This publication represents a condensed version of an extensive report on the distributions of heavy rainstorms in Illinois, based on data for 61 precipitation stations operated during 1901-1983. Shown are annual frequency distributions of point rainfall for periods ranging from 5 minutes to 10 days and for recurrence intervals varying from 2 months to 100 years. Results are presented in two forms: mean relations for ten regions of approximately homogeneous precipitation climate, and statewide isohyetal maps based on the 61-station data The report also discusses the results of a special investigation pertaining to Chicago and the surrounding six counties subject to urban influences on the precipitation distribution. The final section of the report provides information on the urban influences on the two Illinois counties adjacent to St. Louis.
A primary concern in the management of the Lower Cache River is the amount of sediment that is deposited in the river's valley in the vicinity of Buttonland Swamp. From previous monitoring studies it is known that floodwaters from Big Creek convey a significant amount of sediment and create a reverse flow condition in the Cache River that carries the sediment into Buttonland Swamp. This study investigated the potential influence of several management alternatives in reducing or eliminating the reverse flow condition in the Cache River, which would alleviate much of the sediment concern. Management alternatives include various options for detention storage in the Big Creek watershed as well as redirecting the lower portion of Big Creek to the west, away from Buttonland Swamp. To evaluate the impact of these alternatives, the hydrology of the Big Creek watershed and its influence on the hydraulics of the Lower Cache River were investigated using two models. The HEC-1 flood hydrology model was used to simulate the rainfall-runoff response of tributaries draining to the Lower Cache River, with emphasis on Big Creek and estimating the impact of detention storage on the Big Creek flood flows. The UNET unsteady flow routing model was then used to evaluate the flow patterns in the Lower Cache River and the impact of management alternatives on flow direction, flood discharge, and stage. Under existing conditions, the UNET model shows that reverse flow occurs in the Lower Cache River east of Big Creek confluence during all the flood events considered. Various detention alternatives in the Big Creek watershed have the potential to reduce the peak of the reverse flow by 26 to 76 percent. Of the detention alternatives examined, the larger detention facilities in the lower reaches of Big Creek appear to produce the greatest reduction in reverse flows. An alternative to divert the lower portion of Big Creek has the potential to totally eliminate reverse flows in the area immediately east of the Big Creek confluence with the Lower Cache River, but may cause increased flooding to the west. To eliminate most of the reverse flow east of Big Creek, and at the same time not increase flood stages farther west on the Lower Cache River, it may be necessary to use a combination of detention storage and either a partial or total diversion of the lower portion of Big Creek. For example, the use of the split flow alternative in combination with the many ponds and Cache valley detention alternatives reduces the peak reverse flows east of Big Creek by 81 percent for a 2-year flood and 92 percent for a 100-year flood. This combined alternative also accomplishes a reduction in the peak stages farther downstream west of Interstate 57 by approximately 0.5 foot.
Systematic measurements of ground-water levels in Illinois were started in the early 1930s in the Chicago region. Measurements were made in 1961 in 220 observation wells in 42 counties throughout the state. In areas remote from pumping centers, no long-term continuing trends of general rise or decline of the water table are discernible. A large part of central and southern Illinois experienced a severe drought beginning early in 1952 and ending in most areas during the spring of 1955. As a result, ground-water levels declined to record-low stages especially in the southern one-half of Illinois. However, large quantities of ground water taken from storage within the ground-water reservoir were replenished during succeeding years as precipitation increased. In heavily pumped areas, changes in water levels caused by pumping are superimposed on seasonal and secular fluctuations due to natural phenomena.In some instances large developments of ground water have caused pronounced and serious declines of water levels. There are many areas of ground-water development where serious water-level declines have not occurred.
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.
The effects of river traffic on water and sediment inputs into a side channel were studied in an 18-month research project. McEver's Island, located in the Illinois River, was selected as the study site. The objectives of the research project were: 1) to collect data on factors such as suspended sediment load, water discharge, and types of sediment at a reach of a side channel which directly connects with the main river; and 2) to attempt to estimate the rate of movement of the sediment and water into a side channel in different river stages.Observations indicated that the wave height, velocity, and suspendedsediment concentration showed some significant changes during the passagesof barges. The amounts of water and sediment inputs into side channelsare relatively small compared with the background main channel dischargesand sediment loads.
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.
Fall application of nitrogen (N) fertilizer is a common practice in Illinois to help overcome the uncertainties of spring field work and to reduce the potential for delay in planting of spring crops. If, however, the N is applied while soil temperatures are above 50F, significant N losses can occur before the crop can take up the N. The lost N can pollute the state's water supplies, resulting in harm to the environment. The objective of this work was to provide agricultural community and public access to near real-time, 4-inch bare soil temperatures measured at 10:00 a.m. Central Standard Time (CST) each day. Hourly soil temperatures are measured at 18 automated weather stations in Illinois operated by the Illinois State Water Survey (ISWS). These stations make up the Illinois Climate Network (ICN). Measured weather variables include 4-inch sodded soil temperature, solar radiation, air temperature, relative humidity, barometric pressure, precipitation, and wind speed and direction. These data are collected, quality controlled, and placed on a Web site (http://www.sws.uiuc.edu/warm/soiltemp.asp) for public access. Daily maps of the 4-inch bare soil temperature are derived from a combination of actual 4-inch bare soil measurements at 8 ICN stations and computed bare soil temperature from 4-inch sodded soil temperature measurements from the remaining 10 sites. These maps allow users to see the general pattern of the 10:00 a.m. CST soil temperature from which they can estimate soil temperature at a given location. The other measured weather variables also are presented on the Web site in map format. Steven E. Hollinger and Robert W. Scott, Water and Atmosphere Resources Monitoring Program, Atmospheric Environment Section and Office of the Chief, Illinois State Water Survey, 2204 Griffith Drive, Champaign, Illinois 61820-7945
Brochure describing the research and services available from the Midwestern Regional Climate Center (MRCC) help to better explain climate and its impacts on the Midwest, provide practical solutions to specific climate problems, and allow us to develop issues-based climate information for the Midwest. Our data and information focus primarily on applications to climate-sensitive sectors and scientific research. In addition to providing on-line access to the interactive, subscription-based Midwestern Climate Information System (MICIS), the MRCC web site provides climate statistics for the Midwest and links to climate resources around the country.
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.
The Fox Chain of Lakes is a series of interconnected glacial lakes that are essentially located along the main stem of the Fox River. Originating in Wisconsin, the Fox River flows through northern Illinois before becoming a major tributary of the Illinois River. About 75 percent of the Fox River above the lowest section of the Fox Chain of Lakes lies in Wisconsin. The drainage area above the lowest point of the chain is about 1,184 square miles. The Fox Chain of Lakes has a surface area of more than 6,000 acres. Over the years, significant land-use changes have occurred on this watershed. These changes and the geographical location of the Fox River have resulted in extensive sediment deposition within these lakes. This is especially true for those lakes in the direct path of the Fox River. For example, Grass Lake and Nippersink Lake have lost most of their capacities to sediment deposition. The average depth of Grass Lake in 1975 was 2.7 feet, and the sediment is extremely soft. Within the present research activity, the original research conducted in 1974-1975 by the authors is being examined along with additional data collected by others within the last 25 years. These initial analyses indicated that both in-lake and off-lake sediment management techniques must be implemented to increase water depths within the lakes and decrease sediment loads. Among the in-lake management alternatives that should be considered are dredging and disposing of sediment outside the lake, discharging hydraulically dredged sediment into geotubes or some other type of containment facility within the lake, and creating artificial islands within the lake with dredged sediments. The watershed-based sediment management alternatives could include implementation of best management practices on the watershed, flow and sediment retention basins, side channel sediment traps, sediment management within the stream channel, and the implementation of a systemwide sediment management alternative.