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 2016. 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 2016 at 11 Virginia or near-Virginia locations, along with the normal 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 normal annual precipitation for each location. All values are in inches.
|Normal for Month||May 2015-Apr. 2016 Precipitation
|Normal Annual Precipitation|
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 Southeast Regional Climate Center (Chapel Hill, N.C) at http://www.sercc.com/climateinfo/precip_maps, where you can find maps of total precipitation and percent of normal precipitation for the past 7, 30, 60, or 90 days; 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 Southeast Regional Climate Center’s preliminary maps of the percent-of-normal precipitation for the previous 30 days, 60 days, and 90 days, through May 1, 2016.
According to the U.S. Geological Survey WaterWatch for Virginia (online at http://waterwatch.usgs.gov/index.php?m=mv01d&r=va&w=map), monthly average stream flow values for April 2016 at 153 stream gages in Virginia and just beyond the state border were in the normal range at 28% of gages, below normal at 41%, and much below normal at 31%. The color-coded, flow-percentile map for this period is shown below. The color codes/percentile classes used by USGS to compared flows to historical records for the month are shown in the chart below the map.
An overall look at Virginia streamflow conditions is provided in the USGS WaterWatch summary plot of 7-day average streamflow conditions. Below is the summary plot for 88 Virginia sites during the 45-day period ending April 30, 2016, accessed at http://waterwatch.usgs.gov/index.php?id=pa07d&sid=w__plot&r=va on May 2, 2016.
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 National Drought Monitor map from the University of Nebraska-Lincoln (http://droughtmonitor.unl.edu/) for April 26, 2016, showed 95% of Virginia as abnormally dry or worse, and 4% of the Commonwealth in moderate drought. This was Virginia’s highest percentage of D0 or worse since the Drought Monitor report for March 1, 2011, and the first occurrence of moderate drought since the report for July 15, 2014.
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:
3/29/16 – drought-free;
3/1/16 – drought-free;
1/26/16 – drought-free;
4/28/15 – drought-free.
The Virginia Drought Monitoring Task Force, a collaboration of state and federal agencies, issued its most recent Drought Status Report on March 15, 2016. 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 Task Force’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 next report is scheduled for May 12, 2016.
The Drought Monitoring Task Force also produces a daily map rating drought-status indicators. Shown below is daily map for May 2, 2016. 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.” Any given day’s current map and more information on drought status in Virginia are available the Task Force Web site listed above.
The April 26, 2016, U.S. Drought Monitor rated 37.0% of the United States (including all or parts of 42 states, plus Puerto Rico) as being abnormally dry or worse. The Drought Monitor rated 5.0% of the country (including all or parts of 8 states, plus Puerto Rico), 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 during the week of August 7, 2012).
The nationwide percentages for abnormally dry or worse (D0-D4) and severe or worse (D2-D4) in the previous three months and one year ago were as follows:
3/29/16 – 35.3% abnormally dry or worse; 4.9% severe drought or worse;
3/1/16 – 28.6% abnormally dry or worse; 6.5% severe drought or worse;
1/26/16 – 25.3% abnormally dry or worse; 7.1% severe drought or worse;
4/28/15 – 48.5% abnormally dry or worse; 16.7% severe drought or worse.
In California, 74% of the state was categorized by the 4/26/16 report as being in severe-or-worse drought. While still high and serious, this severe-or-worse percentage for California is the lowest is about two years. California’s current drought began in late 2011 to early 2012.
Following are some comments from the 4/26/16 Drought Monitor on dry conditions in early 2016 in the Ohio Valley, Central Appalachians, and East, including Virginia:
“According to a Southeast Regional Climate Center analysis, for the 90-day period January 26-April 26, Walhalla, South Carolina had the third driest January 26-April 26 period in the last 106 years; Clarkesville, Georgia, ranked fourth driest; Bent Creek, North Carolina, second driest; Jefferson City, Tennessee, third driest; Charlotte, North Carolina, eighth driest out of 75 years; Bluefield, West Virginia, second driest; and Frostburg, Maryland, second driest. The dryness has intensified over the last eight weeks, with many stations experiencing the driest March 1-April 26 on record from Tennessee and North Carolina to West Virginia and Maryland.”
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 2, 2016.