paired values were statistically significant (0.74) at the 95% confidence 

 level. Point source and nonpoint source and urban concentrations typically 

 show positive correlation with low water quality. Not all water pollution is 

 explained by watershed conditions alone; many other factors are involved as 

 well. 



The water assessment report also developed a water quality index (WQI) 

 and a watershed index (WSI) that describes the relationships between changes 

 in standard values of all water quality measurements as a function of land-use 

 types in a watershed. Phosphorus concentrations in aquatic habitats and 

 intense industrial areas such as strip-mining, urban centers, and rangeland 

 exhibited a positive correlation. Watersheds with relatively high sewage 

 flows also exhibit an abundance of phosphorus. 



Nitrogen concentrations (TKN and organic nitrogen) were highest in range- 

 lands and wetlands with high water storage capacity, and high in waters sub- 

 ject to sewage discharges. Inorganic nitrogen is somewhat different from 

 organic nitrogen. High levels of organic nitrogen appears to have been caused 

 by fertilizers used on agricultural lands. 



An increase in the area of urban and range! ands, and sewage inflow, 

 caused an increase in the biological oxygen demand (BOD) in the waters of the 

 watershed. Raw sewage particularly increases the probability of excessive 

 BOD. Dissolved oxygen in rivers and ponds apparently was little altered by 

 runoff from wetlands and rangelands. 



Increased urbanization, industrialization, and water-related development 

 indicate that water quality in some areas will decline over the next several 

 decades. The degree of decline is difficult to predict accurately and there- 

 fore should be identified only in terms of direction and probable magnitude. 



Phosphorous concentrations and nitrogen concentrations probably will 

 increase as agriculture intensifies. As urbanization expands, forests are 

 cleared and marsh wetlands are drained so that BOD, DO, inorganic nitrogen, 

 and phosphorous are likely to increase. On the other hand, regulatory con- 

 trols including point source discharge permits and regulatory management of 

 nonpoint source discharges should minimize violations of water quality stan- 

 dards. 



The best available forecast for sewage treatment plant discharges in the 

 counties of Southwest Florida is shown in Table 2. Increased point source 

 loadings from secondary treatment facilities and associated industrial expan- 

 sion and coastal developments are strongly related with declines in water 

 quality (Florida State Department of Environmental Regulation 1979a). 



The increase in sewage treatment facilities is somewhat in proportion to 

 the increase in population. The rates of growth (3.1% to 5.7%) among the 

 counties of Southwest Florida are among the highest in the State. The popula- 

 tion distribution throughout the State are given in Figure 2. The greatest 

 single concentration is in the Tampa or St. Petersburg area. Future increases 

 probably will be greatest south of Tampa Bay. 



Considering the increase in the population, the increase for sewage 

 treatment also will grow and further stress some of the natural resources 

 (Florida State Department of Environmental Regulation 1979a). 



272 



