Here is the Virginia Water Central News Grouper’s monthly water-status report on precipitation, stream flow, flooding, and drought, as of the end of April 2021. 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, groundwater, 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 2021 at 12 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 2021 Observed||Monthly Normal||May 2020-April 2021 Observed||Annual Normal|
|Reagan National Airport5||2.20||3.06||55.32||39.74|
1 – The Blacksburg location is the Blacksburg National Weather Service Office.
2 – The Bluefield location is the Mercer County, W. Va., airport, near the Va.-W.Va. state line.
3- The Bristol location is the Tri-Cities Airport in Tenn., about 20 miles from Bristol, Va./Tenn.
4 – The Charlottesville location is the Charlottesville-Albemarle Airport.
5 – Reagan National Airport is in Arlington County.
6 – Wallops Island is in Accomack County.
7 – Washington-Dulles Airport is in Loudoun County.
Precipitation sources: Climate pages of the following National Weather Service Forecast Offices:
Blacksburg, Va. (https://w2.weather.gov/climate/index.php?wfo=rnk);
Morristown, Tenn. (https://w2.weather.gov/climate/index.php?wfo=mrx);
Baltimore-Washington (https://w2.weather.gov/climate/index.php?wfo=lwx); and
Wakefield, Va. (https://w2.weather.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. New normals for the period of 1991-2020 were released on May 4, 2021; those normal will be used in the May 2021 edition of this monthly report. For information on the normal values, see the “Climate Normals” 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 from the High Plains Center of the percent-of-normal precipitation for the southeastern United States for the previous 30 days, 60 days, and 90 days, and for Virginia for the previous 30 days, all through May 1, 2021. Please note that the scale is different for the Virginia 30-day map.
Shown below is a color-coded percentile map of monthly average stream flow values for April 2021 at stream gages in Virginia and just beyond the state border, compared to the historical range for each gage. The map is from the U.S. Geological Survey (USGS) WaterWatch for Virginia, accessed online at https://waterwatch.usgs.gov/index.php?m=mv01d&r=va&w=map. The chart below the map shows the color codes/percentile classes used by USGS to compare 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 89 Virginia sites during the 45-day period ending April 28, 2021, accessed on April 30, 2021, at https://waterwatch.usgs.gov/index.php?id=pa01d&sid=w__plot&r=va.
NATIONWIDE FLOODING OVERVIEW
Following is the National Weather Service’s Advanced Hydrologic Prediction Service’s (AHPS) map of stream and river levels relative to flood stage (color-coded) for the continental United States, as of 8:43 a.m. EDT on April 30, 2021. The current map is available online at http://water.weather.gov/ahps/forecasts.php; at that site, one can select Virginia or any other state of interest.
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.
DROUGHT IN VIRGINIA
The weekly U.S. Drought Monitor report from the University of Nebraska-Lincoln (http://droughtmonitor.unl.edu/) for April 27, 2021, categorized Virginia drought-free. This has been the case since the week of April 13, 2021.
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:
3/30/21 – 7.9% abnormally dry;
3/2/21 – drought-free;
1/26/21 – 0.02% abnormally dry;
4/28/20 – drought-free.
On November 1, 2019, the Virginia Drought Monitoring Task Force (DMTF), a collaboration of state and federal agencies, issued its most recent report (as of 5-4-21). A link to that report, along with other current drought-status information, is available online at https://www.deq.virginia.gov/water/water-quantity/drought. 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 Virginia Department of Environmental Quality uses a map rating drought-status indicators, also online at https://www.deq.virginia.gov/water/water-quantity/drought. Shown below is the map for May 3, 2021. 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 April 27, 2021, U.S. Drought Monitor categorized about 60.6% of the United States (including parts of 45 states plus Puerto Rico) as being abnormally dry or worse. (The highest percentage in the abnormally or worse categories—that is, in all categories—reported by the Drought Monitor since it began in 2000 was 72.38 % of the country for the week of July 17, 2012.) The Drought Monitor categorized about 27.1% of the country (including parts of 19 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 38.48% 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:
3/30/21 – 58.6% abnormally dry or worse; 24.7% severe drought or worse;
3/2/21 – 55.0% abnormally dry or worse; 25.8% severe drought or worse;
1/26/21 – 54.7% abnormally dry or worse; 27.2% severe drought or worse;
4/28/20 – 24.0% abnormally dry or worse; 4.7% severe drought or worse.
The following states had 50% or more of their land area categorized by the April 27, 2021, Drought Monitor as being in severe-or-worse drought:
Arizona = 95%.
California = 88%.
Colorado = 60%.
Nevada = 92%.
New Mexico = 99%.
North Dakota = 93%.
Utah = 98%.
Following are comments from the April 13, 2021, Drought Monitor on severe drought conditions in parts of the United States.
From Nationwide Summary: “Parts of the Southwest are now experiencing record levels of dryness for the last 12 months. In New England, year-to-date precipitation ranks in the top 10 driest on record.
From West Regional Report: “In eastern Washington, D0 (abnormally dryness), D1 (moderate) and D2 (severe) drought expanded as precipitation deficits continued to increase, drying out soils and lowering streamflow. Conditions once again deteriorated in Oregon this week with expansions in D2, D3 (extreme) and D4 (exceptional drought). The warm, dry winter added to deficits that had been in place for more than a year, leaving soils extremely dry and limiting runoff. …Drought conditions also expanded in northern and central California. Another week without rainfall has continued to build upon longer deficits. Cooperative Extension notes that the majority of the season’s creeks aren’t flowing and that stock ponds are still dry. Decreases in water allocation and reduced or negligible forage are causing producers to respond by culling and selling herds. Drought conditions are also prompting Cal Fire to bring in fire crews earlier in the season.”
Following are comments from the April 20, 2021, Drought Monitor on dry conditions in several regions of the United States.
From Nationwide Summary:
“Streamflow was well below normal all along the West Coast and in the interior West, in North Dakota and northwest South Dakota, parts of southern Texas, the southern and eastern Great Lakes, and parts of the Northeast. Soils continued to dry out in the West and Southeast, according to U.S. Department of Agriculture (USDA) reports. Satellite and station reports, as well as modeled indices, showed dry soils across the West, northern and southern Plains, the southern and eastern Great Lakes, and into the Northeast, as well as parts of the Southeast. Groundwater observations from wells and estimated from satellite measurements revealed dry conditions across the West, northern and southern Plains, Northeast, and parts of the Southeast.”
Following are comments from the April 27, 2021, Drought Monitor on drought conditions in the western United States and the response by the Biden Administration to form an inter-agency working group.
From West Regional Report: “According to media reports, the Biden-Harris administration announced the formation of an Interagency Working Group to address worsening drought conditions in the West and support farmers, Tribes, and communities impacted by ongoing water shortages. The Working Group will be co-chaired by the Departments of the Interior and Agriculture to build upon existing resources to help coordinate across the federal government, working in partnership with state, local, and Tribal governments to address the needs of communities suffering from drought-related impacts. The Working Group will work to identify immediate financial and technical assistance for impacted irrigators and Tribes.”
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 April 30, 2021.