Organization | • | Illinois State Water Survey | [X] |
| | 41: | | Title: | | | | | Volume/Number: | 1998 | | | | Issuing Agency: | | | | | Description: | In 1993, with funding from the Long Range Water Plan Steering Committee (LRWPSC), the Illinois State Water Survey (ISWS) and the Illinois State Geological Survey (ISGS) began a study of the sand-and-gravel aquifers in southwest McLean and southeast Tazewell Counties to estimate the availability of ground water and determine the hydrogeologic feasibility of possibly developing a regional water supply. The study area includes the confluence of the buried Mahomet and Mackinaw Bedrock Valleys (confluence area) and contains part of one of the largest sand-and-gravel aquifers in Illinois, the Sankoty-Mahomet Sand aquifer. The study had two goals: (1) to determine the quantity of water a well field in the Sankoty-Mahomet Sand aquifer could yield, and (2) to determine the possible impacts to ground-water levels and existing wells that might occur in the Sankoty- Mahomet Sand aquifer and overlying aquifers from the development of a well field pumping 10-15 million gallons of water a day (mgd). Two major tasks were completed to meet the study goals. The first task was a hydrogeologic characterization of the glacially deposited (glacial-drift) aquifers within the confluence area. Results of the hydrogeologic characterization were published in 1995 (Herzog et al., 1995a and b) and a summary of their findings are in the appendices. The second task, and the subject of this report, was the development of a computer-based, mathematical model of the ground-water flow in the glacial deposits (ground-water flow model). The ground-water flow model was used to simulate the effects of a hypothetical well field for various locations within the study area and to provide an estimate of the amount of ground water a regional well field could yield from the Sankoty-Mahomet Sand aquifer within the confluence area. The characterization of the hydrogeology of the glacial-drift aquifer system was simplified to allow the development of a ground-water flow model. The generalized hydrogeology resembled a layer cake with uneven layers, some of which were discontinuous. The layers included relatively impermeable bedrock overlain by three sand-and-gravel aquifer layers that are generally separated by aquitard layers. Due to the complexity of the spatial distribution of the sand-and-gravel deposits above the Sankoty-Mahomet Sand aquifer, these shallower deposits were generalized as two aquifer layers. Although none of the aquifer deposits represented by the shallower aquifer layers are capable of sustaining a 10-15 mgd water supply, the thickness, distribution, and hydraulic properties of these deposits are important for a complete understanding of the hydrology of the model area. In some parts of the area covered by the ground-water flow model, two or more of the aquifer layers are in direct contact, providing a 'window' of hydraulic connection between the aquifer layers. In other parts of the model area, one or more of the aquifer layers are absent. Using the information from the hydrogeologic mapping and water-level data, chloride concentrations, and percent modern carbon data from observation wells, an updated conceptual understanding of the groundwater flow system for the Sankoty-Mahomet Sand aquifer was developed that described the movement of ground water into and out of the model area. Ground water in the Sankoty-Mahomet Sand aquifer generally flows through the Mahomet Bedrock Valley from the southeast, westward to the Illinois River and northward through the Mackinaw Bedrock Valley. The natural ground-water discharge areas for the Sankoty-Mahomet Sand aquifer in the study area are the Mackinaw River in the west-central part of the study area and Sugar Creek in the southwestern part of the study area. In some areas very close to the rivers, ground water is flowing upward from the Sankoty-Mahomet Sand aquifer through the upper aquifers and into the stream beds. There is a slight hydraulic gradient (slope) east of the model area that steepens where the flow enters the study area, even though the aquifer volume increases. This slope increase is caused by a greater amount of recharge entering the aquifer due to hydraulic connections with overlying aquifers. The areas of connection are more numerous in the west and north portions of the model area, as demonstrated by increases in water levels, decreases in chloride concentrations, and increases in modern carbon isotope concentrations in the Sankoty-Mahomet Sand aquifer. Down gradient of these connections, the chloride concentrations remain low, which suggests that the influx of ground water through these connections provides the majority of the recharge in these areas. Water pumped from the Normal west well field south of Danvers, which has wells penetrating into one of these upper aquifer connections, has low chloride values, indicative of water coming from the upper sands. Although the size of the original study area was about 260 square miles, the area to be modeled (model area) was expanded to 1,100 square miles. This expansion was necessary to reduce the effects of the model boundary conditions on simulated water levels in the study area. The simulated water levels are strongly influenced by the boundary conditions, which reduce the accuracy of the simulated water levels near the boundaries. The ground-water flow model was developed using Visual Modflow software. Three aquifer layers sandwiched between four aquitard layers are simulated in the model. Bedrock forms the lowest aquitard; till units form the others. The hydraulic property values of each hydrogeologic unit were assigned to the corresponding layer in the ground-water flow model where the unit was present. When a unit was absent, the layer was assigned the value of an overlying or underlying hydrogeologic layer. The model's boundary conditions control the regional flow into and out of the study area, discharge to and from the streams, infiltration from precipitation, and removal of water by production wells. The model was calibrated to match water levels measured in area wells in 1994 and to match the baseflow gains and losses in the Mackinaw River and Sugar Creek. The mean absolute error of the simulated water levels was 4.99 feet, which was only slightly greater than the errors associated with the potentiometric surface maps, indicating a good match between the model and the characterization of the ground-water flow system. The ground-water flow budget calculated using the model shows that 80 percent of the water coming into the model is from infiltration of precipitation, 11 percent is from the regional Mahomet aquifer in the east, and 8 percent is from river leakage. The budget also shows that 57 percent of the surface and ground water that leaves the model area does so through discharge to the rivers, 33 percent to the regional ground-water flow to the north and to the west, and the remaining 10 percent to existing production wells. (See online pub for remining abstract...) | | | | Date Created: | 9 24 2004 | | | | Agency ID: | COOP-19 | | | | ISL ID: | 000000000797 Original UID: 999999993916 FIRST WORD: Hydrogeology | |
| 42: | | Title: | | | | | Volume/Number: | 1999 | | | | Issuing Agency: | | | | | Description: | In 1997, the Illinois State Water Survey, at the request of the University of Illinois, initiated a test drilling project that included the construction of several 2-inch diameter observation wells at two sites on the Urbana-Champaign campus. The project concentrated on two areas in which cooling water was needed by the University the North Chiller Plant and the Abbott Power Plant. The purpose of the project was to determine whether sufficient ground-water resources could be located from which to develop a water supply. Exploration at both sites focused on sand-and-gravel materials within the Glasford Formation of Illinoian Age. The main area of interest was the North Chiller Plant at the intersection of Clark and Mathews Streets in Urbana, located in the SE of Section 7, T.19N, R.9E. (Urbana Township), Champaign County. If warranted by test drilling results, a seven-day aquifer test was proposed at the site to investigate the potential of pumping approximately 500 gallons per minute (gpm) from production wells. An area of secondary interest was the Abbott Power Plant between Armory and Gregory Streets and just east of the Illinois Central railroad tracks, located in Section 13, T.19N., R.8E. (Champaign Township). Testing at the Abbott site, if warranted, would examine the feasibility of developing 200 gpm from production wells. Exploratory test drilling at both sites, along with additional information from earlier reports and data on file, led to the following conclusions. The Glasford aquifer is present at most sites across the University of Illinois campus, although it varies considerably in both thickness and texture. The texture of the deposit appears to be finer in test holes south of Green Street. The top of the Glasford sand, near University Avenue, commonly occurs at elevations of 615 to 620 feet. However, the top of the sand at the Abbott Power Plant occurs much lower; the top of the aquifer occurs at about 595 feet. The bottom of the sand is more uniform and occurs at both plants at an elevation of approximately 565 feet. A shallower sand occurs at an elevation of about 640 feet, that is not considered part of the Glasford aquifer. It appears oxidized and occurs just below a very dark brown zone, presumably the Robein Silt. The depth to water in study wells finished in the Glasford aquifer is about 115 feet. Ground-water levels in the Glasford aquifer have a natural fluctuation of about 1 to 2 feet in the test holes. Water levels at the North Chiller Plant did not appear to have been affected significantly by water withdrawals at the Northern Illinois Water Corporation East Well Field. Levels were observed to be similar to levels reported in the 1930s. Water in the Glasford aquifer tends to be alkaline, very hard, high in iron concentration, and at a nearly constant temperature of about 57 degrees F. Although there had been some concern about potential contamination of the Glasford aquifer from fuel spills at the Abbott Power Plant, no contamination was evident in samples taken from test wells constructed for this project. Despite their relative proximity to the former locations of University Wells 10 and 11, no test holes drilled near the North Chiller Plant and Beckman Institute indicated a sufficient thickness of suitable sand material in the Glasford aquifer to warrant construction of a test well to conduct an aquifer test at the desired rate of 500 gpm. Test drilling at the Abbott Power Plant indicated a sufficient thickness of Glasford aquifer present to warrant an aquifer test at perhaps 100 gpm. Accordingly, well designs are recommended for the construction of two test wells or production wells at that site, which might be capable of producing the desired quantity of 200 gpm. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-636 | | | | ISL ID: | 000000000798 Original UID: 999999994043 FIRST WORD: Ground | |
| 43: | | Title: | | | | | Volume/Number: | 1999 | | | | Issuing Agency: | | | | | Description: | The Illinois State Water Survey, in cooperation with the Consumers Illinois Water Company (CIWC), conducted a sedimentation survey of Lake Vermilion during the summer of 1998. The survey was undertaken to provide information on the storage and sedimentation conditions of the lake following a 1991 increase in the operational lake level. Lake Vermilion is owned and operated by the CIWC. The CIWC withdraws water from Lake Vermilion as the sole raw water source for direct distribution of finished water to Danville and Tilton, Illinois. The CIWC also provides finished water to the Catlin and Westville public water supplies. Lake Vermilion is located in Vermilion County, one mile northwest of Danville, Illinois. The operating elevation for the reservoir was increased from 576 feet NGVD to 582.2 feet NGVD in 1991. This modification increased storage capacity of the lake by approximately 4,600 acre-feet (ac-ft). Analysis of sedimentation rates for this larger storage capacity required the introduction of the term potential capacity for the reservoir for 1925-1991. The potential reservoir capacity was defined as the capacity of the reservoir if the basin formed by the valley had been filled to the level of the 1991 spillway. Sedimentation has reduced the potential capacity of Lake Vermilion from 13,209 ac-ft (4,304 million gallons) in 1925 to 7,971 ac-ft (2,597 million gallons) in 1998. The sediment accumulation rates in the lake have averaged 71.8 ac-ft per year from 1925-1998. Annual sedimentation rates for three separate periods, 1925-1963, 1963-1976, and 1976-1998 were 89.5, 50.2, and 53.9 ac-ft, respectively. Earlier lake structures affect the lake as it exists in 1999. These early structures also affected the ability to analyze the present sedimentation rate. The 1914 structure (the old dam) impounded water in what is now the upstream, northern half (lengthwise) of the present lake. This structure caused an undocumented amount of sedimentation in the affected lake segments. This sedimentation is included in the calculated sedimentation volume for the 1925-1963 survey period. On the basis of a 38-year (1925-1963) or a 49-year sedimentation period (1914-1963), the average annual sedimentation rate for the lake would be 89.5 and 69.4 ac-ft per year, respectively. Either rate is considerably higher than subsequent rates. The adjustment of the earlier volumes included an accounting of above water-level deposits for the 1963 and 1976 survey calculations and slightly increased the reported sediment volumes for those surveys. The change in reference capacity also significantly altered the presented sedimentation rates in percent of original volume. | | | | Date Created: | 8 31 2006 | | | | Agency ID: | CR-643 | | | | ISL ID: | 000000000799 Original UID: 999999994049 FIRST WORD: Sedimentation | |
| 44: | | Title: | | | | | Volume/Number: | 1999 | | | | Issuing Agency: | | | | | Description: | The Illinois River has become the focus of state and federal agencies interested in integrated management of watersheds. Issues related to habitat restoration, floodplain management, navigation, erosion and sedimentation, water quality, and point and nonpoint source pollution are all being discussed at the watershed level. One major result of these discussions is the Integrated Management Plan (IMP) for the Illinois River watershed. The plan includes 34 recommendations that are in the process of being implemented by different agencies at different paces and levels of intensity. The Illinois State Water Survey (ISWS) has played a major role in the development of the IMP and is actively participating in implementation of the plan. The implementation phase of the IMP involves questions and answers on a watershed-wide basis and is not limited to local or regional issues. Currently, there is no integrated tool to evaluate and predict hydrological and water quality responses to changes in the physical environment of the Illinois River basin. To fill this gap, the ISWS has initiated the development of the Illinois River Decision Support System (ILRDSS) for use in assessing and evaluating the effectiveness of different projects undertaken under the IMP as well as the consequences of other natural or human-induced changes in the watershed. The ILRDSS will integrate and expand existing databases and models for segments of the Illinois River and portions of the watershed into an integrated decision support system for the entire watershed. New databases and models also will be created for the entire watershed and to address important water quantity and quality issues. Links and interfaces will be developed that interconnect various databases and model components. Once developed and tested, the ILRDSS will enable decision-makers to answer "what-if" questions during the implementation phase of the IMP or other programs within the Illinois River system. The scenarios that can be evaluated using the ILRDSS may include climate shifts and fluctuations, land-use changes, and changes in regulations and water management practices. Using various combinations of these variables as input, the ILRDSS will generate output on potential hydrological and water quality responses of the Illinois River system for different temporal and spatial scales. | | | | Date Created: | 3 10 2006 | | | | Agency ID: | CR-648 | | | | ISL ID: | 000000000800 Original UID: 999999994054 FIRST WORD: The | |
| 45: | | Title: | | | | | Volume/Number: | 1999 | | | | Issuing Agency: | | | | | Description: | The Illinois Streamflow Assessment Model (ILSAM) was developed to provideneeded streamflow information to watershed managers and planners. This specialized software program was developed for use on a personal computer to provide estimates of the long-term expected magnitude of streamflow at various frequencies for any stream location along a major stream in a watershed.The purpose of this study was to update ILSAM for the Fox River Basin, a modeloriginally developed in 1988. Over time, climate variability and changes in humanfactors, such as land and water use, and water resource projects, can greatly affect the quantity and distribution (both in space and time) of surface waters in a river basin. For this reason, the data sets used by ILSAM were designed to be updated periodically, perhaps every 5 to 15 years. The frequency of and need for updates are governed by the rate at which streamflow conditions in the watershed change over time. The model update for the Fox River Basin addresses four areas that influence the flow frequencies and their estimation:- Increases in population, overall water use, and the resulting effluent discharges.- A new public water supply withdrawal from the Fox River and increases inmagnitude of existing withdrawals.- General increases in streamflow magnitude caused by climatic variability and the overall increase in average precipitation.- Adoption of improved regional equations from which to estimate flow at ungaged s i t e s . | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-649 | | | | ISL ID: | 000000000801 Original UID: 999999994055 FIRST WORD: Fox | |
| 46: | | Title: | | | | | Volume/Number: | 2000 | | | | Issuing Agency: | | | | | Description: | As a result of increased pollutant loading and low in-stream velocities, dissolved oxygen (DO) levels in the Chicago waterways historically have been low. In 1984, the Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) issued a feasibility report on a new concept of artificial aeration referred to as sidestream elevated pool aeration (SEPA). The SEPA station concept involves pumping a portion of water from a stream into an elevated pool. The water is then aerated by flowing over a series of cascades or waterfalls, returning to the stream. The MWRDGC proceeded with design criteria for SEPA stations as a result of experimental work performed by the Illinois State Water Survey (ISWS). Five SEPA stations were constructed and placed in operation along the Calumet River, Little Calumet River, and the Cal-Sag Channel waterway. In 1995 the ISWS returned to conduct research to evaluate the reaeration efficiencies and their effects on in-stream DO. Continuous monitoring of DO, temperature, pH, and conductivity was performed at 14 locations along the Calumet and Little Calumet Rivers, Cal-Sag Channel, and Chicago Sanitary and Ship Canal to evaluate the effectiveness of the SEPA stations on maintaining in-stream DO concentrations. Also, supplemental cross-sectional measurements were made at the 14 locations and at an additional seven locations. Comparisons of mass balance, completely mixed, in-stream mean DO concentrations at the SEPA station outfalls and those measured at cross-sectional stations immediately downstream of each SEPA station were made. Results showed that each SEPA station has an immediate positive impact on in-stream DO concentrations. At SEPA stations 1 and 2, where the impacts are small, the positive effects can best be demonstrated using completely mixed values. Two important conclusions can be made. One is that the SEPA stations, particularly stations 3, 4, and 5, are fulfilling the intended function of maintaining stream DO standards in the Calumet and Little Calumet Rivers and the Cal-Sag Channel. The second is that DO concentrations less than the DO standard are still observed in the Chicago Sanitary and Ship Canal in the reach beginning above its juncture with the Cal-Sag Channel to the Lockport Lock and Dam. Over the entire study period, DO concentrations were maintained above the standard 98.6 percent of the time from the SEPA station 3 outfall to the intake of SEPA station 4 and 97.5 percent of the time from the outfall of SEPA station 4 to the intake of EPA station 5. Significant improvements in DO concentrations were also achieved for at least 4 miles downstream of SEPA station 5 in the Chicago Sanitary and Ship Canal. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2000-02 | | | | ISL ID: | 000000000802 Original UID: 999999994078 FIRST WORD: Sidestream | |
| 47: | | Title: | | | | | Volume/Number: | 2000 | | | | Issuing Agency: | | | | | Description: | Flooding, upland soil and streambank erosion, sedimentation, and contamination of drinking water from agricultural chemicals (nutrients and pesticides/herbicides) are critical environmental problems in Illinois. Upland soil erosion causes loss of fertile soil, streambank erosion causes loss of valuable riparian lands, and both contribute large quantities of sediment (soil and rock particles) in the water flowing through streams and rivers, which causes turbidity in sensitive biological resource areas and fills water supply and recreational lakes and reservoirs. Most of these physical damages occur during severe storm and flood events. Eroded soil and sediment also carry chemicals that pollute water bodies and stream/reservoir beds. Court Creek and its 97-square-mile watershed in Knox County, Illinois, experience problems with flooding and excessive streambank erosion. Several fish kills reported in the streams of this watershed were due to agricultural pollution. Because of these problems, the Court Creek watershed was selected as one of the pilot watersheds in the Illinois multi-agency Pilot Watershed Program (PWP). The watershed is located in environmentally sensitive areas of the Illinois River basin; therefore, it is also part of the Illinois Conservation Reserve Enhancement Program (CREP). Understanding and addressing the complex watershed processes of hydrology, soil erosion, transport of sediment and contaminants, and associated problems have been a century old challenge for scientists and engineers. Mathematical computer models simulating these processes are becoming inexpensive tools to analyze these complex processes, understand the problems, and find solutions through land-use changes and best management practices (BMPs). Effects of land-use changes and BMPs are analyzed by incorporating these into the model inputs. The models help in evaluating and selecting from alternative land-use and BMP scenarios that may help reduce damaging effects of flooding, soil and streambank erosion, sedimentation (sediment deposition), and contamination to the drinking water supplies and other valuable water resources. A computer model of the Court Creek watershed is under development at the Illinois State Water Survey (ISWS) using the Dynamic Watershed Simulation Model (DWSM) to help achieve the restoration goals set in the Illinois PWP and CREP by directing restoration programs in the selection and placement of BMPs. The current study is part of this effort. The DWSM uses physically based governing equations to simulate propagation of flood waves, entrainment and transport of sediment, and commonly used agricultural chemicals for agricultural and rural watersheds. The model has three major components: (1) hydrology, (2) soil erosion and sediment transport, and (3) nutrient and pesticide transport. The hydrologic model of the Court Creek watershed was developed using the hydrologic component of the DWSM, which is the basic (foundation) component simulating rainfall-runoff on overland areas, and propagation of flood waves through an overland-stream-reservoir network of the watershed. A new routine was introduced into the model to allow simulation of spatially varying rainfall events associated mainly with moving storms and localized thunderstorms. The model was calibrated and verified using three rainfall-runoff events monitored by the ISWS. The calibration and verification runs demonstrated that the model was representative of the Court Creek watershed by simulating major hydrologic processes and generating hydrographs with characteristics similar to the observed hydrographs at the monitoring stations. Therefore, model performance was promising considering watershed size, complexities of the processes being simulated, limitations of available data for model inputs, and model limitations. The model provides an inexpensive tool for preliminary investigations of the watershed for illustrating the major hydrologic processes and their dynamic interactions within the watershed, and for solving some of the associated problems using alternative land use and BMPs, evaluated through incorporating these into the model inputs. The model was used to compare flow predictions based on spatially distributed and average rainfall inputs and no difference was found because of a fairly uniform rainfall pattern for the simulated storm. However, the routine will be useful for simulating moving storms and localized thunderstorms. A test to examine effects of different watershed subdivisions with overland and channel segments found no difference in model predictions. This was because of the dynamic routing schemes in the model where dynamic behaviors were preserved irrespective of the sizes and lengths of the divided segments. Although finer subdivision does not add accuracy to the outflows, it allows investigations of spatially distributed runoff characteristics and distinguishes these among smaller areas, which helps in prioritizing areas for proper attention and restoration. The calibrated and verified model was used to simulate four synthetic (design) storms to analyze and understand the major dynamic processes in the watershed. Detailed summaries of results from these model runs are presented. These summary results were used to rank overland segments based on unit-width peak flows, which indicated potential flow strengths that may damage the landscape, and were based on runoff volumes that indicate potential flood-causing runoff amounts. Stream channel and reservoir segments also were ranked based on peak flows and indicate potential for damages to the streams. Maps were generated showing these runoff potentials of overland areas. These results may be useful in identifying and selecting critical overland areas and stream channels for implementation of necessary BMPs to control damaging effects of runoff water. The model also was used to evaluate and quantify effects of the two major lakes in the watershed in reducing downstream flood flows and demonstrating model ability to evaluate detention basins. The model was run for one of the design storms with and without the lakes. The results showed significant reduction of peak flows and delaying of their occurrences immediately downstream. These effects become less pronounced further downstream. This report presents and discusses results from the above applications of the DWSM hydrology to the Court Creek watershed along with descriptions of the watershed, formulations of the hydrology component of the DWSM, limitations of the model and available data affecting predictions, and recommendations for future work. Efforts are currently under way at the ISWS to add subsurface and tile flow routines to the DWSM that would improve model predictions and their correspondence with observed data. It is recommended that stream cross-sectional measurements be made at representative sections of all major streams in the Court Creek watershed and that stream flow monitoring be continued or established at least at outlets of major tributaries and upper and lower Court Creek. A minimum of four equally spaced raingage stations are recommended for recording continuous rainfall. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2000-04 | | | | ISL ID: | 000000000803 Original UID: 999999994080 FIRST WORD: Hydrologic | |
| 48: | | Title: | | | | | Volume/Number: | 2000 | | | | Issuing Agency: | | | | | Description: | This report describes the status of an initial effort to understand and describe the atmospheric transport of road salt in the form of sodium chloride (NaCl) applied to highways as a deicing material. The study area is a proposed 20.1 kilometer or km (12.5 mile) tollway that is planned to extend Interstate 355 (I-355) located west of Chicago, Illinois, to connect Interstate 55 (I-55) and Interstate 80 (I-80) southwest of Chicago near Lemont, Illinois. Prior to construction, which has not yet begun, the focus of the effort has been to establish background levels of the road salt aerosol, to construct permanent sites along the proposed route corridor from which to better monitor and measure road salt aerosol properties, and to identify important parameters for use in constructing a computer model to describe the salt emission and deposition. The present status of the proposed project is that construction plans have been delayed at least until approval of a supplement to the environmental impact statement. Results from chemical analysis of aerosol and snow samples are reported that show progress toward characterizing the road salt aerosol with respect to its size, mechanisms of emission, range of atmospheric transport, and mechanisms of deposition. Analysis of the preliminary data suggest: 1. A large portion of the salt aerosol that becomes aerosolized is emitted after the road surface has been cleared of snow and ice. 2. Approximately 90 percent of the airborne road salt is contained in aerosol particles of diameter larger than 2.5 micrometers or 10^-4 inches. 3. The salt deposition pattern near a treated roadway as determined by snow samples decreases consistently with distance from the road. Average deposition values for a single snow event are found here to yield an aerial deposition of 0.06 grams per square meter (0.6 pounds per acre) at 500 meters (1,640 feet) from the road. The corresponding value for the total deposition per length of roadway is 85 grams per meter or g/m (300 pounds per mile or lb/mi). Five permanent sampling sites are almost completed and will provide a flexible monitoring capability to better quantify the road salt emission, transport, and deposition. Road salt emissions in aerosol samples collected at the locations of two of the permanent sites are reported here. The sites are located 0.6 km (0.4 mi) and 1.0 km (0.6 mi) southeast of I-55 in the prevailing downwind direction, but could also be affected by salt emission from a secondary road in the vicinity. A comparison of the aerosol measurements at the two sampling sites during periods when salt was applied shows that the site nearer to the sources consistently had higher levels of NaCl. Most of the NaCl was found in particles with diameter larger than 10 micrometers (4x10^-4 inches). | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2000-05 | | | | ISL ID: | 000000000804 Original UID: 999999994094 FIRST WORD: Atmospheric | |
| 49: | | Title: | | | | | Volume/Number: | 2000 | | | | Issuing Agency: | | | | | Description: | A dense raingage network has operated in Cook County since the fall of 1989, to provide accurate precipitation for use in simulating runoff for purposes of Lake Michigan diversion accounting. This report describes the network design, the operations and maintenance procedures, the data reduction methodology, and an analysis of precipitation occurring during Water Year 1999 (October 1998 through September 1999). The data analyses include 1) monthly and Water Year 1999 amounts at all sites, 2) Water Year 1999 amounts in comparison to patterns from network Water Years 1990-1998, and 3) the ten-year network precipitation average for Water Years 1990-1999. Also included are: raingage site description, instructions for raingage technicians, documentation of raingage maintenance, and documentation of high storm totals. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2000-07 | | | | ISL ID: | 000000000805 Original UID: 999999994112 FIRST WORD: Continued | |
| 50: | | Title: | | | | | Volume/Number: | 1999 | | | | Issuing Agency: | | | | | Description: | The Illinois State Water Survey conducted a sedimentation and hydrographic survey of three small lakes at The Morton Arboretum in Lisle, Illinois, during the summer of 1998. The survey was undertaken in support of an Illinois Clean Lakes Program diagnostic/feasibility study of the lakes. The lakes are owned and maintained by The Morton Arboretum and serve primarily as landscape accents on the grounds. The lakes surveyed were: Meadow Lake, constructed in 1960; Sterling Pond, constructed in 1963; and Lake Marmo, constructed in 1922. Lake sedimentation occurs when sediment-laden water enters the reduced flow velocity regime of a lake. As the water velocity is reduced, suspended sediment is deposited in patterns related to the size and fall velocity of each particle. The soil particles are partially sorted by size along the longitudinal axis of the lake during this process. Larger, heavier sand and coarse silt particles are deposited in the upper end of the lake; finer silts and clay particles tend to be carried further into the lake. A sedimentation survey is a measure of the rate of volume and/or depth loss of the reservoir. The sedimentation survey provides detailed information on distribution patterns of sediment within the lake as well as temporal changes in overall sedimentation rates. Sedimentation has reduced the capacity of Meadow Lake by 10 percent, Sterling Pond by 51 percent, and Lake Marmo by 29 percent. The sediment accumulation rates in the lakes averaged 0.10 acre-feet per year for Meadow Lake, 0.29 acre-feet per year for Sterling Pond, and 0.10 acre-feet per year for Lake Marmo. | | | | Date Created: | 3 21 2006 | | | | Agency ID: | CR-638 | | | | ISL ID: | 000000000806 Original UID: 999999994113 FIRST WORD: Sedimentation | |
| 51: | | Title: | | | | | Volume/Number: | 1992 | | | | Issuing Agency: | | | | | Description: | In the Illinois Groundwater Protection Act of 1987 (PA 85-863), the state legislature mandated that the Illinois Department of Energy and Natural Resources (DENR) conduct an "ongoing program of basic and applied research relating to groundwater," including an evaluation of pesticide impacts upon groundwater. "Such evaluation shall include the general location and extent of any contamination of groundwaters resulting from pesticide use. . . . Priority shall begven to those areas of the State where pesticides are utilized most intensively." In response to this mandate, the Illinois State Water Survey (ISWS) and the Illinois State Geological Survey (ISGS), divisions of DENR, developed a plan to assess the occurrence of agricultural chemicals in rural, private wells on a statewide basis (McKenna et al. 1989). In response to the concerns regarding the proposed statewide survey, a separate pilot study was designed, based on the recommended statewide survey, to produce tangible, documented results of well-water sampling and to demonstrate the validity of the survey design.The legislative mandate addressed the pesticide impacts on groundwater. The proposed statewide plan and the pilot study will focus on groundwater drawn from rural, private wells. This approach will maximize data acquisition on the potential for exposure of the rural residents of Illinois to agricultural chemicals (pesticides and nitrogen fertilizers) through drinking water; it will also minimize sample collection costs. Inferences drawn from this project are valid for groundwater drawn from rural, private wells and not from other sources. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | COOP-14 | | | | ISL ID: | 000000000826 Original UID: 999999993861 FIRST WORD: Pilot | |
| 52: | | Title: | | | | | Volume/Number: | 2000 | | | | Issuing Agency: | | | | | Description: | The United States Environmental Protection Agency (USEPA) National Regional Nutrient Criteria Development Program is developing regional-specific criteria for total nitrogen concentrations in surface waters. These criteria will provide the foundation for states to set total nitrogen standards to remedy impairments caused by nutrient overenrichment and to protect designated uses. Reference conditions representing minimally impacted surface waters will be developed for each ecoregion. All nutrient criteria must be based on sound scientific rationale. The first element of a nutrient criterion identified by USEPA is "... historical data and other information to provide an overall perspective on the status of the resource." The second element includes " ... a collective reference condition describing the current status." A further element requires "... attention to downstream consequences." The USEPA recognizes that nutrient concentrations in surface waters are primarily affected by the rate of weathering and erosion from watershed soils. Human activity can affect on the natural load of nutrient inputs to surface waters through, for example, vegetation disturbance of the vegetation, and addition of nutrient-containing material, such as fertilizer. At the heart of the overenrichment problem are the rates of production and decomposition of organic materials, of which nitrogen is a component. This report provides a contribution to the setting of reference/background conditions for Illinois through the evaluation of the current status of water resources against historical conditions, and some attention to downstream consequences. A particular focus of downstream consequences is hypoxia in the Gulf of Mexico, allegedly caused by the flux of excess nitrogen from the Upper Mississippi, Ohio, and Missouri River Basins. The concept of biogeochemical cycling provides an appropriate and necessary framework for understanding landscape influences on water quality throughout the Illinois River Basin. Changes in the Illinois River Valley and its system of tributary streams and lakes are well recognized, but this is the first attempt to assess in some detail how such changes have affected the aquatic carbon, oxygen, and nitrogen cycles; especially the impact of such watershed changes on the nature and quantity of aquatic nitrogen, as well as on the nitrogen cycle within the terrestrial reservoir. This is seen in the accompanying time line of the estimated nitrogen richness of the Illinois landscape. Scientists studying soils and crops from the mid-19th through mid-20th centuries documented that human activities have greatly altered the natural nitrogen cycle. Cultivation of virgin land typically depleted nitrogen and carbon stored in these reservoirs by about 50 percent in the first 60-70 years of cultivation. Some of this nitrogen was transferred to surface waters and ground waters. The depletion of nitrogen from soils in the Mississippi River Basin was so great that crop yields declined throughout the 19th and early 20th centuries. By mid-20th century, the extensive use of nitrogen fertilizer, improved plant varieties, and agronomic practices increased crop yields. Nitrogen fertilizer also began to replenish some of the large amounts of nitrogen previously removed from the soil. In the 1970s, profound changes occurred in the perception of the natural nitrogen cycle and human modification of that cycle. The nitrogen cycle, and human impacts on it came to be defined in terms of atmospheric nitrogen fixation and the return of nitrogen gases by nitrification/denitrification. The 99 percent of the nitrogen cycle which was otherwise cycled within and between the large soil, sediment, and plant reservoirs were no longer acknowledged. From this new definition of the nitrogen cycle, it was concluded that human activities, especially fossil-fuel combustion and fertilizer use, had doubled the nitrogen cycle and many lands, including much of Illinois, had become nitrogen saturated. Increasing concentrations of nitrate-nitrogen in surface waters were given as evidence of nitrogen saturation and leakage. This new limited edition of the nitrogen cycle became cast in concrete and is referred to in this report as "the new, standing nitrogen-cycle paradigm." This report uses the earlier, scientifically more complete and defensible definition of the nitrogen cycle, which includes recognition of the magnitude and importance of soil-plant reservoirs and exchanges. It uses extensive scientific documentation of major changes in ecosystems and soil nitrogen that have occurred over centuries, to place into perspective the present status of nitrogen resources -- as required by USEPA. This report examines the impact on nitrogen concentrations in surface waters in Illinois during occupation of the land by Native Americans, bison, and many other animals and birds. Theoretical impacts are complemented by written accounts of early settlers and scientific observations made under similar conditions. It is concluded that the landscape and surface waters were more nitrogen saturated at this time than today. These pre-European-settlement conditions were selected as the reference/background conditions. Just prior to and during the period of early European settlement, the populations of Native Americans and bison were eliminated and the landscape became less nitrogen saturated. Nevertheless, even in the 1820s, the Illinois River was hypertrophic, i.e. nutrient overenriched. As late as the 1850s, the amount of eroded soil transported by the Mississippi River was more than twice that transported in recent decades. Since soil erosion is reported to be the major sort of N delivery from agricultural lands, the N load in the Mississippi River was declining. The average annual concentration of total nitrogen in the Lower Illinois River in 1894-1899 was 3.68 mg N/l, and additional large amounts of nitrogen not measured were stored in plankton and luxuriant aquatic vegetation and transported downstream in copious amounts of organic debris. Allowing for the unmeasured flux of nitrogen as plankton and for low flow, the adjusted average annual concentration of total nitrogen in the Lower Illinois River in 1894-1899 is estimated to have been about 5.5 mg N/l. This report also examines the impact of European settlement and agriculture on the nitrogen cycle and water quality. Scientific data show that the average concentration of total nitrogen in the Lower Illinois River increased to about 10 mg N/l by mid-20th century and subsequently decreased to 4.8 mg N/l in the 1990s. The annual concentration of nitrate in the Lower Illinois River peaked at about 6.2 mg N/l in 1967-1971 and subsequently decreased to about 3.8 mg N/l in 1993-1998. These improvements in water quality are associated with an increasing amount of dissolved oxygen in the river. The reductions in the concentrations of all forms of nitrogen are attributable to both point- and nonpoint-source pollution control. The main conclusions of this report are that, in establishing scientifically sound reference/background conditions, it is necessary to quantify in a common unit all forms of nitrogen (in solution, as solids, and as gases; and organic and inorganic forms) and all sources, reservoirs, transformations, and fluxes of nitrogen in a common unit; and to understand interactions between nitrogen and other biogeochemical cycles of, for example, water, oxygen, carbon, and phosphorous. Criteria for setting nitrogen standards must recognize the great complexity of the nitrogen cycle and its interdependence with other variables, cycles, and anthropogenic influences. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2000-08 | | | | ISL ID: | 000000000827 Original UID: 999999994193 FIRST WORD: Contribution | |
| 53: | | Title: | | | | | Volume/Number: | 2000 | | | | Issuing Agency: | | | | | Description: | The Champaign County Forest Preserve District (CCFPD) applied for and received a grant to conduct a diagnostic-feasibility study on Homer Lake commencing in April 1997. Homer Lake is an 83-acre public lake within the Salt Fork River Forest Preserve in Champaign County, Illinois. The lake is located in the Second Principle Meridian, Township 19N, Range 14W, Section 31; it is 3 miles northwest of the town of Homer. Homer Lake has a maximum depth of 19 feet, a mean depth of 7.4 feet, a shoreline length of .3 miles, and an average retention time of 0.097 years. The Homer Lake watershed, including the lake surface area, is 9,280 acres. The two inflow tributaries are Conkey Branch and the west branch (unnamed). The diagnostic study was designed to delineate the existing lake conditions, to examine the cases of degradation, if any, and to identify and quantity the sources of plant nutrients and any other pollutants flowing into the lake. On the basis of the findings of the diagnostic study, water quality goals were established for the lake. Alternative management techniques were then evaluated in relation to the established goals. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2000-13 | | | | ISL ID: | 000000000828 Original UID: 999999994305 FIRST WORD: Phase | |
| 54: | | Title: | | | | | Volume/Number: | 2000 | | | | Issuing Agency: | | | | | Description: | In the East St. Louis vicinity, the Illinois Department of Transportation, Division of Highways (IDOT) owns 55 high-capacity wells that are used to maintain the elevation of the ground-water table below the highway surface in areas where the highway is depressed below the original land surface. The dewatering systems are located at five sites in the alluvial valley of the Mississippi River in an area known as the American Bottoms. The alluvial deposits at the dewatering sites are about 90 to 115 feet thick and consist of fine sand, silt, and clay in the upper 10 to 30 feet, underlain by medium to coarse sand about 70 to 100 feet thick. The condition and efficiency of a number of the dewatering wells became suspect in 1982 on the basis of data collected and reviewed by IDOT staff. Since 1983, IDOT and the Illinois State Water Survey (ISWS) have conducted a cooperative investigation to more adequately assess the operation and condition of the wells, to attempt to understand the probable causes of well deterioration, and to evaluate rehabilitation procedures used on the wells. Work conducted during FY 95 (Phase 12) included monitoring the rehabilitation of four wells, step-testing the rehabilitated wells and checking the discharge from two wells for sand pumpage, checking the quality of the water discharged during the step tests, and monitoring the ground-water levels at the dewatering system sites. Posttreatment step tests were used to help document the rehabilitation of four dewatering wells, Interstate-70 (I-70) Wells 3A, 5, 11A, and 15, during FY 95 (Phase 12). Chemical treatments used to restore the capacity of these four wells were moderately successful. The improvement in specific capacity per well averaged about 103 percent based on data from pre- and posttreatment step tests. The specific capacity of I-70 Well 15 was restored to about 109 percent of the average observed specific capacity of wells in good condition at the I-70 site and the other three wells were restored to about 72 to 87 percent of the average observed specific capacity for wells in good condition. The sand pumpage investigation conducted during the posttreatment step tests on I-70 Wells 3A and 11A showed little or insignificant amounts of sand in the portable settling tank after the step tests. The tank was required to divert the discharged water into the stormwater drainage system during the other two step tests, precluding a check for sand pumpage. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2000-10 | | | | ISL ID: | 000000000829 Original UID: 999999994306 FIRST WORD: Dewatering | |
| 55: | | Title: | | | | | Volume/Number: | 2000 | | | | Issuing Agency: | | | | | Description: | The Illinois State Water Survey (ISWS), under contract to the Imperial Valley Water Authority (IVWA), has operated a network of rain gauges in Mason and Tazewell Counties since August 1992. The ISWS also established a network of ground-water observation wells in the Mason-Tazewell area in 1994. These networks are located in the most heavily irrigated region of the state. The region's major source of water for irrigation, municipal, and domestic water supplies is ground water pumped from thick sand and gravel deposits associated with the confluence of two major ancient river valleys, the Mississippi and the Mahomet-Teays. Relatively recent extreme weather events (e.g., the drought of 1988 and the great flood of 1993) resulted in large fluctuations in ground-water levels in the Imperial Valley area. The purpose of the rain gauge network and the ground-water observation well network is to collect long-term data to determine the rate of ground-water drawdown in dry periods and during the growing season, and the rate at which the aquifer recharges. This report presents data accumulated from the rain gauge and observation well networks since their inception through August and November 1999, respectively. Precipitation is recorded for each storm that traverses the Imperial Valley, and ground-water levels at the 13 observation wells are measured the first of each month. The database from these networks consists of seven years of precipitation data and five years of ground-water observations. At the beginning of the ground-water observations in late 1994, the water levels were at their highest in the five years of observation. These high ground-water levels were the result of the very wet 1992-1995 period when annual precipitation was above the 30-year normals at both Havana and Mason City. From September 1995-August 1997 precipitation in the region was below the 30-year normal. The 1997-1998 observation year had rainfall above the 30-year normal. Ground-water levels in the observation wells mirrored these rainfall patterns, showing a general downward trend during the dry years and a recovery in the wet 1997-1998 year. Seasonal increases in the ground-water levels were observed at most wells during the late spring and early summer, followed by decreases in August-November ground-water levels. Analysis indicates that the ground-water levels are affected by both the precipitation in the Imperial Valley area and the Illinois River stages. The observation wells closest to the Illinois River show an increase in water levels whenever the river stage is high. Generally, the water levels in the wells correlate best with precipitation and Illinois River stages one to two months before the water levels are measured, i.e., the June ground-water levels are most highly correlated with the Illinois River stage or precipitation that occurs in either April or May. The analyses conducted indicate the need for continued operation of both networks due to inconsistencies associated with ground-water levels, precipitation, and the Illinois River stage. For instance, the Mason-Tazwell observation well number 2 (MTOW-2) is located near the center of Mason County well away from the Illinois River, but it has an equal correlation with the Illinois River stage and the precipitation in the area. Additional analysis needs to be undertaken to explain this unusual finding. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2000-12 | | | | ISL ID: | 000000000830 Original UID: 999999994307 FIRST WORD: Operation | |
| 56: | | Title: | | | | | Volume/Number: | 2000 | | | | Issuing Agency: | | | | | Description: | Lake Decatur is the water supply reservoir for the City of Decatur. The reservoir was created in 1922 by constructing a dam to impound the flow of the Sangamon River with an original water volume of 20,000 acre-feet and an area of 4.4 square miles. The dam was later modified in 1956 to increase the maximum capacity of the lake to 28,000 acre-feet. Water withdrawal from the lake has been increasing over the years, averaging 37 million gallons per day (mgd) in 1994. The drainage area of the Sangamon River upstream of Decatur is 925 square miles. The watershed includes portions of seven counties in east-central Illinois. The predominant land use in the watershed is row crop agriculture comprising nearly 90 percent of the land area. The major urban areas within the watershed are Decatur, Monticello, and Gibson City. Lake Decatur has high concentrations of total dissolved solids and nitrates, and nitrate concentrations have been exceeding drinking water standards in recent years. This has created a serious situation for the drinking water supply of the City of Decatur. The Illinois Environmental Protection Agency (IEPA) has issued nine nitrate warnings to the city from 1979 to 1996 for noncompliance with Nitrate-N concentrations in Lake Decatur have exceeded the Illinois Environmental Protection Agency (IEPA) drinking water standards for nitrate when concentrations exceeded of 10 milligrams per liter (mg/l) for the period between 1979 and 1998, except from 1993 to 1995. On June 10, 1992, a Letter of Commitment (LOC) was signed between the IEPA and the City of Decatur. The LOC requires the city to take several steps to reduce nitrate levels in Lake Decatur to acceptable concentrations within nine years of signing the LOC. Nitrate-N cannot be removed from finished drinking water through regular water purification processes. One of the steps required the city to conduct an initial two-year monitoring study of the Lake Decatur watershed to better understand nitrate yields in the watershed. In 1993, the Illinois State Water Survey received a grant from the City of Decatur, conducted a two-year monitoring study, and developed land use management strategies that could assist the city comply with the IEPA drinking water standards (Demissie et al., 1996). This technical report presents the annual data for all six years of monitoring (May 1993-April 1999) and monthly data for the sixth year of monitoring (May 1998-April 1999). | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2000-06 | | | | ISL ID: | 000000000831 Original UID: 999999994310 FIRST WORD: Watershed | |
| 57: | | Title: | | | | | Volume/Number: | 2000 | | | | Issuing Agency: | | | | | Description: | This report summarizes the research and surveying that were conducted in 1995 to determine the amount and severity of bank erosion that existed on the entire length of the Illinois River. The study reach extended from Grafton, River Mile (RM) 0 to Joliet, RM 286. A multi-disciplinary team of scientists traveled the entire length of the river, mapped bank conditions and erosion sites, and selected 29 reaches for detailed data collection and two sites as observation sites. Bank erosion types were developed by studying and analyzing the erosion features. The team also used fluvial and bank failure processes to guide detailed data collection at the 29 sites. Color-coded bank feature maps were developed for the entire 286 miles of the river. | | | | Date Created: | 8 16 2005 | | | | Agency ID: | CR-2000-11v.2 | | | | ISL ID: | 000000000832 Original UID: 999999994312 FIRST WORD: Bank | |
| 58: | | Title: | | | | | Volume/Number: | 2001 | | | | Issuing Agency: | | | | | Description: | A dense raingage network has operated in Cook County since the fall of 1989, to provide accurate precipitation for use in simulating runoff for purposes of Lake Michigan diversion accounting. This report describes the network design, the operations and maintenance procedures, the data reduction methodology, and an analysis of precipitation for Water Year 2000 (October 1999 through September 2000). The data analyses include 1) monthly and Water Year 2000 amounts at all sites, 2) Water Year 2000 amounts in comparison to patterns from network Water Years 1990-1999, and 3) the 11-year network precipitation average for Water Years 1990-2000. Also included are raingage site descriptions, instructions for raingage technicians, documentation of raingage maintenance, and documentation of high storm totals. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2001-02 | | | | ISL ID: | 000000000833 Original UID: 999999994313 FIRST WORD: Continued | |
| 59: | | Title: | | | | | Volume/Number: | 2001 | | | | Issuing Agency: | | | | | Description: | The long-term temporal trends of water quality in the Illinois Waterway system upstream of Peoria are described in this report. The time period investigated was from 1965 to 1995. The seasonal Kendall trend test was used to detect statistically significant trends. A related test, the seasonal Kendall slope estimator, was used to calculate the magnitude of the trend. Box plots were also used to visualize differences in data over time. The water quality analytes considered in this report include dissolved oxygen, ammonia-nitrogen, nitrate and nitrite-nitrogen, total Kejeldahl nitrogen, total phosphorous, sulfate, turbidity, total suspended solids, fecal coliform, cyanide, and phenol. Water quality was generally found improved at all stations. Substantial improvements were found at most stations for dissolved oxygen, the nitrogen species, phenol, and cyanide concentrations. Fecal coliform densities generally decreased at most locations. Little or variable change was found for turbidity, total suspended solids, and total phosphorus concentrations. Increasing trends were detected for sulfate concentrations. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2001-03 | | | | ISL ID: | 000000000834 Original UID: 999999994314 FIRST WORD: Water | |
| 60: | | Title: | | | | | Volume/Number: | 2001 | | | | Issuing Agency: | | | | | Description: | Sedimentation detracts from the use of any water supply lake by reducing lake depth and volume, with a reduction of reserve water supply capacity and possible burying of intake structures. Sedimentation of a reservoir is a natural process that can be accelerated or slowed by human activities in the watershed. Silver Lake is Located in Madison County, one mile northwest of Highland, Illinois. The location of the dame is 38 degrees 46' 00" north latitude and 89 degrees 42' 05" west longitude in Section 30, T.4N., R.5W., Madison County, Illinois. The dam impounds the East Fork of Silver Creek, a tributary of Silver Creek in the Kaskaskia River basin. The watershed is a portion of Hydrologic Unit 07140204 as defined by the U.S. Geological Survey. Construction of the lake was completed in 1962. The Silver Lake watershed consists of the 47.1-square-mile area drained by the East Fork of Silver Creek above the dam site. Land use in the watershed of the lake is mainly agricultural. Average annual precipitation in the area is 38.98 inches as measured at Greenville (1961-1990), and the average runoff (1912-1998) is approximately 10.0 inches (Shoal Creek near Breese). Average annual lake evaporation rates are 35.2 inches per year at St. Louis, Missouri. The Illinois State Water Survey conducted sedimentation surveys of Silver Lake in 1981 and 1984. In 1981, cross sections were laid out at 14 lines across the lake and surveyed. Sedimentation surveys of Silver Lake in 1984 and 1999 repeated as closely as possible the series of survey lines established during the 1981 survey. Sedimentation has reduced the capacity of Silver Lake from 7,322 acre-feet or ac-ft (2,386 million gallons) in 1962 to 5,832 ac-ft (1,900 million gallons) in 1999. Sediment accumulation rates in the lake have averaged 40.3 ac-ft per year from 1962-1999. Annual sedimentation rates for three separate periods, 1962-1981, 1981-1984, and 1984-1999, were 51.2, 63.0, and 21.9 ac-ft, respectively. Density analyses of the sediment samples indicate that sediment in the northern (upstream) portions of the lake has greater unit weight than sediment in the southern end of the lake. In general, coarser sediments are expected to be deposited in the upstream portion of a lake where the entrainment velocity of the stream is reduced to the much slower velocities of a lake environment. These coarser sediments tend to be denser when settled and are subject to shallow drying and higher compaction rates as a result of more frequent drawdown exposure in the shallow water environment. As the remaining sediment load of the stream is transported through the lake, increasingly finer particle sizes and decreasing unit weight are observed. The sedimentation rate for Highland Silver Lake is similar to the rates for other Illinois lakes of similar size and character. The sedimentation for Silver Lake is in the low to average ranged compared to other Illinois lakes. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2001-05 | | | | ISL ID: | 000000000835 Original UID: 999999994316 FIRST WORD: Sedimentation | |
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