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'Cross The Wide Missouri

Sakakawea Headwaters Area

by
Fred Ryckman*

JPG-Sakakawea Headwaters Area Map

A "headwater" is a transition zone where a river's flowing water slows down and becomes part of slack water at the upper end of a reservoir. The exact boundary of any headwater varies depending on factors such as reservoir level and magnitude of inflows.

Lake Sakakawea's headwater is generally defined as the area from U.S. Highway 85 downstream to the Lewis and Clark State Park area. During the drought of the late 1980s and early 1990s, the transition zone shifted downstream many miles because of Sakakawea's low level. During 1993, the transition zone was pushed farther down into Lake Sakakawea because of heavy inflows. In 1997, when Sakakawea reached a near-record lake elevation, the transition zone moved several miles upstream of Highway 85.

Since the U.S. Army Corps of Engineers acquired fee title to all land that would potentially flood if Lake Sakakawea was at full pool, all of the headwaters area and immediate shoreline is owned by the Corps. Much of the Corps land along either side of Highway 85 is leased to and managed by the North Dakota Game and Fish Department as the Lewis and Clark Wildlife Management Area. Since high lake levels and high inflows often flood this land, agricultural use or development within the floodplain is often difficult under the best circumstances. Wildlife populations fluctuate considerably, but the area generally contains substantial numbers of white-tailed deer, pheasants and other species.

Regardless of the exact boundary, Sakakawea's headwater area is an important aquatic habitat. It receives a tremendous amount of silt and nutrients from the Yellowstone and Missouri rivers. Highly turbid Yellowstone River water usually creates a "mud line" visible at times well past the New Town area in Lake Sakakawea.

  JPG-Lake Sakakawea's Headwaters
Lake Sakakawea's headwaters are extremely important to paddlefish, especially younger fish.

The magnitude of the Yellowstone's silt load is truly incredible; the Corps of Engineers estimate that 30,000 acre-feet of sediment — enough to cover nearly 47 square miles with one foot of dirt — are annually deposited in the headwaters of Lake Sakakawea. As this sediment settles it has filled in virtually all of the old Missouri River channel in the upper end of Lake Sakakawea. As a consequence, much of the headwaters is a broad, shallow, silt-bottomed floodplain.

No estimate is available for the amount of nutrients, but these annual inputs are considered critically important to the productivity of upper Sakakawea. Lower lake levels allow for regrowth of terrestrial vegetation, which becomes important aquatic habitat when the lake level rises and floods the regrowth.

Although the overall ecological value to most fish inhabiting Lake Sakakawea and the Missouri River upstream of the headwaters is not yet well known, its value for paddlefish is beyond doubt. Beginning in 1991, research efforts have documented extensive seasonal use of a small portion of the headwaters area by paddlefish, especially young-of-the-year and yearlings. Concentrations of these juvenile paddlefish were found throughout the 1990s, despite dramatic fluctuations in Sakakawea water levels.

Standard annual visual transects of juvenile paddlefish have been completed in a 30-mile-long portion of upper Sakakawea since 1992. Observers surveying these transects have documented several hundred young-of-the-year and lesser numbers of yearling paddlefish in seven of the last eight years. The only exception occurred in 1994, when only one YOY was observed. Although several factors may have affected this apparent paddlefish reproduction bust, extremely low late spring and early summer flows were likely the biggest factor.

Preliminary results from a radio-telemetry project also indicate the headwaters area is seasonally used by adult paddlefish. Some of the area's value to paddlefish might simply relate to its "remoteness." There is currently little boating and open water angling on the entire upper end of Lake Sakakawea west of Lewis and Clark State Park, because of lack of access, and extremely turbid water throughout much of the recreational season. Turbid water limits desirability for boating and recreation, and it also limits the number of walleye and other sight-feeding fish that use the area. Because of limited value for recreational use, further development of public access and use facilities in this area is not likely.

  JPG-Paddlefish
Young-of-the-year and yearling paddlefish have been documented using the area in seven of the last eight years, despite some dramatic water fluctuations. Preliminary results from a radio-telemetry project also indicate a seasonal use of the headwaters area by adult paddlefish.

Because of Lake Sakakawea's fluctuating water level, and the annual sediment load in the Yellowstone River, silt will continue to build a delta at the lake's upper end. Regardless, the headwaters will remain a critically important area on the Missouri River System in North Dakota.


*Fred Ryckman is a fisheries biologist at the Game and Fish Department's Williston office.


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