Monthly Archives: February 2014


The water that flows from Blue Spring comes from rainfall in the 130 square mile springshed, which encompasses portions of five cities within Volusia County. The rainfall seeps down into the aquifer and slowly flows through the limestone
before discharging at the spring. It takes less than 43 years for most of the rainfall to make its way through the aquifer to the spring. Along the way, the water picks up pollutants that are ultimately discharged at the spring and that affect the ecological health of the spring run.

Blue Spring Springshed

Spring Flows

Blue Spring, one of more than a thousand springs in Florida, is the largest spring on the St. Johns River and the 17th largest in Florida in terms of rate of discharge. With an average discharge of 102 million gallons per day, Blue Spring is one of Florida’s 27 first-magnitude springs. The average daily discharge is equivalent to a pool of
water the size of a football field (360 x 160 feet) that is 240 feet deep. The discharge varies based on rainfall and withdrawals of water from the springshed. Blue Spring is a designated manatee refuge, and an important part of the St. Johns River ecosystem.

Water Quality Trends

Nutrient pollutants in springs adversely affect the aquatic ecosystem by promoting algae and undesirable plant growth. Nitrate is one of the nutrients with a particularly harmful effect on springs. Nitrates enter the groundwater through atmospheric deposition, fertilizers, and animal and human wastes, and remain stable even as
they pass through the aquifer. An overall increasing trend in concentrations of nitrate in Blue Spring appears to have occurred since 1975. Since 1998, concentrations of nitrate have averaged over nine times the expected
background concentration. This increase coincides with visible declines in the aquatic habitat of the spring run, which is of particular concern to the Alliance.

Manatee Refuge

Blue Spring is well known as a winter refuge for the Florida manatee. Manatees are gentle, slow-moving mammals related to the dugong, and more distantly, the elephant. They are herbivores and eat a wide variety of aquatic plants. Adults are
about 10 feet long and weigh between 1,500 and 2,200 pounds. During the warmer months, manatees travel widely through warm, shallow, coastal estuarine waters of central and south Florida. They cannot survive for extended periods
in water colder than about 68 degrees, so they migrate to warmer spring waters during the cold winter months.

The number of manatees using the Blue Spring run as a winter refuge is increasing. Since the mid-1980s, the winter population of manatees has increased almost fivefold, from less than 60 to more than 400 individuals. Manatees usually
arrive in small numbers as early as October and leave sometime in April, with the largest population using the spring run during December and January. Decreasing the volume of discharge from Blue Spring threatens wintering manatees by
reducing the size of the warm water refuge. Other threats to manatee survival in Florida are mostly due to human activities, such as operation of boats
and habitat degradation.