Understanding NO3 Dynamics in the Middle Rio Grande Basin Irrigation Network in the Context of the FEW Nexus
Abstract
Wastewater treatment plants (WWTPs) use a combination of secondary and tertiary treatment to process waste and reduce effluent nutrient concentrations, but WWTPs still remain the primary source of nutrients to arid river systems. In the Middle Rio Grande Basin, the Rio Grande River is diverted below the nitrate-rich Albuquerque WWTP (ABQWWTP) effluent into the Middle Rio Grande Conservancy District (MRGCD) irrigation network, where it is used to flood irrigate pasture crop consisting of mainly grass and alfalfa. Previous studies have indicated the irrigation network serves as a sink to the ABQWWTP nutrients during the growing season, but little is known about the underlying mechanisms of nutrient removal in this system. Understanding such mechanisms would promote resource sharing by the ABQWWTP and MRGCD by means of the irrigation network, thus reducing water and energy consumption by both entities. We explored nitrate processing in the network by calculating a monthly nutrient budget between Oct 2017 and Nov 2018 along 20km reaches of two major agricultural canals (a delivery canal and a receiving drainage canal) and the Rio Grande River, supplementing this analysis with nutrient uptake experiments and NO3 stable isotope analysis. We used δ15N-NO3 and δ18O-NO3-to determine the cause of the source/sink behavior within the three reaches and nutrient uptake metrics to quantify the removal capacity of the agriculture canals. Results from the non-growing season indicate the drainage canal releases a flux of approximately 10.1 kg/km2.day. During the growing season, the drainage canal removes approximately 34.8 kg-NO3/km2.day while the delivery canal removes approximately 36.2 kg-NO3/km2.day. The nutrient uptake experiments indicated the drainage canal was not saturated in N and thus has the capacity to processes larger nitrate loads and stable isotope analysis revealed processing by likely done by aquatic plants. Our data suggest that we could use the irrigation network to optimize FEW resources by allowing primary producers in the drainage canals to further treat secondary or limited tertiary WWTP effluent, while simultaneously limiting uptake in delivery canals to maximize WWTP nutrient delivery to the fields.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B33G2767B
- Keywords:
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- 0402 Agricultural systems;
- BIOGEOSCIENCESDE: 0428 Carbon cycling;
- BIOGEOSCIENCESDE: 0495 Water/energy interactions;
- BIOGEOSCIENCESDE: 1843 Land/atmosphere interactions;
- HYDROLOGY