U.S. River Conditions, Water Year 2020
This animation shows the changing conditions of USGS streamgages from October 1, 2019 to September 30, 2020. The conditions shown range from the driest condition seen at a gage (red open circles) to the wettest (blue closed circles). There is also a purple ring added to indicate gages that are flooding.
Most of the East Coast was experiencing dry conditions in October until frontal systems in early November improved conditions. The Upper Midwest was experiencing high flows and flooding for much of October into November. Storms in early December caused high flows and flooding in the Ohio and Tennessee Valleys, while New England rivers experienced high flows in mid-December and the Southeast experienced wet conditions and flooding in late December after multiple fronts passed through the region. A low-pressure storm system swept through the Midwest at the end of December causing high flows and floods.
During most of January and into March, much of central and southeastern Colorado experienced persistent low flows. In early January, 5 inches of rain were forecast for parts of Indiana and USGS deployed crews to respond to flooding. The Pacific Northwest was hit with an atmospheric river in early February which caused major flooding in northwest Washington. On the other side of the country, several record-breaking flows were measured in the Southeast as 18 USGS crews responded to flooding and repaired gages in early to mid-February. In early March, the Las Vegas Wash flooded as it rose to the highest flows seen in 8 years. In Florida during March, above average temperatures and below average rainfall amid the height of the dry season intensified low flows. Flooding in Ohio near the end of March resulted in a collapsed state road; USGS gage data were used to provide flood guidance in the area.
Drought conditions in Florida continue from March through the end of May. At the end of May, we start to see drought conditions in parts of the Southwest that last through June. By mid-June we see drought conditions develop in Puerto Rico and also in New England. While parts of the country are experiencing drought conditions, other parts are experiencing wetter than normal conditions. Frontal systems in April cause high water conditions in much of the Eastern U.S. From mid-April to early may, we see flooding in the Eastern Dakotas along the Red River of the North, the James River, and the Sioux River. In mid-May, flooding in the Upper Midwest leads to two dam failures in Michigan. Rivers are flooding in the Mid-Atlantic (Virginia and the Carolinas) at the end of May. Then, Tropical Storm Cristobal brings high water from the Gulf Coast to the Upper Midwest between June 8 to 14. Lastly, flooding on the James River in South Dakota continues from the beginning of April through the end of June.
At the beginning of July, the Southwest US experienced severe drought. During August and September, extreme drought conditions began to grow throughout the West. New England experienced dry conditions for almost the entire time period with severe drought conditions spanning from mid-August to the end of September. Rain briefly interrupted theses dry conditions in New England due to Tropical Storm Fay in mid-July and the remnants of Hurricane Isaias in early August. In the Upper Midwest, high flows and some flooding were seen in mid-to-late July. At one gage along the James River in South Dakota, river levels finally dropped below flood stage on September 30 after 545 days. At the end of July, Hurricane Hanna brought rain to the Texas coast. This hurricane was followed up by 4 more tropical events in the Gulf Coast: Hurricane Marco and Hurricane Laura made landfall in Louisiana at the end of August, Hurricane Sally made landfall in mid-September and caused flooding in the Southeast, and finally Tropical Storm Beta made landfall in Texas near the end of September.
Note that both USGS gage height and National Weather Service flood stage levels are necessary to determine flooding conditions and were available for 38% of streamgages at the time this graphic was produced. Only publicly available data from the National Water Information System Website was used and some gages are missing gage height even when they have flow.