Linking Water Quantity to Water Quality in the Jordan River, Utah
Water quality in urban rivers is linked to both total discharge and the dominant source of water, which can vary with season and location along a river's flowpath. However, urban rivers are still capable of processing high nutrient loads with adequate hydrologic flow.
Full AbstractArid and semi-arid regions face increasing challenges for provisioning water for human consumption and ecosystem services under a changing climate and population growth. The role of urban water diversions and inputs on water quality in rivers remains poorly understood in many cities. We conducted synoptic surveys over three seasons in one year to evaluate the variability in water sources and geochemistry of an urban river with complex water infrastructure in the state of Utah, USA. Using stable isotopes of river water (δ18O and δ2H) within a Bayesian mixing model framework and a separate hydrologic mass balance approach, we quantified both the proportional inputs and magnitude of discharge associated with ‘natural’ (lake, groundwater, and tributary inputs) and ‘urban’ (effluent and canal inflows) sources. The relative importance of these major contributors to streamflow varied both spatially and seasonally. Spatio-temporal patterns of dissolved oxygen, temperature, pH, calcium, chloride, nitrate (NO3-N), and orthophosphate (PO4-P) indicated that seasonal shifts in dominant sources of river water played an important role in determining water quality. We show that although urban rivers are clearly influenced by novel water sources created by water infrastructure, they continue to reflect the imprint of ‘natural’ water sources, including diffuse groundwater. Analyses of changes to nutrient load in three sections of the river located between water reclamation facilities suggest the river is capable of processing up to 30% of NO3-N loads and over 50% of PO4-P loads, but this capacity is significantly diminished with major hydrologic diversion. In short, water quantity is linked to water quality through the magnitude of total discharge, as well as the dominant source from which water is derived.
Learning Objectives:
- learn how stable isotopes and hydrologic mass balance models can be used in tandem to infer discharge from different water sources to urban rivers
- describe relationships between variation in discharge from different water sources and variation in water quality parameters
- assess biological and physical processing capacity through nutrient load analyses
Primary Author: Jennifer Follstad Shah
