Human populations in Colorado, New Mexico and Texas depend on the Rio Grande for municipal water, agricultural irrigation, and recreation. The Rio Grande and its riparian corridor also support thousands of species of plants, invertebrates and vertebrates, some of which include over 300 species of migratory birds and the endangered Rio Grande silvery minnow and southwestern willow flycatcher. Eutrophication and salinization are the two most important types of water quality degradation which negatively impact the human and nonhuman biological communities in this water poor region. In spite of their significance, few published studies have investigated anthropogenic and natural sources of nutrients and dissolved solids to the Rio Grande. This study investigated the patterns and trends of nutrients and dissolved solids in the Middle Rio Grande (MRG) on a monthly basis from September 2005 – January 2008. During all months, wastewater treatment plants were the major source of nutrients to the MRG. Under high flow conditions, nutrient levels remained elevated for 260 river kilometers below the wastewater inputs. During months when significant portions of the river flow were diverted for irrigation, nitrate and phosphate were removed from the MRG and concentrations at the downstream end of the reach were returned to levels comparable to the un-impacted northern reach of river. Dissolved solids were added to the river by both wastewater and saline tributary inputs. Both anthropogenic and natural inputs of dissolved solids were found to affect water quality in the MRG. Continuous real-time measurements of temperature, pH, turbidity, dissolved oxygen, and conductivity also were initiated at four sites above and through the urban reach of the City of Albuquerque. Preliminary results show increasing turbidity and dissolved oxygen depletions associated with storm runoff from urban areas.
The objectives of this study were to: 1) conduct a detailed assessment of the temporal and spatial trends in water quality of the MRG, 2) determine sources of eutrophication and salinization along the MRG, 3) estimate instream nutrient processing and retention, 4) calculate the effects of urbanization on dissolved oxygen and stream metabolism values in the MRG, and 5) provide baseline data for future water-quality monitoring and assessment in the MRG.
Four sites were chosen within the Albuquerque reach for continuous measurement of five water-quality field parameters; temperature, conductivity, pH, turbidity, and dissolved oxygen. Sites were chosen to provide instrument stability and a gradient of urban influence with the most northern site located above urban wastewater inputs and the southern site below the Bernalillo, Rio Rancho, and Albuquerque wastewater treatment plants.
Readings were collected every fifteen minutes.
Sondes were recalibrated in the field every two to four weeks following manufacturers specifications.
* Instrument Name: Multi-Parameter Water Quality Sonde
* Manufacturer: Yellow Spring Instruments
* Model Number: YSI 6920
This data has been visually inspected to: 1) identify outliers and periods when the units were buried by sediment or were not functioning properly, and 2) examine the data for consistency of individual observations with temporal and spatial trends seen at upstream and downstream units.
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