The last time Houston had to use Lake Conroe as a water supply backup was in 1988.
Mayor Annise Parker says the lake was built for that very purpose, but it's rare for the need to arise.
"Lake Conroe was completed in the early '60s. This is only the third time we've been required to draw down water from Lake Conroe into Lake Houston in order to support water levels in Lake Houston."
Lake Houston is now five feet below its normal level. Boats are getting stranded on sand bars, vegetation is growing rampant and docks are dry. But a big problem is water levels are barely high enough to keep the city's pumps that pull water into the water treatment system working.
By next week it will be low enough to trigger mandatory conservation efforts, including the drawdown of about 150 million gallons of water from Lake Conroe.
"It's long overdue."
That's Councilmember Mike Sullivan, who represents the area around Lake Houston. He says the mayor should have taken action before things got this bad.
"The mayor and public works director can draw water down from Lake Conroe any time they want to."
Reporter: "So you feel like it should have been done earlier. We're approaching the mandatory level where it has to be done, but you feel like action should have been taken already?"
"I think that it should have been taken before now and it would have benefitted those that live on Lake Houston and live around Lake Houston, as well as Houstonians in general."
Sullivan says as the water gets lower, the quality of Houston's drinking supply goes down because the pumps are pulling from the bottom of the lake.
But Parker says they didn't want to do this arbitrarily and will hold off until mandatory conservation levels kick in.
"We are not going to draw down Lake Conroe in order to raise the level of Lake Houston. We're drawing it down in order to stabilize the level of Lake Houston at the minimum level above our water intake plant."
The mayor expects to issue the order for water conservation some time next week. At that point, Houston residents and businesses will be required to water their lawns only at night or in the morning with a limit of twice a week. There's also a requirement to repair detectable water leaks within 72 hours, or face possible citations.