Drought

Much of Arizona was gripped by moderate to severe drought at the beginning of the water year, while most of New Mexico was drought free (Figure 4a). At the beginning of the water year, drought conditions across Arizona were the result of a poor 2009 monsoon season, which was one of the driest on record. A lack of rain created numerous impacts to rangeland and water resources and led to the rapid development of moderate to severe drought across the state by the end of the summer. Unusually dry conditions persisted through October and November, leading to an expansion of severe drought that covered the eastern half of Arizona by the beginning of December. New Mexico remained largely drought free through this early period of the water year.

Relief began arriving in Arizona in January. Pacific storms drifted into the region, in part as a result of the El Niño event, which often causes the winds of the Pacific jet stream to flow over the region. These storms brought copious amounts of rain and high-elevation snow. Drought conditions dramatically improved across central and southern Arizona, where the bulk of the precipitation fell (Figure 4b). Winter storms continued to push improvements across Arizona and helped keep New Mexico in the clear through March and April. By the end of May, only a small area of moderate to severe drought remained in northeastern Arizona, where winter precipitation totals were slightly less and longer-term drought impacts continued to linger (Figure 4c).

A sluggish start to the summer monsoon season caused drought conditions to expand across northern New Mexico in early July. These largely subsided as monsoon rains began in earnest late in the month. Not all areas received near- or above-average rains, and some areas experienced expansion in drought conditions (Figure 4d). At the close of the monsoon season and the water year, drought conditions were confined to northern New Mexico and northern and western Arizona, where monsoon season rains were light and spotty.

Click figures to enlarge.