Seeing the San Antonio River turn green on St. Patrick's Day is not that unusual, but seeing it green in April has sparked some questions.
According to the San Antonio River Authority, recycled water pumped into the river is treated by San Antonio Water Works and has nutrients that cause the water to turn green.
Rainfall also washes pollutants into the river, raising the bacteria level of the river, which also changes its appearance. Officials say this is temporary and the river will return to normal.