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Holistic approach to Gila diversion would help environment

The New Mexico Interstate Stream Commission has recently agreed to take Gila River water, made possible by the Arizona Water Settlement Act. Considering our changing climate, many of us would agree that it makes sense for our state to take this water, even if the end use is not immediately evident.

Unfortunately, the public debate over the ISC’s decision has been framed as an “all-or-nothing” proposition: Build expensive dams, reservoirs, tunnels and pipelines to take this water, or leave the river free-flowing and meet future demands by implementing conservation measures.

A prudent and reasonable person might ask: Aren’t there other alternatives we should consider? Do we have to build the whole thing right away? What can we do now with the money the feds have offered?

The ISC wants to divert the full volume of water each year, to store up to five years’ worth of that water in reservoirs where half the water will be lost to evaporation. Surely there are less costly and ambitious alternatives.

My 28 years of work as a civil engineer specializing in ecologically sustainable river restoration gives me a different perspective on this debate. I know there are ways to divert water that won’t destroy the river, and there are ways to store water without building dams and reservoirs.

Nature has stored water underground for millennia, with no evaporative loss.

There is groundwater under the Gila River right now, but there is a lot more soil in the valley and in the side drainages which is not saturated. Think of the soil in the Cliff valley as a gigantic sponge: It’s already wet at the bottom, and if we pour water onto the top of the sponge it will hold a lot more water than it does now.

And just like a sponge, it will leak water slowly, so we will have to add water on the top to keep it full. To retrieve this water we would need shallow groundwater wells.

This is not a new idea: Right now the city of Albuquerque is soaking water into Bear Canyon Arroyo to store it for future use.

Nature’s system for diverting water is to let the river flood onto the floodplain. A “riffle” built with large boulders will allow the river to spill out of its banks in planned locations.

This is much less expensive and more environmentally acceptable than a concrete dam. Instead of a high-tech metal screen to clean debris and sediment from the flood flow, we can build a broad, shallow pond area where the sediment and woody debris would collect. This type of ephemeral pond creates some very interesting habitat for birds, terrestrial creatures and wetland plants.

The Arizona Water Settlement Act requires a conservation element. River restoration work is badly needed in this valley. Restoration work will reestablish a functioning ecosystem, and it will improve the connection between the river and the sponge.

A healthy river is a critical element in the overall conservation plan.

These ideas are an alternative approach to diverting and storing water under the settlement act. They represent a paradigm shift from the 20th century model of dams and reservoirs. Instead, they follow nature’s model, and they cost a lot less than the ISC’s current preferred alternative.

But they are not a silver bullet.

Rough estimates of storage capacity are closer to a one-year’s supply of water, albeit with no evaporation loss. The important point here is that the list of alternatives should be more comprehensive than the all-or-nothing approach.

The citizens of New Mexico deserve a better set of choices; we deserve practical solutions that we can afford.

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