Evaluating sources of hydrochemical variability and mixing in the upper Gila river, New Mexico

This study of the upper reaches of the Gila River basin in southwestern New Mexico reveals both spatial and seasonal patterns in physical and hydrochemical parameters. Monsoonal precipitation, temporal variability in water chemistry of streams in the upper Gila watershed is significantly impacted by surface runoff due to variability in landscape cover features, as well as surface area of the catchment. However, during base flow regimes spring inputs are the dominant drivers of solute concentrations and chemical variability. Geothermal sources play a major role in salinization of the southwestern stream systems. Prolonged water/rock interaction combined with high temperature, pressure result in chemical change which alters the composition of the surface runoff. This study investigates correlations of solute loading of the Gila River on temporal and spatial scales implementing geochemical, statistical and modeling analysis of the period of record. Significant spatial variability is evident by progressive downstream increases in solute concentrations. This report includes a 108 river mile reach of the upper Gila River. Regional climate change scenarios predict an increase occurrences of base flow regimes resulting in increased frequency of peak salinization. Implications of such scenarios could result in stress on a wide range of ecological communities and negative effects on water quality for downstream users. This study provides a crucial baseline information for determining system’s response to projected climate change, and data which allows to delineate natural salinization sources from anthropogenic impacts on water quality.