TY - JOUR
T1 - Seasonal and longitudinal water quality dynamics in three effluent-dependent rivers in Arizona
AU - Hamdhani, Hamdhani
AU - Eppehimer, Drew E.
AU - Quanrud, David M
AU - Bogan, Michael T.
N1 - Funding Information: 27 °C) and cold winters (average low January temp: −12 °C). Annual average precipitation is ~588 mm, and rainfall is bimodal. The months of February and August are wettest, and June and November are driest (data provided by NOAA ESRL Global Monitoring Division, Boulder, Colorado, USA; http://esrl.noaa.gov/). However, because of underlying volcanic geology, only 0.25 cm per year becomes stream flow within the Rio de Flag, making it one of the lowest percentage runoff systems in Arizona (Bills & Enyedy, 2015). Our ‘Central’ reach (~3 km long) is supported by the Rio de Flag Water Reclamation Plant in central Flagstaff. This plant began discharging into the river in 1993, was upgraded in 2009, and discharges approximately 2.4 million liters of tertiary treated effluent per day into the reach (City of Flagstaff, 2020; personal correspondence: Erin Young, City of Flagstaff). Our other Rio de Flag study reach, ‘Wildcat’ (~4 km long), is located approximately 10 km downstream of the Central reach, and is supported by the Wildcat Funding Information: The following grant information was disclosed by the authors: Indonesia Endowment Funds for Education. University of Arizona. Lincoln Institute’s Babbitt Dissertation Fellowship Program. Funding Information: During the sampling and writing of this study, Michael T Bogan was supported by start-up funding from the University of Arizona and Drew Eppehimer was supported by the Lincoln Institute’s Babbitt Dissertation Fellowship Program. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Publisher Copyright: Copyright 2023 Hamdhani et al.
PY - 2023/3
Y1 - 2023/3
N2 - Effluent-fed streams, which receive inputs from wastewater treatment plants, are becoming increasingly common across the globe as urbanization intensifies. In semi-arid and arid regions, where many natural streams have dried up due to over extraction of water, many streams rely completely on treated effluent to sustain baseflow during dry seasons. These systems are often thought of as ‘second-class’ or highly disturbed stream ecosystems, but they have the potential to serve as refuges for native aquatic biota if water quality is high, especially in areas where few natural habitats remain. In this study, we investigated seasonal and longitudinal water quality dynamics at multiple sites across six reaches of three effluent-dependent rivers in Arizona (USA) with the objective (1) to quantify changes in effluent water quality due to distance traveled and season/climate and (2) to qualify whether water quality conditions in these systems are sufficient to support native aquatic species. Study reaches ranged in length from 3 to 31 km and in geographic setting from low desert to montane conifer forest. We observed the lowest water quality conditions (e.g., elevated temperature and low dissolved oxygen) during the summer in low desert reaches, and significantly greater natural remediation of water quality in longer vs. shorter reaches for several factors, including temperature, dissolved oxygen and ammonia. Nearly all sites met or exceeded water quality conditions needed to support robust assemblages of native species across multiple seasons. However, our results also indicated that temperature (max 34.2 °C), oxygen levels (min 2.7 mg/L) and ammonia concentrations (max 5.36 mg/L N) may occasionally be stressful for sensitive taxa at sites closest to effluent outfalls. Water quality conditions may be a concern during the summer. Overall, effluent-dependent streams have the capacity to serve as refuges for native biota in Arizona, and they may become the only aquatic habitat available in many urbanizing arid and semi-arid regions.
AB - Effluent-fed streams, which receive inputs from wastewater treatment plants, are becoming increasingly common across the globe as urbanization intensifies. In semi-arid and arid regions, where many natural streams have dried up due to over extraction of water, many streams rely completely on treated effluent to sustain baseflow during dry seasons. These systems are often thought of as ‘second-class’ or highly disturbed stream ecosystems, but they have the potential to serve as refuges for native aquatic biota if water quality is high, especially in areas where few natural habitats remain. In this study, we investigated seasonal and longitudinal water quality dynamics at multiple sites across six reaches of three effluent-dependent rivers in Arizona (USA) with the objective (1) to quantify changes in effluent water quality due to distance traveled and season/climate and (2) to qualify whether water quality conditions in these systems are sufficient to support native aquatic species. Study reaches ranged in length from 3 to 31 km and in geographic setting from low desert to montane conifer forest. We observed the lowest water quality conditions (e.g., elevated temperature and low dissolved oxygen) during the summer in low desert reaches, and significantly greater natural remediation of water quality in longer vs. shorter reaches for several factors, including temperature, dissolved oxygen and ammonia. Nearly all sites met or exceeded water quality conditions needed to support robust assemblages of native species across multiple seasons. However, our results also indicated that temperature (max 34.2 °C), oxygen levels (min 2.7 mg/L) and ammonia concentrations (max 5.36 mg/L N) may occasionally be stressful for sensitive taxa at sites closest to effluent outfalls. Water quality conditions may be a concern during the summer. Overall, effluent-dependent streams have the capacity to serve as refuges for native biota in Arizona, and they may become the only aquatic habitat available in many urbanizing arid and semi-arid regions.
KW - Aquatic organism
KW - In-stream natural purification
KW - Urban arid region
KW - Wastewater
KW - Wastewater treatment plant
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U2 - 10.7717/peerj.15069
DO - 10.7717/peerj.15069
M3 - Article
SN - 2167-8359
VL - 11
JO - PeerJ
JF - PeerJ
M1 - e15069
ER -