We have found that the segments of stream that flow year-round have shortened in length substantially since the 1980s. Prior to 1984, the creek flowed continuously through the length of the Preserve year-round but, in contrast, since 1999 an average of only 28 percent of the stream channel within the Preserve has perennial flow. PAG’s hydrologic monitoring at Cienega Creek reveals that drought impacts have been noticeable since 2002. Although the creek saw some recovery in 2006-2008, the drought has since become more severe. In September 2009, the shortest flow extent for any autumn quarter was recorded, and in June 2011, the shortest flow extent ever was recorded.
The heavy monsoon of 2008 played a significant role in drought relief, improving groundwater levels so that seasonal fluctuation was nearly back to pre-drought levels. Then, with 50 percent of the average precipitation during the 2009 monsoon at Cienega Creek, the Preserve groundwater levels were reduced to the lowest levels of the heaviest part of the drought. The conditions have remained severe through 2010. The severity of drought impacts improved each month with winter rainfall through March 2010, decreasing from five feet below last year’s monthly groundwater depth to approximately three feet below. However, current groundwater levels remain significantly below pre-drought levels.
PAG contributes hydrologic monitoring data to the Local Drought Impact Group through the AZ Drought Watch, in order to help the Governor’s Drought Task Force assess the status of drought statewide. Thanks to Pima County support, PAG’s data is highly valued by this effort because it is the only consistent long-term data set that has been collected along Cienega Creek. Because Cienega Creek has been monitored for many years and is relatively un-impacted by urban development, these findings provide insight into how drought affects our natural environment.