The City of Houston uses three important criteria in declaring a drought. The first is the amount of water used. The number is in millions of gallons per day (mgd) and an average over the previous three days is used so that a one day temporary spike in water usage does not cause a shortage to be declared. Stage triggers are based on percentage of total available production capacity, so that 80% is a stage two, 85% stage three, and 90% would result in a stage four.
The second criteria looks at the lake levels to determine how much surface water is available to be treated. Lake levels are calculated in acre feet (ac-ft) which is equal to 325,851 gallons. The City’s reservoir system can store up to 1,625,000 ac-ft from Lake Livingston, Lake Conroe, and Lake Houston. Engineers have calculated how much water the City needs for 24 months, 18 months, and 12 months. As the reservoir levels reach each of these criteria, a drought event may be issued.
The third criteria is related to average distribution system pressure. Water pressure within the city’s distribution system is monitored continuously. There may be isolated areas that may experience pressures at or below the trigger values due to main breaks or high usage. However, this trigger is related to the entire distribution system pressure not being maintained above 45 psi for stage two, 40 psi for stage three or 35 psi for stage four water shortage declarations.
Reminder: The Fall season of The City Hall Farmers Market comes to a close on Wednesday December 23rd. You can go to Hermann Square in front of City Hall for a tasty selection of local fresh produce grown by local farmers, cheeses, breads, roasted coffees, and a variety of prepared meals.
