Droughts and heat waves can degrade water quality in a number of ways. Reduced river and stream flows caused by heat and draught can make bodies of water more stagnant— leading to emergence of pollutants and bacteria. Heat waves also lower oxygen levels in water, which in turn endangers fish and other marine life and reduces water quality.  Heat waves and droughts can create conditions that lead to wild fires that in turn bring sediment, ash, charcoal and debris into fresh waters and ground water. Fulton Schools Professor Rolf Halden, director of ASU’s Biodesign Center for Environmental Health Engineering, notes that hot weather can also contaminate water in plastic bottles. The hotter it gets, Halden says, the more likely that substances in plastic can move into and affect food or drinking water in the bottles.