Seasonal and Longitudinal Water Quality Dynamics in Three Effluent-Dependent Rivers in Arizona

Abstract

The seasonal and longitudinal water quality dynamics across different geographic and climatic factors were investigated across six reaches of three effluent-dependent rivers in Arizona. We observed water quality deterioration (e.g. elevated temperature and low dissolved oxygen) in some reaches during the hottest summer months and significantly greater natural remediation of water quality in longer reaches for several factors (temperature, dissolved oxygen and ammonia). Nearly all sites met or exceeded water quality conditions needed to support robust assemblages of native species (except Tres Rios reach during elevated ammonia in summer and fall measurement). However, this study also indicates that conditions based on temperature, oxygen level and ammonia may be stressful for the most sensitive taxa at sites closest to effluent outfalls, especially in summer. Overall, effluent-dependent streams have the capacity to serve as refuges for native biota, and they may become the only aquatic habitat available in many urbanizing arid and semi-arid regions.