2016 Salt Lake County Watershed Symposium

Jordan River Valley & Water Resources Status in the 2040s & 2090s
One of the major challenges faced by local municipal authorities and regulators in the US is developing a future implementation plan to protect water availability (i.e., water quantity and quality) and attain Total Maximum Daily Load (TMDL) considering uncertain future change drivers including climate change, land use changes, population growth and other water management practices.

In this presentation, we consider a case study of the Jordan River and its tributaries, a watershed which encompasses mountainous headwaters that supply water to a highly urbanized valley with irrigation canals, stormwater and treated wastewater return flows. We present our research findings in four areas by a group of multidisciplinary experts on: (a) Climate change and climate variability: what are the major climatic parameters that will have significant changes in their magnitude, and how will these changes in climate impact water resources in the Jordan valley? (b) Land use and land cover changes in Jordan valley: (i) how will land use and land cover change in the valley based on socio-economic drivers? (ii) How land use and land cover will change in the valley if we consider Wasatch Choice 2040 – the shared regional vision established by Wasatch Front communities? (c) Hydrological impact: (i) what will be the impact of the climate change and land use on water availability in creeks that are the major sources of water supply for the valley? (d) Water quality impact: (i) what will be the impact of future climate, land use changes and population growth on nutrient loading and dissolved oxygen levels in different sections of the Jordan River.

The results are based on our coupled modeling work: (i) dynamically downscaled regional climate model (Weather Research and Forecasting; WRF) output at 4-km horizontal resolution and hourly time step covering Utah State for 1985 to 2010, and in the decades of 2040s and 2090s; (ii) A probabilistic equilibrium land use model for 2040, and the regional land use vision embodied in in Wasatch Choice 2040; (iv) The HSPF model (Hydrologic Simulation Program-Fortran) - calibrated and validated based on the stream flow data available from 1993 to 2006, and simulated for decades 2040s and 2090s considering the future changes.

This body of research is an example of integrated and coupled modeling for watershed science in the face of variability, uncertainty and complexity. This holistic modeling approach and results will be helpful in analyzing water availability and water quality in Jordan River Valley for periods of time to the end of the current century, and will support development of rational watershed plans to protect vulnerable water resources.

Keywords: Climate change; land use change; watershed modeling; water availability; Total Maximum Daily Load.