I25SONDE (Van Horn)

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 to 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.