Sac River Basin - Physical Features
Streams flow in a network and grow in size and capacity from their headwaters until they flow into another stream or river. Hydrologists characterize stream size by assigning them an ‘order’. For instance, a first order stream has no streams that drain into it. When two first order streams flow into one another, a second order stream is created. Similarly, when two second order streams flow into one another, a third order stream is created, and so forth.
What is a watershed? A watershed is any area of land on which rain falls and drains into a river system. Each river has its own watershed. The land area making a watershed is bound on each side by a divide. On the other side of the divide, the water flows towards another river system.
The Sac River starts near Springfield, MO, and flows north from Springfield to the Osage River which then empties into Truman Reservoir. The entire basin is 1,981 square miles, and is made up of 10 smaller basins (sub-basins). These basins and their stream information is listed below.
Tributaries to the Sac River
Little Sac River, Turnback Creek, Sons Creek, Horse Creek, Cedar Creek, Coon Creek, Turkey Creek, Brush Creek, and Bear Creek are some of the streams located in the Sac River Basin. Stockton Lake and Truman Reservoir connect to and sometimes flood the banks of the Sac River.
See what else was happening when the Ozark Dome was being formed!
The quality of the water that drains through a watershed is affected by the type of physical features that are found within the watershed. One measure of physical features is called land cover. Land cover is measured by looking at aerial photographs and calculating area of forest, grassland, agriculture, and urban area that can be seen on the photograph. The land use within the Sac River Watersheds consists of 59% grassland, 23% woodland, 3% reservoirs, and 14% other uses. Much of the grassland is fescue and is used for cattle grazing or hay production.
The Sac River Basin lies within The Ozark Plateaus and the Ozark Plains physiographic regions. The basin lies on the Springfield and Salem plateaus within the larger Ozark Dome structure. A dome is a geologic structure that is high in the center and is surrounded by layers of rock sloping away from its center.
The Ozark Dome was created over 500 million years ago when volcanic activity in the southwest corner of the state created the St. Francois Mountains. These mountains are the highest point of the Ozark Dome. When this uplift was occurring, there was also a shallow sea covering the area surrounding the St. Francois Mountains, including the area we now know as the James River Basin. As the sea rose and receded, it left behind layers of sediment that eventually became rock over many years. This is what is termed sedimentary rock. These rock layers are higher in elevation nearer to the St. Francois uplift, forming the Springfield and Salem plateaus. Since the rock is now exposed, weathering processes have eroded away the top layers, making the older layers more visible. In the northeastern half of the basin, Ordovician dolomite is the primary rock formation while Mississippian limestone, shale, and sandstone are found in the southwestern half of the basin
If you live in the Sac River Basin, you probably know that the area is known for having a lot of caves. This is because of all of the limestone layers that make up the geology of the basin.
Limestone is very soluble in water, so rain slowly dissolves it away, making passageways for the water to pass through. This type of topography is termed Karst. If a cavity has dissolved out near the earths surface, it could cave in, creating a sinkhole. Many sinkholes are found in the Sac River Basin (insert sinkhole map).
Coal deposits are also found in the northwestern portion of the Sac River Basin.
The Sac River Basin is characterized by many springs, resulting from the Karst formations. Below is a map of springs in the basin, followed by a map of spring locations. (Missouri Department of Conservation)
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Page last updated August 26, 2008