Organization | • | Illinois State Water Survey | [X] |
| | | | Title: | | | | | Volume/Number: | 2003 | | | | Issuing Agency: | | | | | Description: | Levels of Lakes Superior, Michigan-Huron, and Erie were assessed to identify key temporal fluctuations in their averages and extreme values during the 1861-2001 period. Behavior of levels of Lakes Michigan-Huron and Superior since 1861 has included vastly different long-term distributions, differences in amount of variability over time, and differences in occurrence times of their record-high and low levels. Record high or low 15-year periods were present on one or more lakes in 64 years, and record events based on 25-year periods were present in 96 of 141 years, both representative of records during a much longer period than if the record events had occurred simultaneously on all lakes. These lake-level differences reflect significant differences in climate conditions between basins, and principally precipitation over time. There were two eras when levels of all lakes exhibited exceptional variability and extreme high and low levels, 1923-1938 and 1973-2001, reflecting considerable climatic instability over the entire Great Lakes basin. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | CR-2003-09 | | | | ISL ID: | 000000000875 Original UID: 999999994414 FIRST WORD: Temporal | |
| | | Title: | | | | | Volume/Number: | 2005 | | | | Issuing Agency: | | | | | Description: | Deep bedrock aquifers in northeastern Illinois are an important source of drinking water, but there is evidence of temporal increases in concentrations of dissolved contents in the groundwater. Large groundwater withdrawals may be inducing groundwater movement from adjacent units or downdip areas containing high concentrations of dissolved solids. Archived data were used systematically to examine temporal trends in water-chemistry data for deep bedrock aquifers in northeastern Illinois. Most data suggest that concentrations of major ions and total dissolved solids (TDS) are not increasing in wells open to deep bedrock aquifers in most of northeastern Illinois. There are some locations where concentrations of some ions and TDS are increasing, including the major pumping centers at Joliet and Aurora, however. The increasing concentrations may be affected by aquifer geology. Increasing trends are more likely in wells open to deep Ordovician aquifers than in wells open only to deeper Cambrian aquifers or open to shallower Ordovician aquifers. There also appears to be some areal control on water-chemistry changes. Most of the positive trends occurred in the southern twothirds of the study area. Correlating withdrawal rates with water-chemistry data is problematic due to data limitations, but withdrawal rates do not appear to influence water chemistry of most wells for which data were available. | | | | Date Created: | 6 7 2005 | | | | Agency ID: | CR-2005-05 | | | | ISL ID: | 000000000909 Original UID: 999999994455 FIRST WORD: Temporal | |
| | | Title: | | | | | Volume/Number: | 2003 | | | | Issuing Agency: | | | | | Description: | Temporal fluctuations in the annual and summer precipitation across the Midwest during the 1898-2002 period are defined and described. Precipitation amounts were assessed for 15-year periods to show how patterns of precipitation have shifted spatially over the 20th Century. The early part of the century featured near average precipitation conditions, followed by predomi-nately dry conditions from 1928 through 1957. For example, during 1928-1942, 96 percent of the Midwest had below average precipitation. After 15 years with near average conditions from 1958 to 1972, extremely wet conditions developed during 1973-2002, with 91 percent of the Midwest experiencing above average precipitation. Extreme precipitation values sampled during each 15-year period revealed temporal differences with much more extreme amounts during wet and dry periods than during near average periods. Annual totals reflected the long-term variations in summer rainfall, revealing the importance of summer rainfall in determining annual amounts. Regionally, amounts were below average more frequently in the southern Midwest than in the central and northern Midwest. Values were above average more frequently in the northern Mid-west than in the central and southern Midwest. The results provide information that should be useful for hydrologic and agricultural planning and assessments. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | DCS-2003-01 | | | | ISL ID: | 000000000903 Original UID: 999999994402 FIRST WORD: Temporal | |
| | | Title: | | | | | Volume/Number: | 1990 | | | | Issuing Agency: | | | | | Description: | 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. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | C-173 | | | | ISL ID: | 000000000763 Original UID: 999999993833 FIRST WORD: Time | |
| | | Title: | | | | | Volume/Number: | 2003 | | | | Issuing Agency: | | | | | Description: | 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. | | | | Date Created: | 9 24 2004 | | | | Agency ID: | DCS-2003-02 | | | | ISL ID: | 000000000904 Original UID: 999999994405 FIRST WORD: Two | |
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