Chemical and hydrologic assessment of the Caloosahatchee River basin, Lake Okeechobee to Franklin Lock, Florida

Annual discharge (1970-79 water years) from Lake Okeechobee to the Caloosahatchee River averaged 51 percent of the total river discharge at Franklin Lock and ranged from 10 to 71 percent of total discharge. Excluding rainfall on the river surface and upstream seepage, surface and subsurface runoff from the basin accounted for the remaining total river discharge at Franklin Lock. Nitrogen and phosphorus were in sufficient supply most of the time to support algal growth in the river. During algal blooms, however, nitrite plus nitrate nitrogen was depleted and probably became limiting. Nitrite plus nitrate was the predominant form of inorganic nitrogen in the river and in most tributaries. Average concentrations in the river were 0.18 to 0.21 milligram per liter. Average concentrations in most tributaries were less than those in the river. Average concentrations of total phosphorus in many tributaries fell within the same range as that in the river (0.08 to 0.15 milligram per liter), but some tributaries in the eastern part of the basin had greater average concentrations.