Sixteen years of #drought in the #ColoradoRiver Basin: Reality or talking point? — Eric Kuhn

From The Grand Junction Daily Sentinel (Eric Kuhn):

I was recently reading an article on the negotiations among the Lower Basin states concerning their use of Colorado River water when I came across this phrase: “after 16 years of drought.” It’s a phrase I’ve been seeing for many years now. Except, of course last year it was “after 15 years of drought” and two years ago it was “after 14 years of drought” and so on.

That same day I read another article discussing a forecast by the National Oceanic and Atmospheric Administration (NOAA) that the El Niño is waning and the atmospheric models are predicting that by fall we have a 70 percent chance of a La Niña. These two conditions in the Pacific Ocean greatly influence Colorado precipitation patterns. Why do these two seemingly unconnected events concern me? I’m concerned because the term drought implies conditions will get better. The reality may be otherwise. [ed. emphasis mine]

First, if we look at inflows to Lake Powell since the year 2000, they’ve been below the long-term average. Therefore, we can make the case that the Colorado River Basin is in a drought. However, if we look to our local conditions in Colorado, we are certainly not in a drought. In fact, since the flooding rains in the fall of 2013 I believe we’ve been in time of plenty or “pluvial.”

Let’s look at water supply conditions in Colorado. In the Upper Colorado River Basin, Granby Reservoir, the largest reservoir in the transmountain Colorado-Big Thompson Project, spilled last year and may again this year. Granby Reservoir, the second largest in the state, spills quite rarely. It last happened after the mid-1980s and late-1990s wet cycles.

Last year Denver Water barely operated the Roberts Tunnel that delivers Dillon Reservoir water under the Continental Divide to its service area. This year, it may not have to turn on the tunnel until July or August. On the West Slope, in 2015, the Colorado River through Glenwood Canyon saw the highest run-off flows since 1984. And since 2013, West Slope river calls by senior water rights holders have been infrequent. In the Arkansas River basin, Pueblo Reservoir and John Martin Reservoir, its two largest, are close to full. Again, all of this only happens after multi-year wet spells.

OK, if Colorado has not been in a drought, and Colorado’s mountains produce about two-thirds of the total run-off of the Colorado River system: Why is total storage in Lake Powell and Lake Mead continuing to decline?

I believe there several reasons: First, the demand for Colorado River water in the Lower Basin exceeds the available supply. As required by the 2007 Interim Operating Criteria, Lake Powell has been delivering a little extra water to Lake Mead. It did so in 2015, will this year and will most likely do so again in 2017. Even with this extra water, the demand for water below Lake Mead exceeds its inflow, thus it continues to lose storage.

Which in turn requires Lake Powell to continue delivering extra water. This means that even with decent inflows to Lake Powell, it can’t gain storage. Lower Basin water officials refer to this imbalance as the “structural deficit.”

They are working on solutions, but the solutions will be painful. Thus it helps to refer to what is happening in the basin as a “16-year drought.” Second, it’s looking more and more likely that warming regional temperatures have turned above-average to abundant precipitation into just average run-off. Recently published science papers have zeroed in on this problem and the consequences of warming on the Colorado River basin are very serious.

Finally, what does this have to do with a potential La Niña? Just like they have in the past, our current period of plentiful precipitation in Colorado will come to an end and it may well be replaced with a period of real drought. Often, but not always, this happens as a strong El Niño is replaced by La Niña conditions. After the 1957-58 strong El Niño, 1959, 1960 and 1961 were all dry years. After the 1973 strong El Niño, three out of the next four years, 1974, 1976 and 1977 were dry and 1977 remains the lowest single year of record for inflow to Lake Powell.

After the 1998 strong El Niño, 1999 was an OK year, but it was followed by the 2000-2004 drought, one of the driest on record for Colorado. There are, of course, exceptions. After the 1982-83 strong El Niño, conditions in Colorado remained very wet for the next four years. So I’m not making a prediction.

We don’t know exactly how deep or how long the predicted La Niña will last or if it will bring drought conditions. But, I’m putting out a warning. If we are headed for a real drought as opposed to a talking point, the consequences for the Colorado River basin are frightening. Unlike, the beginning of the 2000-2004 drought period when the Lake Mead and lake Powell were brim full, today they are only about 40 percent capacity when measured jointly!

What does this mean for western Colorado? I believe the answer is that we can’t be fooled by talk of continuing drought. Instead we need to be diligent and fully prepared for the next drought. It means a continued focus on conservation, the development of drought contingency plans, the wise use of our existing, and where possible, the expansion of water storage reservoirs. Finally, we need to better inform and educate our public on the vulnerability our water resources. If indeed, our current pluvial is replaced by drought in the next few years and we are not prepared — shame on us!

Eric Kuhn is the general manager of the Colorado River Water Conservation District, based in Glenwood Springs.

From CBS Las Vegas:

Lake Mead’s already low water levels are expected to drop even further. The “Las Vegas Sun” says the man-made reservoir could surpass its historic low after next Wednesday. And by the end of June, Lake Mead’s water level could be the lowest since its creation in 1935.