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A large undeveloped ground-water reservoir underlies an area along the Illinois and Sangamon Rivers in west-central Illinois. The area is called the Havana region in this report.This report is based on data collected during the investigation and additional data on file at the Illinois State Water Survey and the Illinois State Geological Survey and in published reports. It presents geologic and hydrologic information, the geologic history of the area, present hydrologic conditions, and effects of possible future development on the ground-water resources of the region. Special emphasis is placed on the extensive unconsolidated sand and gravel deposits, which are the principal aquifers in the region, and their potential yield is evaluated. The geology and hydrology of the bedrock formations are discussed only briefly as these formations contain limited quantities of ground water, and it is of relatively poor quality. Data on water levels, pumpage, well construction features, water temperature, mineral quality of water, well-production and aquifer tests, and other hydrologic information were collected by the State Water Survey. Well logs, drilling samples, geophysical logs, and other geologic information were collected by the State Geological Survey.
Recharge conditions in several areas of northeastern Illinois are described, and recharge rates for several aquifers in central and southern Illinois are given. Recharge rates to deeply buried bedrock and sand-and-gravel aquifers vary from 1300 to 500,000 gallons per day per square mile (gpd/sq mi). The lowest rate is for an area where the Cambrian-Ordovician Aquifer is overlain by the Maquoketa Formation consisting mostly of shale; the highest rate is for an area where a sand-and-gravel aquifer is overlain by permeable coarse-grained deposits. Groundwater recharge generally is at a maximum during wet spring months; in many years there is little recharge during the five-month period July through November. The theoretical aspects of recharge from precipitation are discussed; recharge rates vary with the coefficient of vertical permeability, the vertical head loss associated with recharge, and the saturated thickness of deposits through which vertical leakage of water occurs. Recharge rates are not constant but vary in space and time. A summary of coefficients of vertical permeability and leakage of deposits overlying aquifers within the state is presented. Coefficients of vertical permeability of glacial deposits range from 1.60 to 0.01 gallons per day per square foot (gpd/sq ft). The average coefficient of vertical permeability of the Maquoketa Formation is 0.00005 gpd/sq ft. Coefficients of leakage of glacial deposits and bedrock confining beds range from 2.3 x 10-1 to 2.5 x 10-7. Annual ground-water runoff from 109 drainage basins scattered throughout Illinois is estimated with streamflow hydrograph separation methods and flow-duration curves. The relations between groundwater runoffs during years of near, below, and above normal precipitation and basin characteristics such as geologic environment, topography, and land use were determined by statistical analysis. Groundwater runoff is greatest from glaciated and unglaciated basins having considerable surface sand and gravel and underlain by permeable bedrock. Groundwater runoff is least from glaciated basins with surface lakebed sediments and underlain by impermeable bedrock. Groundwater runoff during a year of near normal precipitation ranges from 0.06 to 0.43 cubic feet per second per square mile (cfs/sq mi). Groundwater runoff is at a maximum during spring and early summer months, and is least in late summer and fall months. Annual groundwater runoff depends upon antecedent moisture conditions as well as the amount and distribution of annual precipitation. Because many aquifers in Illinois are deeply buried, not all groundwater runoff can be diverted into cones of depression because there is some lateral as well as vertical movement of water in surface deposits. Data on groundwater runoff can be useful in estimating recharge to aquifers and in evaluating the potential yield of groundwater reservoirs. However, studies indicate that no simple relation exists between groundwater runoff and the potential or practical sustained yields of aquifers.
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. Lake Decatur is located in Macon County, northeast of Decatur, Illinois. The location of the dam is 39 49 28" north latitude and 88 57 30" west longitude in Section 22, T.16N., R.2W., Macon County, Illinois. The dam impounds the Sangamon River in the Sangamon River basin. The watershed is a portion of Hydrologic Unit 07130006 as defined by the U.S. Geological Survey. The lake was constructed in 1922 with a spillway level of 610 feet above mean sea level (feet-msl). In 1956, a set of hydraulic gates was installed on the original spillway to allow variable lake levels from 610 feet-msl to 615 feet-msl. The portion of the lake surveyed for the present study was Basin 6 located above Rea's Bridge Road. This basin of the lake is the headwater area of the main body of the lake. Lake Decatur has been surveyed to document sedimentation conditions eight times since 1930. Five of these survey efforts (1936, 1946, 1956, 1966, and 1983) were sufficiently detailed to be termed full lake sedimentation surveys. The present survey is not considered to be a full lake sedimentation survey. Sedimentation has reduced the basin capacity from 2,797 acre-feet (ac-ft) in 1922 to 1,451 ac-ft in 2000. The 2000 basin capacity was 48.1 percent of the 1922 potential basin capacity. For water supply purposes, these volumes convert to capacities of 911 million gallons in 1922 and 473 million gallons in 2000. Sedimentation rate analyses indicate a decline in annual sediment deposition rates from 35.4 ac-ft for the period 1922-1936 to 8.3 ac-ft annually from 1983-2000. The long-term average annual deposition rate for 1922-2000 was 17.3 ac-ft. Density analyses of the sediment samples indicate that the unit weight of sediment in the northern (upstream) portions of the lake is greater than the unit weight of 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 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.
GENTLEMEN : Herewith I submit a report on the ground water resources of the State of Illinois and recommend that it be published as Bulletin No. 21. Since the Directors' report includes a statement of the general activities of all divisions, it has seemed advisable to discontinue the publication of an annual report of this division and to prepare instead summaries of our various investigations as they are completed. This policy was adopted with the publication of Bulletin No. 18 in May of 1922, and has been followed since that date. A portion of this material has appeared in abstract form in annual reports published prior to 1920. That material was too meager and scattered to be of practical value. In the present collected form we believe this data will be of very considerable value to the State of Illinois. Respectfully submitted, A. M. BUSWELL, Chief.
The State Water Survey of Illinois began the investigation of the waters of the State in 1895. While the Survey has laid special stress on the determination of the character of the waters from a sanitary standpoint, it has also often been called upon to make analyses of the mineral content to determine its character from a medicinal or commercial standpoint. In the various reports so far issued by the Survey only results of the sanitary investigations were published. It had been the intention to publish the results of the mineral analyses in a previous report but this had to be postponed until the present time when, in cooperation with the Geological Survey, it has become possible. This Bulletin, primarily, contains the records of the analyses made to determine the composition of the mineral residue with reference to the value of the water for manufacturing and medicinal uses, but there are also included the sanitary analyses, wherever such analyses have been made.
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).
In response to expanding urban development, the use of Lake Michigan and other sources for public water supplies, and a growing interest in regional water resources development, this report provides a detailed discussion of groundwater withdrawals and water levels in northeastern Illinois. The water-level portion of this report covers a 15-county area from Lake Michigan to north-central Illinois and from the Wisconsin border south to Kankakee County. Particular emphasis, however, has been given to deep well pumpage in the eight counties of the Chicago region because of the significant shift in the late twentieth century from groundwater supplies of the deep bedrock aquifers to Lake Michigan and other sources. This report details the fall 2000 water-level measurement of wells reaching to the St.Peter and Ironton-Galesville sandstones (deep bedrock aquifers), provides a map illustrating the slope of groundwater levels, and compares the fall 2000 levels to the fall 1995 observations. The rapid decrease in groundwater pumpage from the deep bedrock aquifers during the 1980s initially resulted in a rapid recovery of groundwater levels. However, the rate of water-level change has slowed since the mid-1990s. The greatest recovery during the past five years occurred in Cook County. Groundwater levels in several wells were observed to have risen more than 50 feet since 1995. Where the deep bedrock aquifers of Cambrian-Ordovician age continue to be used, declines in groundwater levels were observed. Most notable declines were in southeastern Kane and northern Kendall Counties, southwestern Lake County, and southeastern McHenry County. Outside the Chicago region, water-level declines were observed in deep wells at Loves Park in Winnebago County and in the vicinity of DeKalb and Sycamore in DeKalb County.
As part of a study to estimate corn and soybean yields using satellite remote sensing techniques, biomass measurements, ground-level spectral measurements, and weather and energy flux measurements were taken at three locations in McLean County, Illinois. The locations were near Colfax, Lexington, and Stanford, Illinois. Plant samples and leaf area measurements were taken during the weeks of 12-17 June, 26-30 June, 10-14 July, 31 July-4 August, and 14-18 August 2000 in McLean County, Illinois. Corn plants were separated into leaf, stem, husk, and ear components, and soybean plants into leaf, stem, and pod components. The wet weights of the different plant parts were determined. To determine the plant dry biomass, the plant parts were dried in an oven until there was no weight change over two consecutive days. Leaf area for both corn and soybean canopies was measured using a LiCor-2000 instrument. Corn leaf area was also determined by manual measurements of leaf length and width. The smallest corn and soybean plants were at the Lexington location. The largest corn plants were at Colfax, and the largest soybean plants were at Stanford. The smaller plants at Lexington were a result of sandier soils containing less organic matter than the soils at either Stanford or Colfax. Although final yield was not measured as part of this sampling protocol, the size of the plants would indicate that Lexington should have the smallest corn and soybean yields, while the highest corn yields should have occurred at Colfax, and the highest soybean yields at Stanford.
This report on the 1993 flood on the Mississippi River in Illinois and on the lower reaches of the Illinois River was prepared by the Illinois State Water Survey with assistance from the Illinois Department of Transportation/Division of Water Resources and the Illinois Natural History Survey. The report begins with a brief description of the physical setting of the Upper Mississippi River System, including historical facts on climate, precipitation, hydrology, and floods. The 1993 flood is discussed with regard to precipitation, soil moisture, stages, flows, levee breaches, and discharge through levee breaches. Also discussed are impacts of the flood on social, economic, hydraulic and hydrologic, and environmental aspects of the river and its residents. Impacts on water quality, the environment, and public water supplies, including the beneficial and detrimental aspects of the flood, also are included. The lessons learned from this flood focus on the performance of the levees, governmental responses, the effects of flood fighting, change in stages due to levee breaches, flood modeling, and the lack of information dissemination to the public on the technical aspects of the flood. These lessons point out information gaps and the need for research in the areas of hydraulics and hydrology, meteorology, sediment transport and sedimentation, surface and groundwater interactions, water quality, and levees. The report presents a comprehensive summary of the 1993 flood as far as climate, hydrology, and hydraulics are concerned.
The Illinois River is at a crossroads. All the events in its history, both natural and those accomplished through human intervention, are now poised to change the river in ways that may render it unrecognizable in our own lifetimes. This publication is intended to introduce you to the Illinois River and the issues that will shortly determine its very survival.