USE OF SPRINGS TO MONITOR AQUIFER RESPONSE TO RECENT CLIMATE CHANGE, A CASE STUDY IN THE VERDE RIVER WATERSHED, CENTRAL ARIZONA

Natural response to climate change has been noted in a variety of media from tree rings to species distribution to stream flow. Monitoring the response of such media can assist in the understanding of how changes in climate have affected natural systems in the past and also give insight on how they may react to future stresses including drought conditions. Physical and chemical data were collected from springs in the Verde River watershed to correlate climate data to responses by the springs and therefore by association the aquifer systems supplying them. Central Arizona has been experiencing drought conditions for over a decade. Within this overall drought, however, fluctuations in climate patterns have afforded a variety of situations in which to observe the response of springs to these changes. One of the most severe drought years in the last century (2002) was followed two years later by an anomalously wet winter (2004-2005), and 2006 is presently on track to be another historically dry year. Springs monitoring during these climatic fluctuations provides valuable insight into the behavior of the aquifers supplying the springs. Analysis of discharge rate trends and chemical constituent and isotope concentrations of spring water allow for determinations of aquifer size and volume, recharge area, aquifer hydraulic properties, residence time within the aquifer, and a system's sensitivity to drought conditions. These responses were used in conjunction with preexisting hydrologic measures of climate change to better understand the response of the watershed as a whole.