Texas State University Logo


Online Resources

Join the Conversation

adjust type sizemake font smallermake font largerreset font size

Stream Flow

Daily Water Readings for Edwards Aquifer at Bexar, Uvalde, San Marcos Springs and Comal Springs.

Spring Flow

The average flow of the San Marcos River is around 140 cubic feet per second (cfs). When spring flow is around 100 cfs, the flow rate is considered low. When the spring flow is around 500 cfs, the flow rate is considered high. The rate at which the San Marcos Springs flow is ultimately a result of Edwards Aquifer levels. This means that spring flow will fluctuate with different rates of consumption and rainfall. Since Texas is known for periods of droughts followed by flooding, spring flow is constantly changing. The continued lack of rainfall within the recharge zone and the resulting low spring flow demonstrates that the Edwards Aquifer is a limited resource, which is why water conservation is significant.

USGS Water Data for the San Marcos River

Low Spring Flow

Low spring flow and water levels have the potential to negatively influence flora and fauna in Spring Lake and its related ecosystem. In addition, low water levels make volunteer scuba diving in Spring Lake unsafe.

Diving Drought Protocol

When the flow rate of the San Marcos Springs is 100 cfs, Aquarena Center will implement a Diving Drought Protocol in accordance with the Habitat Conservation Plan. The protocol requires limiting the number of Diving for Science volunteers submerged in Spring Lake. Only two to three volunteer scuba divers may be submerged at a given spring location at the same time. Unfortunately, this might affect convenience of dive times, where scheduling will be on a first come first dive basis. However, the purpose of the Diving Drought Protocol is to preserve the unique aquatic ecosystem as well as to protect the safety of volunteer scuba divers. At 100 cfs, Diving for Science volunteers will find themselves in closer proximity to glass bottom boat traffic as the water level of Spring Lake will continue to drop in response to the declining spring flow. At 75 cfs, the Diving Drought Protocol requires all scuba diving activities to be suspended in Spring Lake. We apologize for any inconvenience. Again, the Diving Drought Protocol is necessary to protect the unique ecosystem at Aquarena as well as the safety of all Diving for Science volunteers.