Groundwater is a critical source of ACWD’s water, making up 30 to 60 percent of our total supply. This sampling ensures its safety. As part of the sampling protocol, a limited amount of groundwater must be removed from wells and discharged to nearby storm drains. As a result, you may notice water temporarily flowing in the gutters near the sampling sites. While ACWD is attempting to minimize water use during drought, protecting our groundwater resources is key to our mission of providing a reliable supply of high-quality water to our customers.