The Electronic Documents of Illinois provides permanent public access to official publications of the State of Illinois which have been deposited in electronic form.
Soil erosion and nonpoint source pollution runoff rates are estimated using output from the Revised Universal Soil Loss Equation (RUSLE). The underlying influence of climate on surface transport processes as represented in the RUSLE is carried within one constant, the R-factor. It has been assumed that the R-factor is temporally stationary; that is, it does not change with time. The purpose of this study was to process climate information from the most recent decades to update the R-factor, to examine the nature of precipitation variation and change and their impacts on the R-factor over space and time, and, specifically, to test the hypothesis that storm erosivity and the R-factor are temporally stationary. This was addressed by developing a database of precipitation data and related information needed to calculate single-storm erosivity and cumulative R-factor for each half-month of the year and for the total year. In addition the 10-year, single-storm erosive index for each station is provided. The R-factor, a nonlinear, cumulative measure of the erosive energy contained in storm precipitation, was calculated directly from 15-minute rainfall data. However, because of some undocumented quality difficulties with the 15-minute data, single-storm erosivity index statistics for accumulation into R-factors were calculated from more reliable daily data through the use of a power law transfer function. These new R-factors were tested for spatial covariation, which was found to be minimal in even terrain, and related to the limited amount of station R-factor data from past studies. Comparison with past R-factor studies indicated strongly that the methodologies used adequately duplicated old R-factors based on data from the 1930s to the 1950s. General increases observed in R-factors in this study were related to increasing amounts of precipitation and storms with rainfall greater than 12.7 millimeters, especially in the western United States. Mean seasonal patterns of storm precipitation total, duration, intensity, 30-minute and 15-minute maximum intensity, kinetic energy, erosivity, and the numbers of storms also were mapped for the conterminous United States. These analyses showed distinct patterns of precipitation change with seasons and identified regions of strong gradients where climate change first may be noticed. Trend analyses of storm precipitation variables over the 1971-1999 period indicated the lack of temporal stationarity of storm characteristics. Storm duration changes were especially an important cause of the observed changes in storm precipitation totals. However, storm trends in 30-minute maximum intensity seemed to be more important in changing the patterns of storm erosivity. Examination of storm characteristic response to interannual and interdecadal variations also indicated that storm characteristics were responding at these time scales to large-scale climate system forcings. In the winter season, atmospheric teleconnections such as the Pacific/North American Pattern and the North Atlantic Oscillation were shown to influence not only storm track positions and the number of storms at a location, but also the characteristics of individual storms. El Nio and La Nia events of the Southern Oscillation (ENSO events) had distinctive impacts on storm variables in every season of the year. Even the Pacific Decadal Oscillation showed a clear effect on storm characteristics, especially in the western United States. The results of R-factors derived from modern data compared to previous R-factors combined with storm characteristic trend and variability studies indicate conclusively that storm precipitation characteristics change sufficiently over time to warrant an evaluation of the necessity to recalculate R-factors on a regular basis.
The Vermilion River and Little Vermilion River watersheds lie in seven counties in east-central Illinois and west-central Indiana. The drainage areas of the Vermilion River and Little Vermilion River at their confluences with the Wabash River are 1434 and 244 square miles, respectively. The Vermilion River meets the Wabash River at river mile 257.4 and has three tributaries: North Fork, Middle Fork, and Salt Fork. The Little Vermilion River is a direct tributary of the Wabash River at river mile 247.8. Lake Vermilion, a 660-acre impounded reservoir located on the North Fork Vermilion River, is the main municipal drinking water supply for the City of Danville, Illinois. The Little Vermilion River is the main tributary for the 63-acre Georgetown Reservoir, the municipal drinking water supply for the community of Georgetown, Illinois. Approximately 88 percent of the watersheds for both rivers are in agricultural production with approximately 5 percent in forest/woodlands and wetlands. The Illinois State Water Survey (ISWS) conducted a two-year watershed monitoring study of the Vermilion River and Little Vermilion River watersheds for the Vermilion River Ecosystem Partnership-Conservation 2000 Ecosystem Program. The purpose was to assist the partnership by establishing a baseline of hydrologic and water quality data to provide a better understanding of the cumulative impacts of future best management practices implemented in the watersheds. The ISWS established a streamgaging station on the Little Vermilion River near Sidell and monitored the hydrology, sediment, and nitrate-nitrogen (nitrate-N) there and at three U.S. Geological Survey (USGS) streamgaging sites in the Vermilion River watershed (Middle Fork Vermilion River above Oakwood, North Fork Vermilion River near Bismarck, and Vermilion River near Danville). Annual sediment loads for the three Vermilion River watershed stations were approximately three times higher than loads at the Little Vermilion station. The Middle Fork station had the highest sediment loads among the three Vermilion River stations for both project years. The North Fork station had the highest annual nitrate-N load for both monitoring years. In general, annual sediment and nitrate-N loads were lower during the first monitoring year, due to below average spring season runoff. Sampling for three pesticides (atrazine, alachlor, and metolachlor) was done on a weekly basis from June to October 2002. Atrazine was the only pesticide detected during this period. The highest level sampled was 20.93 micrograms per liter (and#956;g/L) and, and all others were below 2.65 and#956;g/L.
The United States Environmental Protection Agency (USEPA) National Regional Nutrient Criteria Development Program is developing regional-specific criteria for total nitrogen concentrations in surface waters. These criteria will provide the foundation for states to set total nitrogen standards to remedy impairments caused by nutrient overenrichment and to protect designated uses. Reference conditions representing minimally impacted surface waters will be developed for each ecoregion. All nutrient criteria must be based on sound scientific rationale. The first element of a nutrient criterion identified by USEPA is "... historical data and other information to provide an overall perspective on the status of the resource." The second element includes " ... a collective reference condition describing the current status." A further element requires "... attention to downstream consequences." The USEPA recognizes that nutrient concentrations in surface waters are primarily affected by the rate of weathering and erosion from watershed soils. Human activity can affect on the natural load of nutrient inputs to surface waters through, for example, vegetation disturbance of the vegetation, and addition of nutrient-containing material, such as fertilizer. At the heart of the overenrichment problem are the rates of production and decomposition of organic materials, of which nitrogen is a component. This report provides a contribution to the setting of reference/background conditions for Illinois through the evaluation of the current status of water resources against historical conditions, and some attention to downstream consequences. A particular focus of downstream consequences is hypoxia in the Gulf of Mexico, allegedly caused by the flux of excess nitrogen from the Upper Mississippi, Ohio, and Missouri River Basins. The concept of biogeochemical cycling provides an appropriate and necessary framework for understanding landscape influences on water quality throughout the Illinois River Basin. Changes in the Illinois River Valley and its system of tributary streams and lakes are well recognized, but this is the first attempt to assess in some detail how such changes have affected the aquatic carbon, oxygen, and nitrogen cycles; especially the impact of such watershed changes on the nature and quantity of aquatic nitrogen, as well as on the nitrogen cycle within the terrestrial reservoir. This is seen in the accompanying time line of the estimated nitrogen richness of the Illinois landscape. Scientists studying soils and crops from the mid-19th through mid-20th centuries documented that human activities have greatly altered the natural nitrogen cycle. Cultivation of virgin land typically depleted nitrogen and carbon stored in these reservoirs by about 50 percent in the first 60-70 years of cultivation. Some of this nitrogen was transferred to surface waters and ground waters. The depletion of nitrogen from soils in the Mississippi River Basin was so great that crop yields declined throughout the 19th and early 20th centuries. By mid-20th century, the extensive use of nitrogen fertilizer, improved plant varieties, and agronomic practices increased crop yields. Nitrogen fertilizer also began to replenish some of the large amounts of nitrogen previously removed from the soil. In the 1970s, profound changes occurred in the perception of the natural nitrogen cycle and human modification of that cycle. The nitrogen cycle, and human impacts on it came to be defined in terms of atmospheric nitrogen fixation and the return of nitrogen gases by nitrification/denitrification. The 99 percent of the nitrogen cycle which was otherwise cycled within and between the large soil, sediment, and plant reservoirs were no longer acknowledged. From this new definition of the nitrogen cycle, it was concluded that human activities, especially fossil-fuel combustion and fertilizer use, had doubled the nitrogen cycle and many lands, including much of Illinois, had become nitrogen saturated. Increasing concentrations of nitrate-nitrogen in surface waters were given as evidence of nitrogen saturation and leakage. This new limited edition of the nitrogen cycle became cast in concrete and is referred to in this report as "the new, standing nitrogen-cycle paradigm." This report uses the earlier, scientifically more complete and defensible definition of the nitrogen cycle, which includes recognition of the magnitude and importance of soil-plant reservoirs and exchanges. It uses extensive scientific documentation of major changes in ecosystems and soil nitrogen that have occurred over centuries, to place into perspective the present status of nitrogen resources -- as required by USEPA. This report examines the impact on nitrogen concentrations in surface waters in Illinois during occupation of the land by Native Americans, bison, and many other animals and birds. Theoretical impacts are complemented by written accounts of early settlers and scientific observations made under similar conditions. It is concluded that the landscape and surface waters were more nitrogen saturated at this time than today. These pre-European-settlement conditions were selected as the reference/background conditions. Just prior to and during the period of early European settlement, the populations of Native Americans and bison were eliminated and the landscape became less nitrogen saturated. Nevertheless, even in the 1820s, the Illinois River was hypertrophic, i.e. nutrient overenriched. As late as the 1850s, the amount of eroded soil transported by the Mississippi River was more than twice that transported in recent decades. Since soil erosion is reported to be the major sort of N delivery from agricultural lands, the N load in the Mississippi River was declining. The average annual concentration of total nitrogen in the Lower Illinois River in 1894-1899 was 3.68 mg N/l, and additional large amounts of nitrogen not measured were stored in plankton and luxuriant aquatic vegetation and transported downstream in copious amounts of organic debris. Allowing for the unmeasured flux of nitrogen as plankton and for low flow, the adjusted average annual concentration of total nitrogen in the Lower Illinois River in 1894-1899 is estimated to have been about 5.5 mg N/l. This report also examines the impact of European settlement and agriculture on the nitrogen cycle and water quality. Scientific data show that the average concentration of total nitrogen in the Lower Illinois River increased to about 10 mg N/l by mid-20th century and subsequently decreased to 4.8 mg N/l in the 1990s. The annual concentration of nitrate in the Lower Illinois River peaked at about 6.2 mg N/l in 1967-1971 and subsequently decreased to about 3.8 mg N/l in 1993-1998. These improvements in water quality are associated with an increasing amount of dissolved oxygen in the river. The reductions in the concentrations of all forms of nitrogen are attributable to both point- and nonpoint-source pollution control. The main conclusions of this report are that, in establishing scientifically sound reference/background conditions, it is necessary to quantify in a common unit all forms of nitrogen (in solution, as solids, and as gases; and organic and inorganic forms) and all sources, reservoirs, transformations, and fluxes of nitrogen in a common unit; and to understand interactions between nitrogen and other biogeochemical cycles of, for example, water, oxygen, carbon, and phosphorous. Criteria for setting nitrogen standards must recognize the great complexity of the nitrogen cycle and its interdependence with other variables, cycles, and anthropogenic influences.
The Cache River located in the southernmost part of Illinois flows through an area containing the Cache River Wetlands. These unique and important wetlands were designated as a Ramsar Site in 1996. Drainage activities divided the Cache River in half in the early 1900s, effectively separating the river into the Upper and Lower Cache Rivers. The Lower Cache River contains a remnant of a vast wetland system called the Lower Cache River State Natural Area (LCRSNA), commonly referred to as Buttonland Swamp. Sediment inflow from several tributary streams has an impact on the wetland. Previous research has determined that 217,000 tons of sediment were deposited in Buttonland Swamp between 1986 and 1988. The wetlands of the Lower Cache River have been targeted for preservation and restoration by state, federal, and private environmental organizations. A program to monitor the sediment deposition rate within the wetland area at regular intervals would be useful in evaluating and guiding preservation and restoration efforts. This project established a benchmark measure of the deposition rates and cross-sectional profiles at selected locations in the LCRSNA wetland.
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.
Soil organic carbon (SOC) sequestration is important to climate change and cropland agriculture. Crops naturally use the greenhouse gas, carbon dioxide (CO2), from the atmosphere; the greater the crop productivity, the greater the amount of CO2 used. Agronomic practices that enhance sequestration of crop biomass in soil as SOC also enhance removal of CO2 from the atmosphere, and improve and sustain soil fertility. To effectively reduce the concentration of CO2 in the atmosphere and mitigate climate change, sequestration of SOC must be long term, defined as decades or longer. This report presents a review and synthesis of scientific understanding of SOC sequestration, based on the history and genesis of soils and vegetation in Illinois, and the response of SOC and crops to agronomic practices. Recommendations for future cropland SOC research are made. The scientific literature is reviewed in light of the Illinois conditions affecting the five interactive soil-forming factors that are widely recognized (biology, parent material, climate, topography, and time). The literature also shows that human activity can be considered a sixth soil-forming factor. Native American land-use practices of whole ecosystem manipulation were important in governing soil formation and SOC contents in Illinois, as were the land-use practices of the settlers who displaced them. An important finding of this work is that to reduce the atmospheric CO2 content and sustain cropland agriculture, SOC must be sequestered throughout the soil profile. The modern literature reports SOC increases when tillage is changed from conventional to conservation tillage practices. However, SOC measurements are surficial, usually no more than the top 30 cm, with most of the C being sequestered in the top 15 cm. The unstated assumption in the modern literature is that surficial SOC changes represent all the SOC changes in the soil profile. This work shows that the SOC losses in the deeper soil layers may overwhelm surficial SOC increases. In order to assert that C is being sequestered in the soil, the whole-soil profile must be considered. It is recommended that future research into SOC sequestration be conducted from a whole-plant/whole-soil perspective in a soil genesis context using the following strategies. Mine the Literature. Most of the literature needed to provide the requisite whole-plant/whole-soil perspective and soil genesis context is scattered and not organized, summarized, or synthesized in the current SOC sequestration literature. The evolution of SOC sequestration research has been a narrowing of perspective away from the more holistic whole-plant/whole-soil perspective of the foundational agronomic literature to the perspective of the near-surface soil layer. This vast foundational literature needs to be located, restored, and incorporated with the current literature on crop rhizosphere and C and nutrient cycles throughout the whole-soil profile, soil genesis, soil fertility, subsoil amelioration, and other literatures to be organized, summarized, and synthesized into the SOC sequestration literature. Long-term Whole Plant/Whole Soil Monitoring and Assessment. Assessment of the effects of agronomic practices on SOC must be expanded to include the whole-soil profile. Improved estimates of presettlement soil SOC contents are needed to better assess SOC loss and SOC sequestration potential of Illinois' prairie and forest soils. The magnitude and swiftness with which natural factors govern SOC contents need to be better identified and quantified while incorporating a more comprehensive definition of soil aging along with consideration of presettlement and postsettlement anthropogenic landscape management practices as soil-forming factors. SOC Sequestration Research. Finally, research on how agronomic practices can increase SOC throughout the soil profile needs to be conducted from a whole-plant/whole-soil perspective in a soil genesis context. This report indicates that the optimal way to sequester SOC is to convert land back to native prairie, burn frequently, add fertilizers, and remove anthropogenic surface and subsurface drainage. Such an approach is not practical. Constraints on optimizing cropland SOC sequestration include: 1) the need to maintain good soil drainage in Illinois soils for timely spring planting that allows for growth of long-season corn hybrids and soybean varieties; and 2) maintaining soil-nutrient levels that do not result in water-quality issues. Within these constraints, the authors hypothesize that SOC sequestration can best be done by 1) developing balanced soil-fertility programs and other agronomic practices that restore soil nutrients to levels optimum for plant growth, promote movement of plant nutrients throughout the root zone using organic and/or inorganic carriers, and promote deep rooting of plants with minimal mechanical disturbance of the soil by tillage; and 2) developing chemical pest control programs that minimize the effects of pesticides on soil bacteria, and microfauna and macrofauna, thus promoting conversion of biomass to SOC, pedoturbation and net movement of SOC through the soil profile, and creation of soil structure and aggregation that optimize biomass production and conversion to stabilized SOC. Research on the development of these practices must include evaluation of nutrient movement into ground and surface waters. Losses of SOC have occurred on the order of the century time scale. SOC sequestration and the measure of its success (permanence of SOC sequestration) are also necessarily measured on the order of the century time scale. Therefore, long-term (20- to 30-year) agronomic SOC sequestration research at both the farm and individual plot level needs to be designed and conducted for hypothesis and model testing, as well as evaluation of the permanence of SOC in the surface and whole-soil profile. Even longer term research needs to be designed and conducted for hypothesis refinement and for monitoring.
This report presents extensive information from recently published findings related to the following two critical questions about climate change: andlt;ULandgt; andlt;LIandgt;What will the future climate be like? andlt;LIandgt;What will the effects be, both good and bad? andlt;/LIandgt;andlt;/ULandgt;Chapter 1 introduces the two main chapters of the report that provide insights to the above two critical questions about climate change. Chapter 2 provides examples from a wide spectrum of scientists, scientific organizations, and the media of contradictions and confusion about whether human-induced climate change is predictable over the time scale of a century. It then explains why such climate change is unpredictable in the traditional deterministic sense. It describes the climate system and documents improvements and remaining uncertainties of global climate models relevant to evaluating human-induced climate change on the century time scale. Climate measurements in Illinois since the mid-19th century document major climate swings not evident in a 50- to 100-year record. Illinois is no warmer or wetter today than it has been over the last 150 years, and extreme precipitation events across the country are reported to be no more frequent than they were a century ago. Important conclusions from these data are that i) regional climate trends over the past 50-100 years that are consistent with theoretical expectations of an enhanced greenhouse effect (for example, higher precipitation and more heavy rainfall events in northern mid-latitudes) do not necessarily establish causality; and ii) global warming has not resulted in warming in all parts of the globe. Chapter 3 focuses on the issue of economic impacts of weather and climate in the United States (US). The first section addresses known financial impacts of recent (1950-2000) weather and climate conditions. Descriptions follow of temporal trends of weather and climate extremes and their impacts, causes for on-going increases in economic impacts, and estimates of future financial impacts under a changed climate. The frequency of most types of storms and droughts either has not changed or has decreased during 1940-2000. Yet, losses (1997 dollars) for most storm types have increased over time. Possible causes for increased losses include a shift in climate related to global warming, questionable insurance practices, and aging infrastructure. Study also shows increasing losses due to societal factors, including population growth, more people residing in more weather vulnerable areas, shifts in business-product development that are weather sensitive, and growing wealth. Various studies of weather- and climate-induced economic impacts were used to develop national loss and gain estimates. Projections for the US, depending upon varying assumptions about the future climate (combinations of warmer, wetter, drier, or more storms), show annual climate-related losses ranging from $2 billion to $69 billion, and others estimate annual gains of $30 billion to $40 billion. In all cases, the projected outcomes are small in relation to the expected Gross Domestic Product.
The Illinois State Water Survey (ISWS), under contract to the Imperial Valley Water Authority (IVWA), has operated a network of rain gauges in Mason and Tazewell Counties since August 1992. The ISWS also established a network of groundwater observation wells in the Mason-Tazewell area in 1994. These networks are located in the most heavily irrigated region of the state. The region's major source of water for irrigation and municipal, industrial, and domestic water supplies is groundwater pumped from thick sand-and-gravel deposits associated with the confluence of two major ancient river valleys, the Mississippi and the Mahomet-Teays. Recent extreme weather events (e.g., the drought of 1988 and the great flood of 1993) resulted in large fluctuations in groundwater levels in the Imperial Valley area. The rain gauge network and the groundwater observation well network collect long-term data to determine the rate of groundwater level decline in dry periods and during the growing season, and the rate of groundwater level recovery during recharge periods. This report presents data accumulated from the rain gauge and observation well networks since their inception through August 2001. Precipitation is recorded continuously at 20 rain gauges for each storm that traverses the Imperial Valley. Groundwater levels at the 13 observation wells are measured the first of each month. The database from these networks consists of nine years of precipitation data and seven years of groundwater observations. At the beginning of groundwater observations in late 1994, the water levels were at their highest in the seven years of observation. These high groundwater levels were the result of the very wet 1992-1995 period when annual precipitation was above the 30-year normals at both Havana and Mason City. From September 1995-August 1997, precipitation in the region was well below the 30-year normal followed by the 1997-1998 and 1998-1999 observation years with rainfall totals slightly above and slightly below normal, respectively. Groundwater levels in the observation wells reflected the multi-year rainfall patterns, showing a general downward trend during dry years, a recovery in wet 1997-1998, and a leveling off in near-normal 1998-1999, followed by declines in dry 1999-2000. Despite a dry July, near-normal precipitation in 2001 brought a return to more typical seasonal hydrographs. This report includes new regression analyses of data collected through August 2001, similar to regression analyses first conducted on data collected through August 1998. The analyses indicate that groundwater levels are affected by precipitation in the Imperial Valley area and, for wells close to the Illinois River, by river stage. Generally, water levels in wells follow antecedent precipitation and Illinois River stage by one to two months; e.g., a high correlation between June groundwater levels and the Illinois River stage or precipitation that occurs in April or May. However, additional data collected since 1998 did not improve the results of the regression analyses. In fact, coefficients of determination for many regressions worsened. This suggests that regressions of observed groundwater levels versus river stage and precipitation are not adequately describing all the variables affecting groundwater levels. Using the data collected to verify, test, and improve the existing Imperial Valley groundwater flow model is highly recommended. Continued data collection also is recommended to create long-term data sets of precipitation and groundwater levels for use in modeling analyses. Collection of additional groundwater level and irrigation pumpage data also is highly recommended.
A detailed climatological study of all severe winter storms occurring in Illinois during the 1900-1960 period has been pursued to obtain extensive information concerning these frequently quite damaging snow and ice storms. This study provides information that enlarges our knowledge of the basic climatological aspects of winter storms, statistics concerning the amount and types of damage they produce, descriptions of the meteorological conditions producing these storms, and data helpful in the design and planning for these events.