 Blackwater NWR is one of over 540 units in the National Wildlife Refuge System, which is managed by the United States Fish and Wildlife Service.Blackwater Refuge is fed by the Blackwater River and the Little Blackwater River.The name "blackwater" comes from the tea-colored waters of the local rivers, which are darkened by the tannin that is picked up as the water drains through peat soil in the marshes.