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When watersheds have been modified due to human activities, it can be complex to characterize hydrological drought using streamflow percentiles. For example, in areas downstream of dams, streamflow that falls below normal percentiles may reflect drought in systems with irrigation and water supply reservoirs that store water from year to year. However, reservoirs are often managed together. Reviewing other data sources and multiple sites in the region can provide a clearer picture.
In areas where rivers depend on melting snow, changes in the timing of snowmelt can shift when water arrives in streams. Our tool flags streamflow conditions that are much lower than expected based on the 1981–2020 normal. Sometimes a shift in timing may trigger drought-like conditions in the data even if the total amount of water over the year is similar. In these cases, the hydrologic impacts can vary:
Because of this, drought indicators linked to changing snowmelt timing should be interpreted in context. A streamflow drought identified by the tool may reflect real, important disruptions for some users, even if annual totals are near normal, while in other cases the impacts may be limited.
In River DroughtCast, we define drought at regulated sites based on past patterns of how reservoirs store and release water from 1981 to 2020. Some streamgages are below dams, where reservoir operations can affect streamflow. The tool uses icons at each site to highlight conditions that may affect how forecasts should be read. These icons show whether a site is influenced by reservoirs, has year-round flow, is affected by snowmelt timing, or may freeze during part of the year.
To download data on past streamflow percentiles and droughts, please refer to this recent USGS article in Water Resource Research. Weekly streamflow drought observations, along with meteorological data and other factors used in forecasting models can be found at: https://doi.org/10.5066/P1X5VH96. In addition, the daily streamflow drought forecasts can be downloaded in parquet format from the River...
The beginning of a drought is difficult to determine. Several weeks, months, or even years might pass before people know that a drought is occurring. The end of a drought can occur as gradually as it began. The first evidence of drought is usually seen in records of rainfall. Within a short period of time, the amount of moisture in soils can begin to decrease. The effects of a drought on flow in...
We use machine learning models to forecast streamflow drought by training them on 20- and 40-year periods of past streamflow, weather, and watershed data. For a summary of our methods and how we evaluate the models, see: Publication summarizing modeling methods and performance. Interactive guide showing how drought models work. Model input data, including daily weather, snow, soil moisture, and...
To view the USGS streamflow information on drought, see the drought map on our WaterWatch site, which shows below-normal, 7-day average streamflow compared to historical streamflow for the United States. Links to additional maps and drought data are listed on the USGS Drought website and the National Integrated Drought Information System (NIDIS).
Hydrological drought happens when there is unusually low flow in rivers and streams, as well as low levels in lakes, reservoirs, and groundwater. It usually follows meteorological drought, which occurs first when a lack of rainfall over a long period leads to a water shortage. Meteorological drought can be tracked using the Standardized Precipitation Index (SPI) or the Standardized Precipitation...
Rainfall in any form will provide some drought relief. A good analogy might be how medicine and illness relate to each other. A single dose of medicine can alleviate symptoms of illness, but it usually takes a sustained program of medication to cure an illness. Likewise, a single rainstorm will not break the drought, but it might provide temporary relief. A light to moderate shower will probably...
River DroughtCast is a new machine learning system that predicts streamflow droughts — specifically “streamflow” droughts when rivers and streams drop to unusually low levels— up to 90 days in advance. Each prediction comes with uncertainty information to help users understand the confidence level of the forecast.
River DroughtCast is a new machine learning system that predicts streamflow droughts — specifically “streamflow” droughts when rivers and streams drop to unusually low levels— up to 90 days in advance. Each prediction comes with uncertainty information to help users understand the confidence level of the forecast.
River DroughtCast delivers current streamflow drought conditions and weekly forecasts of streamflow drought at select streamgages with long-term, complete records across the lower 48 states (the conterminous U.S., or CONUS).
River DroughtCast delivers current streamflow drought conditions and weekly forecasts of streamflow drought at select streamgages with long-term, complete records across the lower 48 states (the conterminous U.S., or CONUS).
Stream in Glacier National Park experience severe streamflow drought. The rocks that are normally at the bottom of the river are dry.
Stream in Glacier National Park experience severe streamflow drought. The rocks that are normally at the bottom of the river are dry.
Drought Intensity Map compiled by the U.S. Drought Monitor for the area of NOAA's Colorado River Basin River Forecast Center, which includes part of the Great Basin drainage area in western Utah, for April 19, 2024.
Drought Intensity Map compiled by the U.S. Drought Monitor for the area of NOAA's Colorado River Basin River Forecast Center, which includes part of the Great Basin drainage area in western Utah, for April 19, 2024.
2020 drought impact on Little River near the USGS station 01124500 near Oxford, Massachusetts
2020 drought impact on Little River near the USGS station 01124500 near Oxford, Massachusetts
2020 drought impact on Segreganset River near USGS station 01109070, Dighton, Massachusetts
2020 drought impact on Segreganset River near USGS station 01109070, Dighton, Massachusetts
Natural resource managers face increasing challenges in dealing with drought. As competition for water increases between its various uses (water supply, energy demands, ecological services, recreation, and other environmental and ecological needs), our ability to forecast the onset and termination of drought becomes ever more important.
Natural resource managers face increasing challenges in dealing with drought. As competition for water increases between its various uses (water supply, energy demands, ecological services, recreation, and other environmental and ecological needs), our ability to forecast the onset and termination of drought becomes ever more important.
A hydrologic technician from the USGS Idaho Water Science Center measures streamflow in Lightning Creek at Clark Fork, ID. The USGS is collecting data at hundreds of sites on rivers and streams in six western states to document the 2015 drought. USGS scientists will analyze the data to identify which rivers and streams may be most vulnerable to future droughts.
A hydrologic technician from the USGS Idaho Water Science Center measures streamflow in Lightning Creek at Clark Fork, ID. The USGS is collecting data at hundreds of sites on rivers and streams in six western states to document the 2015 drought. USGS scientists will analyze the data to identify which rivers and streams may be most vulnerable to future droughts.
A hydrologic technician from the USGS Idaho Water Science Center measures streamflow in Fall Creek near Anderson Ranch Dam in southwestern Idaho. The USGS is collecting data at hundreds of sites on rivers and streams in six western states to document the 2015 drought.
A hydrologic technician from the USGS Idaho Water Science Center measures streamflow in Fall Creek near Anderson Ranch Dam in southwestern Idaho. The USGS is collecting data at hundreds of sites on rivers and streams in six western states to document the 2015 drought.
To download data on past streamflow percentiles and droughts, please refer to this recent USGS article in Water Resource Research. Weekly streamflow drought observations, along with meteorological data and other factors used in forecasting models can be found at: https://doi.org/10.5066/P1X5VH96. In addition, the daily streamflow drought forecasts can be downloaded in parquet format from the River...
The beginning of a drought is difficult to determine. Several weeks, months, or even years might pass before people know that a drought is occurring. The end of a drought can occur as gradually as it began. The first evidence of drought is usually seen in records of rainfall. Within a short period of time, the amount of moisture in soils can begin to decrease. The effects of a drought on flow in...
We use machine learning models to forecast streamflow drought by training them on 20- and 40-year periods of past streamflow, weather, and watershed data. For a summary of our methods and how we evaluate the models, see: Publication summarizing modeling methods and performance. Interactive guide showing how drought models work. Model input data, including daily weather, snow, soil moisture, and...
To view the USGS streamflow information on drought, see the drought map on our WaterWatch site, which shows below-normal, 7-day average streamflow compared to historical streamflow for the United States. Links to additional maps and drought data are listed on the USGS Drought website and the National Integrated Drought Information System (NIDIS).
Hydrological drought happens when there is unusually low flow in rivers and streams, as well as low levels in lakes, reservoirs, and groundwater. It usually follows meteorological drought, which occurs first when a lack of rainfall over a long period leads to a water shortage. Meteorological drought can be tracked using the Standardized Precipitation Index (SPI) or the Standardized Precipitation...
Rainfall in any form will provide some drought relief. A good analogy might be how medicine and illness relate to each other. A single dose of medicine can alleviate symptoms of illness, but it usually takes a sustained program of medication to cure an illness. Likewise, a single rainstorm will not break the drought, but it might provide temporary relief. A light to moderate shower will probably...
River DroughtCast is a new machine learning system that predicts streamflow droughts — specifically “streamflow” droughts when rivers and streams drop to unusually low levels— up to 90 days in advance. Each prediction comes with uncertainty information to help users understand the confidence level of the forecast.
River DroughtCast is a new machine learning system that predicts streamflow droughts — specifically “streamflow” droughts when rivers and streams drop to unusually low levels— up to 90 days in advance. Each prediction comes with uncertainty information to help users understand the confidence level of the forecast.
River DroughtCast delivers current streamflow drought conditions and weekly forecasts of streamflow drought at select streamgages with long-term, complete records across the lower 48 states (the conterminous U.S., or CONUS).
River DroughtCast delivers current streamflow drought conditions and weekly forecasts of streamflow drought at select streamgages with long-term, complete records across the lower 48 states (the conterminous U.S., or CONUS).
Stream in Glacier National Park experience severe streamflow drought. The rocks that are normally at the bottom of the river are dry.
Stream in Glacier National Park experience severe streamflow drought. The rocks that are normally at the bottom of the river are dry.
Drought Intensity Map compiled by the U.S. Drought Monitor for the area of NOAA's Colorado River Basin River Forecast Center, which includes part of the Great Basin drainage area in western Utah, for April 19, 2024.
Drought Intensity Map compiled by the U.S. Drought Monitor for the area of NOAA's Colorado River Basin River Forecast Center, which includes part of the Great Basin drainage area in western Utah, for April 19, 2024.
2020 drought impact on Little River near the USGS station 01124500 near Oxford, Massachusetts
2020 drought impact on Little River near the USGS station 01124500 near Oxford, Massachusetts
2020 drought impact on Segreganset River near USGS station 01109070, Dighton, Massachusetts
2020 drought impact on Segreganset River near USGS station 01109070, Dighton, Massachusetts
Natural resource managers face increasing challenges in dealing with drought. As competition for water increases between its various uses (water supply, energy demands, ecological services, recreation, and other environmental and ecological needs), our ability to forecast the onset and termination of drought becomes ever more important.
Natural resource managers face increasing challenges in dealing with drought. As competition for water increases between its various uses (water supply, energy demands, ecological services, recreation, and other environmental and ecological needs), our ability to forecast the onset and termination of drought becomes ever more important.
A hydrologic technician from the USGS Idaho Water Science Center measures streamflow in Lightning Creek at Clark Fork, ID. The USGS is collecting data at hundreds of sites on rivers and streams in six western states to document the 2015 drought. USGS scientists will analyze the data to identify which rivers and streams may be most vulnerable to future droughts.
A hydrologic technician from the USGS Idaho Water Science Center measures streamflow in Lightning Creek at Clark Fork, ID. The USGS is collecting data at hundreds of sites on rivers and streams in six western states to document the 2015 drought. USGS scientists will analyze the data to identify which rivers and streams may be most vulnerable to future droughts.
A hydrologic technician from the USGS Idaho Water Science Center measures streamflow in Fall Creek near Anderson Ranch Dam in southwestern Idaho. The USGS is collecting data at hundreds of sites on rivers and streams in six western states to document the 2015 drought.
A hydrologic technician from the USGS Idaho Water Science Center measures streamflow in Fall Creek near Anderson Ranch Dam in southwestern Idaho. The USGS is collecting data at hundreds of sites on rivers and streams in six western states to document the 2015 drought.