Construction of Canyon Dam on the Guadalupe River Mile 303 began in 1958. It was constructed to serve two purposes - flood control and water conservation. Flood protection is provided to 157,250 acres of land downstream from the dam. The high canyons of the upper Guadalupe have a channel capacity of 40,000-50,000 cubic feet per second. The channel on the lower Guadalupe River has a capacity of only 13,000-30,000 cubic feet per second; therefore, the lower Guadalupe River Basin had been especially subject to serious flooding. The construction of Canyon Dam on the edge of the Balcones Escarpment has been very effective in protecting the lower Guadalupe River Basin. One example of this came in August 1978. Within two days' time, 40 inches of rain fell on the upper Guadalupe River. The river flowed into the lake at 115,000 cubic feet per second causing the lake to rise 21.6 feet above the conservation pool level of 909.0 feet above mean sea level. It was estimated that 24 million dollars of downstream damage was averted due to the flood protection of Canyon Dam.

At conservation pool level the lake has a capacity of 382,000 acre-feet. It has a surface area of 8,230 acres and 80 miles of shoreline. At flood control pool level of 943-ft msl, the lake has an additional capacity of 346,000 acre-feet making total storage 728,400 acre-feet.

The Guadalupe-Blanco River Authority (GBRA) is the local agency with rights to the water in the conservation pool of the lake. The Authority contributed to the construction costs and currently pays the U.S. Government annually for the portion of operation and maintenance costs attributed to the conservation pool water. The water is used to operate several small hydroelectric plants downstream from New Braunfels. It is also used by the GBRA for municipal water supply, irrigation, and industrial uses. GBRA began construction of a hydroelectric facility at Canyon Dam in August 1987; it was first put into service in February 1989.

Water impoundment began in 1964 and the conservation pool level was reached in 1968. To date, it has been estimated that millions of dollars in flood damage has been averted from several major flood events in the area. The first major flood event occurred in August 1978 when the lake elevation reached 930.6-ft msl. However, the flood of record occurred in July 1987 when the lake level reached 942.67-ft msl. In 1991-1992 floods, maximum elevation reached 937.77-ft msl. Another flood event occurred in late June to early August 1997 when the maximum elevation was 937.6-ft msl. Canyon Dam controls floods originating on the 1,432 square miles of drainage above the dam. The lowest lake elevation recorded was December 1984 at 899.7-ft msl.

LAKE LEVELS:

909.0 ft msl - conservation pool

943.0 ft msl - spillway crest

948.0 ft msl - spillway crest, plus 5 feet spillway flow-high elevation of flowage easement lands

899.7 ft msl - all time lowest lake pool after impoundment on December 13, 1984

950.32 ft msl - all time highest lake pool after impoundment on July 6, 2002.