U.S. Streamflow in Water Year 2016: A Wetter-Than-Average Year

From a U.S. Geological Survey water year summary by Xiaodong Jian, David M. Wolock, Harry F. Lins and Steven J. Brady, 2017.

These results describe national streamflow in water year 2016 — October 1, 2015, to September 30, 2016 — ranked against the 87 years from 1930 to 2016, using data from the USGS National Streamflow Network. The record starts in 1930 because before then there were too few streamgages to give representative statistics for most regions.

Reading the numbers

• Runoff is the depth of water that would cover a river basin, state or other area if all the streamflow in it over a period were spread evenly across it. It lets flows be compared between places.
• Ranks: 1 means the highest flow of all years analysed, 87 the lowest.
• Categories, by percentile of flow: much below normal (below 10 percent), below normal (10–24), normal (25–75), above normal (76–90) and much above normal (above 90).

Some of the data are provisional and may change.

The nation

Average runoff in 2016 was 10.81 inches, above the long-term (1930–2016) mean of 9.31 inches for the contiguous United States. Nationwide, 2016 ranked 12th highest of the 87 years. (Before 2011, some USGS summaries compared median rather than average runoff.)

Annual runoff in the United States, 1930–2016. USGS.

The states

Most states had normal streamflow.

• Below normal: Connecticut, Rhode Island, Alaska, Massachusetts, Arizona, New Jersey, Montana, New York, Pennsylvania and Puerto Rico–Virgin Islands.
• Above normal: Michigan, Kansas, Kentucky, Oklahoma, South Carolina, Illinois, Nebraska and Minnesota.
• Much above normal: North Carolina, Missouri, Arkansas, Wisconsin, Louisiana, Iowa and Texas.

Statewide streamflow ranks for 2016, relative to 1930–2016. For Puerto Rico–Virgin Islands, 73 years of data were used. USGS.

The regions

The country, including Puerto Rico–Virgin Islands and the District of Columbia, is divided into 21 water-resources regions based on topography: the basin of a major river such as the Columbia, a group of rivers such as the Texas-Gulf region, or an island or island group.

• Below normal: Alaska, Lower Colorado and Caribbean.
• Above normal: South Atlantic-Gulf and Lower Mississippi.
• Much above normal: Upper Mississippi, Arkansas-White-Red and Texas-Gulf.

The seasons

Very high and very low flows

In any month, about 5 percent of streamgages are expected to report very high flow (above the 95th percentile) and 5 percent very low flow (below the 5th).

• Very high flows were more common than expected in November, December, January, February and August: 7, 19, 7, 9 and 6 percent of gages.
• Very low flows exceeded the expected share in only one month, September (6 percent).

More data

The USGS ran more than 8,200 streamgages in 2016, almost all in real time; current conditions are at https://waterwatch.usgs.gov, and state runoff tables back to water year 1901 at https://waterwatch.usgs.gov/?id=statesum. Real-time and archived data are at https://waterdata.usgs.gov/nwis. The same information serves water management, flood and drought monitoring, bridge design and recreation. The National Streamflow Network, part of the Groundwater and Streamflow Information Program, is run mainly by the USGS and funded by the USGS and about 850 federal, state, tribal, regional and local partners.

Sources

• Xiaodong Jian, David M. Wolock, Harry F. Lins and Steven J. Brady, Streamflow of 2016 — Water Year Summary, U.S. Geological Survey Fact Sheet 2017–3063. https://doi.org/10.3133/fs20173063 — two figures recovered from the PDF.
• Rewritten in hubnx's own words.