Hydrology

Hydrological Information

Drought Information - Current and Future

Drought Information - General and Historical

* The Palmer Drought Index: "The Palmer Drought Index has become a management tool for decision making in government, industry, and agriculture. It is used as a standard of comparison by government for defining drought intensity throughout the United States. ...The Palmer [Drought] Index is an index of relative moisture deficiency under a wide range of climatic conditions. Its general concept is one of supply vs. demand. The supply is represented by precipitation and stored water in the form of soil moisture, groundwater, lakes, and reservoirs. The demand is the combination of potential evapotranspiration and the amount of water needed to recharge soil moisture, plus the run-off needed to keep lakes, reservoirs, and stream flow at a normal level. It is a water balance accounting procedure that results in a positive or negative anomaly estimate weighted by the climatic conditions in time and space. The final product is an index that expresses the abnormality for a given place over a particular time period." (The Encyclopedia of Climatology, edited by John E. Oliver and Fhodes W. Fairbridge, Van Nostrand Reinhold Company, New York, 1987, pages 682-683.)