U.S. River Conditions, Water Year 2021
This is an animation showing the changing conditions of USGS streamgages from October 1, 2020 to September 30, 2021. The river conditions shown range from the driest condition seen at a gage (red open circles) to the wettest (blue closed circles). A purple outer ring around a gage indicates it is flooding.
As the 2020 hurricane season came to a close in October 2020, two final hurricanes made landfall in the Southeast and caused flooding: Hurricane Delta in Louisiana during early October and Hurricane Eta in the Florida peninsula during early November. In contrast, large areas experienced drought conditions at the beginning of October including parts of the Western U.S., the Northeastern U.S. and Hawaii.
In January, the Pacific Northwest experienced higher-than-normal water due to an atmospheric river. Simultaneously, North and South Carolina had flooding that lasted through the month. Meanwhile, much of the West and Southwest were dry, with over 90% of Utah experiencing extreme drought into late January. Throughout February and into early March, the Southeastern coast was hit by successive periods of high water and flooding. Heavy rain coupled with melting snow brought about high flow conditions and flooding in Washington state at the end of February. Intense rain over Hawaii in March resulted in flooding and a new record-high water level at USGS gage 16587000 in East Maui, which has over 108 years of data.
In April, drought conditions spread throughout the Western U.S., stretching from Western Texas to Idaho. From mid-May to mid-June, the South-Central U.S. experienced wet conditions and flooding. Dry conditions spread across the Northeast U.S. starting at the end of May with drought conditions continuing to the end of June. Tropical Storm Claudette moved over the Southeast U.S. from June 17 to June 22 bringing wet conditions and flooding. Midwestern states saw flooding in the final days of June.
In early July, high water levels spread across the Midwest while severe to exceptional drought spread in the Southwest. Tropical Storm Elsa brought rain to Florida and New England in July. From August 16-20, Tropical Storm Fred brought rain to the Southeast and New England, followed by catastrophic flash flooding in Tennessee. Tropical Storm Henri brought high water to the East Coast in late August. Shortly after, Hurricane Ida impacted the Gulf Coast and New England with flooding. Tropical Storm Nicholas also brought high water to the Gulf Coast while drought in the West continued through the end of September.
USGS gage height and National Weather Service flood stage levels are used to determine flood conditions and were available for 38% of gages Some gages are missing gage height even when they have flow.