Today’s Bulletin had an article titled “Redmond concerned about irrigation pipeline’s impact on groundwater“. The City of Redmond has long been concerned about declining groundwater levels and their need to support a growing population via their groundwater wells. Redmond objected to the renewal of the Deschutes Basin Groundwater Mitigation Program which protects flows in parts of the Deschutes River and has objected to canal piping which is believed to contribute a small amount to aquifer recharge. The story outlines Redmond’s desire to take water from the Deschutes and directly recharge the aquifer. This is going to be a long term debate with many hurdles to overcome but I’ll make a few comments below.
It really is not known how much water leaking from canals makes it down to the aquifer and where that recharge occurs. A 2008 USGS study states that while canal piping plays a small role in groundwater declines, “climate variations have the largest influence on groundwater levels throughout the upper Deschutes Basin”. This study used a model for those conclusions, not direct measurement, and it was done at a time when there was much more significant annual snowpack and wetter soil conditions. Many have been asking for an update to this study for a long time. It seems plausible to me that given a drier climate, drier soil conditions, and increased rates of evapotranspiration, that current aquifer recharge from leaky canals is lower than in the past and piping them will have even less impact.
Given the 20+ year drought we have been experiencing and the historically low flows in the Deschutes recently, removing any water will clearly have a negative impact. Aquifer recharge has been discussed in a few places and more questions than answers have been raised. Some believe that there will soon be “excess” water in the Middle Deschutes in the winter due to increased flows required by Deschutes Basin Habitat Conservation Plan and these flows could be diverted for recharge.
Personally, I don’t understand this position. From a historical perspective, in terms of flows, the Middle Deschutes is in far worse shape than the Upper Deschutes. Taking away any water from the Middle will be controversial.
In any event, this idea is in its infancy, will play out over a long time, and has many hurdles to overcome. The bottom line however is that global warming is the primary issue, it is unlikely to go away, and we all need to learn to live with the resources we have and the declines that are likely to come.
