By Simon Wang |
Utah's Water Future
Drought and heat are no strangers to Utah. The proud residents of the nation’s second driest state have in the past century built dams, dug canals, drilled wells, and used every source of water to build sustainable towns and cities. Today this massive and sophisticated water supply system dutifully supports 2.9 million people, providing convenient and plentiful water for irrigation, homes, and electricity. When there was not enough precipitation, more groundwater was pumped; when there was too much, we pumped it out to the desert. We controlled water. On the few occasions we teetered on the brink of real drought, our mountains — reservoirs of frozen water — and a little extra snow would always save the day, and so it will again.
Or will it?
Modern settlements in Utah are barely 150 years old. But data describing the climate of a deeper past — a paleoclimate — tell a story of conditions often different from the ones the state’s modern residents have experienced. The climate information stored in tree rings reveals episodes of drought much longer in time and deeper in magnitude. Such prehistoric mega-droughts (by modern standards) were not only common in the past millennium but periodic, having come and gone every 50 years or so. The perceived severity of droughts of the 1930s and 1950s was no match for droughts of the hundred years before. Additionally, while our most recent drought, lasting from 2000-2004 and responsible for the record low water level of Lake Powell, was the worst in 800 years for its intensity, it’s duration was, by comparison, mercifully short.
Then came 2013. By July 2013, all Utah counties were federally declared as drought disaster for the second year. In Salt Lake City, August daily minimum (mostly nighttime) temperatures not only broke the previous record but shattered it by 3 degrees Fahrenheit — a true outlier! Moreover, July and August’s mean temperatures set new records going back more than a century. As of September, more than half of Utah’s reservoirs were are below 50% of capacity and dropping. High temperature combined with shallow water also degraded water quality. Being a kayaker myself, it proved difficult to find lakes with deep water, free of mud and stench, by late summer.
We need a winter with big snow.
For the past 60 years, Utah’s precipitation has exhibited a clear oscillatory feature alternating between wet and dry periods every 10-15 years. This unique “wet/dry cycle” is highly influenced by the Pacific Ocean’s slow changes over a similar period; warm water pools in the central tropical Pacific, then transitions to cool water over the next six years or so. As it turns out, winter precipitation over Utah, especially northern Utah, is affected by this cycle. Specifically, a wet cycle develops about three years after the Pacific waters begin their transition from warm to cool; similarly, a dry cycle develops about three years after the Pacific waters begin their transition from cool to warm. This provides a climatic signal, allowing scientists to forecast Utah’s precipitation change, years in advance. The climate faculty in USU’s College of Agriculture and Applied Sciences, including myself, with support from the Utah Agricultural Experiment Station, researched this approximately three-year time lag extensively within the 10-15 year cycle. It is important to note that this Pacific influence is not to be confused with the better-known El Niño/La Niña phenomenon. El Niño/La Niña only explains less than 20% of Utah’s precipitation variation, and such a mild impact prevents operational prediction models from producing reliable seasonal forecasts beyond one month. The late Fredrick Liljegren of the Bureau of Reclamation once said, if he could have 20% confidence in any prediction for the next season, he’d be happy.
Our research group has been working hard to make Fred happy: In a 2010 paper published in the Journal of Hydrometeorology, we have predicted that the years of 2012 and 2013 will be at the driest phase of the 10-15 year wet/dry cycle with a climbing lake level. This has proven to be the case given 2013’s continued drought status of the state. The good news is we may soon begin to enter the recovery phase of this drought cycle. Three years from now we shall see at least one winter with above-normal snowfall. As to this coming winter of 2013-14, models are predicting a near normal, slightly warm and dry snow season. That means it is unlikely we’ll see a break from the two-year-old drought. Even though there is a chance for above-average precipitation, it’s not something we should plan on from a risk-management perspective. Consequently, water managers are worried.
Back-to-back drought is what water managers in the West are uniformly concerned about. Any drought longer than two years rapidly reduces water reliability and severely strains our water supply systems, and Utah is prone to such drought. In 2012 the research team held a “water-climate roundtable meeting”, where 12 governmental and other private water agencies were presented with the latest research on water and climate. The meeting’s intent was to connect regional water managers with years of research and help them seek solutions to current and future challenges in water resources. The meeting produced marked interest in paleoclimate data and the need for climate (rather than weather) prediction in order to mitigate water demands from a growing population. Everyone recognized that water supply estimates driven by paleoclimate data could fundamentally assist in planning. Meanwhile, those mega-droughts of the past millennium, seen through the eyes of trees, could be persuasive to the public and policymakers alike, that the severe water shortages of the distant past may reappear with or without a warming climate.
Over two-thirds of Utah counties depend on groundwater for at least 70% of their public supply. Everyone can see a shrinking snowpack in the mountains, but falling levels of groundwater are invisible to public eyes. The fact that groundwater levels across Utah have been declining since the late 1970s poses a threat to farming. Fights over groundwater – “water grabs” – threaten rural communities and wildlife as people compete for water rights. A vivid example is the long-running fight over eastern Nevada’s groundwater, some of which flows into Utah and supports some of the driest parts of the state. This legal battle for water won’t dry up anytime soon, though it will become increasingly costly. Not surprisingly, we have found that Utah’s groundwater fluctuates in concert with our 10-15 year wet/dry cycle, meaning that multi-year droughts can and will worsen groundwater depletion, drying up wells and fueling yet more water grabs.
What do we do?
The Bureau of Reclamation has already announced that water supply of the mighty Colorado River will no longer meet its current water demand. To mitigate for foreseeable water shortage, Utah has implemented statewide water conservation programs aiming for a 25% reduction by 2050. However, if future population projections are accurate, an additional 540 million cubic meters (approximately 440,000 acre-feet) will still be required over and above conservation to meet anticipated demand. Meeting future demands under variable climate conditions further challenge water suppliers to provide for agricultural and urban water users. This is a delicate problem requiring all sides of expertise, from climate science to political science, from hydrological engineering to water managing. It is a challenge, but also an opportunity; an opportunity to open dialogues and open minds.
Writer: S.Y. Simon Wang, 435-757-3121, firstname.lastname@example.org