Advancing the Food-Energy–Water Nexus: Closing Nutrient Loops in Arid River Corridors
2016
Mortensen, Jacob G. | González-Pinzón, Ricardo | Dahm, Clifford N. | Wang, Jingjing | Zeglin, Lydia H. | Van Horn, David J.
Closing nutrient loops in terrestrial and aquatic ecosystems is integral to achieve resource security in the food-energy-water (FEW) nexus. We performed multiyear (2005–2008), monthly sampling of instream dissolved inorganic nutrient concentrations (NH₄–N, NO₃–N, soluble reactive phosphorus-SRP) along a ∼ 300-km arid-land river (Rio Grande, NM) and generated nutrient budgets to investigate how the net source/sink behavior of wastewater and irrigated agriculture can be holistically managed to improve water quality and close nutrient loops. Treated wastewater on average contributed over 90% of the instream dissolved inorganic nutrients (101 kg/day NH₄–N, 1097 kg/day NO₃–N, 656 kg/day SRP). During growing seasons, the irrigation network downstream of wastewater outfalls retained on average 37% of NO₃–N and 45% of SRP inputs, with maximum retention exceeding 60% and 80% of NO₃–N and SRP inputs, respectively. Accurate quantification of NH₄–N retention was hindered by low loading and high variability. Nutrient retention in the irrigation network and instream processes together limited downstream export during growing seasons, with total retention of 33–99% of NO₃–N inputs and 45–99% of SRP inputs. From our synoptic analysis, we identify trade-offs associated with wastewater reuse for agriculture within the scope of the FEW nexus and propose strategies for closing nutrient loops in arid-land rivers.
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