Nolan J Doesken

Isohyetal maps of average annual precipitation have long been and continue to be a backbone and starting point for many climatic, hydrologic and basic water resource and land use studies. In 1982 the Colorado Climate Center initiated the effort to update the Colorado precipitation map.

This project was undertaken to adapt the Palmer Index model to Colorado. The state was divided into 25 climatic region rather than 5. Comparisons with the original indexes show noticeable differences and considerable small scale detail which previously could not be resolved. With the new small regions it is now reasonable to use contour analysis of Palmer Index values to visually describe local variations in drought severity across Colorado.