Thursday, May 30, 2013

Rain not enough to cause flow in Onion Creek; Recharge minimal

Stage III Critical Drought
Barton Springs: 28.3 cfs 10-day average
Lovelady monitor well: 461.3 ft-msl

The rains that came through the area last weekend (May 25-26) helped diminish the rainfall deficit that has grown over the course of the drought declared in November 2012. As of May 30, 2013  the total rainfall deficit since November 2012, compared to the historical average of 19.4 inches over that time period, is -6.2 inches according to district rain gauge totals.

As welcome as any rain during periods of drought, the recent rains were not large enough to generate substantial runoff, and consequently flow in the creeks responsible for the majority of the recharge that enters the Barton Springs segment of the Edwards Aquifer was also minimal. Despite not having generated substantial recharge to the aquifer, the rains have replenished soil moisture such that another storm in the coming days would be more likely to create the much needed recharge.

Barton Springs flow experienced a spike in discharge reaching a 35 cfs day-average on May 26, but is once again on the decline with a 10-day average of 28.3 cfs as of today and the USGS reporting 28 cfs as the most recent instantaneous discharge measurement. Lovelady monitor well showed a small leveling out of its water level due to the rain but is once again on the decline.

The U.S. Drought Outlook by the National Weather Service shows ongoing drought with "some improvement" and the U.S. Drought monitor rates the drought in Travis and Hays counties as moderate to severe.

Wednesday, May 22, 2013

Aquifer Update

Drought Status: Stage III Critical Drought
Barton Springs: 23 cfs 10-day average
Lovelady Monitor Well: 461.5 ft-msl

Since the declaration of Stage II Alarm drought on November 15, 2012 water levels in the aquifer have been in steady decline. Sporadic minor rain events delayed entry into Stage III Critical drought, but did not provide enough moisture to reverse the trend in water levels. The storms that have brought much of the precipitation to the area have not been close enough together in time to overcome soil moisture deficits.  Dry soils have prevented much of the water from the recent storms from reaching creeks and consequently the aquifer. As a matter of course, the District declared Stage III Critical drought on April 17, 2013 when the water level in the Lovelady monitor well, one of the District’s drought triggers, dropped below its Stage III drought threshold of 462.7 ft-msl (see figure 1). Discharge at Barton Springs, the other drought trigger site, is declining but has not dropped below its threshold of 20 cfs due to its nature of responding quickly to minor rains over the recharge zone of the aquifer. Even though the rains that have kept flow at Barton Springs above its Stage III Critical drought threshold are a welcome reprieve from dry conditions, they have not been large enough to generate substantial runoff in the creeks where most of the recharge to the aquifer occurs. The total rainfall so far for the drought that started in November is 8.6 inches, compared to the historical average of 18.2 inches over the same time period, leaving a rainfall deficit of -9.6 inches. Onion Creek, where many of the most significant recharge features for the aquifer are found, has not had significant flow since July 2012. Currently the US Drought Monitor rates the drought in Hays and Travis counties as severe to extreme. The National Weather Service shows central Texas as having “ongoing drought” but with “some improvement” possible in the future.