Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for determining turbidity of water using machine learning. One of the methods includes obtaining, by a camera, an image of water; detecting, using a blob detector, a plurality of blobs in the image that represent particles suspended in the water; determining a distribution of the plurality of blobs; determining, from the distribution of the plurality of blobs, a measurement associated with turbidity of the water; and providing a signal associated with the measurement.