Climate and Drought
The Republican River Basin has a semi-arid continental climate where annual temperatures and precipitation are influenced by its central location on the continent and its position to the east (or leeward side) of the Rocky Mountains. Annual rainfall ranges from less than 15 inches in the west to more than 25 inches in the eastern portion of the basin.
Historical records show drought, including multiple-year drought, can occur in any part of United States. Figure 1 illustrates the percent area of the United States in severe and extreme drought between January of 1895 to November of 2008. On average, approximately 14% of the United States experienced severe or extreme drought each year.
Figure 1. Percent area of United States in severe and extreme drought
from January 1895 to February 2010 (Source: NDMC, 2009)
Historical maps of the Palmer Drought Severity Index (PDSI) are available through the National Drought Mitigation Center (NDMC). These maps, available for multiple time scales between 1895 and 1995, portray the percent time an area in the United States was experiencing severe or extreme drought. (The map for the 100-year period is depicted in Figure 2.) These maps are useful tools for understanding historical drought in the basin.
Figure 2. Depiction of drought in U.S. 1895-1995 (Source: NDMC, 2006)
Figure 2 shows that the Republican River Basin experienced severe or extreme drought conditions 10-20% of the time from 1895 to 1995. When examining the maps on shorter time scales, it was found that the Republican River Basin experienced severe or extreme drought more than 50% of the time between 1930 and 1939, as seen in Figure 3.
Figure 3. Depiction of drought in U.S. 1930-1939 (Source: NDMC, 2006)
The National Oceanic and Atmospheric Administration (NOAA) maintains graphs of the PDSI for a variety of areas. You can click on the state of your choice below to see the PDSI for the regions of the Republican River Basin from January 1895 to January 2009.
Historical drought information for a particular region can be used to determine overall risk to drought as well as frequency and severity of drought for individual locations. The National Drought Mitigation Center provides links to many sources of historical climate and drought information.