Nonprofit nature center at San Marcos Springs. Includes information on exhibits, ecology of the springs and their endangered species, educational programs, scientific diving, and facilities rental for special events.

Birding locations, descriptions, maps, plus pictures and descriptions of the birds of central Texas.

Collect water quality data from the headwaters of the San Marcos River at Aquarena Springs to Prairie Lea. Features mission statement, river profile, and monitoring schedule and sites.