With all of the water in the western United States spoken for, there’s an increasingly common problem in water policy and politics discussions in which a seemingly simple solution to a water problem in fact just creates a different problem somewhere else.
An article in the March/April Southwest Hydrology from my old stomping grounds of eastern Washington nicely makes the point. Bob Brower and Aristides Petrides write about what happened when 23 miles of irrigation canals in the Walla Walla Basin were piped or lined to reduce water losses.
What the found was that the water “lost” when it drained into the ground from unlined canals was not being lost at all. Springs and seeps that were being fed by the “lost” water went dry:
This seemingly successful restoration overlooked an important aspect of surface-water management: the role of groundwater. As conservation measures were implemented, the spatial distribution, timing, and volume of recharge to the shallow aquifer system changed. In fact, surface water gains observed in the main tributaries can generally be attributed to a net loss of aquifer recharge. This is because significant amounts of water that used to infiltrate throughout the watershed now flow directly into the river.
There are often, in other words, unintended consequences.
Same thing happens around Durango – one of the big areas of exurban development relies on wells. There’s a perched water table due to irrigation on an old, high river terrace, where the gravels are very permeable.
Same thing happens when you line irrigation canals/ditches (see All American Canal lining).
The article nicely illustrates why watershed management/hydrology should consider groundwater. Most watershed folks are clueless about groundwater.
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I’d say that the consequence WAS intended, and that the beneficiaries were happy to leave the losers in the “dust.” It’s all about property rights — even those of nature…
I see that CP&DR have a ‘Top 10 Sac-San Joaq water myths’ (Delta’s ‘Age Of Reason’ May Be Nearing ) one of them is
3. Groundwater is separate from surface water. (“Groundwater is not separated from surface water except by lawyers.”)
7. Water markets will solve the Central Valley’s problems.
Nonetheless, our population growth and resource overshoot is all unintended consequences as we learn how much we don’t know…