Use one of the options to select a station.
Select a state.
Enter part of a station name, or station ID.
Enter a latitude and longitude (in decimal degrees) or click on the map.
Select a station from the list below or from the map. After making your selection, click Update selection to view Atlas data.
A statistics analysis has not been performed on the streamflow stations in the current version of the drought atlas. Basic information about this station is available in the whtie column.
(Click to select)
Each station was clustered using summer precipitation values into homogenous regions and tested for homogeneity for each season. Some stations were discordant in the clusters for certain seasons, but not in others. These results are:
Clusters passing and failing the H(1) Homogeneity tests are noted.
Stations which were discordant are identified by COOP identification numbers. For some seasons, no stations may have been found to be discordant.
Information - provides an overview of the Climate section of this page.
SPI Time Series Chart - plots SPI values for the selected station and timestep(s).
SPI Time Series Table - a chart of SPI values for the selected station and timesteps(s).
Analog SPI Rankings - displays the highest and lowest SPI values in the selected time period of record for the selected timestep(s).
SPI Heatmap - visual display of SPI values.
The Standardized Streamflow Index (SPI) is an index based on the probability of precipitation for any time scale. The underlying assumption is that a deficit of precipitation has different impacts on groundwater, reservoir storage, soil moisture, snowpack, and streamflow. The SPI was designed to quantify the precipitation deficit for multiple time scales. These time scales reflect the impact of drought on the availability of the different water resources. Soil moisture conditions respond to precipitation anomalies on a relatively short scale. Groundwater, streamflow, and reservoir storage reflect the longer-term precipitation anomalies.
The SPI calculation for any location is based on the long-term precipitation record for a desired period. This long-term record is fitted to a probability distribution, which is then transformed into a normal distribution so that the mean SPI for the location and desired period is zero (Edwards and McKee, 1997). Positive SPI values indicate greater than median precipitation, and negative values indicate less than median precipitation. Because the SPI is normalized, wetter and drier climates can be represented in the same way, and wet periods can also be monitored using the SPI.
A drought event occurs any time the SPI is continuously negative and reaches an intensity of -1.0 or less. The event ends when the SPI becomes positive. Each drought event, therefore, has a duration defined by its beginning and end, and an intensity for each month that the event continues. The positive sum of the SPI for all the months within a drought event can be termed the drought's "magnitude".
Time Series
Table
Analog Ranks
Heatmap
Information - provides an overview of the Station Trends section of this page.
Frequency Statistics - displays the selected index and trendline for the current station.
The trends displayed on the individual plots represent 1) magnitudes of linear trends in data, and 2) whether or not these trends are deemed to be statistically significant at different confidence intervals.
Trends Chart
To download the chart, right-click on the image below and select "Save Image As..."