Friday, May 29, 2015

Water Shortages in the West

Lake Mead

An ongoing story of 2015 is the drought in California. 

As I understand it, we are in the fourth year of a significant water shortage in the western United States -- California in particular. Based on the articles I've read, I'm not sure whether (most) scientists believe the drought is related to climate change, or whether it's a distinct weather-related phenomenon.

The New Yorker has written several stories about the drought. Because I have always been interested in water and its centrality in our lives, I am fascinated.  In the recent article Where the River Runs Dry (here), David Owen focuses his attention on the Colorado River.

Water rights in the river are governed by a 1922 agreement (the Colorado River Compact) that was entered into by seven states. The Compact divides the river into an Upper Basin and a Lower Basin, and each basin is allocated 7.5 million acre-feet of water per year (an acre foot is the amount of water that would fill one acre of land to a depth of twelve inches). 

The Upper Basin states (Wyoming, Colorado, New Mexico and Utah) do not use their entire allocation. However, the two main reservoirs on which the Lower Basin depends for reserve water -- Lake Mead and Lake Powell -- have, since 1998, been significantly depleted.

The most fascinating part of the article is Owen's explanation that decreasing water usage can actually exacerbate the water shortage. I would never have guessed this, but here is the explanation:
Reducing waste seems like an obvious solution to overuse, but it can actually make the problem worse. Bradley Udall, a scientist at Colorado State University’s Colorado Water Institute—his family has been prominent in conservation and in regional and national politics for decades—told me that water use can be divided broadly into two categories: consumptive and non-consumptive.  
When a farmer irrigates a field with river water, he said, some of the water is consumed by whatever the farmer is growing and by evaporation, but some is returned to the stream. The ditch system in the Grand Valley carries runoff and surplus irrigation water back to the river, and that water is used again, mainly by other farmers. (Kent Holsinger told me that, on average, river water is used more than half a dozen times before it leaves the state.)  
Excess irrigation water also soaks into the earth, replenishing groundwater and, eventually, feeding surface streams. 
Udall said, “Efforts to improve water efficiency in agriculture almost always lead to increases in the consumed fraction. On an individual field, they make it look like we are using water better, but they actually move us in exactly the wrong direction.” Modern, efficient irrigation techniques can cause crop yields per acre-foot to rise, but also increase water consumption, so downstream users who relied on excess from upstream—the non-consumed fraction—now have to find water somewhere else.
587. What is the current status of water usage in Charlottesville? Several years ago, the size and location of the reservoir were contentious issues. Has everything been resolved, or are their lingering questions and disputes?

588. Do I consume more or less water than the average American (drinking, bathing, gardening, etc.)?

589. Am I correct that people use Lake Powell and Lake Mead recreationally, with lots of motor boats, jet skis, and swimming? If so, how has the depletion of the reservoirs affected recreational use (and property values)?

590. Will water conservation play any significant role in the 2016 Presidential election? Which candidate is most likely to focus on this issue?

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