Here is the Virginia Water Central News Grouper’s monthly water-status report on precipitation, stream flow, and drought, as of the end of May 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 May 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. The values are in inches.
|Location||May 2017 Observed
|Monthly Normal||June 2016-
May 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 May 31, 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 May 2017 at 153 stream gages in Virginia and just beyond the state border were in the normal historical range at about 17% of gages, above normal at about 21%, and much above normal at about 62%. 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 May 29, 2017, accessed on June 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 May 30, 2017, showed Virginia as drought-free. This was the first week that the Drought Monitor showed no areas of at least “abnormally dry” since the week of April 5, 2016.
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:
4/25/17 – 46.4% abnormally dry or worse, 16.0% moderate drought;
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;
5/31/16 – 2.5% abnormally dry.
The Virginia Drought Monitoring Task Force, a collaboration of state and federal agencies, issued its most recent (as of 6/2/17) Drought Status Report on May 12, 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 June 8, 2017. Following is an excerpt from the May 12 report:
“Abundant precipitation during the first half of May reduced or eliminated dry conditions over most of Virginia. Groundwater levels and water-year-to-date precipitation in two drought-evaluation regions, Northern Virginia and Northern Piedmont, continue to be well below normal. The Virginia Department of Environmental Quality (DEQ) issued a drought Watch for these two regions on March 22, 2017. Based on the remaining deficits in these areas, the task force agreed to continue the Drought Watch for now.”
The Drought Monitoring Task Force also produces a map rating drought-status indicators. Shown below is the map for May 31, 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 May 30, 2017, U.S. Drought Monitor rated about 20.7% of the United States (including all or parts of 25 states) as being abnormally dry or worse. The Drought Monitor rated 0.94% of the country (including parts of 4 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:
4/25/17 – 23.6% abnormally dry or worse, 0.92% severe drought or worse;
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;
5/31/16 – 29.4% abnormally dry or worse; 3.6% severe drought or worse.
No state had 50% or more rated by the May 30 Drought Monitor in severe-or-worse drought. The highest percentage of those categories was in Florida, at about 38%.
In California, just over 1% of the state was rated on 5/30/17 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 31, 2017.