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Nothing is taken for granted more than water. Until, that is, the water runs out.
That is why LCRA, the steward of the waters of the lower Colorado River, has a state-approved Water Management Plan that determines how to allocate water from lakes Travis and Buchanan among various groups of users in times of plenty and scarcity.
The two lakes are actually reservoirs – created by damming the river – that store water for later use by cities, industry, agriculture, recreation and to keep enough fresh water in the river and Matagorda Bay to sustain aquatic life. The lakes and the river are managed together to make the best use of the water supply.
Under the LCRA Water Management Plan, the water supply is divided into “firm” and “interruptible” stored water. Firm water is available even during a severe drought. Interruptible water is subject to rationing or curtailment. Rice irrigators are the primary users of interruptible water in the lower Colorado River basin. A significant amount of the interruptible supply is also used to meet environmental needs.
Based on a 10-year horizon, the plan describes how water is allocated as water storage drops during droughts. It directs how interruptible water supplies are curtailed, if necessary, so that demands on firm stored water are fully met throughout a repeat of the critical drought – a drought as severe as the worst on record, which was in the 1950s.
LCRA takes action at key points as lakes Buchanan and Travis drop from their combined full capacities of about 2 million acre-feet (an acre-foot is about 326,000 gallons). As of Feb. 1, 2006, the combined storage capacity in lakes Buchanan and Travis was 1.57 million acre-feet.
Some of the key actions are:
- When the combined volume of the lakes falls below 94 percent of total capacity on either Jan.1 or July 1, interruptible customers other than the large downstream irrigation operations are required to cease diversions. These customers use the water primarily for municipal, golf course and crop irrigation.
- When the combined volume of the lakes is less than 1.6 million acre-feet, LCRA begins an aggressive public information campaign to encourage water conservation. LCRA already began taking this step last fall when the combined capacity of the two lakes fell below 1.6 million acre-feet.
- If the shortage intensifies so that the volume drops to less than 1.1 million acre-feet on Jan. 1, the large irrigation operations downstream are required to reduce diversions of water.
- If the volume continues to fall to less than 900,000 acre-feet, LCRA would ask water customers to begin mandatory conservation measures.
- Extremely low levels – worse than the drought of record – would trigger the pro rata curtailment of water for firm customers. This “trigger point” probably would not be reached until after several years of continuous drought.
The plan also provides for the needs of aquatic life in the lower Colorado River below Austin and in Matagorda Bay on the Gulf Coast. Fish and other aquatic life depend on fresh water from the river to maintain healthy habitats. The extent of releases from the lakes for this purpose depends on the amount of water stored in the lakes at the beginning of each year and inflows coming into the lakes. It also depends on how much water LCRA is entitled to store after allocating the inflows for downstream senior water rights.
If the lakes are full, LCRA makes releases for the remainder of the year to maintain a good quality habitat. If the lakes are low – less than 1.7 million acre-feet in combined storage – LCRA releases smaller amounts of water that would continue to meet the critical needs of the bay and estuaries, enough to keep salinity in the bay from getting too high to sustain aquatic life.
A combined storage of less than 1.1 million acre-feet would trigger a gradual curtailment of releases for irrigation. Also, the target for instream flow would be reduced to meet critical needs. |
