Wednesday, May 28, 2014

Flow in Creeks means Recharge to Aquifer!

Stage II Alarm Drought
Barton Springs discharge: 51 cfs (10-day average)
Lovelady Monitor Well:  474 ft-msl

The District rain gauge received 4.5 inches over the last couple of days. Many of the area creeks are flowing after the strong and steady rain that started on Memorial Day morning. Rains over the last couple of weeks had increased soil moisture and primed conditions for runoff and sustained flow in creeks to occur after a sizable precipitation event like this one.  Most of the recharge that the Barton Springs Segment of the Edwards Aquifer receives comes from karst features (caves, sinks) in creek beds. In other words, when our creeks are flowing, recharge is occurring. The LCRA Hydromet is a good resource to see rain distribution and flow in creeks over time.
In the coming days it is likely water levels in the aquifer will rise. It is unlikely that water level will rise enough in the Lovelady monitor well (one of the District's drought-trigger sites) to prompt the Board to remove the current drought declaration, but the storm will have certainly prolonged descending into deeper stages of drought. Barton Springs, the District's other drought trigger site is well above its drought threshold. It however, is not as reliable an indicator of how much water is being stored in the aquifer as Lovelady well because it is better connected to karst conduits that quickly bring water from the surface to the spring outlet and make it susceptible to flashy changes in discharge. On the other hand, water in Lovelady monitor well comes from between the grains that make up the limestone aquifer, and is therefore not prone to flashy water level changes. Only one of the District's drought-trigger sites needs to be below it drought threshold for a drought declaration to be enacted. Hopefully we will receive more rains like this one as summer progresses and El Niño development becomes more favorable. 
Below see some pictures of flowing creeks and active recharge features.
Brodie Sink

Williamson Creek near Brush Country Road

Onion Creek near Driftwood

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