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 2017. 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 2017 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. All values are in inches.
|Location||April 2017 Observed
|Monthly Normal||May 2016-
April 2017 Observed
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 April 30, 2017.
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 2017 at 156 stream gages in Virginia and just beyond the state border were in the normal historical range at about 65% of gages, below normal at about 3%, above normal at about 18%, and much above normal at about 14%. 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 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 29, 2017, accessed on May 1 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 National Drought Monitor map from the University of Nebraska-Lincoln (http://droughtmonitor.unl.edu/) for April 25, 2017, showed about 46.4% of Virginia as “abnormally dry” worse; and about 16.0% in “moderate drought.”
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:
3/28/17 – 61.0% abnormally dry or worse, 41.0% moderate drought or worse, 2.2% in severe drought;
2/28/17 – 80.5% abnormally dry or worse, 17.1% moderate drought or worse, 2.9% in severe drought;
1/31/17 – 30.0% abnormally dry or worse, 0.5% moderate drought;
4/26/16 – 95.1% abnormally dry or worse; 4.1% moderate drought.
The Virginia Drought Monitoring Task Force, a collaboration of state and federal agencies, issued its most recent (as of 5/1/17) Drought Status Report on April 17, 2017. 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 Task Force is next scheduled to meet on May 11, 2017. Following is an excerpt from the April 17 report:
“Although precipitation in early April increased streamflow rates, it was not enough to offset dry conditions that extend over most of central Virginia due to below-normal winter precipitation. Portions of Northern Virginia, especially those areas within the Northern Virginia and Northern Piedmont drought evaluation regions, continue to experience the driest conditions. The Virginia Department of Environmental Quality (DEQ) issued a drought watch for these two regions on March 22. Recognizing that dry conditions also exist within other drought evaluation regions extending southward through central Virginia, DEQ distributed a message to water users in those areas to raise awareness of the long-term water supply impact of the dry winter conditions. The task force discussed the possibility of recommending issuance of a drought watch for some of these regions, particularly the Middle James drought evaluation region, but agreed to continue to closely monitor conditions for now. …For the current water year (October 1, 2016–April, 13, 2017) precipitation totals have so far been below the April drought watch indicator level for precipitation (81.5% of normal) for nine of Virginia’s thirteen drought evaluation regions. The Northern Virginia and Northern Piedmont regions have received just 66% and 59% of normal precipitation, respectively. The Shenandoah and Roanoke regions have received 72% and 74% of normal precipitation, respectively. …The Virginia Department of Game and Inland Fisheries (VDGIF) reported no low water level issues with the Department’s fish stocking program. However, there have been a few complaints regarding recreational water access due to low water. The Virginia Department of Forestry (VDOF) reported that we are nearing the end of the spring wildfire season. VDOF does not have any current concerns regarding drought related fires or insect/disease issues.”
The Drought Monitoring Task Force also produces a map rating drought-status indicators. Shown below is the map for April 29, 2017. 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 25, 2017, U.S. Drought Monitor rated about 23.6% of the United States (including all or parts of 39 states) as being abnormally dry or worse; this was the lowest nationwide percentage of abnormally dry-or-worse conditions since the week of November 17, 2009. The Drought Monitor rated 0.92% of the country (including parts of 8 states), as being in severe drought or worse (categories D2, D3, and D4); this was the lowest nationwide percentage of severe-or-worse drought since the Drought Monitor began on January 4, 2000. (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:
3/28/17 – 34.9% abnormally dry or worse, 2.4% severe drought or worse;
2/28/17 – 34.0% abnormally dry or worse, 3.1% severe drought or worse;
1/31/17 – 28.3% abnormally dry or worse, 3.2% severe drought or worse;
4/26/16 – 37.0% abnormally dry or worse; 5.0% severe drought or worse.
No state had 50% or more rated by the April 25 Drought Monitor in severe-or-worse drought. The highest percentage of those categories was in Florida, at about 33%.
In California, just over 1% of the state was rated on 4/25/17 as being in severe-or-worse drought. This severe-or-worse rating, in effect since the week of March 14, 2017, was the lowest for the Golden State since the week of February 14, 2012. Most of California is out of the drought that began in late 2011 to early 2012 and continued into early 2017.
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, 2017.