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
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.
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.