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';Water in the Balance'; ... Colorado is a dry state. Annual precipitation in Colorado averages only 17 inches statewide. The majority of the state is considerably drier with only 12-16 inches of precipitation annually. The San Luis Valley in south-central Colorado is the driest region, averaging only seven inches in the center of the valley. In comparison to the large majority of the area of the United States, these precipitation totals are meager -less than half of the precipitation that falls over the U.S. corn belt, for example. But Colorado benefits from much higher precipi- tation amounts on the ranges of the Rocky Mountains that cover the state from nonh to south. Most of the areas above 10,000 feet in elevation average more than 25 inches of moisture annually. with more than 50 inches in a few isolated high-mountain locations. farmers, for hydropower generation. and for rapidly growing thirsty cities. So far. we have done a fairly good job meeting these diverse demands while still delivering the water to down- stream states as prescribed by interstate compacts. We have been able to meet these demands in part through changes in water management, but also (and perhaps most importantly) through the abundance of water availability that we have enjoyed. The last multi-year drought in Colorado ended in 1978. The last two decades have brought Colorado the most reliable precipitation since before the "dust bowl" drought of the 1930s. When drought returns to Colorado, as it surely will, it will be challenging to see just how far we can stretch Our water. With great effort. some planning, and a history of diligence and creativity, Colorado has adapted to this dry climate such that the state successfully maintains a large agricul- tural industry, large and growing urban population centers, a vast and diverse recreational industry and a high quality ofIife for the citizens of the state, while still sending large volumes of water to downstream states on the major rivers. A study of historical dry and wet periods in Colorado was recently completed by the Colorado Climate Center at Colorado State University. This study, which is summa- rized in this report, analyzed precipitation, snowpack, and streamflow data over the last 100 years or so. and provides some important insights into the nature of drought in Colorado. -I But a threat looms over Colorado and its vibrant economy. It is the threat that is with us nearly every year but which often goes unnoticed or ignored. It is the threat of drought -- and the social, economic, and environmental impacts that come with drought. Before we can understand dry, or "below normal", and wet, or "above normal" precipitation, we need to understand what is considered "normal" in Colorado, a state that experiences a wide range of climate patterns in different parts of the state and at different times of the year. We also discuss how and when water is used in Colorado, since this gives us an understanding of who will be impacted by "single season" droughts. We consider some implications of the new uses of water and new demands for water availabil- ity that have developed in Colorado. Finally. we look at Colorado's drought history and what that history can tell us about droughts in Colorado's future. Colorado's population continues to grow rapidly. this population growth has occurred since the last major statewide drought in 1981. In recent decades, there has also been an introduction of several newer uses of water in the state. Water is now needed to support populations of endangered species, mountain snow making. and river and reservoir recreationists as well as more traditional uses for Much of I~ I 1 .Cokmdo :>.-_-'* ""'-'raceJl\iuwalPo. -- r-I_-'l. ;~' , . ....'" ~ 1., - u..,. i, ; ....l' ; th." ; '.' I::: ' ; .."" ; ...,. I 11>..10 ... ... .-. a... ..- ... ....... n;pnl. Colod<M........._~"'"i'_~I.t.r_~c.,..CliooaScniot~ 4