Why Lake Mead keeps dropping

sprinklers at Tucson Museum of Art, August 2014

sprinklers at Tucson Museum of Art, August 2014


Water released from Lake Mead, through Hoover Dam’s turbines, travels downstream about 150 miles to Lake Havasu. There, massive pumps on the river’s left bank push the water up on the start of a 336 mile journey that ends in groundwater spreading basins west of Tucson. The Colorado River’s water then recharges an aquifer, where it can then be pumped and mixed with others sources of supply so that, at 3:35 p.m. on a hot August afternoon, you can keep this little patch of lawn at the Tucson Museum of Art green, and the patio wet.

Annals of Indian water: “hot, scorching sands”

Whitehorse Lake, Navajo Nation, January 2014

Whitehorse Lake, Navajo Nation, January 2014

Most of the land in these reservations is and always has been arid. If the water necessary to sustain life is to be had, it must come from the Colorado River or its tributaries. It can be said without overstatement that when the Indians were put on these reservations they were not considered to be located in the most desirable area of the Nation. It is impossible to believe that when Congress created the great Colorado River Indian Reservation and when the Executive Department of this Nation created the other reservations they were unaware that most of the lands were of the desert kind — hot, scorching sands — and that water from the river would be essential to the life of the Indian people and to the animals they hunted and the crops they raised.

U.S. Supreme Court, in the decision of Arizona v. California, 1963

Stuff I wrote elsewhere: forest health = watershed health

From last Sunday’s newspaper, a solutions-oriented piece on an effort to scale up forest and watershed restoration in the mountains around me:

Trees being cut last week on Forest Service land near the Sandia Crest Road can be used as firewood, but there is not enough money to be made from cutting the small timber clogging the unhealthy forests to make such work self-supporting, Racher said. “There’s not enough value in that wood to pay for what needs to be done,” Racher said.

That is at the heart of the Forest Trust, which is attempting to raise $15 million per year in government money and private contributions to pay to expand the work, said Laura McCarthy, director of New Mexico conservation programs for the Nature Conservancy, an environmental group.

Desert Poor

dead pickup truck in a desert arroyo, somewhere - anywhere - in the southwestern U.S.

dead pickup truck in a desert arroyo, somewhere – anywhere – in the southwestern U.S.

Wandering up an arroyo this evening after dinner. Seen through a barbed wire fence festooned with ominous “no trespassing” signs, behind some trees, old junk cars, classic American desert poor.

Total storage behind Hoover, Glen Canyon Dams

While all eyes have been on Lake Mead’s bathtub ring, Lake Powell is forecast to rise by nearly 1.4 million acre feet by the end of September. But Mead’s 2 million acre foot drop will more than offset the increase, leaving us with the lowest end-of-year total storage in the two reservoirs combined since 1967, when they were first filling Lake Powell:

Total storage in Mead and Powell

Total storage in Mead and Powell

Data courtesy USBR, my summary spreadsheet is here.

Tucson considering potable reuse

It’s always interesting to see who, among western municipal water agencies, is considering paying top dollar for the next acre foot of water. Today’s episode comes from Tucson, where Tony Davis explains discussions of turning wastewater into drinking water. The usual “yuck factor” discussion of course is engaged, but the really interesting part to me is the price:

Wastewater recycling is a very expensive, at times controversial, process, costing many times more than the delivery of Central Arizona Project water to Tucson.

It could, for instance, cost anywhere from $1,500 an acre-foot to $3,300 an acre-foot to treat effluent for drinking, the city’s effluent recycling plan says. Pumping CAP water uphill for more than 300 miles from the Colorado River, by contrast, costs $146 an acre-foot for Tucson Water today, and could rise to $157 an acre-foot in 2015.

But as effluent’s use for drinking grows around the arid Southwest, it’s a water supply that many local officials say is inevitable, given the region’s ongoing drought and population growth. They see it as the region’s only sustainable, locally generated water supply, particularly given the strains on the Colorado River due to continued drought.

And as always, it’s important to remember that wastewater almost always isn’t really being “wasted”. It’s already going somewhere, being used for something:

The city of Tucson is entitled to take 21,000 acre-feet of that — enough to serve at least 50,000 homes if the water was drinkable — but it currently takes only about 13,400 acre-feet for turf irrigation or to recharge for future use.

The remaining 11,700 acre-feet of city-owned effluent rolls down the Santa Cruz River — a boon for cottonwood and willow trees that support bird life, to be sure. But Tucson Water’s recycled water master plan sees that differently: “A significant portion of the city’s entitlement left its service area as surface flow after it was discharged to the Santa Cruz River channel without further physical or economic benefit to the city.”

 

 

Michael Campana on stocks, flows, and Colorado River Basin groundwater research

Michael Campana offers some cautions about over-interpreting what the Castle et al. paper on the loss of Colorado River Basin groundwater is telling us. It’s a question of stocks versus flows. The GRACE measurements that have gotten such extensive attention can tells us the latter, but not the former:

Why is such a number – the groundwater stock – important? In my class I likened it to managing a checking account without knowing the balance (S; the stock) but just the deposits (I; inflows) and withdrawals (O; outflows). As long as I = O, you’re fine, regardless of the S (we’re assuming no fees or problems with crediting deposits and floating checks). You may feel uncomfortable but you’ll be okay. However, as soon as O > I in a given time period you had better start worrying simply because you don’t know how long you can keep running a deficit before hitting bottom. That’s the problem we have with groundwater in many places.

In the CRB, as in many other groundwater basins, we are likely in the O > I phase, but we don’t know how much water is in storage. But we need to know the storage to properly manage the groundwater.

There is much more in the post worth reading if you are interested in what we know and don’t know about Colorado River Basin water.

In the United States, irrigation’s eastward spread

Fascinating piece by Brett Walton about the eastward spread of U.S. irrigation:

The canals, reservoirs, pumps, and pivoting sprinklers that transformed the American West in the 20th century from desert and grassland into the nation’s primary fruit and vegetable producing region are spreading eastward.

From the Deep South, the Mississippi River Delta, and across the Midwest, the basic equipment of modern irrigated agriculture is producing more reliable harvests, more productive use of scarce water supplies, and bigger paychecks. Just as in the West, eastern farmers also say irrigation is a tool for managing risk, providing insurance against erratic rainfall and rising temperatures brought by a warming world.

Significant implications, the entire thing is worth a click.