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Back to the Future Part 2

Project ID: 1967
Principal Investigator: Fred Liljegren
Research Topic: Supporting Irrigation Districts
Priority Area Assignments: 2013 (Climate Change and Variability Research)
Funded Fiscal Years: 2013
Keywords: climate change

Research Question

How can Reclamation guided research studies help maintain water supplies for the future existence of the Wasatch Front metropolitan region through planning efforts that are complicated by climate change, increasing temperatures, greater evaporative demand, possible earlier snowmelt and late season shortages, and emergence of cyclic drought?

Can planning for future water supply and demand in a changing climate fraught with the uncertainty of high impacts from droughts be aided by past precipitation and streamflow data re-created from a suite of tree ring chronologies and can Decadal Cycles from these models be identified? (Proposed refinement)

Water Districts participating in this research now all agree climate change is occurring and requested more analysis of quasi-decadal (12-15 year and 30-50 year) wet and dry cycles from the tree ring analysis to concur with research by S. Wang, and R. Gillies ( Great Salt Lake, Winter Precip Change). A significant change in climate in this region began in 1977 as the Water Districts now realize. Historical stream flow models may not be good predictors of future events. The cycles identified are more valuable for use as noted by the Water Districts. Particular interest is where inflection points for wet and dry cycles occur. Water Districts will need to deal with wet and dry extremes in precipitation, longer growing seasons with increased water demand for irrigated crops and landscapes. Less late season water stored in reservoirs will result in more conservation programs and efforts to use less water for irrigation. However, knowing when changes to wet and dry cycles occur will be critical to Water Districts as they implement conservations efforts months and years in advance. Coordinating this work with S. Wang and R. Gillies should help refine some of the "noise" in decadal cycles in this research.

Need and Benefit

Maintaining water supplies for the future existence of the Wasatch Front metropolitan region is uncertain. Meeting needs of increasing population will require balancing reduction in need per capita use demand through conservation with politically adroit increase in supplies. Planning for this balance is complicated by climate change, increasing temperatures that will increase evaporative demand of urban plant water use, while creating earlier snowmelt and late season shortages. Planning for future water supply and demand in a changing climate is fraught with the uncertainty of unforeseen, high impact (but predictable in hindsight) droughts.

The Wasatch Front metropolitan region, from Logan through Ogden, Salt Lake City, and past Provo, depends on regular input of mountain snow to exist. Approximately two million people consume treated, potable water impounded from snow runoff or pumped from percolated ground water for indoor personal use and outdoor irrigation of largely turfgrass landscapes.

Long-term water supplies for the Wasatch Front metro region's future are strained and threatened. Utah has one of the highest population growth rates in the country, nearly 30% from 1990-2000, and a similar trajectory since then. High population growth and very high per-capita water use rates will create future demand that is projected to exceed limited existing supplies. Water wholesalers and the Utah State Division of Water Resources are focused on bringing future water demand and supply into balance: water conservation, particularly in irrigated urban landscapes, to reduce demand and limited expansion of water impoundment structures to increase supply.

Balancing future urban water supply and demand is threatened by climate uncertainty. Year-to-year climate variability characterizes northern Utah, including years of below normal snowfall that causes socio-economic drought, and hotter years that increase evapotranspiration and, hence, urban water demand.

However, future climate change projections suggest increased demand and reduced supply. Climate models suggest that spring precipitation will increase at mid to higher elevations but decrease at lower elevations (Wang et al. 2010), suggesting drier early growing seasons and increased water demand for irrigated landscapes in the lower elevation urban areas. Increased high elevation precipitation is unlikely to help water supplies because it is predicted to come as rain, rather than snow, due to increased temperatures (Wang et al. 2009). Increased rain will melt the snowpack sooner, reducing late-season urban water supplies for urban areas dependent on historically slow snowmelt that keeps reservoirs full well into the summer. Less late season water stored in reservoirs means less water for urban irrigation and greater chance of late season water shortages.

Historical climate variability indicating extreme drought also is a significant threat to urban water supplies and may interact with projected climate in unforeseen and potentially worrisome ways. Utah's water wholesalers' drought contingency plans to reduce water demand are based on short duration dry periods as observed in the recent historical record. However, drought over the past 50 years in northern Utah has been very mild compared to the historical record (Gray et al. 2004). Peering further back in time through dendrochronology shows the potential for severe drought far surpassing that observed in the historical record and shows the potential for "Black Swan Theory" droughts; unforeseen, high impact, but predictable in retrospect. In particular, data suggest droughts appear cyclically, about every 12, 50,and 150 years, that can align harmonically in a megadrought. Future harmonic interaction of drought cycles could interact with projected climate changes to have a particularly negative impact on water supplies and Utah's water wholesalers at several levels.

Contributing Partners

None

Research Products

Research Paper(s) identifying:
1.Reconstruct paleo-climate of northern Utah:
a.Develop a range of working chronologies from existing and preliminary tree ring chronologies collected from climate sensitive trees in the Wasatch Mountains
b.Explore correlation between a unique range of northern Utah tree ring chronologies and SST oscillation indices
c.Analyze response function of tree ring indices for precipitation, temperature, evaporative demand, and PDSI.
2.Analyze reconstructed northern Utah high snowpack/drought cycles:
a.Assess the potential for "climate instability" that may characterize the Wasatch Front and establish a baseline for our subsequent work
b.Investigate how droughts may change in the future. The range of outcomes amongst the different models will then serve as an estimate for the range of prediction uncertainty.
c.Contribute these outcomes to the scientific literature and extend to the general public, water managers, and policy maker stakeholders.

This information was last updated on October 30, 2014
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