Proposal to Temporarily Lower Lake Conroe Stirs Fight with Lake Conroe Association Over Likely 4.8 Inches

At its board meeting last month, the San Jacinto River Authority (SJRA) voted to temporarily lower Lake Conroe. This temporary lowering would only be by one foot in the rainiest months of spring and up to two feet during the peak of hurricane season, late August and September. However, due to seasonal evaporation, the amount of the actual lowering would most likely amount to 4.8 inches in September. Assuming this is an average year, that’s just 20% of the 2 feet previously anticipated.

The temporary lowering of the lake level would provide a welcome buffer against flooding for Humble and Kingwood residents, yet has sparked a blizzard of backlash from the Lake Conroe Association.

The Lake Conroe Association has said it will accept a temporary 1-foot lowering, but not 2-feet. Read the full text of the open letter by the Association’s president. Their president asserts that that extra foot will reduce property values, hurt commerce and undermine tourism. He repeatedly refers to the temporary measure as an attempt to turn Lake Conroe into a flood-control lake, rather than a water supply lake. He has vowed to take the fight to Austin, the Texas Council on Environmental Quality (TCEQ) and the City of Houston. Here’s the kicker.

Nature already lowers the lake through evaporation during the peak of hurricane season – an average of more than 19 inches in September. Therefore, the Lake Conroe Association is not really fighting about two full feet, or even an extra foot; they’re fighting about a reduction that would be just 4.8 inches if this is an average year. Only in one year out of the last 18 has the average level of Lake Conroe exceeded 201 feet in September; that was last year after Harvey.

Bill Fowler, Co-chair of Lake Houston Area Flood Prevention Initiative, researched seasonal fluctuations of Lake Conroe due to evaporation. He found that the lake normally goes down during hurricane season, often by much more than a foot. See the table below taken from USGS data. The 18-year averages for August and September, the two months in question, are:

  • August = 199.6
  • September = 199.4

USGS data showing the average monthly levels of Lake Conroe for the last 18 years. 

Four-tenths of a foot equals just 4.8 inches.

4.8 inches will cause property values to collapse? 4.8 inches is going to make or break marinas? 4.8 inches will ruin tourism?  The temporary lowering would not even last the entire two months.

Below is the exact proposal, with details supplied by Jace Houston, general manager of SJRA. It must still be approved by the City of Houston and the Texas Council on Environmental Quality (TCEQ).

Note that SJRA wouldn’t start lowering beyond one foot until August 15 and wouldn’t get down to the target level until September 1.

Also note that the temporary lowering is relative to the level SJRA tries to maintain – 201 feet above mean sea level. It does NOT begin at the actual lake level which is, on average, 199.4 feet above MSL in September.

Details of Temporary Lowering of Lake Conroe

  • As a point of reference, the normal pool level of Lake Conroe is 201’ above mean sea level (msl).
  • Spring season – April 1 through May 31.
    • Starting on April 1, gradually reduce to and maintain the level of Lake Conroe at 200’ msl (one foot below normal pool).
    • Starting on June 1, begin to capture flows to restore normal lake elevation.
  • Fall season – August 1 through September 30.
    • Starting on August 1, gradually reduce the level of Lake Conroe with a goal of reaching 200’ msl (one foot below normal pool) by August 15.
    • After August 15, continue gradually lowering the level of Lake Conroe with a goal of reaching (and maintaining) 199’ msl (two feet below normal pool) by August 31.
    • Starting October 1, begin to capture flows to restore normal lake elevation.
  • If the lake level has already dropped to the target elevation just due to evaporation, no releases would be made.
  • If a storm enters the forecast while releases are being made to lower the lake level, releases would be stopped and the river allowed to drain out until rainfall is out of the forecast.

The Lake Conroe association is really only being asked to give up the difference between 199 msl and whatever the lake level is on August 15. The full reduction would not be reached until September 1 and the lake would fill again beginning October 1.

Note that any temporary, seasonal lowering would only last until downstream mitigation projects can be implemented. For instance, the Army Corps of Engineers should begin a dredging project in June that will remove the equivalent of approximately two and half Astrodomes worth of sand from the West Fork between Humble and Kingwood. That sand currently blocks the river and drainage ditches, causing higher-than-normal flooding with modest rains.

The Lake Conroe Association speaks for its members, but not all Lake Conroe residents. Many of the lake’s residents also flooded during Harvey and have indicated they would welcome a temporary reduction in lake level, as they too struggle to rebuild their lives and homes.

The Lake Houston Area Grass Roots Flood Prevention Initiative has invited LCA’s president to see the river siltation and devastation in this area caused by Harvey and the Lake Conroe release of 79,000 cubic feet per second. He has accepted. Let’s hope that what he sees changes his desire to fight a measure that could help so many people.

Posted on May 18, 2018 by Bob Rehak

262 days since Hurricane Harvey