Geology topics
Source-linked reports with geographic coverage including Illinois.
Using 3D Elevation Program data, a modern illustration of each State's landscape showcases its elevation differences in vivid detail. Each State has been consistently adjusted and colorized according to its highest and lowest elevations, accentuating differences even in States with low relief. To further emphasize landforms, shaded relief has been added on top of the elevation colors.
Hicks Dome hosts breccias enriched in rare earth elements (REE), Y, Th, F, Ba, Ti, Nb, and Be, alongside spatially associated lamprophyre dikes (ca. 271 Ma). Hicks Dome is located within the Illinois–Kentucky Fluorspar District, which hosts fluorite, Pb–Zn, and barite resources. This study investigates the genetic relationships between Hicks Dome mineralization in breccias, alkaline magmatism, and Illinois–Kentucky Fluorspar District mineralization. Lamprophyre dikes are light REE–enriched with chondrite-normalized abundances decreasing from La to Lu. The Host Breccia exhibits middle and heavy REE–enriched patterns that mirror those of the principal REE–Th host minerals, including fluorapatite, xenotime, and thorite. Textural evidence suggests recrystallization of phosphates, sulfates, and Ti–Nb oxides in the Host Breccia. U–Pb geochronology constrains multiple mineralizing events, with ages of 277 ± 18 Ma from low-Th apatite interpreted as main-stage mineralization, and 121.6 ± 9.7 Ma from high-Th apatite indicating later overprinting. O–H–C stable isotope data provide evidence for multiple stages of fluid-rock interaction and fluid mixing: (1) early magmatic fluids dissolved limestone country rock, (2) mixing between magmatic fluids and basinal brines led to main-stage mineralization in the Host Breccia, and (3) late-stage mineralization occurred following mixing of meteoric water and basinal brine. These results indicate that heavy REEs, high field strength elements, and fluorine precipitated proximal to its alkaline magmatic source because of fluid–rock interactions and fluid mixing. Subsequent fluid mixing drove late-stage recrystallization and additional fluorite formation, a process that may be similar to mineralization in the Illinois-Kentucky Fluorspar District.
Species interactions among multiple invasive species can present hidden challenges for management and eradication efforts. Bighead and Silver carp ( Hypophthalmichthys nobilis and H. molitrix , respectively) are closely related species that have co-invaded the Mississippi River and many of its tributaries, including the Illinois River. We used a combination of causal inference and dynamic models to test for interspecific interactions in a 10-year data set of hydroacoustic density data from the Illinois River. The results suggest that Bighead and Silver carp are exploiting different ecological strategies; where Bighead carp shows fast initial growth but low equilibrium density and Silver carp had a lower low-density growth rate but larger equilibrium population density. Further, we found evidence for a positive interspecific effect of Silver carp on Bighead carp. The mechanism leading to the observed positive interactions is unknown, but could be an effect of ecological facilitation, differential responses to harvest of both species, or hybridization and introgression. Finally, while these results provide valuable information in the ecological strategies and relationships between these species, simulations of the resulting models suggest that the magnitude of the positive interaction is likely too small to be exploited for innovative multispecies management interventions.
Illinois contributes substantial nutrient loads to the Gulf of America, warranting watershed-scale assessment. This study estimated nitrate-nitrogen (nitrate-N) and total phosphorus (TP) loads and yields for 49 Illinois 8-digit hydrologic unit code (HUC8) watersheds draining to the Mississippi River Basin from 1997–2022, comparing recent (2018–2022) to baseline (1997–2011) conditions. Estimates included point and nonpoint source contributions, dissolved phosphorus, and water yields. During the recent period, nonpoint sources dominated nutrient export (82% nitrate-N, 78% TP), though point sources drove high yields in the Chicago area. Spatially, nonpoint source nutrient hotspots persisted with nitrate-N yields highest in east-central and northern Illinois and TP yields higher in southern and western Illinois. Temporally, statewide nitrate-N loads decreased 9%, while TP loads increased 27%. Nitrate-N yields increased in 22 HUC8s and decreased in 20, while TP yields increased in 32 HUC8s and decreased in 9. For both nutrients, baseline yields were negatively correlated with yield changes, indicating high-yielding watersheds tended toward larger decreases or smaller increases. Water yields increased 19% on average but were weakly correlated with nutrient yield changes ( r = 0.23 and 0.20 for nitrate-N and TP). These results reveal spatially persistent yet temporally divergent nutrient export across Illinois, with contrasting nitrate-N and TP trajectories for nonpoint sources.
The escape and subsequent spread of invasive carp (notably, bighead carp [ Hypophthalmichthys nobilis ] and silver carp [ H. molitrix ]) from aquaculture ponds and sewage lagoons into the Mississippi and Illinois Rivers poses a significant risk to further spread of these fish into the Great Lakes. Prior research demonstrated that commercial tows can transport juvenile invasive carp through locks and other barriers to fish migration. A recent physical model study recommended a linear array of bubble diffusers, the Automated Barge Clearing Deterrent (ABCD), for further evaluation in mitigating the transport of small fish in commercial tows. The present field study evaluated the ABCD for navigation safety and barge junction flushing capacity. An instrumented commercial tow executed 119 lock approaches with the ABCD both operating and idle. Pilot interviews and tow trajectory analysis indicated no significant navigation safety issues. The measured velocity data, fish recapture data, and a simple fish displacement model indicated that the ABCD produced sufficient flow to expel all passive objects and many small juvenile invasive carp. However, the ABCD is less likely to expel large juvenile invasive carp due to their stronger swimming ability. The ABCD and two alternative configurations prove strong contenders for further development and application.
1. Phytoplankton form the base of large river food webs but there are limited studies on the nature and drivers of communities over longer time scales. Further, climate change is projected to favor taxa associated with harmful algal blooms, but our knowledge of the timing, locations, and drivers of cyanobacteria in rivers lags that of lakes and marine environments. 2. We used a summer phytoplankton community dataset collected from 2010-2020 across main channel, side channel and backwater areas in the La Grange reach of the Illinois River to assess: 1) How much do summer phytoplankton communities across diverse aquatic areas within a large river vary from year to year?, 2) What environmental conditions are associated with that variation?, and 3) Do cyanobacteria respond differently than the full phytoplankton community? 3. We found greater differences in phytoplankton communities across years than among aquatic areas. Further, we showed that annual variation in phytoplankton communities was synchronous among taxa in the same aquatic area, rather than specific to each taxonomic group or taxa-area combination. After accounting for this spatial variation in annual dynamics, phytoplankton reflected river conditions across seasons, responding positively to summer total phosphorus and invasive carp abundance and negatively to winter discharge and spring silica to nitrogen ratio. Annual variation in cyanobacteria was similarly distinct among main channel, side channel and backwater areas but was best explained by the ratio of summer air temperature to discharge, representing conditions that favored growth over transport. 4. These results show that annual variation in summer phytoplankton and cyanobacterial communities both reflected the spatial diversity of the river landscape and responded to conditions that occurred at different spatial and temporal scales. Further, in this highly modified river basin, we showed that a mix of anthropogenic pressures including eutrophication, invasive species, and potential changes to winter and spring conditions affected the phytoplankton communities present in the summer. Thus, when evaluating long-term change and the potential for harmful algal blooms in rivers it is important to consider spatial diversity of phytoplankton communities, how their sensitivity to environmental change may vary across the river landscape, and the suite of human modifications acting on those communities.
The Cook County Precipitation Network is a set of 25 precipitation gages established within Cook County, Illinois, on approximately a 5- to 7-mile square grid and used by the U.S. Army Corps of Engineers to help account for diversions of water from Lake Michigan to the State of Illinois. The transition from the precipitation gage network operated by the Illinois State Water Survey to the precipitation gage network operated by the U.S. Geological Survey (USGS) was compared for periods of overlapping data. This transition took place from May through September during the 2019 water year. The USGS was able to establish replacement precipitation gages at 17 of the 25 sites by the conclusion of the overlapping operational period. The double-mass curve method was used to compare the two networks by creating a graph of the cumulated data collected by the Illinois State Water Survey and the comparable data collected by the USGS. Breaks in the double-mass curve method are caused by a change in the relation between variables. The eight sites that were installed following the overlapping period have a gap in the recorded data; however, the slope of the line for each of the eight sites is nearly equivalent to the previous data. In general, the cumulated precipitation data from the two networks were similar. Three sites had greater than 8-percent difference in their cumulative data ratios, located at Cicero, Ping Tom Park at Chicago, and South Shore, Ill.
The Meadow Bank scarp (MBS) in southeastern Illinois is a linear geomorphic expression, ∼10 km long and ∼8 m high above a relatively flat landscape. It parallels an underlying northeast‐oriented Late‐Precambrian–Early‐Cambrian structural fabric, called the Wabash Valley fault zone, and is within an area of modern, historic, and paleo seismicity, called the Wabash Valley seismic zone. In addition, the MBS acts as a boundary of the Wabash River floodplain, as well as Pleistocene glacial outwash channels, which show evidence of frequent outburst flood events. To better understand the MBS’s equivocal origin in this complex geologic environment, we acquired a 917‐m‐long seismic‐reflection survey across its axis to assess the subsurface geologic configuration. The resultant image indicates a complex set of faults that antiformally fold and displace the top of Paleozoic bedrock by ∼12 m across the survey. Moreover, fault and/or fold deformation extends into the shallowest imaged Quaternary strata at ∼6 m below the ground surface. This suggests the MBS origin is related to underlying Quaternary reactivated, positively inverted faults rather than exclusively to glacial outburst flood erosion. These results provide rare paleoearthquake spatial constraints for central U.S. regional seismic hazard consideration.
Spatial and temporal distribution data provide critical information for invasive species management. For example, distribution data can help managers with early detections and guiding other response actions. Environmental DNA (eDNA)-based sampling exists as one tool for monitoring invasive species. As part of bigheaded carp Hypophthalmichthys spp. monitoring efforts in the Illinois River, USA, we compared eDNA-based sampling results at multiple habitats across an invasion gradient in 2015. Greater densities of carp occurred downriver in the Illinois River and lower densities occurred upriver. We sampled from five locations along this gradient and from three habitat types (backwater, main channel, and shoreline) within each location. We sampled each location in April and June. A priori , we hypothesized that more eDNA detections would occur downriver, where higher densities of carp occur; that more eDNA detections would occur in backwater habitats compared to areas of the river with more fish movement; and that more eDNA detections would occur in April, because bigheaded carps are thought to use our sampling areas more during the spring. We compared the proportion of samples positive across this gradient, the habitat type, and the two sampling time periods. The most downriver location had the highest proportion of samples with eDNA detections, the backwater habitats had the highest proportion of samples with eDNA detections, and April had more positive detections than June. Our results highlight the importance of sampling across multiple habitat types and across time to gain a clear understanding of distribution when using eDNA-based sampling. Thus, being cognizant of the interactions between seasonal habitat use and eDNA-based detections is important for managers who rely upon eDNA-based monitoring.
Illinois is a major contributor of nutrients to the northern Gulf of Mexico. As such, the State of Illinois initiated efforts to curb nutrient runoff over the last several decades. To evaluate progress towards these reductions, water-quality data were used to estimate incremental loads and yields of nitrate plus nitrite (NO3) and total phosphorus (TP) from 1997–2022 for 49 Illinois watersheds, defined using eight-digit hydrologic unit codes (HUC8), draining to the Mississippi River Basin. To estimate changes in NO3 and TP loads, recent loads from the period 2018 through 2022 were compared to baseline loads from 1997 through 2011. Nonpoint and point source loads, dissolved phosphorus (DP) loads, and water yields were also estimated. The sum of the incremental NO3 loads from the 49 HUC8s decreased 9% despite a 19% increase in water yield. Much of this decline occurred in HUC8s that had NO3 yields greater than 17 pounds per acre per year (lbs/acre/yr) during a 1997–2011 baseline period. The sum of all incremental HUC8 TP loads increased 25% despite a 27% reduction in point source discharge. Loads and yields were substantially larger for both NO3 and TP in the Chicago area. Outside the Chicago area, central and northern Illinois had higher NO3 yields than southern Illinois and a reverse pattern for TP where higher yields occur in southern Illinois. Nonpoint sources made up an estimated 82% and 78% of the NO3 and TP yields, respectively, across the HUC8s. In general, point source yields have mostly decreased over time, while nonpoint source yields varied depending on location and reflect the changes in the total yield.
A hydrologic model of the Silver Creek Basin in southwest Illinois, and a hydraulic model of a selected reach of Silver Creek and local tributaries on and near Scott Air Force Base, Illinois, were developed to assess the effects of temporal land-use development in the Silver Creek Basin, the potential effects of projected changes based on future precipitation, and the effects of added detention storage in selected tributaries near Scott Air Force Base. The hydrologic model consists of a total of 52 scenarios—24 scenarios for an assessment of basin-wide changes in hydrology, and 28 scenarios for the hydraulic analysis of a focus area of Silver Creek and tributaries on and near Scott Air Force Base. Scenarios were run for precipitation events of 2-year through 500-year recurrence intervals (50-percent through 0.2-percent annual exceedance probability) and 24-hour durations. The effects of detention structures added to Silver Creek tributaries throughout Scott Air Force Base were greater on water-level profiles (about 1 to 3 feet) than the effects of projected (2050) changes in precipitation (about 1 foot or less) in these basins. The results indicated that despite the increases in water-surface elevations resulting from projected increases in precipitation, the detention structures could provide a net reduction in water-surface elevations in the flood-prone western tributaries on the base. The effects of detention structures and projected precipitation also were assessed using the mapped extent of inundation for the simulated probabilistic precipitation scenarios. As an example, limited inundation of a residential area along Ash Creek was evident in the 5-year recurrence interval event for the scenarios without detention storage, whereas the first indications of flooding in the residential area from the scenario with detention storage were in the 50-year recurrence interval event. Changes in hydrologic conditions followed a spatial pattern similar to that of the changes in land-cover development, with the greatest changes in the downstream one-half of the Silver Creek Basin and most pronounced in subbasins on and surrounding Scott Air Force Base. There was up to an estimated 54.6-percent increase in peak streamflows in subbasins on or near Scott Air Force Base from historical (1992) to current (2019) conditions, but changes in peak streamflows of as much as 144 percent are anticipated under the planned (to about 2050) land cover plus projected (2050) precipitation. The changes in the timing of peak streamflows were towards earlier peaks, with cumulative changes between historical and projected conditions approaching 0.75 hour (45 minutes) for a 2-year recurrence interval event. Results of the percentage change in cumulative event volume were similar to those of percentage change in peak streamflows in terms of magnitude of change and temporal and spatial distribution of changes. The greatest magnitude of percentage change in the assessed hydrologic properties was associated with the 2-year recurrence interval event, and the magnitude of the percentage change decreased with increasing probabilistic event recurrence interval. Subbasins with a substantial change in runoff yield between historical and current conditions were primarily in the downstream one-half of the Silver Creek Basin and most were within or adjacent to Scott Air Force Base. The magnitude of runoff yield changes increased with recurrence interval, and maximum changes were associated with subbasins on base and with the changes between the historical and current conditions.
Natural resource managers commonly use population-level models to aid in understanding the status of target populations or the potential implications of management actions. Sensitivity analyses, specifically, local sensitivity analysis (LSA) and global sensitivity analysis (GSA), exist as tools to improve understanding of these models, the importance of specific parameters to model outcomes, and the assumptions inherent to population models. However, applied ecology and closely related fields such as fisheries and wildlife management rarely use LSA or GSA. Here, we apply LSA and GSA to the Spatially Explicit Invasive Carp Population model, a population-level model used to simulate and compare management actions on the invasive silver carp Hypophthalmichthys molitrix population in the Illinois River. The spatial structure within the model arises from the navigation “pools” that exist between navigation lock-and-dam in the river and are also the focus of fisheries management in the river. We completed LSA and GSA for two reasons: (1) to compare the importance of model input parameters on simulated model populations and (2) to demonstrate the use of LSA and GSA for population-level models. In our system, the most important sensitivity values generally were detected in Alton Pool. This pool is the farthest downstream and includes a direct connection with the Mississippi River. These results indicate that the population dynamics in Alton Pool are an important driver of the population dynamics throughout the Illinois River. Management outcomes in this system will, therefore, be strongly dependent on the dynamics of Alton Pool.
The Chicago Area Waterway System (CAWS) is a potential route for the migration of aquatic invasive species from the Mississippi River Basin into the Great Lakes. Electric dispersal barriers were installed in the Chicago Sanitary Ship Canal, within CAWS, to prevent invasive fish from reaching the Great Lakes. Despite the high efficiency of these barriers, occasional maintenance events create a vulnerability that fish can exploit to access the Great Lakes. This study aimed to assess the feasibility of a carbon dioxide (CO 2 ) infusion system to deter fish during the maintenance of the electric barriers. An algebraic slip mixture model was implemented in the OpenFOAM solver to represent the underwater CO 2 bubble plume and predict the concentration of dissolved CO 2 in the canal. Simulations under three canal flowrates and two sparger systems were conducted assuming a constant gas flowrate. Numerical results indicate that, for all simulated conditions, the CO 2 concentration is not fully mixed creating passageways that invasive fish could potentially use to migrate upstream. Injecting 4-mm bubbles induces two large-scale recirculations that are expected to synergistically improve fish avoidance. On the other hand, injection of 20 μ "> μ m bubbles results on almost immediate dissolution with minimal effect on the flow pattern. To improve effectiveness, a gas pulse system was proposed and numerically evaluated. Based on the simulations, this system not only extends the operation of the CO 2 barrier but also increases efficiency creating CO 2 gradients that can promote a more responsive behaviour from fish. Moreover, the pulse concept mitigates potential effect of elevated CO 2 downstream from the treated area.
Understanding the movement patterns of an invasive species can be a powerful tool in designing effective management and control strategies. Here, we used a Bayesian multistate model to investigate the movement of two invasive carp species, silver carp ( Hypophthalmichthys molitrix ) and bighead carp ( H. nobilis ), using acoustic telemetry. The invaded portions of the Illinois and Des Plaines Rivers, USA, are a high priority management zone in the broader efforts to combat the spread of invasive carps from reaching the Laurentian Great Lakes. Our main objective was to characterize the rates of upstream and downstream movements by carps between river pools that are maintained by navigation lock and dam structures. However, we also aimed to evaluate the efficacy of the available telemetry infrastructure to monitor carp movements through this system. We found that, on a monthly basis, most individuals of both species remained within their current river pools: averaging 76.2% of silver carp and 75.5% of bighead carp. Conversely, a smaller proportion of silver carp, averaging 14.2%, and bighead carp, averaging 13.9%, moved to downstream river pools. Movements towards upstream pools were the least likely for both species, with silver carp at an average of 6.7% and bighead carp at 7.9%. The highest probabilities for upstream movements were for fish originating from the three most downstream river pools, where most of the population recruitment occurs. However, our evaluation of the telemetry array’s effectiveness indicated low probability to detect fish in this portion of the river. We provide insights to enhance the placement and use of these monitoring tools, aiming to deepen our comprehension of these species’ movement patterns in the system.
Forecasts of flows entering and leaving the Chain of Lakes on the Fox River in northeastern Illinois are critical information to water-resource managers operating the Stratton Dam at McHenry, Illinois. These managers determine the optimal operation of the Stratton Dam at McHenry, Ill., to manage Chain of Lakes pool levels and to help mitigate flooding in the Chain of Lakes system. In 2020, the U.S. Geological Survey (USGS) and the Illinois Department of Natural Resources–Office of Water Resources (IDNR–OWR) began a cooperative study to develop a system to enable engineers and planners to simulate and communicate water-surface elevations and flows and to proactively prepare for runoff events forecasted for the Chain of Lakes. The hydraulic model described in this report may be helpful to the IDNR–OWR for optimizing the operation of the Stratton Dam and includes the implementation of three newly installed torque-tube crest gates that became operational in 2020. The hydraulic model for the Chain of Lakes was developed using the Hydrologic Engineering Center–River Analysis System program (version 6.5). The hydraulic model was used to simulate water-surface elevations and flows through the 18.5-mile Chain of Lakes system to 1.7 miles downstream from the Stratton Dam. Five USGS streamgages within the study area were used as reference points for model calibration and initial water-surface elevations for beginning a simulation. The hydraulic model was calibrated to three runoff events that incorporated the design specifications and observed gate operations of the Stratton Dam; furthermore, the hydraulic model simulated a validation event and a substantial flooding event during July 2017. The July 2017 event predated the torque-tube crest gate installation but nevertheless tested the performance of the model for such a substantial event. The model simulation results were a good fit to observed records at USGS streamgages with simulated peak water-surface elevations within −0.36–0.15 foot of observed events. The hydraulic model was then implemented into a forecast workflow that streamlines implementation of model inputs and documents the model outputs tailored to IDNR–OWS Stratton Dam operations and interpretations of simulated water-surface elevations and flows.
This report characterizes changes in peak streamflow in Illinois and the relation of these changes to climatic variability, and provides a foundation for future studies that can address nonstationarity in peak-flow frequency analysis in Illinois. Records of annual peak and daily streamflow at streamgages and gridded monthly climatic data (observed and modeled) were examined across four trend periods (100 years, water years 1921–2020; 75 years, 1946–2020; 50 years, 1971–2020; 30 years 1991–2020) for trends, change points, and other statistical properties indicative of changing conditions. Median peak streamflows generally exhibit upward trends across the State for the 100- and 75-year trend periods and in northern and southern Illinois for the 50- and 30-year trend periods. The medians of the trend magnitudes (normalized by median peak streamflow) range from a 23-percent increase during the 30-year trend period to a 41-percent increase during the 100-year trend period. Streamgages with trends in peak streamflow often also have change points, or abrupt changes, in streamflow magnitude. More than two-thirds of streamgages at the 100- and 75-year trend periods exhibit a trend and change point in median peak streamflow in the same direction. Temporally, clusters of change points are observed in the late 1960s through early 1980s for the 100- and 75-year trend periods and around 2006 for the 50- and 30-year trend periods. Trends in the 90-percent quantile of peak streamflow, which correspond to the 10-percent exceedance probability often used for the design of drainage structures, increased about the same amount as the 50-percent quantile peak streamflows, except at the 100-year trend period, where the 50-percent quantile peak flow increased more for almost all streamgages. The frequency of high flows has also increased in Illinois, with increases in peaks-over-threshold observed across much of the State for the 100- and 75-year trend periods and in northern and southern Illinois for the 50- and 30-year trend periods. Upward trends in observed temperature and observed annual precipitation dominate in all trend periods, with clusters of likely upward trends observed in northern and southern Illinois at the 50- and 30-year trend periods. As expected in response to increasing temperature, the modeled proportion of precipitation falling as snow has largely decreased in the study basins across the State, and modeled potential evapotranspiration has increased. Upward trends in modeled annual runoff, which in this report incorporates only the effects of climatic variation, are observed in the same geographic areas where there are increases in observed annual precipitation. The widespread upward trends in the magnitude of median peak streamflows and the frequency with which high flows occur across the State at the 100- and 75-year trend periods and in northern and southern Illinois at the 50- and 30-year trend periods appear to be driven largely by increases in precipitation based on spatial patterns of these changes and statistical relations between streamflow and climate metrics. Other effects not considered in this report, like urbanization, may be important drivers for certain streamgages in the State. The prevalence of nonstationarity in peak streamflow in Illinois has important implications for peak-flow frequency analysis. Average annual precipitation and the occurrence of extreme precipitation events are expected to increase across the State. If precipitation continues to increase as expected, peak-flow frequency estimates based on older records may no longer represent the hydrologic regime of today, and methods for nonstationary peak-flow frequency analysis may be needed.
The Space to Grow program helps transform aging and neglected schoolyards of Chicago Public Schools into outdoor community spaces with the goal of promoting health and learning while addressing neighborhood flooding issues. Virgil I. Grissom Elementary School and Donald L. Morrill Math and Science School were selected in 2014 for schoolyard upgrades and the installation of various green infrastructure (GI) improvements. The U.S. Geological Survey installed sensors to measure precipitation, groundwater levels, and stormwater runoff volumes from September 1, 2016, to July 1, 2017. At Virgil I. Grissom Elementary School, about 933,000 gallons of water fell on the schoolyard during the monitoring period. No discharge was recorded coming from the GI sewer lines, but backflow indicated water was flowing from the sewer line draining the impervious running track into the combined manhole structure and backwards into the GI retention basins (as designed). This design allowed for a 100-percent capture rate. Native soil at Virgil I. Grissom Elementary School also was conducive to rapid infiltration. Soil borings at Virgil I. Grissom Elementary School indicated about 10.5 feet (ft) of fine sand overlying silty clay to a depth of at least 16 ft. At Donald L. Morrill Math and Science School, about 1,120,000 gallons of water fell on the schoolyard during the monitoring period. About 72.5 precent of this water was discharged into the sewer system, and the other 27.5 percent was captured by the GI. Unlike Virgil I. Grissom Elementary School, the soil profile at Donald L. Morrill Math and Science School consisted of about 5 ft of clay loam overlying stiff blue clay to a depth of at least 12 ft. The sewer line coming from the GI under the football field was at the bottom of the reservoir. This design seemed to allow water to flow out of the line before being absorbed by the retention basin.
This report describes the development of a CE-QUAL-W2 river hydrodynamics and temperature model of a 21-mile reach of the Illinois River including a 3-mile reach of a major tributary, the Fox River. Model outputs consist of streamflow, water velocity, water-surface elevation, and water-temperature time series that can be used to simulate summer conditions in years with and without extensive development of harmful algal blooms (HABs). These analyses may provide a better understanding of some complex factors contributing to HAB development along the Illinois River. Such an understanding may provide more accurate HAB timing and location predictions and may help determine potential mitigating activities to prevent or limit the size and duration of HABs. Using the observed and simulated hydrodynamic conditions in the Illinois River study reach, it was possible to compare and contrast streamflow, velocity, and temperature conditions in years with varying HAB distributions. Occurrences of extensive HABs were documented in the study reach in June 2020 and June 2021, but only a small HAB restricted to the Marseilles Lock and Dam pool occurred in the summer of 2022. The objective then was to find similarities in site conditions between 2020 and 2021 that may contrast with the conditions in 2022. Among the 3 years included in the study, the variability in simulated water temperature exceeded variability in observed streamflow and simulated velocities. The longest period of water temperatures greater than 27 degrees Celsius (°C) in the selected locations in June of the three analysis years was in the second half of June 2022, yet no study-area wide HAB was documented in 2022. Simulations indicated that after warm water temperatures were established in the reach in June 2022, a cooling period broke up the warming period. This period of cooling was greater in magnitude and duration downstream from the location of a localized HAB perhaps limiting the spread of the bloom. Residence times differed substantially in segments representing different channel features; values ranged from 0.28 to 17.3 (days per 500 meters of channel) between the main stem and backwater areas, respectively. Variation in average June residence times was also greater among different channel features than among different years in the study period. The HABs in 2020 and 2021 at Starved Rock Dam were documented when water temperatures were about 26 °C. River backwater areas at some locations did attain these temperatures 2 to 3 days before the conditions in the main stem. Residence times in the backwater areas, however, generally exceeded 9 days, thus limiting the exchange of water carrying algal biomass into the main channel. Hydrodynamic model calibration involved adjusting model parameters until observed and simulated daily water-surface elevations, daily streamflows, discrete velocities, and channel areas were similar. Temperature calibration was done with near-surface continuous time-series data and discrete vertical profile temperatures. Observed and simulated water temperatures generally were within 1 °C at all monitoring locations.