January 2012 Aquifer Update

Drought Stage: Critical Stage III
Barton Springs Flow: 22.2 10-day average
Lovelady: 193.3 ft

Despite the above-average rainfall in November and December for central Texas, we remain firmly in Critical Drought conditions. The rains provided some recharge to the aquifer, but the rise and benefit will only be temporary unless substantial rainfall occurs over the next 6 months. Unfortunately La Nina conditions exist, which generally mean drier-than-normal conditions.

Drought story and photos

Click here for an audio story from KUT and the Texas Tribune on the future impacts of the drought.

Click here for images of the 2011 drought from the AAS photo blog "collective vision."

December Aquifer Update

Drought Status: Critical Stage III
Barton Springs: 18 cfs (19.5 cfs 10-day average)
Lovelady: 194.0 ft

The recent rainfall totals for November were near average, and above-average for December. That has brought about some relief to the dryness, but very nominal recharge and relief to the aquifer. Barton Springs discharge has temporarily spiked in response to the rainfall, but minimal response in the Lovelady well indicates very little addition to storage.

A great summary of the recent rains can be found on Bob Rose's (LCRA) blog. Click here.

The District's December newsletter highlights the current drought.

The Office of the Texas State Climatologist (OTSC) has a good statewide summary of the 2011 drought--click here.

November-December Rains Help, but....

Recent rainfall totals of up to 5 inches throughout central Texas since mid-November have been a welcome addition to record-breaking dry year. In fact, the rainfall for November and December total just above average for those two months. Consecutive above-average rainfall months haven't occurred since June and July of 2010 with passing of Hurricane Alex and other tropical storms.

Although these rains have set the conditions for runoff that could help alleviate the groundwater drought, the recent rains have not produced runoff and are far from ending our drought. The Blanco River (at Wimberley) and some of the more urbanized creeks in the Austin area, such as Williamson and Slaughter, had temporary rises in stage and flow due to the flow. However, Onion Creek has not had any substantial flows from these rainfalls. Barton Springs has also had a temporary rise due to the localized (urban-runoff) effects, but will quickly decline to pre-rainfall levels in the next few days.

Many months of above-average rainfall, or sufficiently large rainfall events (>10 inches) under the right conditions, are needed to help alleviate the drought conditions.

Summary of 2011 Drought by the Office of the State Climatologist

A great summary article from the Fountainhead of the 2011 drought by the State Climatologist (Nielsen-Gammon) can be found by clicking here. The Office of the State Climatologist also has an excellent summary of the 2011 drought. Click here for a link to the summary report. The figure below is from the Nielsen-Gammon article and shows just how unusually hot and dry the 2011 summer was. Note the average summer temperatures were >2 degrees hotter and about 1 inch drier than previous record-breaking summers.

A drought for the centuries: It hasn’t been this dry in Texas since 1789

Click here to read an article from the Texas Climate News (by Bill Dawson).

SNAPSHOTS OF THE DROUGHT

A drought for the centuries: It hasn’t been this dry in Texas since 1789

There was only one other year in almost five centuries when Texas’ summer drought was as severe as it was in 2011, federal climate experts have concluded.

Instrumental weather records used to measure drought severity don’t go back much before the 20th century. (In Texas, they date to 1895.)

To establish a longer-range record, scientists at Columbia University’s Lamont-Doherty Earth Observatory have analyzed tree-ring data and calculated how drought conditions dating back hundreds of years (to 1550 in Texas) ranked on the standard Palmer Drought Severity Index (PDSI).

Positive numbers on the PDSI represent wet conditions and negative numbers indicate dry conditions. The more severe a drought is, the lower its PDSI number.

Texas’ average PDSI this past summer (June through August) was -5.37 – the lowest, indicating the most severe drought conditions, since the start of the instrumental record in 1895.

And according to the federal government’s National Climatic Data Center, there was apparently only one other year during the last 461 years when Texas had a drought so severe.

Going back to 1550, the tree-ring reconstructions reveal that only in 1789 was Texas’ PDSI number so low, the center reported recently. (For our readers who don’t readily recall key historical dates, 1789 was the year when George Washington was inaugurated as the United States’ first president and also when the French Revolution started.) Here’s part of the National Climatic Data Center’s report:

The tree-ring record can put the droughts of the last century across Texas, including 2011, into a much longer perspective. The frequency of severe one-year statewide droughts appears not to have significantly changed between the “paleo” period (1550-1894) and the instrumental period (after 1895). Both the instrumental and reconstructed PDSI records indicate that “severe” or “extreme” statewide summer drought (PDSI below -3) occurred in about 1 in 15 years. “Extreme” statewide summer droughts (PDSI below -4) such as 2011 and 1956 are seen in about 1 in 40 years in both the instrumental and reconstructed records.

So how does the 2011 summer PDSI (-5.37) compare to the worst one-year paleo-droughts? We first need to consider that the tree rings are imperfect recorders of past drought, and so the reconstructed values have confidence intervals (or “error bands”) associated with them. When this error band is taken into account, there is only one value in the paleo record, 1789 (-5.14), that can be said to be equivalent to the 2011 observed value. Thus, 2011 appears to be unusual even in the context of the multi-century tree-ring record.

[…]

The current drought in Texas has been unprecedented relative to the century-long observed record in a number of ways: the record-low precipitation, the extreme summer heat, and the enormous wildfires. The tree-ring record of PDSI confirms that, in a much longer context, the 2010-2011 Texas drought is an extraordinary event.

And it appears no relief is in sight, the federal Climate Prediction Center said last week in its Winter Outlook for December through February:

With La Niña in place Texas, Oklahoma, New Mexico and parts of surrounding states are unlikely to get enough rain to alleviate the ongoing drought. Texas, the epicenter of the drought, experienced its driest 12-month period on record from October 2010 through September 2011.

– Bill Dawson

November Aquifer Update

Drought Stage: Critical Stage III
Barton Springs flow: 17 cfs (estimated)
Lovelady Well: 193.9 ft depth to water

Recent rains of up to 1 inch were very welcome, but did almost nothing for the aquifer in terms of recharge.

Oct 27th Aquifer Update

Barton Springs 10-day average ~17 cfs*
Lovelady: 193.0 ft depth to water

*this is our best estimate at this time.

October Aquifer Update

Drought Status: Critical Stage III
Barton Springs Flow: 20 cfs (19.4 10-day average)
Lovelady Depth to Water: 192.4 ft

The recent rainfall of about 1.5 inches was very good for vegetation and soil moisture. However, very little of that rainfall provided recharge to the aquifer.

Drought could last unitl 2020 says State Climatologist

Cick here for a link to the brief Austin American Statesman article on the topic. Click here for an extended article.