268 



FRESH WATER INFLOWS 



The quality of estuarine areas is dependent not only on direct waste 

 sources but also on the quality of the streams and runoff entering the 

 system. Tributary influent quality is generally a good index of the 

 type and intensity of land use in the surrounding area and upstream 

 from an estuarine system, and it can be a major cause of ecological 

 stress within the system. The complex interactions between fresh and 

 salt water may magnify the effects of pollutants carried into the tidal 

 regime, resulting in quality anomalies completely alien to either fresh 

 or oceanic environments. It is, therefore, imperative to examine the 

 secondary or relatively uncontrollable pollutant source of tributary 

 inflow. 



The first item to be considered is the quality of major rivers and 

 streams entering the estuarine area. Many streams are subjected to 

 various uses and abuses in their upstream reaches; by the time they 

 reach the coastal area the full cumulative effects of pollution are ex- 

 erted. If no regulatory actions were taken, there probably would be 

 severe quality deterioration throughout the coastal regions of the 

 country. However, the implementation of the water quality standards 

 program through joint Federal -State effort has provided a two- 

 pronged attack on pollution with two levels of regulatory power. Rigid 

 enforcement of this program should result in a steady improvement 

 of the quality of water entering the estuary systems. Table IV.5.10 

 summarizes the tributary inflow quality from upstream pollution for 

 selected streams entering the estuarine zone. These data are for the 

 first station above tidal influence and show the baseline for manage- 

 ment planning. These data may be contrasted with natural river water 

 quality shown in table IV.1.8. 



TABLE IV.5.10.— EXAMPLES OF RIVER WATER QUALITY AS STREAMS ENTER THE ESTUARINE ZONE 



Biophysical 

 region River Typical observed water quality conditions in inflowing river 



North Atlantic Merrimack Bacterial counts (MPN) above 1,000,000; dissolved oxygen (DO) 



below 50 percent saturation. 



Middle Atlantic Connecticut MPN above 10,000; DO near saturation. 



Chesapeake.. _._ Potomac MPN less than 1,000; DO near saturation; high turbidity during 



moderate to high flows. 

 South Atlantic. Savannah High turbidity during moderate to high flows; high natural dissolved 



organic load, low DO. 



Caribbean.. _. Canals from Everglades High natural dissolved organic load; low DO. 



Gulf of Mexico Mobile __ MPN above 10,000. 



Pascagoula MPN above 10,000. 



Pearl High natural dissolved organic load, low DO. 



Pacific Southwest Russian MPN above 5,000. 



Pacific Northwest Willamette _ MPN above 10,000. 



Alaska Yukon.. Very high turbidity. 



The second item to consider is the quality of the inflow from land 

 runoff". The pollutional potential of this source is dependent on land- 

 use patterns, the rainfall-land runoff relationship, and rainfall inten- 

 sity. If the land is essentially natural marshland or covered by natural 

 vegetation, runoff does not pose a serious water quality problem. Run- 

 oft' from agricultural land, however, can be a threat, depending upon 

 the amount of chemical fertilizers and pesticides used and the degree 

 to which the land can be eroded. If the land is urbanized with lar^e 

 paved areas, the runoff can be up to twice as strong as normal domestic 



