Critical Period/Drought Management

In times of declining groundwater levels, the EAA implements a Critical Period Management (CPM) Plan to help sustain aquifer and springflow levels. This program helps slow the rate of decline in aquifer levels and spring discharges during periods of little or no rain by reducing the amount of groundwater permit holders may withdraw.

Triggers, Stages and Reductions

Critical Period Chart

Download Critical Period PDF

The CPM Plan is divided into four stages of increasing restrictiveness. Triggers—10-day average spring and index well levels—are used to determine stages of mandatory water use reductions. Reduction amounts are calculated based on the number of days a CPM stage is in effect, with reductions increasing as aquifer levels decrease. For instance, Stage 1 of CPM is declared in the San Antonio Pool when the 10-day average level at the J-17 Index Well drops below 660 feet mean sea level (msl) or if the 10-day average spring flow at Comal or San Marcos Springs falls below 225 cubic feet per second (cfs) or 96 cfs, respectively. During Stage I, permit holders must reduce groundwater withdrawals by 20% of their authorized annual withdrawal rights based on the number of days CPM is in effect. A calculator to help you determine exactly how various stages of CPM affect you as a permit holder is available on the EAA’s website.

View Critical Period Management Tools


Reporting Requirements

During critical periods, all municipal, industrial and irrigation users are required to submit withdrawal reports monthly. These reports are reconciled at the end of the year to ensure permit holder compliance with the CPM reductions. 


Options for Irrigators

Finishing Out a Crop

Irrigators wanting to finish out a pre-critical period crop without being affected by CPM reductions must submit a Notice of Intent to Finish Out a Crop (PDF) form within 30 days after the effective date of Stage 1 CPM. Irrigation users who submit these forms and qualify do not need to submit monthly CPM withdrawal reports. However, monthly use reports are required for crops that do not qualify.

Planting an Additional Crop

Irrigators who want to plant an additional crop during a critical period stage may do so, but must submit a Notice of Planting an Additional Crop (PDF) form within 15 days after the crop has been planted, along with well meter reading(s) at the time of planting. Please note however, water for irrigating these additional crops is subject to CPM reductions of a permit’s remaining authorized withdrawal amounts.