The Nisqually River begins in the glaciers of Mount Rainier and rushes 78 miles (125 km) to its mouth on the shores of Puget Sound. The Nisqually Delta is protected by the Nisqually National Wildlife Refuge, and the river is one of the largest contributors of freshwater to the south Puget Sound ecosystem.
The Nisqually Delta is in a relatively healthy condition, and supports diverse migratory bird and salmon species. However, the landscape has been drastically altered throughout its history. When early settlers arrived in the area, the delta was diked in order to produce fertile farmland. The Brown Farm Dike–essentially a wall of earth–drained the delta of saltwater and removed tidal influence. The newly created freshwater habitat changed everything, from the local elevations, to the types of plants and animals that thrived there.
The Brown Farm Dike remained in place for over a century. During that time, the Nisqually delta transitioned from being a working farm to a treasured wildlife refuge. Its status as a National Wildlife Refuge protected the delta from plans to convert it into a landfill or deepwater port. Today, the delta is managed to protect fish, birds and wildlife that find refuge there.
The dikes limited the ability for the Nisqually Delta to function as an intact estuary. Beginning in the late 1990s, the Nisqually Indian Tribe began to complete small restoration projects on the eastern side of the Delta, totaling over 140 acres (57 ha.) In 2005, the Nisqually National Wildlife Refuge’s Comprehensive Conservation Plan (CCP) identified delta restoration as one of its biggest priorities. The next step was to remove the dikes and return tidal influence to the delta.
The Brown Farm Dike was finally removed on November 11, 2009, returning tidal influence to 760 acres (308 ha) of the Nisqually National Wildlife Refuge. This was the largest tidal marsh restoration project in the Pacific Northwest to assist in the recovery of Puget Sound salmon and wildlife populations, some of which are listed on the Endangered Species Act. In all, the Refuge, the Nisqually Indian Tribe and Ducks Unlimited have restored over 21 miles (35 km) of historic tidal sloughs and re-connected historic floodplains to the salty waters of Puget Sound. The project has resulted a 50% increase in the potential salt marsh available in south Puget Sound.
The Nisqually Delta Restoration represents one of the most extensive delta restoration projects to-date in the Puget Sound, providing a unique opportunity to expand scientific knowledge related to large-scale restoration and estuary response. Because the Delta contains a diverse mosaic of estuarine habitats, this large-scale restoration is expected to result in a considerable increase in regional environmental and cultural services, representing one of the most significant advances towards the recovery of Puget Sound.
Monitoring has been on-going restoration efforts first began in 1996. Changes in environmental features such as water quality, sediment, vegetation communities and fish habitat use have been measured over the course of several decades. The US Geological Survey (USGS) has collaborated with the US Fish and Wildlife Service and the Nisqually Indian Tribe to document habitat development and ecosystem function with large-scale restoration. The results of these monitoring efforts are summarized by topic.