Kansas Water Science Center
Sediment Science in Kansas
Neosho River at high flow (photo by Kyle Juracek, USGS)
In Kansas and nationally, sediment is a concern for both physical and chemical reasons. Physically, problems caused by excessive sediment may include degraded water quality, degraded aquatic habitat, increased water-treatment costs, decreased channel capacity, clogged water intakes, and loss of water-storage capacity in reservoirs. Chemically, sediment serves as a carrier for various contaminants and, under certain conditions, as a source of contaminants to water and biota. Sediment-associated contaminants include nutrients (nitrogen, phosphorus), trace elements, certain pesticides, and polychlorinated biphenyls (PCBs). Nationally, sediment has been identified as the most important contaminant of concern by the U.S. Environmental Protection Agency. In Kansas, concern about sediment is evidenced, in part, by the fact that the Kansas Department of Health and Environment has developed total maximum daily loads (TMDLs) to reduce sediment loads to several reservoirs in the State. Effective management of sediment requires an understanding of sediment erosion, transport, deposition, and quality and how such processes and characteristics vary spatially and temporally in response to various natural and human factors.
Over the past several years, the USGS has completed several studies in Kansas that have examined various sediment issues including sediment erosion, sediment transport, sediment deposition, sediment quality, and sediment sources. Results of these studies are summarized below.
Erosion is a concern for several reasons. Land-surface erosion removes topsoil, degrades soil quality, and contributes potentially harmful sediment to nearby streams. In-channel erosion of streams also is problematic. Channel-bank and channel-bed erosion represents a persistent threat to property, structures, and habitat located in or near stream channels. Erosion often is increased by various human disturbances including dam construction, channelization, land-use change (e.g., urbanization), and land-management practices (e.g., row-crop production, overgrazing). Nationally, billions of dollars have been spent over the past several decades to control erosion and mitigate its effects (Pimentel et al., 1995; Shields et al., 1995; Morris and Fan, 1998; Tegtmeier and Duffy, 2004).
Several USGS studies have investigated channel erosion in response to human disturbances. To address concerns about possible downstream effects of John Redmond Reservoir on the Neosho River, a study was done to determine whether or not the channel had widened substantially since the reservoir was completed. The post-dam response of the river was determined to be minor with no evidence of substantial widening (Juracek, 2000). In a study to assess the downstream effect of large reservoirs on channel-bed elevation, Juracek (2001) found that degradation lowered channel beds by several feet at some locations (fig. 1). Along Soldier Creek, it was determined that channelization caused substantial channel degradation (widening and deepening). The degradation migrated several miles upstream from the original site of disturbance (Juracek, 2002, 2004a). Additional information on these and other USGS studies is available at Fluvial Geomorphology.
Figure 1. Change in stage for mean annual discharge (300 cubic feet per second) of Smoky Hill River near Langley, Kansas (gage number 06865500), 0.8 mile downstream from Kanopolis Lake, 1940-97.
Effective management of sediment requires information on the amount of sediment being transported at specific locations and how sediment transport varies with time. Currently, the USGS operates a suspended-sediment monitoring network in Kansas that provides several types of useful suspended-sediment information. For example, continuous turbidity and streamflow data are used to provide continuous (hourly) estimates of suspended-sediment concentration and load (fig. 2). The information also is useful for evaluating variability in suspended-sediment load in relation to streamflow during individual runoff events, seasonally, and over the long term. Rasmussen and others (2005) used multi-year data from three continuous water-quality monitoring sites to estimate average annual suspended-sediment (and nutrient) loads and yields for the Kansas River.
Lee and others (2009) used data from nine continuous water-quality monitoring sites to estimate suspended-sediment loads for subwatersheds of the urbanizing Mill Creek watershed in Johnson County, Kansas. Within the Mill Creek watershed, monitoring sites located downstream from areas with increased construction activity had substantially larger (per unit area) sediment loads compared to sites downstream from mature urban areas or less-developed watersheds.
Suspended-sediment information also can be used to document and explain differences among sites (e.g., because of differences in basin characteristics including precipitation, soils, topography, and land management) as well as provide baseline information to assess the effectiveness of implemented erosion control practices. Information on the USGS suspended-sediment monitoring network for Kansas is available at http://nrtwq.usgs.gov.
Figure 2. Estimated real-time suspended-sediment concentration in Little Arkansas River at Highway 50 near Halstead, Kansas (stream-gaging station 07143672).
While in-stream sediment deposition may degrade aquatic habitat, the current priority concern regarding sedimentation in Kansas is lost water-storage capacity in reservoirs. In particular, sedimentation is a concern because it reduces the function of reservoirs for various important uses including water supply, flood control, and recreation.
Since 1996, the USGS has completed about 30 reservoir sediment studies in Kansas and neighboring states (fig. 3). Available information (projected through 2005) for five large reservoirs indicates that conservation-pool, water-storage capacity lost because of sedimentation ranges from less than 10 percent for Cheney Reservoir (Mau, 2001), Hillsdale Lake (Juracek, 1997), and Webster Reservoir (Christensen, 1999), to about 25 to 40 percent for Perry and Tuttle Creek Lakes (Juracek, 2003; Juracek and Mau, 2002). Among the smaller reservoirs, water-storage capacity lost because of sedimentation has been documented at about 50 percent or more for Crystal and Mission Lakes (Juracek, 2004b). Compared in terms of mean annual sediment yield from the basins, the five large reservoirs range from 0.03 acre-feet per square mile for Webster Reservoir to 1.59 acre-feet per square mile for Perry Lake (table 1). Sedimentation in Perry Lake has occurred at a rate almost twice as fast as originally projected by the U.S. Army Corps of Engineers.
Figure 3. USGS reservoir sediment studies
Table 1. Mean annual sediment yield and mean annual precipitation for selected reservoir basins in Kansas. (source: Juracek, 2004b).
In an attempt to explain differences in sediment yield among reservoir basins in Kansas, Juracek (2004b) compared estimated mean annual sediment yields for 11 reservoirs with factors that affect soil erosion. Specifically, the factors included were precipitation, soil permeability, slope, and land use. The analysis indicated that only the relation between mean annual sediment yield and mean annual precipitation was statistically significant (at the 0.05 level of significance). That is, as mean annual precipitation increased, mean annual sediment yield also increased. Thus, for the 11 reservoirs included, mean annual precipitation was the best predictor of sediment yield. Given the pronounced decrease in precipitation from east to west across Kansas, a similar east to west decrease in reservoir sedimentation rates is likely.
The ability of reservoirs to trap and permanently store sediment can be considerable. For large reservoirs, sediment trap efficiencies typically are greater than 90 percent (Brune, 1953; Williams and Wolman, 1984; Shotbolt and others, 2005). Lee and others (2008) estimated the trap efficiency for John Redmond Reservoir (east-central Kansas) from February 21, 2007 to February 21, 2008 to be 91 percent.
Sediment quality is an important environmental concern because sediment may act as a sink for various contaminants and, under certain conditions, as a source of contaminants to the overlying water column and biota (Baudo and others, 1990; Zoumis and others, 2001). Examples of sediment-associated contaminants include phosphorus, trace elements, certain pesticides, and PCBs. Once in the food chain, some sediment-derived contaminants may pose an even greater concern because of bioaccumulation. Sediment-associated contaminants also are a concern because they tend to persist in the environment. For example, even after the source of a particular contaminant has been eliminated in a basin, it may take several decades before newly-deposited sediment in a reservoir recovers to baseline concentrations of the contaminant (Van Metre and others, 1998; Juracek and Ziegler, 2006). Information on sediment quality is important for reconstructing historical conditions, providing a baseline for future assessments, providing a warning of potential problems, understanding effects of human activity, and providing guidance for management (e.g., TMDLs). Important issues requiring sediment-quality information include reservoir eutrophication, aquatic habitat, and dredging.
The USGS has completed several studies of sediment quality in Kansas that mostly have focused on reservoir bottom sediments. Sediment concentrations of total nitrogen and total phosphorus varied substantially from site to site but typically were relatively uniform over time at specific locations. Trace element concentrations were spatially variable and substantially affected by human activity at some sites. Generally, arsenic, chromium, and nickel concentrations exceeded threshold-effects guidelines for toxic biological effects but were less than probable-effects guidelines. Conversely, cadmium, copper, lead, mercury, and silver concentrations typically were less than the threshold-effects guidelines. For zinc, the results were mixed. Human effects included copper concentrations increased above the probable-effects guideline by copper sulfate applications to control algal blooms, and lead concentrations increased above the threshold-effects guideline by the historical use of leaded gasoline (Juracek, 2004b). At one location affected by historical lead and zinc mining, cadmium, lead, and zinc concentrations were increased far above the respective probable-effects guidelines (Pope, 2005; Juracek, 2006). Organochlorine compounds (i.e., certain pesticides, PCBs) typically were either not detected or detected at concentrations less than the threshold-effects guidelines. The frequent detection of DDE indicated that the historical use of DDT was widespread in Kansas (Juracek, 2004b). Additional information on sediment quality in Kansas is available at Reservoir Sediment.
Of fundamental importance for reducing sediment loads and yields is a determination of the sources of sediment for a given stream or reservoir. The sediment-source question can be answered both geographically and geomorphically. The geographic aspect involves the quantification and comparison of sediment loads for selected basins through the establishment and operation of a suspended-sediment monitoring network. The geomorphic aspect involves a sampling, chemical analysis, and comparison of source materials (e.g., channel banks, cropland soils, and grassland soils) with suspended or deposited sediment to ascertain the relative contribution from each source. Determination of the sediment contribution from specific source types is necessary for the design of effective sediment management strategies (Walling, 2005). Because the relative contribution of sediment from different sources can vary within and between basins and over time, basin-specific information on sediment sources is needed.
Using a combination of several chemical tracers, an investigation of suspended-sediment sources for the rural Perry Lake Basin (northeast Kansas) indicated that, while the relative importance of channel-bank and surface-soil sources varied among the subbasin reservoirs, channel-bank sources were dominant for Perry Lake. Thus, the importance of channel-bank sediment sources increased with distance downstream in the Perry Lake Basin (Juracek and Ziegler, 2007, 2009). However, in a study using chemical tracers to determine suspended-sediment sources in the urbanizing Mill Creek watershed in Johnson County, Kansas, Lee and others (2009) found that variability in source estimates among tracers precluded estimation of sediment sources. The results from these and other studies demonstrate that chemical tracers are useful for estimating sediment sources in some, but not all, environments.
The following studies are currently in progress.A stream monitoring network to characterize suspended-sediment transport to and from Kansas reservoirs, 2008-2013.
In response to concerns about in-stream sediment loads and reservoir sedimentation, this study was undertaken in cooperation with the Kansas Water Office with objectives being to: (a) characterize sediment loads into and out of large federal impoundments in Kansas to estimate reservoir sedimentation and reservoir trap efficiency, (b) characterize sediment concentrations and loads during high-flow events at sites throughout Kansas; and (c) characterize channel stability at selected USGS stream-gage locations upstream and downstream of monitored impoundments. Currently, this study is focused on Kanopolis and Tuttle Creek Lakes.
Occurrence and trends of selected trace elements in bottom sediment, Grand Lake O’ the Cherokees, northeast Oklahoma, 2008-2010.
In response to contamination concerns related to historical lead and zinc mining, this study was undertaken in cooperation with the U.S. Department of the Interior with objectives being to: (a) assess the spatial and temporal variability of cadmium, lead, and zinc concentrations in the bottom sediment of Grand Lake O’ the Cherokees, (b) assess the quality of Grand Lake bottom sediment with respect to background conditions and available sediment-quality guidelines, (c) relate, to the extent possible, any observed trends in bottom-sediment concentrations to documented changes in mining-related activity and other factors in the Grand Lake Basin, and (d) provide a baseline of information on Grand Lake conditions with which to compare future conditions that may represent a response to changes in mining-related activity in the basin.
Sedimentation and occurrence and trends of selected nutrients, other chemical constituents, and cyanobacteria in bottom sediment, Clinton Lake, Kansas, 2008-2010.
In response to concerns about sedimentation and water quality, this study was undertaken in cooperation with the Kansas Department of Health and Environment with objectives being to: (a) estimate the volume, mass, mean annual deposition, and mean annual yield of sediment for the reservoir, (b) determine the occurrence and trends of selected water-quality constituents in the bottom sediment of the reservoir, (c) determine the mean annual loads and yields of selected nutrients from the reservoir basin, and (d) determine the occurrence and relative abundance of cyanobacteria in the bottom sediment as an indication of eutrophication over the life of the reservoir.
John Redmond Reservoir, Kansas: Sedimentation, sediment quality, and channel stability, 2009-2012.
In response to concerns about sedimentation in John Redmond Reservoir, this study was undertaken in cooperation with the U.S. Army Corps of Engineers with objectives being to: (a) determine the amount and quality of sediment deposited in the reservoir, (b) assess channel stability at selected sites upstream from the reservoir, (c) characterize sediment transport through an area of streambank stabilization, and (d) characterize the potential of altered reservoir management to decrease sediment accumulation in the reservoir.
Mining-related contamination of the Spring River flood plain in Cherokee County, Kansas, 2009-2011.
In response to contamination concerns related to historical lead and zinc mining, this study was undertaken in cooperation with the U.S. Environmental Protection Agency with objectives being to: (a) determine the magnitude of soil contamination in the Spring River flood plain, (b) determine how flood-plain soil contamination along the Spring River varies with distance from the channel, with distance downstream, and in relation to particle size, and (c) determine the depth of soil contamination, and the variability of contamination with depth, in the Spring River flood plain.
Characterization of sediment loading from selected research watersheds in northeastern Kansas, 2009-2012.
In response to a need to understand sediment transport in small streams to help identify best management practices to decrease sediment loads, this study was undertaken in cooperation with the Kansas Water Office. The objective of the study is to characterize streamflow and sediment transport in three small research watersheds.