The Watershed Tour Grades 4 - 8. 30 students in groups. Learn about stream and river ecosystems and their water quality with this virtual "tour" using weeklong hands-on activities. Trace the life of a river from headwaters to mouth at four sites along its path. Includes: Testab? reagent tablets (single-packed) - 20 dissolved oxygen, 10 each wide-range pH, nitrate wide range, chloride, nutritab, buffer 7.0; 24 test tubes, 5 and 10 mL; 8 glass vials; data sheets and posters. Qty :