News in the Arizona Republic that Lake Mead is nearing its lowest level since 1956. Further reductions in the lake’s level may trigger reductions in shares of the Colorado River to Arizona.
Some observations from a life-long career in water issues:
When rights to the Colorado River were divided up among the various states, the allocations were based on some of the wettest years in history. The river–on a long term basis–is not going to be able to fulfill those allocations on an annual basis, especially if the projections about global warming impacts prove to be true.
Arizona has 2.8 million acre feet of Colorado River water allocated to it. Of that total, 1.2 million acre feet is allocated to the Central Arizona Project and the rest for farming in Yuma and to Indians. In the event of shortages, the CAP diversion is the first off the river. Arizona can absorb about a 50% loss of its share before Phoenix and Tucson are impacted.
California has an allocation of 4.4 million acre feet per year, most of which is for agricultural uses in the Imperial Valley.
Mexico has a US Treaty allocation of 1.5 million acre feet per year.
If the Colorado River is going to be short, Arizona and California are going to have to seriously decide whether cities have priority for water, or farms. That will probably mean Arizona having to buy out Colorado River water rights in Yuma and California having to buy out water rights in the Imperial Valley. These would be very costly efforts as well a controversial. The end result is the cost of water to Arizona and California’s cities would have to increase.
Another alternative is to lease Colorado River water from Indian Tribes that hold allocations. This will not be cheap.
Another alternative is to construct some massive “water augmentation” project to increase the supply of Colorado River allocations via dealting, or whatever. Also a very costly and controversial option.
While it is not likely Arizona and California’s cities will not have Colorado River water, it is likely that water will cost a lot more due to having to buy out agriculture or lease water from Indian Tribes or augment the river.
And, I can remember in 1984 when the water level in Lake Mead was so high that the lake nearly spilled over the top of Hoover Dam.
by Shaun McKinnon on Aug. 12, 2010, under Arizona Republic News
Drought-stricken Lake Mead has dropped an additional 10 feet since last summer, and now, Arizona and other Colorado River users are scrambling to keep the reservoir full enough to avoid water rationing.
Before year’s end, the lake will likely sink to within 9 feet of the level that would trigger the first round of restrictions – and the first such restrictions ever on the river. They begin with a reduction in water deliveries to Nevada and Arizona, where farmers would be affected first.
To slow the lake’s years-long decline, river users have built a reservoir west of Yuma to catch unused runoff, paid farmers to leave fields unplanted and are negotiating with Mexico to leave some of its allocation in Lake Mead while its farmers recover from an earthquake.
National Parks: Lake Mead
None of the steps will yield significant amounts of water, but together, they could keep Lake Mead from sinking below the drought triggers, buying time until a wet winter can replenish some of the water lost to drought.
“It’s time that we need,” said David Modeer, general manager of the Central Arizona Project, which moves water from the Colorado River to Phoenix and Tucson. “The reservoirs have shown they’re resilient. After a 12-year drought, they’re still half-full. What we do now will be worth it to stay out of a shortage.”
Lake Mead water levels determine drought status on the river under a set of guidelines adopted in 2007 by the seven Colorado River states: Arizona, California, Nevada, Utah, Wyoming, Colorado and New Mexico.
If the lake reaches the first drought trigger, measured at an elevation of 1,075 feet above sea level, water deliveries below Lake Mead are reduced by a little more than 10 percent. Additional cutbacks would occur if the lake continued to drop.
The reservoir is now at an elevation of 1,087 feet above sea level – its lowest level since 1956 – and is projected to drop an additional 3 feet this year, which is why water users are trying almost everything short of hauling water in buckets.
For Arizona, the stakes are high. Arizona absorbs 96 percent of any water rationing on the river under a decades-old agreement that ensured construction of the 336-mile CAP Canal. Nevada absorbs the other 4 percent under a separate deal with Arizona.
Although rationing would affect some users on the river in western Arizona, most of the cuts would come from the canal, whose annual flow of 1.5 million acre-feet would be reduced in stages. (An acre-foot is 325,851 gallons, enough to serve two average families for one year.)
Farmers and users of excess water, such as underground-storage programs, would be affected first. It’s unlikely cities and business in Phoenix and Tucson would lose any water in the earliest stages.
Nevada faces similar pressures. It would absorb 4 percent of any cutbacks but, more critically, if the reservoir fell below elevation 1,050 feet, one of the tunnels Nevada uses to draw water from the lake would sit above the waterline and would be useless. Nevada is working on a new, deeper tunnel, but it is not expected to be completed before 2012.
“Right now, we’re trying to keep the lake above 1,075 as much as we can,” said Herb Guenther, director of the Arizona Department of Water Resources. “We’re trying to build incentives with other users, with Mexico, to put as much unused water in Lake Mead as we can.”
The goal is to take less water out of Lake Mead. Every 100,000 acre-feet of water kept in the reservoir buys 1 foot of elevation. Conservation is the fastest and, in most cases, the cheapest alternative, so that’s where the states have begun.
The biggest project so far is the Drop 2 reservoir at the end of the river west of Yuma. It will collect water requested but not used by farmers.
That water, as much as 23 billion gallons a year, now flows into Mexico. It is not subtracted from that country’s annual allocation, but it results in lower water levels at Lake Mead.
When Drop 2 opens later this year, unused water will be diverted into the reservoir until someone needs it, allowing more water to remain in Lake Mead.
Finding new sources of water is more expensive and time-consuming. State and federal officials have been talking with Mexico about building an ocean-water desalination plant to augment the river’s supply.
In the meantime, the two countries are working on another agreement that would give Lake Mead a shorter-term boost.
Farmers in the Mexicali area just south of the U.S. border suffered devastating losses during an April earthquake and, as a result, Mexico can’t use its full Colorado River allocation.
Officials are working on an agreement to let Mexico store that unused water in Lake Mead until farmers have recovered. Although the water would still belong to Mexico, it would help keep the reservoir above drought triggers.
The fact that river users are talking about leaving water in storage rather than hoarding it has encouraged water managers, even if the change in attitude was caused by a fear of shortage. The states, which fought over the Colorado River from the day it was first apportioned in 1922, have worked together on broader water issues, such as severe water shortfalls in California caused by drought and a court case involving an endangered fish.
“We have rules now, and everyone knows what they are,” said Lorri Gray-Lee, director of the Lower Colorado region of the Bureau of Reclamation, the federal government’s water agency. “Any time you have Arizona willing to work with California and help them through the tough issues they’re dealing with, you know something has changed.”
There are still tensions. One provision of the 2007 agreement allows the bureau to release extra water from Lake Powell if winter runoff is plentiful, raising Lake Mead levels faster. The four upper-river states are uneasy about letting extra water flow downstream, but the rules are clear, Gray-Lee said.
No extra water was released from Lake Powell this year because precipitation runoff into the upper Colorado through July was 73 percent of average. But the winter was not without its benefits for Arizona: Runoff from state tributaries added enough water to the lower river to account for about 1 foot of elevation at Lake Mead.
And every little bit helps.
“Every normal year rolls back the drought a year or so,” said Tom McCann, an assistant general manager of the CAP. “These two reservoirs are doing exactly what they were intended to do. They’ve helped us to weather the drought. And if you can manage to get through another year of drought, maybe the next year is a wet year.”