The Electronic Documents of Illinois provides permanent public access to official publications of the State of Illinois which have been deposited in electronic form.
The Illinois Climate Network (ICN) consists of 19 automated weather stations operated by the Illinois State Water Survey. Stations are located on the University of Illinois Agricultural Experiment Station Farms, the Southern Illinois University Agronomy Experiment Farms, and on community college campuses around the state. The ICN is part of the Water and Atmospheric Resources Monitoring (WARM) Network, which also collects information on soil moisture, groundwater, surface water, and suspended stream sediments. The ICN data have been used for agricultural purposes, such as for irrigation scheduling and to evaluate the progress of insect and crop development during spring and summer. The Illinois Department of Agriculture frequently requests the wind data when evaluating spray drift complaints. The ICN data are also used to assess the potential for using solar radiation and wind as alternative energy sources in Illinois. At each station a 10 meter tower equipped with weather instruments records hourly average air temperature, relative humidity, solar radiation, wind speed and direction, barometric pressure, and soil temperatures at 10 and 20 centimeters. Detailed descriptions of station sites are presented, including areal photographs of a 1,000 meter radius of each station. Hourly wind speed mean and variances were used to estimate the effect of obstructions around the weather towers on wind flow at each tower. Total hourly precipitation and hourly standard deviations of each weather variable are also recorded. The barometric pressure, including hourly maximum and minimum pressures and the time of the maxima and minima, have been recorded since early 1992. Daily data that are saved include maximum and minimum air temperature, maximum and minimum relative humidity, maximum and minimum soil temperatures, maximum wind gusts and direction, and their times of occurrence. The data are automatically retrieved from the stations once each day between midnight and 4:00 a.m. At least three times a week, a database management technician checks the data for quality control, and then the data are made available to the public on the Midwestern Climate Center's Midwestern Climate Information System.
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.
The objectives of this study were to 1) identify locations along the Fox River wherereductions in the flow rate and/or river water quality are likely to degrade any use of water along the river, 2) assess the prevailing water quality and ecology of a critical reach of the river, e.g., from one dam to the other, and 3) estimate and evaluate water supply and water quality conditions at present and in the future.
Brochure describing the Illinois State Climatologist, which is located in Champaign, Illinois, at the Illinois State Water Survey (ISWS). The ISWS, a division of the Illinois Department of Natural Resources Office of Scientific Research and Analysis and an affiliated agency of the University of Illinois at Urbana-Champaign, is the primary agency in Illinois for research and information on surface water, groundwater, and the atmosphere.
An anomalously warm El Nio event developed in the eastern tropical Pacific Ocean during May-August 1997. El Nio events have become recognized as capable of having major effects on atmospheric circulation patterns over North America and elsewhere, leading to predictable outcomes for future seasonal weather conditions. The source of the nation's official long-range predictions, the National Oceanic and Atmospheric Administration (NOAA) Climate Prediction Center (CPC), began issuing forecasts in May 1997 about the event's development and growth to near record proportions. The emerging El Nio was expected to match or exceed the El Nio of 1982-1983, the strongest of this century. Predictions of the future weather conditions expected over the nation, as a result of El Nio's influence on the atmosphere, also were issued by CPC beginning in June 1997. Basically, these and subsequent predictions called for a fall, winter, and early spring in the Midwest that would have above normal temperatures and below normal precipitation. The predictions also called for storms and precipitation to increase in other parts of the nation, particularly in the South and West Coast areas. Media and wide public interest in the evolving record event brought inquiries to the Midwestern Climate Center (MCC) during June 1997. At that time, MCC leadership launched special studies and efforts related to the El Nio event, which included: a climatological reanalysis of past El Nio events and the associated weather conditions in the Midwest, the issuance of outlooks based on these studies, and the collection and analysis of data on the impacts caused by the El Nio-generated weather conditions in the Midwest. This decision was in keeping with past MCC research policy that has focused on assessing extreme Midwestern weather conditions like the 1988 drought (Changnon, 1991a and b), the 1993 flood (Kunkel, 1996; Changnon, 1996), and the 1995 heat wave (Kunkel et al., 1996; Changnon et al., 1996). These studies also focused on identifying and quantifying the impacts of these extreme events. The findings of such activities help the MCC respond rapidly and accurately to numerous regional inquiries for data and information about such extreme events. They also help the MCC prepare for effectively addressing similar events in the future. During the El Nio event, beginning in June 1997 and ending in May 1998, the MCC scientists issued several climate outlooks about future Midwestern conditions. These were basically probabilistic-based statements and focused on the winter of 1997-1998, spring 1998, and summer 1998 outcomes. During the El Nio event, the MCC staff collected and recorded all the relevant weather data for the Midwest. Data defining the impacts of El Nio-generated weather events were collected from August 1997 through August 1998. This report presents information about MCC activities related to El Nio in 1997-1998. It includes three sections: the predictive outlooks issued, a climatic assessment of monthly and seasonal weather conditions during the event, and a description of societal and economic impacts caused in the Midwest. Recommendations are offered in the section "Conclusions and Recommendations" for addressing future El Nio events and the handling of long-range predictions.
In the last decade, Illinois has seen many changed attitudes and laws governing the use and withdrawal of ground water. Almost certainly, the next decade will see continued change as the legal structure is adapted to increasing demand for ground water and to the resultant and growing pressures on our ground-water resources. This report summarizes groundwater quantity laws and management programs in Illinois and a number of other states. It compares the present system in Illinois with those in other states and lists recommendations for improvements in Illinois laws.
Driven by the force of gravity, water continually moves between the land surface and the subsurface environments. Our knowledge of this process is limited by the large number of interdependent factors involved. A better understanding of these factors and their effects is needed if we are to effectively manage our water resources in a comprehensive manner.This study addresses the problem by quantifying the groundwater contributionto streamflow over a large range of discharges for 78 watersheds in Illinois.Quantification is the first step toward understanding the dynamics of thiscomplex phenomenon.
The hydraulics of flow was investigated at two reaches in the Kaskaskia River. The discharge varied from 58 to 4000 cubic feet per second and the flow frequency varied from 5 to 88 percent. The head loss varied from 0.96 feet/ mile for high flows to 1.98 feet/mile for low flows. The vertical velocity distribution was found to follow a logarithmic distribution. A theoretical distribution predicted the lateral velocity distribution in the bends reasonably well. In all, 79 isovels were developed for all flow conditions. The average value of the energy coefficient was 1.45 for straight reaches and 1.43 for bends. Similarly, the average value of the momentum coefficient was 1.22 for straight reaches and 1.18 for bends. Manning's roughness coefficient varied from 0.039 to 0.053. During low flows, the river flows through a series of pools and riffles. The median diameter of bed materials varied from 40 millimeters in the riffle to 0.04 millimeters in the pool, whereas the Froude number changed from 0.7 to 0.01. During high flows, the effect of the pool and riffle on the flow condition is minimal or nonexistent.
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 portions of the lake surveyed for the present study were the Big and Sand Creek basins. These basins are the two major tributary stream basins formed to the south (Sand Creek) and east (Big Creek) of the main body of the lake. They receive the flow of Sand, Big, and Long Creeks. Lake Decatur has been surveyed to document sedimentation conditions nine 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 survey discussed in detail in this report is not a full lake sedimentation survey. However, additional work included in the present study could be combined with the 2000 survey of Basin 6 of Lake Decatur to provide a complete baseline survey for future reference. Sedimentation has reduced Big Creek basin capacity from 2,754 acre-feet (ac-ft) in 1922 to 1,512 ac-ft in 2001. The 2001 basin capacity was 54.9 percent of the 1922 potential basin capacity. For water-supply purposes, these volumes convert to capacities of 897 million gallons in 1922 and 493 million gallons in 2001. Sedimentation rate analyses indicate a decline in annual sediment deposition rates from 28 ac-ft (1922-1946) to 9.9 ac-ft annually (1983-2001). The long-term average annual deposition rate was 15.7 ac-ft (1922-2001). Sedimentation has reduced the Sand Creek basin capacity from 610 acre-feet (ac-ft) in 1922 to 246 ac-ft in 2001. The 2001 basin capacity was 40.3 percent of the 1922 potential basin capacity. For water-supply purposes, these volumes convert to capacities of 199 million gallons in 1922 and 80 million gallons in 2001. Sedimentation rate analyses indicate a decline in annual sediment deposition rates from 8.4 ac-ft (1922-1946) to 2.3 ac-ft annually (1983-2001). The long-term average annual deposition rate was 4.6 ac-ft (1922-2001).
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. The dam was modified in 1956 to increase the maximum capacity of the lake to 28,000 acre-feet. The drainage area of the Sangamon River upstream of Decatur is 925 square miles and includes portions of seven counties in east-central Illinois. Lake Decatur has high concentrations of total dissolved solids and nitrates, and nitrate-N 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, since nitrate-nitrogen (N) cannot be removed from finished drinking water through regular water purification processes. Nitrate-N concentrations in Lake Decatur have exceeded the Illinois Environmental Protection Agency (IEPA) drinking water standard of 10 milligrams per liter (mg/l) on occasions each year for the period between 1970 and 2000, except from 1993 to 1995. Since 1993, the Illinois State Water Survey has been monitoring the Lake Decatur watershed for trends in nitrate-N concentrations and loads and to identify any significant changes in the watershed. The purpose of the monitoring is to collect reliable hydrologic and water quality data throughout the watershed for use by city planners and resource managers to develop watershed management alternatives based on scientific data. This report presents the annual data for all seven years of monitoring (May 1993-April 2000) and monthly data for Year 7 of monitoring (May 1999-April 2000). Based on the seven years of data, it can be concluded that the unit of nitrate-N loads are relatively uniform over the entire watershed but tend to be slightly higher at the tributary streams in the upper Sangamon River watershed than at the Sangamon River stations closer to the lake. Nitrate-N loads vary with concentrations and streamflow and were the lowest in Year 7 because of the low streamflows during that year. Flow-weighted nitrate-N concentrations have been increasing during the study period at the Monticello station. The highest nitrate-N concentrations during the monitoring period were observed in years 6 and 7.