Recharge and Recirculation 101

In a region of periodic droughts and floods, managing our surplus in wet years could provide enough for reliable water supply and for critical springflow during the dry years.  Our problem is not shortage, but storage.

SUCCESSFUL FEASIBILITY ANALYSIS

Three categories of water have now been evaluated by the Edwards Aquifer Authority for a system of Recharge and Recirculation for management of the Edwards Aquifer.  The primary conclusion of the R&R feasibility analysis presented by Todd Engineers in February, 2009 is that “an R&R program can be developed that increases water supply while maintaining minimum required springflow.” 

Three categories of potential recharge were considered: 

• Rainwater crossing the recharge zone that can be slowed down so that more water can soak in.

• Transfers from rivers

• Unused permits in wet years
  

Of twenty-nine individual sources identified, specific recharge sites and unused permits were shown to provide a substantial amount of cost-effective recharge (roughly equivalent to SAWS present usage).

Modeling water entering and discharging from the Edwards Aquifer show multi-year residence times for recharge at certain locations.  Direct data analysis confirms recharge water is stored.  EAA rules for Recharge Recovery Rights permit withdrawal of enhanced recharge that remains in aquifer storage, as long as baseline springflow that would have occurred without the project in critical times is not decreased.  They allow otherwise unused Recharge Recovery Rights to be recirculated into aquifer storage so that there will be more carry-over for dry times.

TIME TO MOVE FORWARD

Follow-up is needed to develop an optimal, cost effective program.   EAA 2011 proposed budget provides for hiring a full time Recharge Engineer for the first time, additional data collection, and improvements in the Edwards computer model.

There is urgency to find a cost effective solution for springflows.  The EAA statute requires the agency ensure critical minimum springflows at the Comal and San Marcos Springs according to federal law by the year 2012.  That is no small task.  Comal Springs stopped flowing in the drought of the 50’s with less than half our present population. Reducing Aquifer pumping to Pre-1956 levels, and replacing the water would be very expensive.  It is important to develop our aquifer management options as a cost effective and sensible alternative.

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