Deschutes Groundwater Mitigation 101 and Thornburgh

Surface water (rivers & streams) in the Deschutes Basin has been fully allocated since the early 1900s, primarily to irrigators.  To accommodate for continued growth, groundwater pumping became the primary source of new water supplies.  In the 1990s studies showed that this pumping was impacting surface water.  In the Deschutes Basin, snowmelt in the Cascades seeps through porous volcanic rock, slowly replenishing the aquifer.  As the aquifer overfills it releases the water via springs, which create our local lakes and rivers.  Variability in snowpack and pumping impacts the aquifer and therefore stream flow.

In response, WaterWatch of Oregon led an effort to control groundwater pumping.  They argued that protection of local scenic waterway designations required any new pumping to be “mitigated” (offset) by other sources of water and in 2002 the Deschutes Groundwater Mitigation Program was created. A typical scenario is that an irrigator sells their surface water rights to a groundwater permit seeker.  For example, you could buy rights to Deschutes River water, keep that water “instream”, and thereby mitigate for a well you want to drill.  A “water bank” was created to facilitate these transfers.

While the mitigation program has helped control groundwater use, it has limitations.  Groundwater pumping has continued to increase, causing the aquifer to continue to drop, which imperils local waterways and future water availability needed for growth.

Here are some of the flaws in the Deschutes Groundwater Mitigation Program and how they relate to the proposed Thornburgh Resort.

  • Not full mitigation.  Groundwater pumping does not have to be fully mitigated.  The amount of required mitigation is determined by the Oregon Water Resources Department on a per-permit basis.  The concept is that some groundwater pumped from the aquifer will not be “consumed” and will return to the aquifer.  Thornburgh has permits for six deep wells.  Water at depth came from snowpack in the Cascades many years ago, potentially decades ago, and is not going to be replenished by water percolating down from excess applied to a golf course.
  • No verification.  There is no requirement to verify by measurement the amount of mitigation water provided.  This absolutely blows my mind.  In the case of Thornburgh, they are purchasing rights to water in Deep Canyon Creek, water previously used for irrigation.  The problem is that the “mitigation credit” associated with this creek is based on a paper water right that has not been verified to match the actual amount of water in the creek (the “wet water”).  Unfortunately, this is common.
  • Location.  Water drawn from the aquifer in one location does not have to be replaced in the same location.   Thornburgh is upslope from Deep Canyon Creek.  Pumping at Thornburgh could diminish flows at Deep Canyon Creek and reduce the available amount of mitigation water.
  • Timing.  In the Deschutes Basin, springs were historically constant all year.  Mitigation water can be proved at intervals throughout the year.  This can be disruptive to aquatic lifecycles.
  • Quality.  The mitigation program is only concerned with the amount of water, not its quality.  Groundwater is cold and clean when it emerges as a spring and then flows into a waterway.  Mitigation water is typically surface water which may be warmer and potentially contain pollutants.