Beneficial Use Attainment
Thirty-nine miles of the Salt River, 20 miles of Mark Twain Lake, 45 miles of the North Fork, and 49 miles of the Middle Fork are designated for public drinking water supply (MDNR 1986a). Only the lower Salt River from its mouth to Clarence Cannon Dam and Mark Twain Lake are classified for whole-body contact recreation. All streams listed by the Department of Natural Resources are designated for livestock and wildlife watering and protection of aquatic life. The primary deterrents to recreational use in the basin are high turbidity and siltation which are the results of poor soil management and bed scour (MNDR 1986b). Excessive turbidity and siltation have not only decreased the abundance and diversity of aquatic life and habitat (Missouri Department of Conservation 1978), but have also made boating and canoeing more difficult due to locally heavy sedimentation. Fortunately, most streams in the basin have been spared from extensive channelization. Only the North Fork has been significantly channelized (42%). Channelization also affects recreational use by creating high banks and steep-sided channels making access difficult. The lack of public access in parts of the basin also limits recreational use.
Chemical Quality of Stream Flow
Water quality was data was collected from basin streams at 12 sites around Mark Twain Lake prior to impoundment (U.S. Army Corps of Engineers, St. Louis 1974). For the most part, concentrations were within normal ranges during low or moderate stream flows. High measurements of turbidity, fecal coliform, iron, phosphorus, and nitrogen were usually associated with high flows. Although iron concentrations exceeded 20 mg/L at times, most was in the insoluble form which quickly settles out. Preimpoundment water quality information was also collected throughout the basin during 1969-70 by the Missouri Water Pollution Control Board (1970).
More recent water quality data is scarce. Data was recorded from the lower Salt River at the New London USGS gage station from 1967 to 1986. Selected parameters for the 1986 water year are presented in Table Wq01. Most measurements were within normal ranges during 1986 except during periods of high flow when fecal coliform and iron concentrations were high. The U.S. Army Corps of Engineers (St. Louis District) periodically collects water quality data at sites within Mark Twain Lake and just below the re-regulation dam on Salt River. The Clarence Cannon Water Treatment Plant monitors several parameters of raw water entering the plant from Mark Twain Lake. Like many reservoirs in agricultural watersheds, Mark Twain Lake has had atrazine levels above the maximum contamination level for drinking water (U.S. Army Corps of Engineers 1996). Rt. J Reservoir, a water supply reservoir owned by the city of Monroe City, has also had elevated atrazine levels. Although water treatment can remove this and other pesticides, the treatment process is expensive. Monroe City, with cooperation and assistance of several state, federal, and local agencies, and landowners, developed a comprehensive watershed management plan. In 1999, the ?Route J Watershed Atrazine Abatement and Management Project? was implemented with the goal of reducing atrazine losses in field run-off while maintaining effective weed control.
Other water quality research was conducted in the basin during the 1990?s as part of the Agricultural Systems for Environmental Quality Project. This was a joint project of the USDA Agricultural Research Service (ARS), the University of Missouri, University Extension, and the USGS. Information on this project can be obtained by contacting the Cropping Systems and Water Quality Research Unit, USDA ARS, Room 269 Agr. Engineering Building, University of Missouri, Columbia, Missouri 65211. The purpose of the project was to determine the impact of prevailing cropping systems on ground and surface water quality (dissolved herbicides and nutrients). Findings of this work, much of which was conducted in the Salt River basin, can be found in Kitchen et al. (1997), Donald et al. (1998), Blanchard and Donald (1997), Blanchard and Lerch (2000), and Lerch and Blanchard (2003). Among the findings of these researchers was that many stream sites within the Salt River basin had elevated levels of herbicides, and percent losses of herbicides from claypan soil watersheds are high.
Suspended sediment discharge measured at the Middle Fork-Paris gage station during water year 1996 ranged from 0.26 to 26,500 tons/day. At the New London station (partial sediment data site), a suspended sediment discharge of 12,900 tons/day was recorded on May 7, 1996. Although highly variable from year to year, the average annual suspended sediment load in the Salt River at Monroe City from 1941 to 1965 was 1.215 million tons (Finney 1986).
Concerns listed by the Department of Natural Resources for the lower Salt River include chronic exceedences of secondary drinking water standards for manganese, occasional exceedences of whole fish standards for dieldrin and chlordane (MDNR 1986b). In the re-regulation pool below Mark Twain Lake, low dissolved concentrations caused by low flows of hypolimnetic waters from the lake through the turbines may significantly stress fish in the pool (see Dam and Hydropower Influences). Effluent from sewage treatment facilities or infrastructure in Kirksville, Macon, and Mexico have caused water quality problems in Bear Creek and Steer Creek, Sewer Creek, and South Fork, respectively. Facilities and operations in each of these cities have recently undergone improvements which should lessen impacts on receiving streams. Animal waste in streams can cause low levels of dissolved oxygen, high levels of ammonia, and can lead to nuisance agal blooms (MDNR unpublished). Although surface mining for coal in the Lick Creek and Littleby Creek watersheds has increased sulfate levels in the water, these increases are not of concern and are still below permitted maximums for drinking water supply and protection of aquatic life.
Fish Contaminant Levels and Health Advisories, Fish Kills
All of Missouri, including the Salt River basin, is under a Fish Consumption Advisory posted by the Missouri Department of Health. This advisory advises that women who are pregnant, who may become pregnant, nursing mothers, and children 12 years of age and younger not to eat any largemouth bass over 12 inches in length. This advisory was issued due to concerns about mercury contamination in largemouth bass and because of new risks estimates by the U.S. Environmental Protection Agency. North Missouri was once included in a limited consumption advisory for catfish, carp, drum, suckers, and paddlefish. However, this advisory was removed in 2001 because levels of contaminants, mainly chlorodane, have declined.
Low dissolved oxygen concentrations in the re-regulation pool between Clarence Cannon Dam and the re-regulation dam have been a major concern and a persistent problem. However, causes have been identified, water quality is now consistently monitored, and operational procedures at Clarence Cannon Dam are in place that will make oxygen problems in the pool less likely in the future. Other persistent water quality problems and fish kills have occurred in Bear Creek and Steer Creek due to sewage releases and overflows from Kirksville?s wastewater treatment plant and infrastructure. Recent improvements at the plant have made future problems less likely.
Mark Twain Lake is the largest water supply reservoir in the basin. The Clarence Cannon Wholesale Water Commission (CCWWC) currently distributes about 2.5 million gallons daily (mgd) to a large area around the lake and in some adjoining basins. The lake has the capacity to supply about 16 mgd. The CCWWC supplies water to Perry, Shelbyville, Paris, Madison, New London, Farber, Huntsville, Vandalia, Curryville, Lewistown, LaBelle, Edina, Shelby County PWSD (Public Water Supply District) #1, Knox County PWSD #1, Monroe County PWSD #2, Marion County PWSD #1, and Cannon PWSD #1, Thomas Hill PWSD #1, Pike County PWSD #1, and Lewis County PWSD #1. In addition to Mark Twain Lake, there are about 13 other municipal water supply reservoirs in the basin; however, some of these are not currently in use (Vandike 1995). The City of Shelbina occasionally pumps water from the North Fork Salt River into their water supply reservoir. Total surface water withdrawals for North Fork, South Fork, and lower Salt River sub-basins are approximately 2.5, 5.5, and 3.0 million gallons per day, respectively. Industrial water withdrawals in the basin are relatively minor, totaling about 1.7 million gallons per day. Seventy-three percent of the 14,200 acres of irrigated land in the basin occurs in the South Fork sub-basin, mostly in Audrain County.
Point Source Pollution
Overall, point sources have a minor impact on streams in the basin. Waste water treatment facilities are the most common sources of point pollution (Table Wq02). Most have relatively small daily discharges. Only Shelbina, Macon, Mexico, Moberly, and Kirksville discharge more the 0.5 million gallons daily into receiving streams. The Kirksville waste treatment facility has had problems in the past with the rotating biological contactor resulting in permit exceedences and discoloration and sedimentation of several miles of Bear Creek (MDNR unpublished). Recent improvements should lessen the likelihood of detrimental impacts in the future. Numerous small, privately owned point-source discharges (subdivisions, small businesses, schools etc.) occur in the basin. Stormwater run-off from several sand/gravel quarries, limestone settling ponds, clay pits and storage, and coal mining sites are also potential sources of pollution in the basin, especially in the South Fork sub-basin.
Concentrated Animal Feeding Operations
Audrain and Shelby counties are among Missouri?s top swine producing counties. Most swine operations in the Salt River basin are relatively small compared to corporate farms that have recently ventured into the neighboring Chariton River basin. Corporate operations may develop and have significant impacts in the Salt River basin in the future. Currently, the largest hog facility, located in the Spencer Creek watershed, handles about 8,500 head (Table Wq03). Another eleven farms retain more than 1,500 hogs. All of these privately-owned operations use anaerobic lagoons for treatment of excrement.
Sedimentation and turbidity are the basin?s most severe water quality problems (MDNR unpublished, Duchrow 1974). Intensive land cultivation has caused severe soil erosion throughout the watershed. Anderson (1980) reported 18 - 24 tons/acre/year of sheet and rill erosion from tilled land in the basin. Erosion from permanent pasture land averaged 2.5 - 5 tons/acre/year. Gully erosion was considered moderate at 100 - 199 tons/square mile annually. As a consequence, the watershed delivered about 2.9 tons/acre of sediment to basin streams annually and was ranked the tenth worst of 45 basins in the state. Streambank erosion contributes about 3% of the annual sediment load to basin streams. Sediment yield to Mark Twain Lake in 1988 was estimated at 1.85 million tons, 58% of which originated from cropland and 17% from floodplain scour (SCS 1988).
Agricultural run-off, which includes fertilizer, pesticides, herbicides, and animal waste, also poses a significant threat to water quality in the basin. During dry periods when stream flows are low, livestock and their waste concentrate around streams. These waste can promote low levels of dissolved oxygen, high levels of ammonia, and excessive algal growth.