Mixed Blessings

Image: 2011 was a very big runoff year for the Colorado River and its tributaries including the Yampa River shown here. The unusually high flows lasting into early July almost proved to be too much for the author in Warm Springs Rapid (photo by Paul Chelminski)

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At the turn of the new year in 2011 there was nothing remarkable about the snowpack accumulating in the Rocky Mountain headwaters of the Colorado River. But things began to change dramatically in April and May, when storm after storm blanketed the Rockies with record levels of spring snowfall. Unusually cold mountain temperatures forestalled the snowmelt release, until finally, in late May, it began to rush off the mountains in bone-chilling floodwaters.

Figure 1: Heavy snowfall and cold temperatures in spring 2011 produced high flows on the Yampa River that lasted much longer than usual. (Graph from US Geological Survey)

The Yampa River in Dinosaur National Monument peaked on June 9th at nearly 27,000 cfs.  By July 2nd, as we launched our family’s whitewater raft vacation, the river remained at its highest-recorded level for that date at 16,000 cfs. The river was running nearly 8 times higher than what we had expected!

We knew we were in for a wild ride.

Our boats traveled distances in two hours that should have taken eight. The big sand beaches that make for wonderful campsites in normal years were completely under water.  We lost pints of blood to voracious mosquitoes.

But as I like to say, “The worst day on a river is still better than the best day on land.” It was truly a mixed blessing.

With all of that water rushing downstream, 2011 was looking to be a terrific year for water users in the Upper Colorado River Basin. Following a dry decade in which Lake Powell lost one-third of its stored water, the promise of replenishment was a wet blessing. The reservoir was poised to regain most of its lost water in a single year.

But then the US Bureau of Reclamation cranked open Powell’s drain outlets. The reservoir flushed and its hydropower turbines hummed. The reservoir was purging nearly as fast as floodwaters were arriving. Over the course of 2011, the Bureau released 64% more water from Lake Powell than its average annual releases of the preceding decade. As a result, by New Year’s Day of 2012, the reservoir had regained only 10% of its capacity (see green dotted line in Figure 2 below).

Figure 2: If the releases of water from Lake Powell to meet downstream needs would have been limited to 8.23 million acre feet (as many say is the required volume according to the Colorado River Compact), Lake Powell would be nearly full today instead of only 52% of capacity. The releases in 2011 were 64% higher than the average of the preceding decade. (Data source: US Bureau of Reclamation)

It is critically important to note here that the Bureau was playing strictly by the rules that govern its reservoir operations in the Colorado River Basin, or more specifically, the “2007 Interim Guidelines.” As explained by Anne Castle and John Fleck in their recent treatise on The Risk of Curtailment Under the Colorado River Compact, implementation of the Guidelines includes setting criteria for releasing water from Upper Basin reservoirs including Lake Powell in a way that helps balance the contents of Lake Powell and Lake Mead.

During years leading up to 2011, Lake Mead was becoming increasingly in need of help (see green dotted line in Figure 3 below). Between 2000 and the end of 2010 the reservoir had lost nearly 60% of its capacity. As illustrated in the graph below (green dotted line), the high releases of water from upstream Lake Powell were extremely helpful in bolstering its storage.

Figure 3: The high release of water from upstream Lake Powell was very helpful in bolstering water levels in Lake Mead. If the Bureau of Reclamation had instead released only 8.23 million acre feet each year, Lake Mead would be at dead pool (functionally dry) today — see red dotted line. (Data source: US Bureau of Reclamation)

All of which is to say, the Guidelines are a mixed blessing in the Colorado River basin.

In big water years like 2011, the Lower Basin states of Arizona, Nevada, and California benefit by receiving higher releases from Lake Powell into Lake Mead as the Bureau strives to balance their contents. This helps the Lower Basin states to avoid mandatory cutbacks in their water entitlements from Lake Mead. In absence of the Guidelines, if the Bureau had instead been releasing an average of only 8.23 million acre-feet per year (MAF) from Lake Powell over the past two decades (which some have suggested is the minimum required release), Lake Mead would have been completely depleted by now (see red dotted line in Figure 3 above).

On the other hand, the Guidelines limit how much snowmelt the Upper Basin can store or use to replenish Lake Powell. As I explained in a recent blog, if the Bureau had been releasing only 8.23 MAF per year over recent decades, Lake Powell would now be full! (see Figure 2 above for Lake Powell). But instead, without the full benefit of 2011 inflows, Lake Powell sits in a highly precarious situation, one which could lead to disastrous consequences if a repeat of the five extremely dry years experienced at the beginning of this century were to return.

This suggests to me four major policy changes that should be seriously considered as a Sustainable Water Framework for the Upper and Lower Basin states:

• Dump the 2007 Interim Guidelines to balance Powell and Mead and instead release only 8.23 MAF from Powell each year. This will help protect the Upper Basin against another string of really bad years.
• Require the Lower Basin water users to stay within the sustainable limits of water available to them. To keep Lake Mead in balance over the past 20 years under an 8.23 MAF release from Lake Powell, the Lower Basin would have needed to consume 1.36 MAF (18%) less water. In other words, the sustainable allocation to the Lower Basin would be 6.2 MAF, not 7.5 MAF.
• Start implementing an aggressive demand management program — in both the Upper and Lower Basins — capable of restoring reservoir levels in Powell and Mead as swiftly as possible, and thereby providing an urgently-needed buffer against a string of bad water years.
• Start talking turkey about climate change and what it means for the Colorado River. We should expect a time — in the not-so-distant future — when the Upper Basin will not be able to send 8.23 MAF downstream to Lake Mead simply because there won’t be enough water produced from snowmelt to do so. We need to adjust our use of this river in accordance with a warming climate and declining river flows. More specifically, the sub-basins should each set a cap on total consumptive use that progressively ratchets down over time.

As always, I welcome contrary perspectives, corrections of my math, and alternative ideas. Use the comment box below to tell me what you think.