The San Marcos Watershed, located in central Texas and covering an area of about 464 square miles, is an important hydrological region. The watershed is characterized by numerous streams and rivers, with the San Marcos River being the most significant. The area is hot and humid with an annual rainfall ranging from 30 to 40 inches. The watershed is also home to several reservoirs that are used for various purposes such as flood control, drinking water supply, and recreation. The water quality of the reservoirs is monitored regularly to ensure safety. The San Marcos watershed is also affected by changes in snowpack and surface water. The region experiences occasional droughts, which can cause a decrease in surface water and snowpack. Climate change is also affecting the region, with an increase in extreme weather events such as floods and droughts. Overall, the San Marcos watershed plays a crucial role in the region's hydrology, and it is essential to monitor its health and water quality regularly.