pl?state=CA).  This means that the watersheds for these river systems would have to receive approximately 50% of the annual snowpack accumulation in the next 39 days to reach snowpack levels considered to be normal in these watersheds.  If this does not happen, it will be important to prepare for a dry summer with a diminished water supply.  Parts of three counties in Nevada (Washoe, Churchill and Lander) are classified as being affected by "exceptional drought."  These are at the core of parts of eight additional counties that are classified as being affected by "extreme drought."  These (exceptional and extreme) are the highest of five categories used to characterize drought in the United States (http://droughtmonitor.unl.edu/Home/StateDroughtMonitor.aspx?NV -- see the illustration below from the U.S. Department of Agriculture's Drought Monitor web site).  Some areas in the state may be severely affected by water shortages, especially given the lack of snowpack last year. 

Intensity:

• D0 - Abnormally Dry
• D1 - Moderate Drought
• D2 - Severe Drought

• D3 - Extreme Drought
• D4 - Exceptional Drought

The Drought Monitor focuses on broad-scale conditions. Local conditions may vary. See accompanying text summary for forecast statements.

Author(s):

• David Miskus, NOAA/NWS/NCEP/CPC

Soil moisture records tell much of the story about drought conditions.  The graph below, from the U.S. Department of Agriculture's SNOTel site at the Mt. Rose Ski resort, shows 0% water content at 2, 8 and 20 inches below the soil surface.