Lake Brownwood, also known as Brownwood Reservoir, is an artificial lake on Pecan Bayou, eight miles north of Brownwood in north central Brown County (at 31°50' N, 99°00' W). The project is owned and operated by Brown County Water Improvement District Number 1. The surface area is 7,300 acres, and the drainage area 1,535 square miles. The lake's normal capacity is 118,900 acre-feet; its maximum capacity is 448,200 acre-feet. The spillway elevation is 1,425 feet above mean sea level.
On December 3, 1929, following a lengthy publicity war between upstream and downstream interests, the State Board of Water Engineers authorized the construction of the reservoir and annual diversion of 16,800 acre-feet of water for municipal and industrial purposes and 50,590 acre-feet for irrigation. The project was financed by the formation of a water improvement district and the issuance of bonds. The board acquired 7,200 acres. Geological features at the site are Pennsylvanian Age with alternating layers of limestone and shale. The chief engineer, D. W. Ross, advised the board to build an earthen dam, 1,600 feet long and 116 feet high from the bottom of Pecan Bayou, with a concrete core, a spillway twenty-five feet below the top of the dam, and four conduits through the dam. During construction flood gates were added at the intake of the conduits. Work on the dam began in 1931; the deliberate impoundment of water began in July 1933. A survey of the watershed of the lake revealed that two years of normal rainfall were needed before the lake would fill, but on July 3, 1932, torrential rains caused Pecan Bayou and Jim Ned Creek to pour flooding waters into the lake, filling it to a level of 150,000 acre-feet and covering more than 7,000 acres of land in six hours.
Lake Brownwood State Recreation Area was established and later improved by the Civilian Conservation Corps. The district's water board acquired ninety acres of land on the south side of the lake, which was sold between 1932 and 1937. Despite the revenues, financial problems occasionally impeded progress. The Public Works Administration financed a matching grant to build a canal system which was completed in 1939. The district began diverting water into the canal on April 4, 1939. However, few landowners made use of the water, and the board lost money. The filtration plant supplies water for municipal use to Brownwood, Bangs, Early, and Santa Anna.