On August 1, the City of Houston Public Works Department, the San Jacinto River Authority (SJRA) and the Coastal Water Authority (CWA) plan to begin lowering the level of Lake Conroe as part of a joint operations plan to mitigate flooding threats during the peak of hurricane season. The plan calls for lowering Lake Conroe gradually through small releases – about an inch a day – until the lake level reaches 199 msl (mean feet above sea level).
Lake Conroe to Be Lowered 2 Feet Through September
This initial lowering will last through the end of September to create additional storage in Lake Conroe which could delay releases and minimize release rates during a storm, thereby providing a buffer against flooding for residents who live downstream of the dam.
The next lowering would occur during the peak of the spring rainy season – from April 1 – May 31, 2019. However, that lowering would only be by a foot – to 200 msl, because the rain threat is usually lower in spring.
Only Until Dredging Restores River’s Flow
The joint operations plan calls for continuing to lower Lake Conroe seasonally in this manner while the U.S. Army Corps of Engineers dredges the West Fork of the San Jacinto to restore flow.
Hurricane Harvey deposited tremendous amounts of silt in the West Fork which physically changed the river’s ability to safely pass water during storms. Hence, the dredging.
Phase-One Dredging Has Already Started
Phase one will go from River Grove Park to the West Lake Houston Parkway bridge. Great Lakes, the contractor hired by the Corps, has 269 more days to complete the initial phase.
Phase-Two Still Needs Funding
The total project could take longer. Community leaders are now working furiously to arrange funding to dredge the remainder of the west fork, including the mouth bar.
Mobilization and demobilization comprise 25 percent of the total phase one project costs (approximately $18 million out of almost $70 million). Having phase two ready to start before phase one ends could save that money, creating extra value for taxpayers and enabling even more dredging, say for instance, on the East Fork.
Temporary Lake Conroe Lowering Could Last Up to 3 Years
The City, SJRA, and CWA will continue the seasonal lowerings for up to three three years. They will monitor progress of the dredging and annually re-evaluate the need to lower Lake Conroe. If the river’s flow is restored before three years, the temporary lowering would cease.
Lakes will Operate under Two Different Strategies
Lake Conroe is located upstream from Lake Houston. Large pre-releases immediately before a storm run the risk of pushing water into Lake Houston at a rate that could flood residents. Therefore, the SJRA will release at a much more gradual, controlled rate and maintain the lower level until the largest flood threat passes.
Lake Houston, as the lowest lake on the river system, can pre-release more safely. Therefore CWA will pre-release from Lake Houston if the National Weather Service predicts more than 3 inches of rain within the San Jacinto River basin in a 48-hour period. Coastal Water Authority will lower Lake Houston to 41.5 feet from its normal elevation of 42.5 feet.
To track lake levels visit:
- Lake Conroe – www.sjra.net
- Lake Houston – www.coastalwaterauthority.org
4 Million People Depend on City for Water
Lake Conroe and Lake Houston comprise two of the largest parts of the City’s drinking water system. More than 4 million Houstonians and residents of the greater Houston region rely on water provided by the City.
Posted by Bob Rehak on July 30, 2018
335 Days since Hurricane Harvey