Can An Ancient Water Supply Technology Be Adapted to Sustain the San Pedro River, Arizona?

This presentation asks the question: can an ancient and dependable technology, heretofore unused in the United States, be employed in a modernized incarnation to provide sustainable flows to the San Pedro River? This technology, called the qanat, passively taps groundwater at the mountain front and conveys it basinward to a point of discharge and use. Qanat technology, which dates to about the 7th century BC, represents a zenith of sustainability engineering. It has provided reliable water supplies to desert areas in Persia, the Arabian Peninsula, and elsewhere for over two millennia.

 

Qanats need no external power source to operate. They provide sustainable water in arid areas otherwise uninhabitable due to lack of surface water. For example, a 2700 year old qanat system in Gonabad, Iran, still supplies water to 40,000 people.

 

In the U.S., the San Pedro River is one of the most significant remaining desert rivers. However, there is great concern about whether the river’s flow and riparian ecosystem can be sustained due to increasing groundwater pumpage and extended drought. USBR recently prepared a report on water augmentation alternatives including pumping out old mines, extending the Central Arizona Project Canal, and stormwater recharge and water harvesting options. An unexamined alternative is qanat technology. Qanats may provide a passive, cost-effective, and truly sustainable way of maintaining flow in the river with few negative impacts.

 

The key to adapting qanat technology for sustaining the San Pedro River depends on the ability of modern equipment and methods to effectively construct the groundwater collection works in mountain front source areas and the deep underground conveyances leading to downslope points of “daylighting.” This presentation will describe qanat technology, discuss hydrologic settings where it may be used, identify possible construction approaches, and conjecture how a qanat network would work to provide sustainable flows to the San Pedro River.