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EspañolSUISUN MARSH
Located in central California the 'Suisun Marsh' (pronounced "suh-soon") is the largest saltwater marsh on west coast of the United States of America. The marsh land is part of the Suisun Bay tidal estuary, and subjected to seasonal flooding. The marsh is home to many species of birds and other wildlife, and is formed by the confluence of the Sacramento and San Joaquin rivers between Martinez and Fairfield, California and several other smaller watersheds. The marsh is considered the western boundary of the Sacramento-San Joaquin Delta as well as part of the San Francisco Bay estuary.
The Suisun Marsh is named for the Suisunes who inhabited the area around 200 years ago.
Suisun Marsh, 84,000 acres (340 km²) of land, bays, and sloughs, is one of the largest estuarine (where fresh and salt water meet) marshes in the western United States. Rush Ranch is a 2070 acre (8.4 km²) ranch bordering Suisun Marsh that was acquired for wildlife habitat and public access to the marsh by the Solano County Farmlands and Open Space Foundation in 1988.
Geologically, Suisun Marsh is the product of the deposition of water-borne sediments carried by the Sacramento and San Joaquin Rivers to San Francisco Bay. This process, the weathering of the parent rock of the Sierras, transport of the weathered material via
rivers, and ultimate deposition into San Francisco Bay, has taken place over thousands of years and has resulted in the patchwork nature of the marsh.
Originally, Suisun Marsh was a vast stretch of unbroken tidal wetland, alternately flooded and drained with the rise and fall of the tides. From the 1860's until the 1930's, however, this area was used primarily for agriculture, made possible by the construction of channels, levees and dikes to hold the salt water back from cultivated land. Eventually, even these measures proved ineffective in keeping the salt water out and large-scale cultivation ceased. Most of the marsh was then purchased by public and private interests as habitat for ducks and geese, mainly to support hunting. The dedication of duck hunters to maintenance of the marsh for waterfowl lead to strong provisions in legislation authorizing major dams and diversions upstream that made sure enough fresh water is provided to keep Suisun Marsh from becoming too saline. Salt marshes are much less productive of waterfowl (and other wildlife) than brackish water marshes. Today Suisun Marsh supports a diversity of fish and wildlife, including a large population of river otters, a number of native fish species, and birds ranging from marsh wrens to white pelicans.Rush Ranch has only been recently acquired and is managed for both historicand wildlife values, so still retains a ranch-like character. However, its wildlife habitats are being enhanced and many marsh plants and animals can be seen here.
Another "public" part of the marsh is Grizzly Island Wildlife Areawhich managed primarily for waterfowl, although over 230 species of birds have been seen here as well as many mammals, amphibians, reptiles, and fish. Grizzly Island has an unusually dense population of river otters, which can be seen swimming in its numerous sloughs, ponds, and roadside ditches. In the fall the tule elk are breeding, so the bugling of bull elk can be heard, especially in the early morning and evening. Unfortunately, it is off-limits for the non-hunting public during the fall because it is dedicated then to duck and pheasant hunting. [1]
The dikes, or levees, of Suisun Marsh were originally built by 19th Century farmers seeking to create dry farmland from tidal marsh. While this system is still in use in the Sacramento-San Joaquin Delta to the east, it failed in the Suisun Marsh due to unacceptably high salinity in the water and soil. As the marsh was subsequently converted from farming to waterfowl habitat during the 20th Century, the abandoned farmland was converted into ponds, and the 230 miles of levees are now used to keep water in as well as out. Between mid-October and mid-January, 52,000 acres of leveed ponds (managed seasonal wetlands), on Grizzly Island, plus Joice and Morrow Islands, are flooded to a depth of 8 to 12 inches to attract waterfowl.
The rest of the year, the ponds are repeatedly flooded and drained on a schedule designed to optimize conditions for the growth of plant species most useful as waterfowl food, namely alkali bullrush, fat hen, and brass buttons. The flood-and-drain schedule minimizes soil and water salinity by leaching and flushing salt. It keeps the pond bottoms either well above or well below water to prevent wet soils from slowly drying by evaporation, which would deposit salts on their surface. This wetland management program suppresses native salt-tolerant plants such as tules, cattails, saltgrass, and pickleweed, which are less useful to the desired bird populations.Suisun Marsh Monitoring Program, Reference Guide, Environmental Services Office, Department of Water Resources, State of California.. p. 26.[1]
An original motive in creating a waterfowl habitat was to attract migrating and overwintering birds away from croplands in the central valley, reducing crop predation. However, by about 1930 waterfowl hunting had become the primary use of the Suisun Marsh. It is the dominant use today, with 158 private duck clubs and large public hunting areas.Suisun Marsh Facts, Environmental Services Office, Department of Water Resources, State of California. [ http://www.iep.ca.gov/suisun/facts/ ]
The wetland managers for both the private hunting clubs and the state's public land take their pond water from Montezuma Slough, rather than from the bay, in order to minimize salinity. For example, the ironically named "Roaring River Distribution System," a canal which provides pond water to lower Grizzly Island, connects with Montezuma Slough to the east, but not with Grizzly Bay to the west (see map). However Montezuma Slough has a surprising quirk. It is open at both ends, and its flood tide current is longer and stronger than its ebb tide current, causing a net west-to-east flow which draws salty water eastward from Grizzly Bay.
The flood tide pushing through the circuitous slough takes half an hour longer to traverse the marsh than does the matching flood tide following the more direct route in the main Suisin Bay channel.[2] Thus, high tide at the east end of the slough arrives out of phase with high tide in the main channel, and rather than being pushed back, as it would be in the main channel or in a dead-end slough, the slough water keeps flowing eastward, drawing salty water with it.
This tendency for the Montezuma Slough to be saltier than it should be diminished the effectiveness of the Roaring River and other salinity control facilities built around 1980. In 1989 that problem was solved when the Suisun Marsh Salinity Control Gates began operation. They span the Montezuma Slough near the Roaring River intake and are opened and closed twice a day, to block the salty flood tide from Grizzly Bay but allow passage of the freshwater ebb tide from the mouth of the Sacramento-San Joaquin Delta. The slough's net eastward tidal flow is thus reversed, and the saltier bay water is eventually purged from the slough and its connecting waterways.
The Salinity Control Gates have been so effective that other proposed salinity control measures have been deemed unnecessary and canceled. The gates operate from October through May, but are opened to allow uninterrupted flow in both directions during the summer months when all the ponds are dry.p. 44
Although the Suisun Marsh is managed for waterfowl, it is also an important fish habitat, especially for wild salmon. Monitoring stations throughout the marsh measure the impact of water management activities on fish populations, and fish screens prevent the diversion and entrapment of fish in the waterfowl ponds.
1. Moyle, Peter B., Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, November 18, 2006.
2. http://www.saltwatertides.com/dynamic.dir/californiasites.html
Mount Diablo as seen from the Suisun Marsh:
The Suisun Marsh is named for the Suisunes who inhabited the area around 200 years ago.
| Contents |
| Overview |
| Flooded Ponds |
| Water Management |
| Fish |
| Notes |
Overview
Suisun Marsh, 84,000 acres (340 km²) of land, bays, and sloughs, is one of the largest estuarine (where fresh and salt water meet) marshes in the western United States. Rush Ranch is a 2070 acre (8.4 km²) ranch bordering Suisun Marsh that was acquired for wildlife habitat and public access to the marsh by the Solano County Farmlands and Open Space Foundation in 1988.
Geologically, Suisun Marsh is the product of the deposition of water-borne sediments carried by the Sacramento and San Joaquin Rivers to San Francisco Bay. This process, the weathering of the parent rock of the Sierras, transport of the weathered material via
rivers, and ultimate deposition into San Francisco Bay, has taken place over thousands of years and has resulted in the patchwork nature of the marsh.
Originally, Suisun Marsh was a vast stretch of unbroken tidal wetland, alternately flooded and drained with the rise and fall of the tides. From the 1860's until the 1930's, however, this area was used primarily for agriculture, made possible by the construction of channels, levees and dikes to hold the salt water back from cultivated land. Eventually, even these measures proved ineffective in keeping the salt water out and large-scale cultivation ceased. Most of the marsh was then purchased by public and private interests as habitat for ducks and geese, mainly to support hunting. The dedication of duck hunters to maintenance of the marsh for waterfowl lead to strong provisions in legislation authorizing major dams and diversions upstream that made sure enough fresh water is provided to keep Suisun Marsh from becoming too saline. Salt marshes are much less productive of waterfowl (and other wildlife) than brackish water marshes. Today Suisun Marsh supports a diversity of fish and wildlife, including a large population of river otters, a number of native fish species, and birds ranging from marsh wrens to white pelicans.Rush Ranch has only been recently acquired and is managed for both historicand wildlife values, so still retains a ranch-like character. However, its wildlife habitats are being enhanced and many marsh plants and animals can be seen here.
Another "public" part of the marsh is Grizzly Island Wildlife Areawhich managed primarily for waterfowl, although over 230 species of birds have been seen here as well as many mammals, amphibians, reptiles, and fish. Grizzly Island has an unusually dense population of river otters, which can be seen swimming in its numerous sloughs, ponds, and roadside ditches. In the fall the tule elk are breeding, so the bugling of bull elk can be heard, especially in the early morning and evening. Unfortunately, it is off-limits for the non-hunting public during the fall because it is dedicated then to duck and pheasant hunting. [1]
Flooded Ponds
Schedule for flooding ponds during the fall hunting season, then leaching, and finally drying them during the summer.
The dikes, or levees, of Suisun Marsh were originally built by 19th Century farmers seeking to create dry farmland from tidal marsh. While this system is still in use in the Sacramento-San Joaquin Delta to the east, it failed in the Suisun Marsh due to unacceptably high salinity in the water and soil. As the marsh was subsequently converted from farming to waterfowl habitat during the 20th Century, the abandoned farmland was converted into ponds, and the 230 miles of levees are now used to keep water in as well as out. Between mid-October and mid-January, 52,000 acres of leveed ponds (managed seasonal wetlands), on Grizzly Island, plus Joice and Morrow Islands, are flooded to a depth of 8 to 12 inches to attract waterfowl.
The rest of the year, the ponds are repeatedly flooded and drained on a schedule designed to optimize conditions for the growth of plant species most useful as waterfowl food, namely alkali bullrush, fat hen, and brass buttons. The flood-and-drain schedule minimizes soil and water salinity by leaching and flushing salt. It keeps the pond bottoms either well above or well below water to prevent wet soils from slowly drying by evaporation, which would deposit salts on their surface. This wetland management program suppresses native salt-tolerant plants such as tules, cattails, saltgrass, and pickleweed, which are less useful to the desired bird populations.Suisun Marsh Monitoring Program, Reference Guide, Environmental Services Office, Department of Water Resources, State of California.. p. 26.[1]
An original motive in creating a waterfowl habitat was to attract migrating and overwintering birds away from croplands in the central valley, reducing crop predation. However, by about 1930 waterfowl hunting had become the primary use of the Suisun Marsh. It is the dominant use today, with 158 private duck clubs and large public hunting areas.Suisun Marsh Facts, Environmental Services Office, Department of Water Resources, State of California. [ http://www.iep.ca.gov/suisun/facts/ ]
Water Management
Montezuma Slough, to the north and east of Grizzly Island, is the key to wetland management.
Suisun Marsh Salinity Control Gates, open to allow freshwater into the Montezuma Slough.
The wetland managers for both the private hunting clubs and the state's public land take their pond water from Montezuma Slough, rather than from the bay, in order to minimize salinity. For example, the ironically named "Roaring River Distribution System," a canal which provides pond water to lower Grizzly Island, connects with Montezuma Slough to the east, but not with Grizzly Bay to the west (see map). However Montezuma Slough has a surprising quirk. It is open at both ends, and its flood tide current is longer and stronger than its ebb tide current, causing a net west-to-east flow which draws salty water eastward from Grizzly Bay.
The flood tide pushing through the circuitous slough takes half an hour longer to traverse the marsh than does the matching flood tide following the more direct route in the main Suisin Bay channel.[2] Thus, high tide at the east end of the slough arrives out of phase with high tide in the main channel, and rather than being pushed back, as it would be in the main channel or in a dead-end slough, the slough water keeps flowing eastward, drawing salty water with it.
This tendency for the Montezuma Slough to be saltier than it should be diminished the effectiveness of the Roaring River and other salinity control facilities built around 1980. In 1989 that problem was solved when the Suisun Marsh Salinity Control Gates began operation. They span the Montezuma Slough near the Roaring River intake and are opened and closed twice a day, to block the salty flood tide from Grizzly Bay but allow passage of the freshwater ebb tide from the mouth of the Sacramento-San Joaquin Delta. The slough's net eastward tidal flow is thus reversed, and the saltier bay water is eventually purged from the slough and its connecting waterways.
The Salinity Control Gates have been so effective that other proposed salinity control measures have been deemed unnecessary and canceled. The gates operate from October through May, but are opened to allow uninterrupted flow in both directions during the summer months when all the ponds are dry.p. 44
Fish
Although the Suisun Marsh is managed for waterfowl, it is also an important fish habitat, especially for wild salmon. Monitoring stations throughout the marsh measure the impact of water management activities on fish populations, and fish screens prevent the diversion and entrapment of fish in the waterfowl ponds.
Notes
1. Moyle, Peter B., Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, November 18, 2006.
2. http://www.saltwatertides.com/dynamic.dir/californiasites.html
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