Like most of the reservoirs in Texas, the lake was planned and constructed shortly after the record seven-year drought of the 1950s as part of a reservoir-building boom intended by state water planners to prevent a repeat of the water shortages experienced during the drought.

The headwaters of Lake Conroe, formed by the West Fork of the San Jacinto River, are located about 17 miles west of Huntsville in western Walker County.  The river flows southeast for about ninety miles through Montgomery County to its confluence with the East Fork of the San Jacinto River on the northern rim of Lake Houston in northeastern Harris County.

In order to continue the proper management of the agricultural and other natural resources of the Lake Conroe watershed, the State of Texas Legislature created, in 1937, the San Jacinto Conservation and Reclamation District.  Although the Legislature changed the name of the agency to the San Jacinto River Authority (SJRA) in 1951, the primary objectives of the agency have remained the same, namely, to develop, conserve, and protect the water resources of the San Jacinto River basin.

In its early years, from 1937 to 1941, the SJRA devoted most of its resources to providing soil conservation services for farmers and ranchers.  Together, the SJRA and farmers built stock tanks, ponds and small lakes that were used to control stormwater runoff and erosion.  The SJRA engaged in a long-range program of soil conservation and land reclamation beginning in 1946 with the goal of improving the agriculture of the area and preventing negative impacts to the watershed from soil erosion.  The SJRA Board of Directors entered into a joint program with the San Jacinto Soil Conservation District in which the Conservation District would furnish engineering and planning for the reclamation measures undertaken by the SJRA within the area.  The Board of Directors strongly believed that soil conservation projects would not only increase the agricultural productivity of the lands, but would also promote the recharging of the underlying aquifers by allowing runoff water to better infiltrate into the soil.

Despite all the successes the SJRA has achieved in the area of land and soil conservation, the primary focus has always been and will continue to be water supply development.  This objective was the basis of a  partnership agreement the SJRA reached with the City of Houston and the Texas Water Development Board in 1968 to jointly construct a water supply reservoir, Lake Conroe, on the West Fork of the San Jacinto River.  The dam constructed to impound the waters of the reservoir was completed in January, 1973, and it was filled by October 31, 1973.  The lake covers a 21,000-acre area and extends about 21 miles from the dam to the upper reaches of the West Fork of the San Jacinto River, with 5,000 acres lying in the Sam Houston National Forest.  The lake can store up to 430,000 acre-feet of water at the normal pool elevation of 201 feet above Mean Sea Level, i.e., above the National Geodetic Vertical Datum of 1929.

Besides providing an alternative source of water supply for the City of Houston, Lake Conroe began in September 2015, to supplement groundwater sources in Montgomery County as a source of drinking water.  Rapid population growth and the resulting increase in water demand in the county has exhausted the  sustainable groundwater supply and prompted the Lone Star Groundwater Conservation District to mandate a reduction in groundwater withdrawals.  The SJRA responded to this mandate by entering into voluntary agreements with over 90 public and private entities in Montgomery County to construct a water treatment system using surface water from Lake Conroe in order to create a more balanced approach to supplying the water needs of the entire Montgomery County area.

In addition to the water supplies in Lake Conroe, the SJRA has been quietly working over the past 70-plus years to develop long-term water supplies throughout the San Jacinto and Trinity river basins to ensure adequate water for both municipal and industrial customers. These efforts began in 1945 with the acquisition of the old Works Project Administration canal system serving ship channel industries, as well as water rights in the San Jacinto River – before the construction of Lake Houston.  Since that time, the SJRA has acquired additional water supplies in the Trinity River basin.

In September of 2009, following years of negotiations, the SJRA completed a contract with the City of Houston to purchase the right to use the City’s 2/3 share of the water supplies in Lake Conroe. This important acquisition makes all of the water in Lake Conroe available for Montgomery County users.

The SJRA’s history of water supply acquisitions has made it possible for Montgomery County to have reliable, cost-effective water supplies to meet its future water needs.

Lake Conroe Facts:

The Dam:

• Type: Earth Filled.
• Year completed: 1973.
• Outlet structures: two concrete outlets, one service spillway, and one service outlet.
• Service spillway: five gates, 40 feet wide and 30 feet high, utilized for floodwater outflow.
• Service outlet: 3 gates with a 10 foot diameter conduit, utilized for the outflow of water downstream (Lake Houston).
• Top of dam elevation: 212 feet above mean sea level.
• Width of Dam: 2.2 miles (11,280ft).
• Maximum height: approximately 82 feet (top of dam structure).
• Maximum gate opening: approximately 20 feet per gate.
• Maximum possible outflow: approximately 150,000 cubic feet per second (depends on lake level during outflow).
• Highest gate opening in history: 14 feet per gate on August 28, 2017.
  

The Lake:

• Surface acres: 19,640.
• Watershed drainage area: Approximately 450 square miles.
• Shoreline:  approximately 150 miles.
• Capacity: 412,200 acre feet.
• Average depth: 20 feet.
• Normal conservation lake level (also known as full pool or normal conservation pool): 201 feet above mean sea level.
• Maximum outflow in history: 79,141 cubic feet per second on August 28, 2017.
• Flowage easement: (area lake level can rise during a rainfall event) 207 feet above mean sea level.
• Highest level in history: 206.24 feet above mean sea level on August 28, 2017 (previous record was 205.58 feet above mean sea level on October 19, 1994).
• Lowest level in history: 192.68 feet above mean sea level (8.32 feet) on December 2, 2011 (previous record was 196.02 above mean sea level on January 12, 1989).
• Average bulkhead height: elevation 203 feet above mean sea level.
• Annual rainfall: average 48 inches.
• Maximum evaporation rate: approximately 180 million gallons per day.