Lake Houston sits at the bottom of a large watershed that includes North Harris County, all of Montgomery County and parts of Liberty, Waller, San Jacinto, Walker and Grimes counties. According to data from the United States Geological Survey, water from almost 40 creeks and bayous flows into the lake, with much of the water traveling through the West and East forks of the San Jacinto River.
Because of the large area the watershed covers, water levels in the lake and both forks of the river often increase days after a rain event takes place, as it takes time for the water to make it to the Lake Houston area.
For example, the West Fork of the San Jacinto River’s elevation peaked at 51.8 feet at noon Dec. 8 after the Lake Houston area received more than 3 inches of rain. More than 24 hours later, the river’s water level lowered to about 49 feet late in the day Dec. 9, before increasing again to about 50.9 feet at 3 a.m. Dec. 11, according to data from the National Weather Service.