HR: 1340h
AN: H13F-1381    [Abstracts]
TI: Evaluating Riparian and Agricultural Systems as Sinks for Surface Water Nutrients in the Upper Rio Grande
AU: * Oelsner, G P
EM: goelsner@hwr.arizona.edu
AF: University of Arizona, Dept. of Hydrology and Water Resources, 1133 E James E Rogers Way Harshbarger Bldg., Tucson, AZ 85721 United States
AU: Brooks, P D
EM: brooks@hwr.arizona.edu
AF: University of Arizona, Dept. of Hydrology and Water Resources, 1133 E James E Rogers Way Harshbarger Bldg., Tucson, AZ 85721 United States
AU: Hogan, J F
EM: jhogan@hwr.arizona.edu
AF: University of Arizona, Dept. of Hydrology and Water Resources, 1133 E James E Rogers Way Harshbarger Bldg., Tucson, AZ 85721 United States
AU: Phillips, F M
EM: phillips@nmt.edu
AF: New Mexico Tech, Dept. of Earth and Environmental Science, Hydrology Program, 801 Leroy Place, Socorro, NM 87801 United States
AU: Villinski, J E
EM: john@hwr.arizona.edu
AF: University of Arizona, Dept. of Soil, Water and Environmental Science, 1177 E Fourth Street Room 429 Shantz Building #38, Tucson, AZ 85721
AB: We have performed five years of biannual synoptic sampling along a 1200km reach of the Rio Grande to develop relationships between discharge, land use, and major water quality parameters. Both total dissolved nitrogen (TDN) and dissolved organic carbon (DOC) concentrations gradually increase with distance downstream, however for TDN and phosphate this trend is punctuated by large, localized inputs primarily from urban wastewater. Somewhat surprisingly, surface water draining from areas of intensive, irrigated agriculture during the growing season often had lower nutrient and DOC concentrations than the river. To better quantify the effects of urban and agricultural systems on water quality we conducted three years of higher spatial resolution sampling of a 250km reach (between Cochiti Dam and Elephant Butte Reservoir) that contains both major agricultural and urban water users. During the higher flow years of 2001 and 2005 TDN concentrations in the river were higher (x = 1.19mg/L, SD = 0.21) than in the drier years 2002-2004 (x = 0.52mg/L, SD = 0.42). TDN concentrations decreased from 1.97mg/L to 0.78 mg/L in a 5km reach below the Albuquerque wastewater treatment plant during the low discharge year of 2004, but there was little to no decrease in TDN concentrations over the 180km below the wastewater treatment plant in years with higher river discharge. In contrast, water diverted to agricultural fields and returned to the river in drains experienced a 60% reduction in TDN concentrations in dry years and a 30% reduction in wet years compared to initial river water. During the dry years, water in the conveyance channel appears to be a mixture of river and drain water whereas in wetter years the conveyance channel has a lower average TDN concentration than either the river or the drains. These data suggest that the river-riparian-hyporheic system of the Rio Grande can serve at best as a weak N sink, while the combination of agricultural fields and drains serve as a strong nutrient sink. Ongoing research is quantifying the locations and potential rates of N transformation in both the river and agricultural drain systems.
DE: 0458 Limnology (1845, 4239, 4942)
DE: 0469 Nitrogen cycling
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0496 Water quality
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: Fall Meeting 2005