On the Headwaters Coalition website you will learn about the mission of this ministry of the Sisters of Charity. While they have broader goals, they particularly seek to protect and repair the headwaters of the San Antonio River.
They are participating in the Basura Bash on Saturday March 7 from, 9:00 am to 12:00 pm. If you register online they ask that you choose Olmos Creek for a “Preferred Area”and Olmos-Headwaters Sanctuary for "Zone".
If you can't make the bash or if you are volunteering on another part of our watershed, you can join them any third Thursday. This March 19 is “Feline” Fun Workday from 12:30 to 4:30 pm. Non-native catclaw vines will be cut down at the north end of the sanctuary. No heavy lifting is involved. Meet at the entrance to the soccer fields.
UPDATE: Here's a link to the San Antonio Current's 2/25/09 story "San Antonio returns to its ailing Yanaguana" which includes more information on the work of the Headwaters Coalition.