The Electronic Documents of Illinois provides permanent public access to official publications of the State of Illinois which have been deposited in electronic form.
Cambrian and Ordovician strata provide much of the groundwater supplyfor approximately 250 municipalities and 150 industries in the northern halfof Illinois. This report represents the cooperative effort of the IllinoisState Water Survey, Illinois State Geological Survey, and U.S. GeologicalSurvey to provide a current hydrogeologic evaluation of this water resource.
In the East St. Louis vicinity, the Illinois Department of Transportation Division of Highways (IDOT) owns 56 high-capacity wells that are used to maintain the elevation of the groundwater table below the highway surface in areas in which the highways were constructed 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 about 70 to 100 feet of medium to coarse sand. 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 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 scheduled for FY 00 (Phase 17) included conducting 18 condition-assessment and posttreatment step tests, monitoring of the chemical treatment of 11 wells, and observing and documenting the construction of 2 new (replacement) dewatering wells. Of the 18 step tests conducted, 11 were post-chemical-treatment step tests, 5 were routine condition assessment step tests on existing wells, and 2 were condition assessments on newly constructed wells. The results of the five condition assessment step tests indicated specific capacities ranging from 25.1 to 65.2 gallons per minute per foot (gpm/ft), corresponding to very poor to fair well conditions, respectively. It was recommended that all five wells be chemically treated in FY01. Posttreatment step tests were used to help document the rehabilitation of 11 dewatering wells during FY 00 (Phase 17): I-70 Wells 2A and 8A; 25th Street Wells 2, 3, 4, 5, 7, 8, and 9; and Missouri Avenue Wells 2 and 3. Chemical treatments used to restore the capacity of these seven wells were moderately successful. There was a wide range of improvement in specific capacity per well, ranging from 2 percent to 503 percent improvement, and averaging 124 percent based on specific-capacity data from pre- and posttreatment step tests. A sand pumpage investigation, which was conducted during 15 of the 18 step tests during FY 00, revealed that 25th Street Wells 2, 3, and 4 were pumping sand. These conditions may pose a threat to the long-term operation of these wells, especially 25th Street Well 4. Smaller amounts of sand were found following the step test for 25th Street Wells 2 and 3.
The practical application of selected analytical methods to well and aquifer evaluation problems in Illinois is described in this report. The subject matter includes formulas and methods used to quantitatively appraise the geohydrologic parameters affecting the water-yielding capacity of wells and aquifers and formulas and methods used to quantitatively appraise the response of wells and aquifers to heavy pumping. Numerous illustrative examples of analyses based on actual field data are presented. The aquifer test is one of the most useful tools available to hydrologists. Analysis of aquifer test data to determine the hydraulic properties of aquifers and confining beds under nonleaky artesian, leaky artesian, water table, partial penetration, and geohydrologic boundary conditions is discussed and limitations of various methods of analysis are reviewed. Hydraulic properties also are estimated with specific-capacity data and maps of the water table or piezometric surface. The role of individual units of multiunit aquifers is appraised by statistical analysis of specific capacity data. The influence of geohydrologic boundaries on the yields of wells and aquifers is determined by means of the image-well theory. The image-well theory is applied to multiple boundary conditions by taking into consideration successive reflections on the boundaries. Several methods for evaluating recharge rates involving flow-net analysis and hydrologic and groundwater budgets are described in detail. Well loss in production wells is appraised with step-drawdown test data, and well screens and artificial packs are designed based on the mechanical analysis of the aquifer. Optimum well spacings are estimated taking into consideration aquifer characteristics and economics. Emphasis is placed on the quantitative evaluation of the practical sustained yields of wells and aquifers by available analytical methods. The actual groundwater condition is simulated by a model aquifer having straight-line boundaries, an effective width, length, and thickness, and sometimes a confining bed with an effective thickness. The hydraulic properties of the model aquifer and its confining bed, if present, the image-well theory, and appropriate groundwater formulas are used to construct a mathematical model that provides a means of evaluating the performance of wells and aquifers. Records of past pumpage and water levels establish the validity of this mechanism as a model of the response of an aquifer to heavy pumping.
This circular presents basic information on water quality and treatment of domestic and farm groundwater supplies. It describes tests and practices that assure a safe sanitary water quality, and discusses in detail the common minerals and natural gases that are of concern to home water supplies in Illinois. It describes water treatment procedures and equipment for disinfection, iron removal, softening, methane and hydrogen sulfide gas removal, and their costs.
Two August 2002 rainstorms, one centered in Illinois and Indiana on August 18-19, and one in Iowa, Illinois, and Wisconsin on August 21-22, created record-setting point rainfalls of >10 inches and >12 inches, respectively. Return intervals of both storms' heavy rain amounts for 3-, 6-, and 12- hour durations exceeded once in 100-year values. Storm characteristics were similar to those of 36 past rainstorms during 1951-2001 that also were investigated in comparable detail. The similarities included the fact that most of the rain fell over 8 hours at night, storm areas were oriented west-east, and the region with >2 inches covered more than 9,000 square miles. Synoptically, conditions were similar to those of most past rainstorms: the storms developed south of an west-east-oriented front, precipitable water values were exceptionally high, >1.7 inches, and the frontal position and low-level jet stream proximity led to training of thunderstorms along the same path. However, the August 2002 rainstorms were different than past rainstorms in that the two storm events occurred just 2.5 days apart and in relatively adjacent areas. No other major past storms had occurred in such close time proximity. Both storms occurred where the prior 2.5-month rainfall was much below normal, creating much below normal soil moisture and droughtlike conditions for crops. All 36 previous major assessed rainstorms occurred after prolonged periods of average to much above average rainfall. This pre-storm difference in moisture conditions greatly affected the storms' impacts, and both August storms produced small economic losses compared to those of comparable prior storms. A much greater percentage of total storm rainfall infiltrated the soil, resulting in less runoff. High early peak flows in rivers where the heaviest rain fell quickly returned to normal levels within 10-22 days. Flooding, mostly near river courses, quickly dissipated, and flood losses were minimal. The major economic impact of the two August storms related to the added soil moisture and, in turn, the positive effects on soybean crops. Soybeans were in the pod-filling stage and shy of soil moisture when the storms occurred, and the rain-filled soils led to increased yields valued at $51 million in Illinois and Iowa.
This document provides the best available in formation on the time-distribution characteristics of heavy rainstorms at a point and on small basins in Illinois and the Midwest. It is recommended for use in conjunction with Illinois State Water Survey Bulletin 70 and Circular 172 for runoff computations related to the design and operation of runoff control structures. It is also useful for post-storm assessment of individual storm events in weather modification operations. Information is presented in the form of families of curves derived for groups of storms categorized according to whether the greatest percentage of total storm rainfall occurred in the first, second, third, or fourth quarter of the storm period. The time distributions are expressed as cumulative percentages of storm rainfall and storm duration to enable comparisons between storms. The individual curves for each storm type provide estimates of the time-distribution characteristics at probability levels ranging from 10% to 90% of the total storm occurrences. Explanations are provided of how to use the results in design problems.
Biweekly and total irrigation amounts and irrigation scheduling practices were monitored at representative sites in central Illinois during the 1988 and 1989 growing seasons. The purpose was to gather baseline information on average quantities of irrigation water used in normal and drought years and on the general efficiency of irrigation operations in the subhumid climate of Illinois. Soil water-holding capacity is the most important factor in determining irrigation amounts, explaining about 65 percent of the variability in irrigation totals. Other important factors in explaining irrigation variations include weather changes, individual farmer idiosyncrasies, and crop differences. In general, irrigation farmers in Illinois appear to be applying appropriate amounts of irrigation water at appropriate times in the growing season, based on their soil type, crop type, and total evaporative losses.
The Illinois Streamflow Gaging Network has been operated by the U.S. Geological Survey (USGS) since the early 1900s. From its inception, the operation of the network has been maintained through a cooperative partnership between the USGS and state and federal agencies. Hydrologic information provided by the network is vital for the general management of Illinois' water resources. Streamflow data are continually used for forecasting floods and droughts; assessing the biological and chemical health of our streams; operating reservoirs, water supply facilities, wastewater treatment facilities, and hydroelectric plants; assessing and predicting the long-term impacts of climate and land-use trends on our streams; and numerous other important uses. The purpose of this study was to conduct a comprehensive evaluation of the use of Illinois streamflow data, with the goal that this information and analysis will be used by the network's cooperating agencies and others for current and future decisions related to funding and content of the network. Evaluations such as this have been conducted in the past, and should continue to be conducted periodically to assess whether the network meets the data needs of users in an effective manner, to assess emerging needs, and to anticipate needed programmatic changes to the network. This report identifies several emerging applications for which more and additional types of stream data likely will be needed, including applications related to stream and watershed restoration and water quality load assessment. However, in general, it is not possible to anticipate many of the future needs of the streamflow gaging program. More often than not, emerging issues will need to use streamflow data far before there is sufficient time to collect data for that specific use. The only way to have adequate data when these needs arise is to maintain a base network at locations that are representative of the streams of Illinois, such that these long-term data are available to meet a broad range of potential needs. This base network of gaging stations also is needed to provide general streamflow information for ungaged streams throughout Illinois. There are thousands of streams in Illinois, whereas the network currently includes roughly 160 continuous-streamflow gages on fewer than 110 of these streams. For other streams, flow characteristics must be estimated from the available gaging records using regional hydrologic principles. Various methods are available to evaluate the effectiveness of specific gaging records for use in this regional transfer of information. This report includes several descriptive measures of the regional value of gage information and also summarizes a numerical evaluation based on information transfer theory. No single approach can effectively describe the broad range of considerations needed to evaluate the regional value of gages. However, it is clear that applications in regional hydrology will need additional data beyond those which are currently supported by the network. Specifically, the base network is noticeably lacking data from small watersheds in rural Illinois. In addition, several hydrologic regions in Illinois have a limited number of gages for use in regional analysis. Two questionnaires were developed to ascertain the importance and uses of the data from the streamflow gaging network. The first questionnaire was distributed to all agencies that provide cooperative funding to the network. The second questionnaire was developed on an Internet Web site to be accessed and filled out by all interested users of Illinois streamflow data. In both questionnaires, the respondents were asked to identify: 1) the types of data that they most frequently use and/or are most critical for their needs; 2) categories of data applications and their relative importance; and 3) the importance of specific gages for their applications. The report provides a ranking of the relative importance of individual gages based on the responses from the questionnaires. The users indicate that river forecasting/flood warning is the overall most important category of application of streamflow data, followed by long-term flow statistics for analyzing hydrologic trends and determining human impacts to streams. However, the majority of users are more likely to use streamflow data for individual project needs such as those related to hydrologic-hydraulic modeling and design, and biological and conservation assessment. Analysis of gaging records indicates that streamflow conditions are not stationary, and vary not only from year to year but also from decade to decade as influenced by climate variability and other factors. More than half of the long-term flow records in rural areas show statistically significant increases in average and low-flow conditions that appear to occur as a result of climate variability. Statewide, over the past 25 years, there has also been an average increase of 18 percent in the estimates of the 100-year flood peak discharge as represented by long-term records. With the decline in the number of crest-stage peak-flow gages and small watershed gages, many of the records available for certain types of hydrologic analysis are older, discontinued gaging records that may not accurately represent the expected present-day, long-term hydrologic conditions. Shorter gaging records, regardless of period of record, also may not fully represent the expected long-term conditions. There is a need for analytical techniques to assess inherent differences in streamflow records and characteristics such as flood frequency that are caused by climatic variability and other factors. The network appears to be meeting most traditional current-use needs. However, there is a need to reinforce the base network, specifically regarding data for relatively small rural watersheds that are needed to address various emerging issues, long-term regional assessment, and peak flood estimation. The size of the overall network would have to be increased an additional 15-20 percent to more effectively address data needs related to small to medium-sized rural watersheds. Also, there is a growing need for new types of stream data to address specific biological and conservation issues such as stream and watershed restoration. This report only addresses streamgaging issues related to flow quantity, and thus there are no conclusions or recommendations related to water quality, precipitation, or other types of hydrologic data. Funding for the Illinois Streamflow Gaging Network is subject to uncertainties, and this is especially the case regarding potential growth or changes to the network. The National Streamflow Information Program (NSIP), initiated by the USGS in 1999, proposed that the USGS eventually would assume the costs of gages that directly meet specific federal interests. However, it is uncertain whether this or other initiatives from traditional funding sources will produce a prominent change in the size and character of the network. More likely, gaging needs for emerging issues will need to be funded from new sources currently not participating in the network. By its nature, it is essential that the base network be funded mainly through state or federal agencies with a long-term commitment to the streamflow gaging program.
Episodic controls on sources of ozone precursor gases have been suggested as an alternative to continuous controls as a strategy for reducing ozone concentrations to meet current air quality standards. To show the feasibility of episodic controls to meet ozone air quality standards, it is first necessary to show that it is feasible to forecast surface ozone concentrations with sufficient accuracy and sufficient lead time that episodic controls can be instituted. This study examined the feasibility of a statistical forecast of surface ozone concentrations in the Chicago area (Lake, Cook, and DuPage Counties), based on current concentrations and current and expected weather conditions. Forecast methods were developed using historical data on surface ozone concentrations and meteorological variables measured from 1990-1995. Overall, the study included: andlt;ULandgt; andlt;LIandgt;An extensive literature review and summary. andlt;LIandgt;Documentation of forecast methods used to call Ozone Action Days. andlt;LIandgt;Analysis of Ozone Action Days called in 1995-1997. andlt;LIandgt;Creation of air quality and meteorological databases. andlt;LIandgt;Examination of bivariate relationships between ozone and meteorological variables, including back trajectories on days with high ozone concentrations. andlt;LIandgt;Development of four forecasting approaches involving regression equations and two methods of adjusting or enhancing the results of the regression equations. andlt;LIandgt;Analyses of forecasts based on the four approaches.andlt;/LIandgt;andlt;/ULandgt;