Drought Risk Atlas


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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.


Station Map

Station List

Select a station from the list below or from the map. After making your selection, click Update selection to view Atlas data.

    Information - provides an overview of the Station section of this page.

    Similar Stations - shows a list of stations in the same region as the current station.

    Related Links - a list of links relevant to the area in which this station is located.

    L-Moments Statistics - the L-Moment statistics for the selected station.

    Quantiles - seaonal qualtile values for the selected station and it's region.

    Region Discordancy and Homogeneity - homogenous seasons and discordant stations for the region of the selected station.

    Atlas Station General Information

    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.

    Similar Stations

    Atlas Region

    Related Stations:

    (Click to select)

      Related Links for Station

      State Climatologist

      Local Resources

      L-Moment Ratios for Station and Region
      Type Season Moment 1 Moment 2 Moment 3 Moment 4 Moment 5
      Quantiles for Station and Region
      Type Season 0.01 0.02 0.05 0.1 0.2 0.5 0.7 0.9 0.95 0.98 0.99

      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:

      Homogeneous Seasons

      Clusters passing and failing the H(1) Homogeneity tests are noted.

      • Winter
      • Spring
      • Summer
      • Autumn

      Discordant Stations

      Stations which were discordant are identified by COOP identification numbers. For some seasons, no stations may have been found to be discordant.





              Please check your selections.

              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.



              Probability Type



              Standardized Streamflow Index (SSI)

              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".

              To zoom in on the chart, click and drag across the chart area. To return to the complete chart, double-click in the chart area.

              Export Graph
              • Jan
              • Feb
              • Mar
              • Apr
              • May
              • Jun
              • Jul
              • Aug
              • Sep
              • Oct
              • Nov
              • Dec













              Note: Only the shortest duration timestep that is selected will be displayed below.

                To download the chart, right-click on the image below and select "Save Image As..."