Critical period is when one of the aquifer pools fall below a certain level and/or the springflows at Comal or San Marcos springs slows to a certain rate.
The Edwards Aquifer is divided into two pools – the San Antonio Pool and the Uvalde Pool. The pools are separated by a geographic divide called the Knippa Gap. The San Antonio Pool lies below all of Bexar and Medina counties, along with portions of Atascosa, Caldwell, Comal, Guadalupe and Hays counties. The Uvalde Pool lies below Uvalde County. Each pool has different drought triggers and each is monitored by a different index well.
The EAA Critical Period Management Plan is essentially a drought plan. Based on aquifer levels and springflows, pumping reductions are enforced to slow the decline and maintain adequate springflow until rain returns to the area.
The index wells are monitored around the clock and daily highs are recorded. The designated triggers are based on a 10-day rolling average. When the 10-day average falls below a designated measure, the General Manager will implement the appropriate stage of pumping reductions (Stage 1, 2, 3, 4 or 5).
The reductions apply to all groundwater permit holders using more than 3 acre-feet a year.
No. The EAA’s Critical Period Management Plan should not be confused with a public utility’s drought plan. For instance, SAWS can declare stricter or more frequent reductions as a preemptive measure.
For your convenience, a critical period calculator is available on the EAA’s website. But for clarification, the average annual reduction is calculated by averaging the daily reductions. The easiest way for permit holders to ensure they are not over pumping is to reduce their daily pumping by the amount that corresponds with the percentage reduction on a daily basis.
If you are permitted to pump more than 3 acre-feet of groundwater a year, besides complying with the plan’s mandatory pumping reductions, you are also required to submit monthly withdrawal reports to the EAA. Forms are available on the EAA website or you may call the Critical Period Management Team at 210.477.1883 or 866.931.3239 for hard copies of the form.