Since water from our areas drain to the Mokelumne River, potential pollution can move from here to the there. Pesticides, herbicides, trash, even leaf litter can cause problems downstream in our river’s ecosystem, affecting water quality. Veteran Mokelumne River Watershed teachers have led their students to study all sorts of aspects connected to the upper or lower Mokelumne River watershed, including the San Joaquin-Sacramento Delta and beyond.