An Ordinary Year With Extremes Inside It: U.S. Streamflow in Water Year 2022

Taken as a whole, water year 2022 — October 1, 2021, to September 30, 2022 — was unremarkable for the rivers and streams of the contiguous United States. Annual runoff was 8.97 inches, slightly under the 1930–2022 mean of 9.39 inches, and annual mean streamflow ranked 60th highest of 93 years. The national average hid a year of extremes.

Annual runoff in the contiguous United States, water years 1930–2022. USGS.

How the ranking works

• Runoff is the water flowing through a stream divided by its drainage area — an equivalent depth of water over the basin, which lets one area be compared with another. It is computed from every streamgage with a complete record in the area.
• A rank of 1 is the highest annual flow of the 93 years; 93 is the lowest. The record starts in 1930 because earlier there were too few streamgages for meaningful statistics in most regions.
• Ranks fall into five bands by percentile of flow: much below normal (under 10%), below normal (10–24%), normal (25–75%), above normal (76–90%) and much above normal (over 90%).

Where it was dry, and where it was wet

By state (counting the District of Columbia, and Puerto Rico with the Virgin Islands, as one each):

Statewide streamflow ranks for water year 2022, compared with 1930–2022. USGS.

The country also divides into 21 water-resources regions, each the drainage of a major river, of a series of rivers (the Texas-Gulf region takes in several flowing to the Gulf of Mexico), or an island group. Streamflow was much below normal in the Hawaii and Great Basin regions and below normal in the Upper Colorado, Texas-Gulf and California regions. It was above normal in the Ohio region and much above normal in the Souris-Red-Rainy region.

Regional streamflow ranks for water year 2022. USGS.

Season by season

New Mexico went from much below normal in winter and spring to much above normal in summer. Hawaii was much below normal in winter, spring and summer, and California in winter and summer.

The other bands, briefly. Below normal — autumn: Alaska, Arizona, Colorado, New Mexico, North Carolina, Puerto Rico and the Virgin Islands, Utah, Virginia, West Virginia, Wyoming; winter: Arizona, Delaware, Iowa, Louisiana, Maryland, Nevada, New Jersey, Oregon, Texas, Wyoming; spring: California, Colorado, Massachusetts, New Hampshire, North Carolina, Puerto Rico and the Virgin Islands, Rhode Island, Vermont; summer: Colorado, Connecticut, Massachusetts, Nebraska, Nevada, New Jersey, North Carolina, Oklahoma, Rhode Island. Above normal — autumn: Connecticut, Illinois, Indiana, Massachusetts, Michigan, Ohio, Vermont; winter: Alabama, Indiana, Kentucky, New Hampshire, Ohio, Tennessee, Vermont; spring: Arkansas, Michigan, Missouri; summer: Arizona, the District of Columbia, Illinois, Kentucky, Louisiana, West Virginia.

Months of high and low water

If each streamgage behaved independently and normally, 5% of them would report high flow (above the 95th percentile) in any month, and 5% low flow (below the 5th). In water year 2022, only one month reached the expected share for high flow — October 2021, at 7%. Five months met or exceeded it for low flow: February (6%), March (6%), April (5%), May (5%) and August 2022 (5%).

Percentage of streamgages with high and low monthly streamflow, October 1999–September 2022. USGS.

The network behind it

In water year 2022 the USGS ran more than 8,400 year-round, real-time streamgages, whose data serve water management, flood and drought monitoring, bridge design and recreation. The network is part of the Groundwater and Streamflow Information Program, operated mainly by the USGS and funded by the USGS and about 1,885 federal, state, tribal, regional and local partners. Real-time data are at waterwatch.usgs.gov; real-time and archived records are in the National Water Information System.

Sources

Based on "Streamflow — Water Year 2022," U.S. Geological Survey Fact Sheet 2023–3030; a work of the United States government in the public domain.