Long-term Drought Status

The long-term (hydrologic) drought depends on accumulated precipitation over multiple years. The spring of 2006, which was very dry, has been replaced in the drought analyses by the spring of 2010, which, although dry, was comparatively wetter. Similarly, the spring of 2007 has dropped out of the 3 year interval. In terms of cumulative precipitation over the past 2, 3, and 4 years, long-term drought has improved significantly. Four watersheds show a two category improvement, and five others show a one category improvement. The streamflow in many parts of the state is still relatively high, indicating more recharge of groundwater basins, reducing the water deficit we have accumulated over the past decade or more. Reservoir systems within the state, particularly the Salt-Verde watershed, are near 100% of capacity well into the high demand summer season. Unfortunately, the lower Colorado Basin reservoir system (Lakes Powell and Mead), a major water supply for much of the state, remains near 50% of capacity. This means that areas of the state that depend on groundwater and Colorado River water through the Central Arizona Project system are still very much in a long-term drought condition. Seasonal forecasts call for a warmer and drier fall and winter, based on the development of La Niña. Although the monsoon activity began late in many areas of the state, heavy rainfall events have pushed both the calendar and water year precipitation to average or above average levels. Three years ago the La Niña winter was exceptionally wet, while two years ago the La Niña winter was very dry. Whether this winter turns out to be a dry or wet La Niña will determine whether we continue the improvement in long-term drought conditions or not.

Summaries produced by the State Drought Monitoring Technical Committee - August 10, 2010