San Lorenzo Creek, also known as Don Castro Reservoir, is a vital water resource located in Castro Valley, California. Managed by the local government, this dam serves primarily for flood risk reduction and recreation purposes. Constructed in 1964, this earth dam stands at a height of 65 feet and has a storage capacity of 380 acre-feet, covering a surface area of 24 acres.

With a high hazard potential but assessed as satisfactory in condition, San Lorenzo Creek plays a crucial role in managing the region's water resources. The dam is regulated by the California Department of Water Resources and undergoes regular inspections to ensure its safety and reliability. Despite its age, the dam continues to provide flood protection and recreational opportunities for the local community.

San Lorenzo Creek's importance extends beyond flood risk reduction, serving as a significant water infrastructure in Alameda County. As climate change poses increasing challenges to water resources management, this dam remains a key asset in safeguarding against potential disasters and ensuring sustainable water use for the future. With its strategic location and vital role in the region, San Lorenzo Creek stands as a testament to the ongoing efforts to balance water resource management with environmental conservation and public safety.