506 Nutrient spiralling in a human-dominated arid land river

Thursday, May 21, 2009: 9:00 AM
Ambassador West
Clifford N. Dahm , Department of Biology, University of New Mexico, Albuquerque, NM
David Van Horn , Department of Biology, University of New Mexico, Albuquerque, NM
Maceo Carrillo Martinet , Department of Biology, University of New Mexico, Albuquerque, NM
Nutrient spiralling finds application in arid land rivers, where wastewater effluent can make up a significant fraction of total flow. Point sources of effluent commonly come with the conservative tracers (e.g. Cl, Br, and F) and nutrient loads (e.g. NO3, NH4, PO4) necessary to conduct large-scale estimates of spiralling. Caution must be exercised to sample far enough downstream of the point source where thorough mixing of effluent and surface water has occurred. This approach has been used to examine nutrient spiralling in the Rio Grande in central New Mexico for about three years. Arid land rivers commonly function as distributary systems to deliver water for agriculture. This water extraction focuses nutrient spiralling in conveyance systems, ditches, and a diminishing river during the irrigation season. Nutrient spiralling metrics more similar to streams often result when irrigation and water extraction are ongoing. Agricultural lands and their conveyance systems become a strong sink for nutrients downstream of the major point source discharger (the Albuquerque wastewater treatment plant) in the central Rio Grande.