Trends in groundwater levels in wells in the active management areas of Arizona, USA

In 1980, the Arizona legislature passed the Groundwater Management Act (GMA), creating the active management areas (AMAs) to protect shared groundwater resources and to control severe overdrafts occurring in many parts of the state. With the 30-year anniversary of the GMA approaching, this article addresses the question: Have there been notable changes in the trends in observed groundwater levels in the AMAs from before enactment of the GMA until present? New tools developed for the US Geological Survey's National Water Availability and Use Pilot Program are used to analyze and present trends in observed groundwater level data. Trends in groundwater levels in the AMAs were investigated for 10-year time periods from 1970 through 1999 and an 9-year period from 2000-2008. Results indicate that the number of wells with rising trends in water levels increased and the number of wells with falling trends in water levels decreased during the early decades after passage of the GMA in the most-populated Phoenix and heavily agricultural Pinal AMAs. However, these trends in water levels are reversed during the 1995-2004 time period. The value of trend analyses would be improved by consistent groundwater-level monitoring in both developed and undeveloped areas of the region.