Humans have had significant impacts on the water quality of the streams and coastal waters in Coastal Southern California national parks.
Fresh Water Quality
- Cattle and sheep grazing and the introduction of feral pigs on the Channel Islands dramatically degraded stream bank vegetation, caused heavy erosion, and altered stream channels.
- In the Santa Monica Mountains, runoff associated with urban development has resulted in year-round flow in streams that previously only had water in them for part of the year. While more consistent stream flow increases the amount of aquatic habitat, it has also allowed the invasion of non-native species like crayfish, bass, carp, sunfish, the giant reed (Arundo donax), and New Zealand mudsnail (Potamopyrgus antipodarum) which need a perennial water source to survive. The runoff water coming in from developed areas is also generally poor quality and contains chemicals and other pollutants. Nevertheless, park streams support steelhead trout (Oncorhynchus mykiss), a federal and state-listed endangered species, as well as a diversity of other native flora and fauna.
Marine Water Quality
- At Channel Islands National Park, due to its remote location and lack of development, direct sources of anthropogenic marine water pollution are limited to intentional or accidental discharges (i.e., sewage, fuel, bilge water) from private or commercial vessels. Other potential sources of anthropogenic water contamination are indirect and include terrestrial runoff from the mainland (mostly during winter), polluted sediments near the mainland coast, ocean outfalls for mainland wastewater treatment plants, chemical dumps in the ocean, dredge disposal sites, produced water discharges and drilling wastes from offshore oil and gas operations, oil spills, and discharges or spills from marine vessels (including sinkings and groundings).