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Thank you to everyone who attended the 11th Annual Salt Lake County Watershed Symposium! This free two-day conference encourages a comprehensive review of the current state of our watershed while creating learning opportunities for a diverse array of stakeholders. Sessions covered a broad range of topics on water quality and watershed issues with local, regional, and national relevance. Hosted by Salt Lake County Watershed Planning & Restoration.

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Thursday, November 16 • 11:40am - 12:10pm
Nutrient Cycling in the Jordan River: Seasonal & Spatial Variations

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Nutrient Cycling in the Jordan River: Seasonal & Spatial Variations

Water reclamation facilities dominate nutrient loads to the river, although some processing by in-stream biota is also present. The influence of facilities varies spatially and seasonally.

Full Abstract:
Arid regions face increasing pressure to manage water quantity and quality in the face of urban expansion and climate change. As greater percentage of a catchment's water balance flows through engineered urban system, it is crucial to understand how these engineered flowpaths influence downstream ecosystems. The Jordan River, which drains the Salt Lake City urban region receives significant nutrient loading from four water reclamation facilities (WRFs), as well as urban runoff, and natural sources from seven alpine streams which flowing through the urban core before entering the river. The river experiences periods of seasonal hypoxia, especially in low-velocity reaches downstream of several nutrient sources. Nutrient availability can influence microbial respiration of organic matter in rivers. It is therefore crucial to understand the relative role of nutrient inputs and in-stream processing on N, P and C transport. We sampled the Jordan synoptically during three distinct seasonal hydroperiods (spring/snowmelt, summer, and fall drawdown) in order to better understand the river’s role as a transporter and transformer of nutrients throughout the year. Sampling locations included above and below each of three WRFs, as well as and ‘intensive’ reach every 1km downstream of the surplus canal near 1700S. We also sampled effluent outfalls. At each site, we measured concentrations of dissolved N and P species (nitrate, ammonium, organic N, phosphate, and organic P), particulate N and P, as well as DOC in surface water. Cumulative TDN and TDP loads from WRFs upstream of 1700S were equal to or greater than the riverine load at this location, however reach-scale patterns show substantial N and P removal from the water column. In the 13km reach between Jordan Basin and South Valley, TDN and TDP loads declined by 43 and 55% respectively during spring runoff. TDN increased in the reach between South Valley and Central (26 and 3% increase during spring and summer), while this reach remained a sink for TDP (25 and 53% removal in spring and summer). Shifting forms (organic vs. inorganic) of nutrients provided further evidence of biotic processing between WRF outfalls. Across seasons, we found that the organic character of the TDN was highest directly downstream of a WRF outfall, and became dominated by inorganic N downstream. TDP showed the opposite pattern, with the high inorganic P downstream of outfall sites, and increasing organic P content further downstream. Stable isotope content of NO3- increased steadily along the entire reach of the river between Utah Lake and 1700s, as expected in response to cumulative effluent loading. Unexpectedly, however, stable isotopes of N declined along the intensive reach (downstream of 1700), suggesting an additional NO3- sources in this reach. Our results suggest that, while nutrient loading to the river is dominated by point-source anthropogenic inputs, biotic processes and in-stream storage influence the quantity of N and P transported downstream, and additional nutrient inputs offset any ecological uptake.


Rose Smith

Research Assistant Professor, University of Utah
I am an ecosystem ecologist, and my research interests include the ways in which human activities and climate change influences ecological function of river corridors. Much of my work focuses on the interaction of urban infrastructure and freshwater ecosystems, specifically focusing... Read More →

Thursday November 16, 2017 11:40am - 12:10pm MST
Lower Level: Ballroom C