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

Thursday, May 22, 2014

Barton Springs Above Drought Threshold, Lovelady Below

Stage II Alarm Drought
Barton Springs discharge: 50 cfs 10-day average
Lovelady Monitor Well: 474.00 ft-msl

Barton Springs saw a surge in flow after last week's rain, causing a momentary reversal to the trend of decreasing discharge that has been the norm since late last year. As welcome as that change is, the increased flow is not due to a dramatic increase in water storage in the aquifer, but more to do with how well connected Barton Springs is to conduits and fractures that quickly carry water to it from recharge features in creek beds. Substantial recharge to the aquifer occurs when there is prolonged flow in the creeks; last week's rains only generated runoff for a brief period and thus, only minimal recharge. The increased flow at Barton springs has already peaked and is once again trending downward. The District's other drought trigger site, Lovelady monitor well, is not as well connected to conduits and fractures like Barton Springs, and as such is not susceptible to sudden water level rises. The hydrograph for Lovelady monitor well did not experience a sudden change like Barton Springs did, rather, it has just flattened out momentarily. See the most recent Drought Status Chart here. Even though flow at Barton Springs has increased and is well above its Stage II drought threshold, a drought declaration remains in place because Lovelady monitor well is below its threshold of 478.4 ft-msl. With any luck ENSO conditions will develop before too long. The Climate Prediction Center expects that chances of El Niño conditions developing during the summer exceed 65%.

Wednesday, May 14, 2014

Little Recharge, but Rains Prime Soil for Recharge

Stage II Alarm Drought
Barton Springs: 42 cfs 10-day average
Lovelady well: 475.4 ft-msl

The storms over the last few days brought with them much needed precipitation to what has been an exceedingly dry spring. On May 8th, the US Drought monitor reported that the majority of the state was being afflicted by meteorological drought. As of today, the total rainfall at the District office for 2014 is 7.5 inches, barely over half the historic average of 14.3 inches. Dry soil conditions preceding the heavy rains we received this week precluded sustained runoff to the creeks, where the majority of the recharge to the Barton Springs segment of the Edwards Aquifer occurs. The recharge that did occur will not be enough to remove aquifer drought conditions, but will prolong entering deeper stages of drought. Another very welcome effect of the rains is that they will have increased soil moisture, priming them to produce runoff and potential recharge to the aquifer if we get more rain in the next couple of weeks. NOAA predicts that El Niño conditions are likely to develop by the end of summer, generally meaning wetter conditions in Texas. Let's hope in the mean time we get more storms like the ones we saw this week!

Thursday, May 8, 2014

Storm Today Breaks Dry Streak

Stage II Alarm Drought
Barton Springs: 41 cfs 10-day average
Lovelady Well: 475.34 ft-msl

At their last meeting on April 24th, the District's Board of Directors declared Stage II Alarm Drought based on the water level in Lovelady monitor well, one of the District's two drought-trigger sites, dropping below its drought threshold of 478.4 ft-msl. The other drought-trigger site, Barton Springs, remains flowing above its drought threshold of 38 cfs, but may drop below that in the coming weeks if precipitation conditions do not improve. Before today's latest total of 0.16 inches, the rain gauge at the District office had not collected any precipitation since mid-April, breaking an almost 3-week dry period. According to the  U.S. Drought monitor most of Texas currently finds itself in drought with central Texas in particular experiencing drought ranging from Severe to Exceptional. Despite the dry conditions, NOAA has released a statement that there is a 65% chance of El Niño developing during the remainder of the year, which could potentially bring wetter conditions to Texas.