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The Story of Water in Florida

Water is Florida's lifeblood. It is fickle. Abundant one year. Scarce another. Yet, everything that is Florida is defined by the quality of its water resources -- and deserves all the protection we can provide.

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Learn About Your Watershed

Nassau-St. Marys River Watershed

Image of A marsh on St. Mary's River
A marsh on St. Mary's River Daniel

Watershed Stats

Size of Basin: The St. Marys watershed occupies approximately 1,585 square miles in southeastern Georgia and northeastern Florida, with about 942 square miles of the watershed in Florida. The Nassau watershed occupies approximately 464 square miles.

Major Cities and Towns: Yulee, Callahan, Amelia Island, Little Talbot Island, Fernandina Beach, and MacClenny

Counties: Baker, Columbia, Duval, Nassau, and Union

Major Water Features: St. Marys River, Fernandina River, Nassau River, Nassau Estuary, South Amelia River, Sisters Creek, Ft. George River, Okefenokee Swamp, Pinhook Swamp, North Prong, Middle Prong, Cedar Creek, South Prong, Deep Creek, and Baldwin Bay-Brandy Branch, Suwannee Canal, Hampton Walker Lake, Little St. Marys River, Alligator Creek, Ft. George River, Lofton Creek, Mills Creek, Plummer Creek, Pumpkin Hill Creek, South Amelia River, Ft. George River, Simpson Creek, Garden Creek, Harrison Creek, Thomas Creek, Ocean Pond, and Atlantic Intracoastal Waterway

Overview

Image of The George Crady Bridge Fishing Pier connects Talbot Island to Ameilia Island and spans Nassau Sound.
The George Crady Bridge Fishing Pier connects Talbot Island to Ameilia Island and spans Nassau Sound. FDEP

The St. Marys River, a remote blackwater stream with an extensive marsh system, serves as the border between southeast Georgia and northeast Florida. Almost all of the Florida portion of the watershed lies within Baker and Nassau Counties. The river begins in the peat bogs of the Okefenokee Swamp in Georgia. It provides a continuous water and land corridor that extends 125 to 130 miles from the Okefenokee National Wildlife Refuge, Osceola National Forest, and Pinhook Swamp area, through the Ralph E. Simmons Memorial State Forest and large private tracts and preserves, to the Cumberland Island National Seashore, Fort Clinch State Aquatic Preserve, and Atlantic Ocean.

The headwaters contain large floodplain wetlands that store substantial amounts of water. Large, forested areas north of the Osceola National Forest in Baker County provide strategic habitat for the Florida black bear and a number of rare bird species.

Image of At Amelia Island State Park, beautiful beaches, salt marshes, and coastal maritime forests provide visitors a glimpse of the original Florida.
At Amelia Island State Park, beautiful beaches, salt marshes, and coastal maritime forests provide visitors a glimpse of the original Florida. FDEP

Floodplains cover approximately half of the lower St. Marys land area, and the river is tidally influenced as far as 64 miles upstream. The extensive floodplain and its wet soils have limited development in much of this stretch. St. Marys Inlet, which lies at the entrance to Cumberland Sound at the mouth of the river, is an important passageway for commercial, recreational, and naval vessels, providing access to St. Marys Harbor, Georgia; Fernandina Harbor (via the Amelia River); and the U.S. Navy Submarine Support Base at Kings Bay, Georgia.

The Nassau River, a small river with numerous tributaries, forms the boundary between Nassau and Duval Counties just north of Jacksonville. The watershed covers much of Nassau County and a portion of Duval County to the south. It includes approximately 55 river miles and about 10 square miles of estuary. The Nassau River estuary is part of the chain of barrier islands along the Atlantic coast from the St. Johns River north to the Santee River in South Carolina. The vast saltmarsh estuary has numerous interconnecting tidal creeks, channels, and tree islands. The extent to which tidal influence extends upstream varies with rainfall, tides, winds, and evapotranspiration.

The St. Marys River begins in the peat bogs of the Okefenokee Swamp in Georgia and serves as the border between southeast Georgia and northeast Florida.

Image of A railroad bridge over Amelia River which flows into Nassau Sound.
A railroad bridge over Amelia River which flows into Nassau Sound. Jimmy Emerson

The Nassau watershed is largely undeveloped, with upland forests and wetlands constituting over 75 percent of the land cover. Silviculture is the main land use. The Nassau Wildlife Management Area occupies 40,168 acres along the upper river and tributaries.

The Nassau watershed's open water and contiguous saltwater and freshwater wetlands support large and diverse bird populations and several wading bird rookeries. The Florida Fish and Wildlife Conservation Commission has designated two areas with concentrated wading bird populations as Critical Wildlife Areas. The river is also a breeding and nursery area for various fishes, crab, and shrimp.

A number of waterbodies in the Nassau-St. Marys watershed have been given additional protection through designation as Outstanding Florida Waters: Fort Caroline National Memorial, Big Talbot Island State Park, Little Talbot Island State Park, Nassau Valley State Reserve, Ft. George Island, Nassau River-St. Johns River Marshes Aquatic Preserve, Timucuan Ecological and Historic Preserve, Okefenokee National Wildlife Refuge, Amelia Island State Recreational Area, Fort Clinch State Park Aquatic Preserve, and waters in the Osceola National Forest. The interior 353,981-acre portion of the Okefenokee National Wildlife Refuge, which lies in both Florida and Georgia, is also designated as a National Wilderness Area. The Pumpkin Hill Creek State Buffer Preserve protects one of the largest contiguous areas of coastal uplands left in Duval County; these uplands are important to the water quality of the Nassau and St. Johns Rivers.

Human Impacts

Although the population in the Nassau-St. Marys watershed is relatively low compared with the rest of Florida, Amelia Island is a popular coastal tourist destination and has more intense urban development than the rest of the watershed. The highest population densities are found in Fernandina Beach and Macclenny. Continued urban development is expected as the Jacksonville urban area expands and in the Amelia Island, Macclenny/Glen St. Mary, Yulee, and Callahan areas.

The cities of St. Marys and Kingsland at the mouth of the St. Marys River are rapidly growing.

The cities of St. Marys and Kingsland at the mouth of the St. Marys River are rapidly growing because of their association with Kings Bay Naval Base, the settlement of retirees, and ecotourism activity focused on the Cumberland Island National Seashore.

In recognition of these impacts, DEP, the St. Johns River Water Management District (SJRWMD), and local governmental, scientific, educational, and citizen organizations are working to develop strategies for protecting and restoring water quality and quantity to restore and protect the Nassau-St. Marys watershed.

Interesting Facts:

  • The earliest occupation of the Nassau-St. Marys River area dates back to 3,500 B.C.
  • The Nassau River-St. Johns River Marshes and Fort Clinch State Park Aquatic Preserves comprise estuarine and marine waters of exceptional biological and aesthetic value.
  • Rare and endangered species such as the Atlantic sturgeon, Atlantic loggerhead turtle, leatherback turtle, right whale, and Florida manatee have been observed in these Aquatic Preserves.


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