Tuesday, February 26, 2013

Closer to Drought Declaration

On Thursday, February 21st district staff measured flow at Barton Springs to be 20.13 cfs, corresponding to a 10 day average of 21.8 cfs. At that time the USGS website was reporting 26 cfs as it's "most recent instantaneous value." As of February 26th the USGS website is still reporting 26 cfs. Construction be done at the Barton Springs pool is causing flow conditions downstream to be highly variable and making it difficult to get consistent measurements. The case may be that flow at Barton Springs is somewhere between the two values of 20.13 and 26 cfs reported by the District and the USGS respectively.

However, based on the rate of decline of the water level in the Lovelady monitor well (the district's other drought trigger) it appears that the Stage III Critical Drought threshold of 462.7 ft-msl will be passed on approximately March 10, 2013. Drought stage can be declared by the board if thresholds at either of the drought trigger sites have been passed. Stage III Critical Drought corresponds with a 10-day flow average at Barton Springs between 20 and 14 cfs.

Hydrograph of Lovelady monitor well. (click to enlarge)

Thursday, February 21, 2013

Critical Stage III Drought likely by early March

Drought Status: Alarm Stage II
Barton Springs: 21.8 cfs (10-day average)
Lovelady well: 464.5 ft-msl

Today district staff measured discharge to be 20.13 cfs at Barton Springs. Based on the rating curve for Barton Springs, it is likely that the 10-day flow average will drop below the 20 cfs threshold for declaring a Stage III Critical  drought before the end of February or in the first few days of March. The subsequent drought declaration could potentially be made made by the district's board at their meeting on March 7.