Here is the Virginia Water Central News Grouper’s monthly water-status report on precipitation, stream flow, and drought, as of the end of April 2018. The Virginia Water Resources Research Center thanks the agencies mentioned below for providing the data and maps used in this post. Icons for precipitation, stream flow, and drought are by George Wills of Blacksburg, Va. (https://www.etsy.com/people/BlacksburgArt). For previous monthly water status reports, please see this link: https://vawatercentralnewsgrouper.wordpress.com/?s=Water+Status.
Here are National Weather Service (NWS) preliminary (still needing verification) precipitation totals for April 2018 at 11 Virginia or near-Virginia locations, along with the “normal” (three-decade average) for this month of the year at each location. Also shown are the precipitation totals at each location for the previous 12 months and the annual precipitation normals for each location. The values are in inches.
|Location||April 2018 Observed||Monthly Normal||May 2017-
April 2018 Observed
*NWS reported nine days of data missing at Danville in January 2018.
1 – The Bluefield location is the Mercer County, W. Va., airport, near the Va.-W.Va. state line.
2- The Bristol location Tri-Cities Airport in Tenn., about 20 miles from Bristol, Va./Tenn.
3 – The Charlottesville location is the Charlottesville-Albemarle Airport.
4 – Wallops Island is in Accomack County.
5 – Washington-Dulles Airport is in Loudoun County.
Precipitation sources: Climate pages of the following National Weather Service Forecast Offices:
Blacksburg, Va. (http://www.nws.noaa.gov/climate/index.php?wfo=rnk);
Morristown, Tenn. (http://www.weather.gov/climate/index.php?wfo=mrx;
Baltimore-Washington (http://www.nws.noaa.gov/climate/index.php?wfo=lwx); and
Wakefield, Va. (http://www.nws.noaa.gov/climate/index.php?wfo=akq).
The normal values used by the National Weather Service (NWS) in these provisional reports are based on the period from 1981 to 2010. The National Climatic Data Center released these normal values in July 2011. For information on the normal values, see the National Climatic Data Center Web page at http://www.ncdc.noaa.gov/data-access/land-based-station-data/land-based-datasets/climate-normals.
For graphs of precipitation, visit the High Plains Regional Climate Center at https://hprcc.unl.edu/maps.php?map=ACISClimateMaps), where you can find maps of total precipitation and percent of normal precipitation for the past 7, 30, 60, or 90 days for all U.S. regions; or the NWS’ Advanced Hydrologic Prediction Service at http://water.weather.gov/precip/ for a map of precipitation nationwide or by state, with capability to show county boundaries, and archives available for specific days, months, or years. Shown below are the preliminary maps of the percent-of-normal precipitation for the southeastern United States for the previous 30 days, 60 days, and 90 days, through April 29, 2018. Please note that the scale is different for the 60-day map.
According to the U.S. Geological Survey WaterWatch for Virginia (online at https://waterwatch.usgs.gov/index.php?m=mv01d&r=va&w=map), monthly average stream flow values for April 2018 at 159 stream gages in Virginia and just beyond the state border were as follows, compared to the historical range for each given gage:
within the normal historical range – about 59% of gages;
below normal – about 4%;
above normal – about 30%.
much above normal – about 7%.
Shown below is the color-coded, flow-percentile map for this period, accessed at the Web site given in the paragraph above. The chart below the map shows the color codes/percentile classes used by USGS to compared flows to historical records for the month.
An overall look at Virginia streamflow conditions is provided in the USGS WaterWatch summary plot of daily average streamflow conditions, compared to historical records for any given date. Below is the summary plot for 88 Virginia sites during the 45-day period ending April 28, 2018, accessed on May 1, 2018, at https://waterwatch.usgs.gov/index.php?id=pa01d&sid=w__plot&r=va.
Information on current groundwater levels in Virginia monitoring wells is available from the U.S. Geological Survey’s National Water Information System, online at http://waterdata.usgs.gov/va/nwis/current/?type=gw; and from the USGS Climate Response Network, online at http://groundwaterwatch.usgs.gov/net/ogwnetwork.asp?ncd=crn (at that page, you can find a national map showing the status of groundwater monitoring wells compared to historical values).
DROUGHT IN VIRGINIA
The weekly U.S. Drought Monitor map from the University of Nebraska-Lincoln (http://droughtmonitor.unl.edu/) for May 1, 2018, categorized about 29% of Virginia as “abnormally dry” or worse (covering most of the Coastal Plain and Eastern Shore) and about 6% in “moderate drought” (covering parts of Southside).
Drought Monitor categories are as follows:
D0 = abnormally dry;
D1 = moderate drought;
D2 = severe drought;
D3 = extreme drought;
D4 = exceptional drought.
The Drought Monitor notes that it “focuses on broad-scale conditions [and] local conditions may vary.”
For comparison, here are Virginia ratings from previous Drought Monitors from about one month, two months, three months, and one year ago:
3/27/18 – 54.6% abnormally dry or worse; 9.0% moderate drought;
2/27/18 – 59.7% abnormally dry or worse; 12.3% moderate drought;
1/30/18 – 97.9% abnormally dry or worse; 48.6% moderate drought or worse; 2.9% severe drought;
5/2/17 – 32.1% abnormally dry or worse; 15.9% moderate drought.
In early April 2018, the Virginia Drought Monitoring Task Force (DMTF), a collaboration of state and federal agencies, issued its most recent report. A link to the report, along with other current drought-status information, is available online at http://www.deq.virginia.gov/Programs/Water/WaterSupplyWaterQuantity/Drought.aspx. The DMTF’s reports typically include information from some or all of the following agencies: University of Virginia Climatology Office, U.S. Geological Survey (USGS), and the Virginia departments of Agriculture and Consumer Services, Health, and Environmental Quality. The Task Force was next scheduled to meet on May 10, 2018.
The DMTF also produces a map rating drought-status indicators, also online at http://www.deq.virginia.gov/Programs/Water/WaterSupplyWaterQuantity/Drought/DroughtMonitoring.aspx. Shown below is the map for April 30, 2018, followed by a map identifying the Drought Evaluation Regions used by the DMTF. The status-indicator abbreviations on that map are as follows: GW = groundwater levels, Prcp = precipitation deficits, Res – reservoir storage, and Flow = stream flow conditions. For each region of Virginia, the indicators are color coded for “normal,” “watch,” “warning,” or “emergency conditions.”
The May 1, 2018, U.S. Drought Monitor categorized about 37.5% of the United States (including all or parts of 33 states) as being abnormally dry or worse. The Drought Monitor categorized about 13.6% of the country (including parts of 12 states), as being in severe drought or worse (categories D2, D3, and D4). (The highest percentage in the severe-or-worse categories reported by the Drought Monitor since it began in 2000 was 38.5% of the country for the week of August 7, 2012.)
The nationwide percentages for abnormally dry or worse (categories D0-D4) and severe or worse (categories D2-D4) in the previous three months and one year ago were as follows:
3/27/18 – 44.5% abnormally dry or worse; 13.7% severe drought or worse;
2/27/18 – 50.0% abnormally dry or worse; 12.0% severe drought or worse;
1/30/18 – 61.9% abnormally dry or worse; 14.4% severe drought or worse;
5/2/17 – 17.4% abnormally dry or worse; 1.1% severe drought or worse.
The following states had 50% or more categorized by the May 1, 2018, Drought Monitor in severe-or-worse drought:
Arizona – 96%;
Kansas – 59%;
New Mexico – 81%;
Utah – 58%.
90-DAY DROUGHT OUTLOOK
For a look ahead, the National Weather Service/Climate Prediction Center’s “U.S. Seasonal Drought Outlook” is available at http://www.cpc.ncep.noaa.gov/products/expert_assessment/sdo_summary.php. Shown below is the outlook map available on May 1, 2018.