!! v_o_lu_rn_e_2_ • Water Resources
.SHAWNEE AREA ASSESSMENT
':I ~~ DEPARTMENT Of NATURAL RESOURCES SHAWNEE AREA ASSESSMENT
VOLUME2: WATER RESOURCES
Illinois Department of Natural Resources Office of Scientific Research and Analysis Illinois State Water Survey 2204 Griffith Drive Champaign, Illinois 61820 (217) 244-5459
October 2002
Illinois Department of Natural Resources 'One Natural Resources Way Springfield, U1inois 62702-1271
100 Printed by the authority of the State of lllinois ' Other CTAP Publications
Assessments are also available for the following regions: Big Muddy River La Moine River Cache River Lower Des Plaines River Calumet Area Lower Sangamon River Chicago RiverlLake Shore Lower Rock River Driftless Area Mackinaw River Du Page River Prairie Parklands Embarras Ri ver Sinkhole Plain Fox River Spoon River Illinois Big Rivers Sugar-Pecatonica Rivers Illinois Headwaters Thorn Creek Illinois River Bluffs Upper Des Plaines River Kankakee River Upper Rock River Kaskaskia River Upper Sangamon River Kinkaid Area Vermilion River Kishwaukee River Vermilion River (Dlinois River Basin)
Also available: Critical Trends Assessment Program 200i Report Critical Trends in l/linois Ecosystems l/linois Land Cover, An Atlas, plus CD-ROM inventory ofEcologically Resource-Rich Areas in l/linois l/linois Geographic information System, CD-ROM of digital geospatial data
All CTAP and Ecosystems Program documents are available from the DNR Clearinghouse at (217) 782-7498 Or TTY (217) 782-9175. Selected publications are also available on the World Wide Web at http://dnr.state.il.us/orep/inrinlctap, or http://dnr.state.il.us/orep/c2000.
For more information about CTAP, call (217) 524-0500 or e-mail [email protected]; for information on the Ecosystems Program call (217) 782-7940 or e-mail [email protected].
Equal opportunity to participate in programs of the Illinois Department of Natural Resources (IDNR) and those funded by the U.S. Fish and Wildlife Service and other agencies is available to all individuals regardless ohace, sex, national origin, disability, age, religion or other non-merit factors. If you believe you have been discriminated against, contact the funding source's civil rights office and/or the Equal Employment Opportunity Officer. IDNR, One Natural Resources Way, Springfield, Ill. 62702-1271; 2171785-0067; TTY 2171782-9175. This infonnation may be provided in an alternative format if required. Contact the DNR Clearinghouse at 217/782-7498 for assistance. About This Report
The Shawnee Area Assessment, part of a series of statewide regional assessments, examines approximately 623 square miles in southeastern Illinois. The report provides information on the natural and human resources of the area as a basis for managing and improving its ecosystems. The development of ecosystem-based information and management programs in Illinois are the result of three processes - the Critical Trends Assessment Program, Conservation Congress, and Water Resources and Land Use Priorities Task Force.
Background
The Critical Trends Assessment Program (CTAP) documents changes in ecological conditions. In 1994, using existing information, the program provided a baseline of ecological conditions.] Three conclusions were drawn from the baseline investigation:
1. the emission and discharge of regulated pollutants over the past 20 years has declined, in some cases dramatically, 2. existing data suggest that the condition of natural ecosystems in lllinois is rapidly declining as a result of fragmentation and continued stress, and 3. data designed to monitor compliance with environmental regulations or the status of individual species are not sufficient to assess ecosystem health statewide.
Based on these findings, CTAP has begun to develop methods to systematically monitor ecological conditions and provide information for ecosystem-based management. Five components make up this effort:
1. identify resource rich areas, 2. conduct regional assessments, 3. publish an atlas and inventory of Illinois landcover, 4. train volunteers to collect ecological indicator data, and 5. develop an educational science curriculum that incorporates datacollection
At the same time that CTAP was publishing its baseline findings, the Illinois Conservation Congress and the Water Resources and Land Use Priorities Task Force were presenting their respective findings. These groups agreed with the CTAP conclusion that the state's ecosystems were declining. Better stewardship was needed, and they determined that a voluntary, incentive-based, grassroots approach would be the most appropriate, one that recognized the inter-relatedness of economic development and natural resource protection and enhancement.
I See The Changing Illinois Environment: Critical Trends, summary report and volumes 1-7.
111 From the three initiatives was born Conservation 2000, a program designed to reverse ecosystem degradation, primarily through the Ecosystems Program, a cooperative process of public-private partnerships that merge natural resource stewardship with economic and recreational development. To achieve this goal, the program provides financial incentives and technical assistance to private landowners.
At the same time, CTAP identified 30 Resource Rich Areas (RRAs) throughout the state. In RRAs and other areas where Ecosystem Partnerships have been formed, CTAP is providing an assessment of the area, drawing from ecological and socio-economic databases to give an overview of the region's resources - geologic, edaphic, hydrologic, biotic, and socio economic. Although several of the analyses are somewhat restricted by spatial and/or temporal limitations of the data, they help to identify information gaps and additional opportunities and constraints to establishing long-term monitoring programs in the partnership areas.
Shawnee Area
The Shawnee Area is roughly defined as that portion of the Shawnee Hills located in Hardin and Pope counties and the eastern third of Johnson County, as well as small portions of Massac, Saline, and Gallatin counties. The 623-square-mile-area includes the Illinois watersheds that drain into the reach of the Ohio River between its confluence with the Saline River (near Saline Landing, IL) and Hamletsburg, IL, and the watersheds of two tributaries that drain into the Saline River: the Little Saline River and Rock Creek. It falls within the physiographic region called the Shawnee Hills Section. While most of the land is rugged hills, broad bottomlands are located along Bay Creek and, to a lesser extent, along the Ohio River.
This assessment is comprised of four volumes. In Volume 1, Geology discusses the geology, soils, and minerals in the assessment area. Volume 2, Water Resources, discusses the surface and groundwater resources and Volume 3, Living Resources, describes the natural vegetation communities and the fauna of the region. Volume 4 contains two parts: Part I, Socio-Economic Profile, discusses the demographics, infrastructure, and economy of the area; and Part II, Environmental Quality, discusses air and water quality, and hazardous and toxic waste generation and management in the area.
iv ------
t 1
Scale 1:2700000
Drainage basins from 1:24000 scale watershed boundaries as delineated bV the U.S.G.S. Water Resources Division.
Major drainage hasins ofIllinois and location of the Shawnee assessment area j~--? Cre;,l J;' I ;, Springsr_ i, .j Stonefon/ -~J r~Lake of 1_.1;; ,\/'" gyp' "'W..l1L~~Ncol ~ -. J P:; l I
---'--, \ \'1, !r::: ;\:!. " t') n :J Cave-in j \~ Rock rJ~ .bv~ i/ ~~ L~r \~Vienna Q ~v( ,I ~o"" r _ G...,..) _ ~ ;l)\ .... MASSACCO. I N .~ ~ 1, i ~'~. o 15 Miles i I . r-: 1I 20 Kilomeler>; ..::?,, .., ~, 1 - New " '~'c" \ Uberry Z ". I I 1J1..I Metropoi;s ''--~ '" I) Brookporr '" I ~-~ Subbasins in the Shawnee Assessment Area. Subbasin boundaries depicted are those determined by the Illinois Environmental Protection Agency. Contributors Project Coordinator Nani Bhowmik Report Coordinators Linda Dexter, Becky Ho~ard , Maps Kathleen Brown Introduction Rivers and Streams, Lakes, Physiography Michael Myers, H. Vernon Knapp Wetlands Michael Miller, Liane Suloway, Laura Keefer' Land Use Laura Keefer, Sandy Jones Climate and Trends in Climate James Angel Streamflow H. Vernon Knapp, Michael Myers Erosion and Sedimentation Misganaw Demissie, Renjie Xia, William Bogner Water Use and Availability Ground-Water Resources Kenneth Hlinka, Sean Sinclair Surface Water Resources H. Vernon Knapp Ground-Water Quality Kenneth Hlinka, Sean Sinclair, Thomas Holm • Contributor Affiliations: Michael Miller, Illinois State Geological Survey; Liane Suloway, Illinois Natural History Survey; Laura Keefer, minois State Water Survey. VII I .' Table of Contents Introduction 1 Basin Physiography 1 Rivers and Streams ~ .3 Lakes .5 Wetlands 5 Land Use 12 Climate and Trends in Climate 13 Overview 13 Temperature 13 Precipitation 17 Precipitation Deficits and Excesses .20 Severe Weather 20 Tornadoes 20 Hail 20 Thunderstorms 21 Summary 21 Streamflow and Trends in Streamflow 23 Streamgaging Records 23 Human Impacts on Streamflows in the Assessment Area 25 Variability in Annual Streamflows 25 Statistical Trend Analysis 25 Daily and Seasonal Variation in Flows 27 Flooding and High Flows ; 28 .Trend Assessment ~ 29 Seasonal Distribution ofFlood Events · 29 Low Flows and Drought .30 Seven-Day Low Flows 30 Multi-Year Drought Flows 31 Summary 32 Erosion and Sedimentation 33 Instream Sediment Load 33 Sedimentation .36 Water Use and Availability 39 Ground-Water Resources 39 Data Sources ~ .40 Data Limitations ~ .40 Ground-Water Availability .41 2000 Ground-Water Use ,.. .42 Ground-Water Use Trends .43· Surface Water Resources ..43 IX I ,~ Potential for Development of Additional Surface Water Supplies .44 Ground-Water Quality .47 Data Sources .47 Data Limitations 48 Chemical Components Selected for Trend Analysis .49 Aquifer Unit Analysis ..49. Discussion and Results 50 Iron (Fe) 53 Total Dissolved Solids (TDS) 53 Sulfate (S04) 54 Nitrate (N03) 54 Chloride (CI) 55 Hardness (as CaC03) 56 Summary .56 References 59 List of Figures Introduction Figure I. Major Streams in the Shawnee Assessment Area 2 Figure 2. Major Lakes in the Shawnee Assessment Area 6 Figure 3. Wetlands from the National Wetlands Inventory and Quadrangle Map Boundaries for the Shawnee Assessment Area 8 Figure 4. National Wetlands Inventory Information from the Glendale.7.5-minute Quadrangle Maps Showing Wetlands, Deepwater Habitat, and NWI Codes 11 Figure 5. Acreages of Selected Crops in the Shawnee Assessment Area Based on Illinois Agricultural Statistics Data 12 Climate and Trends in Climate Figure 6. Average Annual Temperature for Harrisburg, Illinois, 1901-2001 .14 Figure 7. Annual Number of Days with Maximum Temperatures Equal to Of Above 90°F at Harrisburg, Illinois, 1901-2001 .15 Figure 8. Annual Number of Days with Minimum Temperatures Equal to or Below 32°F at Harrisburg, Illinois, Winters 1901-1902 to 2000-2001..... 16 Figure 9. Annual Number ofDays with Minimum Temperatures Equal to or Below O°F at Harrisburg, Illinois, Winters 1901-1902 to 2000-2001 16· Figure 10. Annual Precipitation in inches for Harrisburg, Illinois, 1901-2001 18 x ~------t Figure 11. Annual Number ofDays with Measurable Precipitation at Harrisburg, Illinois, 1901-2001 : 18 Figure 12. Annual Snowfall at Harrisburg, Illinois, Winters 1901-1902 to 2000-2001 19 Figure 13. Annual Number ofDays with Measurable Snowfall at Harrisburg, Illinois, Winters 1901-1902 to 2000-2001 .19 Figure 14. Annual Number ofDays with Thunderstorms at Paducah, Kentucky, 1901-2001. Missing data occurred from 1965-1969 and from 1982-1984...21 Streamflow and Trends in Streamflow Figure 15. Location ofStreamgages in the Shawnee Assessment Area 24 Figure 16. Average Annual Streamflow for the Gages in and near the Shawnee Assessment Area 26 Figure 17. Flow Duration Curves (Discharge Versus Probability) for Gages in and near the Shawnee Assessment Area 27 Figure 18. Monthly Flow Probabilities for Lusk Creek near Eddyville 28 Figure 19. Annual Peakflows for the Selected Gaging Records 29 Figure 20. Annual 7-Day Low Flows for the Lusk Creek and Cache River Gages 3l Erosion and Sedimentation Figure 2I. Sediment Monitoring Station in the Shawnee Assessment Area 34 Figure 22. Variabilities ofDaily Discharge and Suspended Sediment Concentration and Load for the Lusk Creek near Eddyville (data collected by USGS) ...... 35 Water Use and Availability Figure 23. Potential Reservoir Sites in the Shawnee Assessment Area 45 Xl List of Tables Introduction Table I. Distribution ofLand Slopes for Pope and Hardin Counties .3 Table 2. Major Streams in the Shawnee Assessment Area , .4 Table 3. Significant Lakes and Reservoirs in the Shawnee Assessment Area 5 Table 4. Wetlands within the Shawnee Assessment Area Based on Illinois Wetlands Inventory Data 7 Climate and Trends in Climate Table 5. Temperature Summary for Harrisburg 14 Table 6. Average Annual Temperature during Consecutive 30-Year Periods 15 Table 7. Precipitation Summary for Harrisblrrg 17 Streamflow and Trends in Streamflow Table 8. USGS Continuous Discharge Stations in the Shawnee Assessment Area 23 Table 9. Trend Correlations for Annual Flows 26 Table 10. Trend Correlations for Peakflows 29 Table II. Monthly Distribution of Top 25 Flood Events at Selected Stations 30 Table 12. Trend Correlations for Low Flows .31 Table 13. Drought Flows for the Cache River near Forman; 1914-2000; Average Flow (in cfs) over the Specified Critical Period .32 Erosion and Sedimentation Table 14. Suspended Sediment Monitoring Station within the Shawnee Assessment Area 33 Table 15. Annual Sediment Load for the Shawnee Assessment Area .36 Table 16. Lake Sedimentation Surveys in the Shawnee Assessment Area 37 Water Use and Availability Table 17. Number ofReported Private Wells in the Shawnee Assessment Area ..4l Table 18. Ground-Water Use Trends in the Shawnee Assessment Area .43 Ground-Water Quality Table 19. Chemical Constituents Selected for Trend Analysis, Unconsolidated Aquifer Systems 51 Table 20. Chemical Constituents Selected for Trend Analysis, Bedrock Aquifer Systems 52 xii r . ~, Introduction The Shawnee AssessmentArea, shown in Figure 1, is roughly defined as that portion of the Shawnee Hills located in Hardin and Pope Counties and the eastern third ofJohnson County in southeastern Illinois. Specifically it includes those watersheds in Illinois that drain into the reach ofthe Ohio River between its confluence with the Saline River (near Saline Landing, IL) and Hamletsburg, IL, and also includes the watersheds of two tributaries that drain into the Saline River: the Little Saline River and Rock Creek. The assessment area encompasses approximately 623 square miles. In addition to Hardin, Pope, and Johnson Counties, the assessment area includes small portions of Massac, Saline, and Gallatin Counties. The portion of the Ohio River that is located on the border of the assessment area is roughly 56 miles in length and falls within the two pools ofthe river fonned by the Smithland Lock and Dam near Hamletsburg, IL, and Lock and Dam 52 near Brookport, IL. During low and medium flow conditions, the dams maintain relatively constant water levels in the Ohio River and provide sufficient depth in the navigation channel of the river for use by commercial navigation. The assessment area is rural, with a total population of approximately 12,000. The largest community is Rosiclare, located in the southwest comer ofHardin County, with a population of 1,213 people (Illinois Department Commerce and Community Affairs, 2001). There are no other communities with populations of 1,000 or greater within the assessment area. The population ofthe region has not changed substantially in recent decades. The long-tenn mean annual precipitation for the assessment area, as detennined from records over the last 60 years, is roughly 48 inches. The corresponding average annual streamflow is about 18 inches. Basin Physiography The Shawnee Assessment Area falls within the physiographic region called the Shawnee Hills Section, as described by Leighton et al. (1948). The topography of the region is greatly contrasting. Most of the land is rugged hills, described by Leighton el al. as a "complex and dissected upland." In contrast is the broad bottomlands that are located along gay Creek and, to a lesser extent, along the Ohio River. The predominant hills portion of the assessment area is greatly dissected by streams, with most of the land in steep slopes and only small patches offlat upland. Erosion is very active along both the steep-walled valleys and the upland areas. A few features are also present in the area, such as at Cave-in-Rock, located in Hardin County. Across the northern part of the assessment area, running east to west, is a continuous ridge that 1 I Streams Boundary N t Scale 1:500,000 5~i"""".....-.l0~""""""""~5iiiiiiiiiiiiiiiOOiiil10 Miles Figure 1. Major Streams in the Shawnee Assessment Area. 2 r I contains the highest elevations in the region and rises 300 feet above the relatively flat lowlands in the Saline River watershed to the north of the assessment area. The most prominent lowland in the region is along Bay Creek, in south-central Pope County, which ranges from I Y, to 2Yz miles wide. This is the remnant ofthe ancient Ohio River floodplain that existed prior to the last glacial age when the Ohio River flowed through this lowland and farther west in the valley now occupied by the Cache River. It . is believed that the Ohio River was forced to the south when the Mississippi River was clogged with sediment from glacial outwash, causing the Ohio River to pool and break through a low divide to form its present course. Throughout the assessment area, the width ofthe Ohio River floodplain on the Illinois side is very narrow, typically less than 500 feet wide, and in many areas with bluffs rising from near the rivers edge. In other stretches, such as near Rosiclare, east of Cave-in Rock, and near Hamletsburg, the floodplain widens to more than Yz mile wide. Table I shows the variability ofland slopes for the area, as given for Pope and Hardin Counties. The land in Hardin County is particularly representative ofthe hilly uplands with bluffs along the Ohio River. In the heart ofthe Shawnee forest, elevations average around 700 feet msl where in some spots, elevations can exceed well over 800 feet ms!. Meanwhile, in the Southern part ofthe Shawnee Assessment Area, elevations tend to average about 425 feet. The maximum elevation in the assessment area is approximately 1,064 feet msl at Williams Hill, located approximately 2 miles west ofHerod, IL in the northeast corner ofPope County. The minimum is 302 feet msl, which is the normal pool elevation ofthe Ohio River in pool 19 near Hamletsburg, IL. Table 1. Distribution of Land Slopes for Pope and Hardin Counties Source: Runge et.1. (1969) Percent of land in slope category Slo e Po e County Hatdin COUll 0- 2 % 14.8 10.2 2 - 4 11.8 4.3 4· 7 17.9 12.6 7 -12 23.3 18.1 12 -18 15.6. 23.7 18 -30 11.2 22.8 >30 5.4 8.4 Rivers and Streams There are about 1,168 miles ofrivers and streams in the Shawnee Assessment Area, as identified by I :250,000 scale topographic mapping. Larger streams (those with watersheds greater than 10 square miles) account for about 24 % ofthis total, or 3 -- _._------ approximately 275 river miles (Healey, 1979). The four largest streams in the assessment 2 2 area are Bay Creek, with a drainage area of225 square miles (mi ), Lusk Creek (88 mi ), 2 2 Big Grand Pierre Creek (60 mi ), and Big Creek (42 mi ). These streams are located in Figure 1. Other major tributaries having drainage areas in excess of20 square miles are listed in Table 2. The average channel slopes ofthe streams in the Shawnee Assessment Area are very high when compared to other areas of Illinois. The largest streams have channel slopes averaging between 6 to 12 feet per mile (ft/mi). In general, the slopes ofthe streams are highest in their headwater areas, with slopes decreasing farther downstream to where the lower reaches on the largest streams have fairly gentle slopes. In the northern section of the Shawnee Assessment Area, elevations are greater, causing the slopes ofthe streams to be greater. In the southern part ofthe assessment area, the elevations are relatively flatter making the slopes ofthe streams lower. Exceptionally high slopes can occur at the upper headwater areas ofthe streams, with some streams falling more than 100 feet in their first mile. On average, streams that drain a 10 square mile region can be expected to have Channel slopes of about 20 ft/mi. The lowest slopes obviously occur in the lower reaches ofthe major streams, such as Bay Creek and Lusk Creek, where some slopes may be as low as 2 ft/mi. The streams in the Shawnee Assessment Area are generally well developed and incised and have not been altered to a great degree by channelization or dredging. The major exception is the creation ofBay Creek Ditch, that bypasses 10 miles ofBay Creek in Pope County, along the low-gradient bottomland reach ofthat stream. Short reaches in . other streams, such as Sugar Creek, have also been channelized. From data given in Mattingly and Herricks (1991), it is estimated that roughly 30 stream miles in the assessment area have been modified through channelization. Table 2. Major Streams in the Shawnee Assessment Area Drainage area Stream Name Counties (sq mi) Tribut to Bay Creek Pope, Johnson 225 Ohio River Lusk Creek Pope 88 Ohio River Big Grand Pierre Creek Pope 60 Ohio River Big Creek Hardin 42 Ohio River Cedar Creek Johnson 39 Bay Creek Little Saline River Saline, Pope, Johnson 32 Saline River Rock Creek Hardin 26 Saline River Hayes Creek Pope 24 Bay Creek Barren Creek Pope 22 Ohio River Sugar Creek Pope 21 Bay Creek Dog Creek Pope, Massac 20 Ohio River 4 Lakes The Shawnee Assessment Area has 23 lakes with a surface area of at least 20 acres, with a total surface area of 1,490 acres. The location ofthese lakes is shown in Figure 2. Selected larger lakes are listed in Table 3. Many ofthese larger lakes are natural wetlands in the bottomland areas along Bay Creek and the Ohio River. Some are seasonal lakes that become wetland areas during dry conditions. The Big Sink, in Hardin County, drains into the underlying limestone during the summer ofmany years, to refill later in the fall or winter (Allen, 197Ia). In addition to the major lakes in the region, there are many other small lakes and ponds. Data from Allen (1970, 1971a, 1971b) suggests that there are approximately 1,800 ponds in the assessment area with surface areas ranging from 0.1 to 6.0 acres. Most ofthe lakes and ponds in the assessment area provide recreational and conservation functions. The Vienna Correctional Center Lake also serves as a water supply source. Table 3. Significant Lakes and Reservoirs in the Shawnee Assessment Area Surface area Name County (acres) T e oflake Bell Pond Johnson 229 Bottomland Round Pond Massac 206 Bottomland Big Sink Hardin 171 Natural sink Black Slough Pope 138 Bottomland Lake Glendale Pope 86 Impoundment Bay Creek impoundment north of Glendale Pope 77 Impoundment Hohman Lake Massac 74 Bottomland Vienna Correctional Center Lake Johnson 74 Impoundment Sugar Creek Lake Pope 68 Impoundment Wetlands Wetlands are an important part ofour landscape because they provide critical habitat for many plants and animals and serve an important role in mitigating the effects of storm flow in streams. They are also government regulated landscape features under Section 404 ofthe Clean Water Act. In general, wetlands are a transition zone between dry uplands and open water; however, open water areas in many upland depressional wetlands are dry at the surface for significant portions ofthe year. The Shawnee Assessment Area has about 4.5% (17,836 acres) ofits total area in wetlands (Table 4). Figure 3 shows that the wetlands in the assessment area are mostly confined to the river and stream floodplain areas and are dominated by Palustrine Forested 5 j _ Lakes Boundary 1. Bell Pond 2. Round Pond 3. Big Sink 4. Black Slough 5. Lake Glendale 6. Bay Creek 7. Hohman Lake 8. Vienna Correction Center Lake 9. Sugar Creek Lake Scale 1:500,000 o 5 Figure 2. Major Lakes in the Shawnee Assessment Area. 6 Table 4. Wetlands within the Shawnee Assessment Area Based on Illinois Wetlands Inventory Data %of %of Wetland Assessment Cate 0 Acrea e Area Area Palustrine Wetlands Shrub-Scrub Wetlands' 1,094.53 6.1 0.3 Forested Wetlands Bottomland Forest 12,051.14 67.6 3.0 Swamp 1,079.09 6.1 0.3 Emergent Wetlands Shallow MarshlWet Meadow 1,254.07 7.0 0.3 Deep Marsh 212.26 1.2 0.1 Open Water Wetlands 1,800.39 10.1 0.5 Subtotal Palustrine' 17,491.48 98.1 4.4 Lacustrine Wetlands Shallow Lake 78.24 0.4 0.0 Lake Shore 56.66 0.3 0.0 Emergent Lake 0.00 0.0 0.0 Subtotal Lacustrine 134.90 0.8 0.0 Riverine Wetlands Perennial Riverine 2.20 0.0 0.0 Intermittent Riverine 207.52 1.2 0.1 Subtotal Riverine 209.72 1.2 0.1 Total Wetlands 17,836.10 100.0 4.5 Note: 'Subtotal of shrub-scrub, forested, emergent, and open water wetlands categories. Ninety eight percent ofthe total wetlands mapped in the assessment area, by the National Wetlands Inventory, are classed as Palustrine with Forested Bottomland (67.6%) dominating the subcategories. The remaining wetlands in this class are Shrub Scrub (6.1 %), Swamp (6.1 %), and Emergent, Shallow MarshlWet Meadow (7.0%) with Deep Marsh (1.2%) and Open Water Wetlands (10.1 %). The other categories ofwetlands in the assessment area are Lacustrine (0.8%), and Riverine (1.2%). (For wetland categories, see the table describing wetland and deepwater habitat in Volume 3: Living Resources.) The wetland resources ofthe Shawnee Assessment Area was generally confined to the river and stream bottom lands. This is largely the result ofnatural characteristics ofthis region. Inspection ofthe glacial geology (Figure 6, Volume 1) and the topography (Figure 8, Volume 1) shows a landscape that is highly dissected, with thin soil material over bedrock. This generally only leaves the valley bottoms as areas where wetlands can be naturally sustained., 7 I ,..:( - 'l~ ~ . ~ , \ is·' -- 's, ? \JiZ " J' (1,/1 ,/ rl p ; ~' ~. ,L ~/,l~ "\' ( QJ I:t. ) ., HERODg( K~E~S RIDGE ., r' ::P,' I " \.J~ ~ ' ( \! (" I ":1 '' REPTON il.~l I ,1 '. "l'tl..f..-...if SHETLERVILLE I ROSICLARE CAVE IN ROCK 00 ! r Scale J 355000 o 15 Mile' Brookpo; o 20 Kilom<:!CJ!; Figure 3',~ Wetlands from the National Wetlands Inventory and quadrangle map boundaries for the Shawnee Assessment Area. The inset area is depicted in the following figure. J The hydrogeology ofwetlands allows water to accumulate in them longer than in the surrounding landscape, with far-reaching consequences for the natural environment. Wetland sites become the focus oforganisms that require or can tolerate moisture for extended periods oftime, and the wetland itselfbecomes the breeding habitat and nursery for many organisms that require water for early development. Plants that can tolerate . moist conditions (hydrophytes) can exist in these areas, whereas upland plants cannot successfully compete for existence. Given the above conditions, the remaining wetlands in our landscape are refuges for many plants and animals that were once widespread but are now restricted to existing wetland areas.. The configuration of wetlands enables them to retain excess rainwater, extending the time the water spends on the upland area. The effect ofthis retention on the basin is to delay the delivery ofwater to the main stream. This decreases the peak discharges of storm flow or floods, thus reducing flood damages and the resulting costs. It is important to realize that the destruction ofwetland areas has the opposite effect, increasing peak flood flows and thereby increasing flood damages and costs. The location ofwetlands affects many day-to-day decisions because wetlands are considered "Waters ofthe United States" (Clean Water Act) and are protected by various legislation at the local, state, and federal levels (for example, the Rivers and Harbors Act of 1899, Section 10; the Clean Water Act; and the lllinois Interagency Wetlands Act of 1989). Activities by government, private enterprise, and individual citizens are subject to regulations administered by the U.S. Army Corps ofEngineers. Under a Memorandum ofAgreement between federal regulatory agencies with jurisdiction over wetlands, the Natural Resources Conservation Service takes the lead in regulating wetland issues for agricultural land, and the U.S. Army Corps ofEngineers takes the lead for all nonagricultural lands. In contexts where wetland resources are an issue, the location and acreage of a wetland will be information required by any regulatory agency, whether local, state, or federal. Currently, there are two general sources ofwetland location information for Illinois: the National Wetland Inventory (Nwl), completed in 1980, and Illinois Land Cover, an Atlas (ILCA) by the Illinois Department ofNatural Resources (1996). The State of Illinois used the NWI information to publish the Wetland Resources ofIllinois: An Analysis and Atlas (Suloway and Hubbell, 1994). While this atlas is not of suitable scale for landowners or government agencies to use for individual wetland locations, it can be used by agencies or groups that consider wetlands in an administrative or general government manner and focus on acreage and not individual wetland boundaries. The NWI program involved identifying wetlands on aerial photographs of I :58,000 scale and publishing maps ofthis infonnation using USGS 1:24,000 scale topographic quadrangle maps as the base. NWI quadrangle maps for the Shawnee Assessment Area are shown in Figure 4. Individual quadrangles can be purchased from: 9 r' l Center for Governmental Studies Wetland Map Sales Northern Illinois University De Kalb, IL 60115 Telephone: (815) 753-1901 Digital data by quadrangle are available from the NWI Web site: www.nwi.fws.gov. The ILCA inventory used Landsat Thematic Mapper satellite data as the primary source for interpretation. National Aerial Photography Program photographs verified the land cover classification and helped ensure consistency from area to area within Illinois. The ILCA and companion compact disc can be purchased from: Illinois Department ofNatural Resources' 524 South Second Street Lincoln Tower Plaza Springfield, IL 62701-1787 Telephone: (217) 524-0500 Email: [email protected] . Web site: http://dnr.state.il.us/ctap/ctaphome.htm Although the ILCA and NWI programs were not meant for regulatory purposes, they are the only state or regional wetland map resources available and are the logical sources for beginning a wetland assessment. The presence or absence of wetlands as represented by the wetland maps is not certified by either the ILCA or the NWI mapping program. Figure 4, taken from the Glendale 7.5-minute Quadrangle in the Shawnee area, exemplifies the information that can be expected from NWI maps. In some areas with intense economic development and significant wetland acreage, the NWI maps have been redone or updated for use in designating or locating wetland areas. Whatever the source ofwetland map information, the user should be aware that this information is a general indication ofwetland locations, and the boundaries and exact locations should be field-verified by persons trained or certified in wetland delineation. Given the limitations ofmost existing wetland maps, more complete information can be obtained by comparing mapped wetlands with other regional attributes such as shallow aquifers, subsurface geology, and placement in the landscape. When these comparisons show consistent regional patterns (for example, placement in the landscape or correlation with a particular geologic material), any parcels of land with similar landscape positions or geologic materials can be considered potential wetland sites even ifmaps do not show them as wet. 10 ~UB HX ~BGH \1lUBGH IUBG IJl9UBGH ~UBGH lfu GH .01 ~UB H GiEUBGH 'tUBGH mUBGH ~UBGH ilfUBGH UB H .F01A 1l2UBH ~UBGH ,'" SlA-" ©'UBGH _Iif' tJB'H ~ Wetlands ~ Roads Deepwater habitat /'--/ Sections NI • Scale 1:24000 / Shawnee Assessment Area Figure 4. National Wetlands Inventory information from the Glendale 7.S-minute quadrangle maps showing wetlands, deepwater habitat, and NWI codes. 11 . Land Use Agriculture is a minor land use in the six counties (Gallatin, Hardin, Johnson, Massac, Pope, and Saline) within the Shawnee Assessment Area. Agricultural crop acreage covered 9% ofthe region in 2000, lower than the 20% in 1925. However, Illinois Agricultural Statistics (lAS) data indicate that the acreage ofsome crops significantly changed from 1925-2000, as shown in Figure 5. rr'-'-'--r-T~.-r-,-;rr,-,-rl--CORN 50,000 -- SOYBEANS ----- CORN-BEANS ,, " --SMALL GRAIN , , I l.. _.'. 40,000 , , " " , , (J)w a:: 30,000 ()« 20,000 , ','.' 10,000 -.::i'" '; o 1920 1930 1940 1950 1960 1970 1980 1990 2000 YEAR Figure 5. Acreages ofSelected Crops in the Shawnee Assessment Area Based on Illinois Agricultural Statistics Data The dominant crops in 1925 were com (46,025 acres) and small grains (34,889 acres), whereas in 2000 the dominant crops were com (14,624 acres) and soybeans (18,068 acres). Com acreage decreased from 46,025 acres in 1925 to 10,618 in 1962 then averaged 16,831 acres through 2000. Com has averaged 23,827 acres from 1925 to 2000. The lowest harvested acres for com was in 1983 with 10,343 acres. Soybean acreage increased from 166 acres in 1927 to a high of26,201 acres in 1984 and slightly decreased to 18,068 acres in 2000. Small grains decreased from 34,889 acres in 1925 to 17,302 acres in 1960, increased to a record maximum of38,54l acres in 1984, and decreased to 4,764 acres in 2000. An inverse relationship between soybeans and small grains in the Shawnee Assessment Area from 1925 1960 can be seen in Figure 5. Small grain acreage gradually decreased, while soybean I acreage slowly increased. Small grain and soybean acreage paralleled each other from 1960 through 2000. In 2000, com and soybean acreage accounted for 87% ofthe total crop acreage I in the assessment area, whereas, com and small grains dominated the crop acreage (100%) in 1925. 12 Climate and Trends in Climate This chapter reviews trends in climate in and around the Shawnee Assessment Area since 1901. Climate parameters examined include annual average temperature, the number of days with highs above or equal to 90oP, the number ofdays with lows below or equal to 32°P, the number ofdays with lows below or equal to oop, annual precipitation, the number of days with measurable precipitation, annual snowfall, and the number of days with measurable snowfall. Extreme weather events examined in this report are tornadoes, hail, and thunderstorms. Overview The Shawnee Assessment Area in southern Illinois occupies portions ofHardin, Gallatin, Saline, Johnson, Pope, and Massac counties. The climate of this area is typically continental, as shown by its changeable weather and the wide range oftemperature extremes. Sunnner maximum temperatures are generally in the 80s and 90s, with lows in the 60s, while daily high temperatures in winter are generally in the 30s or 40s, with lows in the 20s and 30s. Based on the latest 30-year average (1971-2000), the average first occurrence of32°P in the fall is October 20, and the average last occurrence of32°P in the spring is April 10. Precipitation is fairly evenly distributed throughout the year. Thunderstorms and associated heavy showers are the major source of growing season precipitation, and they can produce gusty winds, hail, and tornadoes; The months with the most snowfall are December, January, Pebruary, and March. However, snowfalls have occurred as early as October and as late as April. Heavy snowfalls have rarely exceeded 12 inches. The heaviest one-day snowfall was 15.0" on March 27,1947. The climate data used in the following discussions originate from Harrisburg, Illinois (Saline County), the National Weather Service (NWS) Cooperative Observer site with the longest record. Supportive data and analyses for nearby Illinois sites can be found in reports by the Illinois Department ofEnergy and Natural Resources (1994) and Changnon (1984). Temperature The average January maximum temperature is 40 0 P and the minimum is 23°P, whereas the average July maximum and minimum temperatures are 900 P and 68°P, respectively (Table 5). The average annual temperature at Harrisburg is 57°P. Tl;1e warmest year ofrecord since 1901 was 1921, with an average of61.3°P, while the coldest year was 1989, with 53.6°P. 13 Table 5. Temperature Summary for Harrisburg (Averages are from 1971-2000 and extremes are from 1901-2001. Temperatures are inOP) No. of No. of No. of Average Average Record Record days with days with days with Month high low high (year) low (year) high >90°F lows32°F lowsO°F January 40.1 22.9 78 (1943) -22 (1977) 0 23 1.2 FebruliI)' 47.2 27.2 80 (1918) -23(1951) 0 19 0.5 --_.. ~_." March 57.7 36.1 94 (1929) -8 (1960) 0.1 12 0 April 68.8 45.3 93 (1906) 22 (1923) 0.2 2.8 0 May 78.2 54.7 100 (1911) 29 (1963) 3.0 0.1 0 June 86.3 63.6 106 (1913) 40 (1917) 12 0 0 July 90.0. 67.5 113 (1936) 45 (1997) 19 0 0 August 88.5 65.3 111 (1930) 43 (1986) 16 0 0 September 81.9 57.3 109 (1913) 29 (1942) 8.0 0.1 0 October 71.0 45.3 98 (1953) 18 (1981) 0.8 3.0 0 November 57.1 37.1 84 (1933) -3 (1929) 0 11 0 December 45.7 28.1 78 (1982) -II (1917) 0 20 0.4 Although there is a great deal of year-to-year variability, mean annual temperatures at Harrisburg show gradual warming of about 1.5°F from 1900 to 1930, followed by a gradual cooling trend of2.5°F through 2001 (Figure 6). 62 ~ I ~ 60 ::J lA fV\ ! ~, f\ 11 fl. ~ 58 r~ ~ " ., . !II E '1. , t. ~ V" VV ~ \ iii 56 1.eJ ::J V\- c: ~ 54 c: :g ::E 52 ·1900 1910 1920 1930' 1940 1950 1960 1970 1980 1990 2000 2010 Figure 6. Average Annual Temperaturefor Harrisburg, Illinois, 1901-2001 Examination of average temperatures over time is one way to clarify trends. The World Meteorological Organization has adopted 30-year averages, ending at the beginning of the latest new decade, to represent climate "normals." These averages were adopted t6 filter out 14 some ofthe smaller scale features, while retaining the character ofthe longer-term trends. Consecutive, overlapping "normals" for the last eight 30-year periods at Harrisburg are presented in Table 6. The consecutive averages demonstrate the slight warming through the 1931 -1960 period, followed by cooling through the 1971-2000 period. Table 6. Average Annual Temperature during Consecutive 30-Year. Periods Averaging Average period tern erature (OF) 1901-1930 57.9 1911-1940 58.4 1921-1950 58.4 1931-1960 58.2 1941-1970 57.7 1951-1980 57.6 1961-1990 57.1 1971-2000 56.8 The frequency of extreme events is sometimes as important as the average values. The annual number ofdays with temperatures equal to or above 90°F is shown in Figure 7. The time series resembles that ofannual temperature (Figure 6), even though the number ofdays with temperatures above 90°F represents only the high summer temperature extremes. Figure 7 data shows higher values through 1930, followed by a decline through 2001 ofalmost 60%. Based on 1971-2000 data, Harrisburg observes 59 days at or above 90°F per year. 120 ...g 100 1/ ~ 80 Ani r'1 .c:" ~ " 1 :r'" 1/ Ir .... .c: 60 , v .~ J¥j r' ~ " 40 V tAJ I.l. >.. c.. INV ...0 20 'It r o 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Figure 7. Annual Number ofDays with Maximum Temperatures Equal to or Above 90°F at Harrisburg, Illinois, 1901-2001 15 Figure 8 shows the winter frequency ofdaily minimum temperatures equal to or below 32 OF. The frequency ofsuch temperatures shows a slight decline through 1920, followed by a slight increase through 1960, before leveling offthrough 2001. On average, Harrisburg observes 91 days at or below 32°F. 130 U- N M II 110 v ~ tJ, l MN ...J itA} f\, 11 1'-- ""\ \I .<: 90 • • V~ 1\ ~ -'3: ~ ~I \ 70 c , ...0 'It 50 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Figure 8. Annual Number ofDays with Minimum Temperatures Equal to or Below 3JOF at Harrisburg, Illinois, Winters 1901-1902 to 2000-2001 Figure 9 shows the number ofdays per year when the minimum temperature was equal to or below O°F, beginning with the 1901-1902 winter. The frequency ofsuch temperatures shows a decline through 1930, followed by an increase through 1980, before declining once again through the 2000-2001 winter. 20 u 0 II 15 v ~ ....0 .<: 10 :!: ~ »Ul cco 5 ... AI I 0 ~ ~ ~ I AI I" 'It , 11 u \ -1\1 o IJII I 1/\ A I VlJWJ n- 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Figure 9. Annual Number ofDays with Minimum Temperatures Equal to or Below 0 OF at Harrisburg, illinois, Winters 1901-1902 to 2000-2001 I 16 I I Precipitation Average annual precipitation is 45.69 inches, with more rainfall in the spring, summer, and fall than in winter (Table 7). Spring, summer, and fall precipitation is primarily convective in nature, often associated with thunderstorms, with durations of 1 to 2 hours. During the remainder of the year, the precipitation is of longer duration and associated with synoptic-scale weather systems (cold fronts, occluded fronts, and low-pressure systems). The wettest year of record since 1901 at Harrisburg was 1950 (71.84 inches). The driest year was 1930 (25.33 inches). Table 7. Precipitation Summary for Harrisburg (Averages are from 1971-2000 and extremes are from 1901-2001. Precipitation is 10 inches.) Largest one- No. of Avg. Record Record day amount Snow daysw/ Month precip. high (year) low (year) (year) Fall preclp. January 3.14 17.69 (1950) 0.01 (1986) 3.84 (1937) 4.6 8.5 February 2.84 7.06 (1950) 0.14 (1947) 3.06 (1945) 3.5 7.7 March 4.33 13.05 (1964) 0.00 (1910) 5.53 (1964) 1.7 9.9 April 4.69 13.05 (1983) 0.82 (1930) 5.75 (1996) 0.4 10.1 May 4.78 14.29 (1981) 0.80 (1926) 7.38 (1957) 0 9.9 June 4.44 13.95 (1928) 0.41 (1946) 4.24 (2000) 0 8.7 July 3.94 9.40 (1905) 0.15 (1918) 4.30 (1905) 0 7.6 August 3.25 10.93 (1916) 0.17 (1937) 6.75 (1959) 0 7.3 September 3.04 8.85 (1904) 0.00 (1928) 3.05 (1904) 0 6.7 October 3.07 13.17 (1910) 0.03 (1964) 5.47 (1910) 0 6.4 November 4.16 9.71 (1921) 0.24 (1910) 4.50 (1921) 0.6 7.5 December 4.01 13.10 (1982) 0.47 (1955) 5.32 (1982) 1.7 8.6 The annual precipitation at Harrisburg is shown in Figure 10 with no long-term trend evident since 1901. The variability from year to year decreased significantly iq the last 30 years of the record. 17 80 70 ;[ 60 c: o r M 'ii 50 ;I [7J L 'ii.- 7\) A J1 PJ1 u 40 1/ !A lJl e V " II D. 'r W\ 30 V 20 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Figure 10. Annual Precipitation at Harrisburg, Illinois, 1901-2001 The number ofdays per year with measurable precipitation (i.e., more than a trace) is shown in Figure 11. Their frequency has decreased through the 1930s before increasing through the 1980s. The frequency afrain days declined again through 2001. 140 c: 0 ! 120 'is. 'u Q) ,,/\ lA ~ I~,. / ) ~ ft, D. 100 .r:. 1'1 1 l f. -'i ~ :JiM!' c 80 II , ' ...0 'It 60 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Figure II. Annual Number ofDays with Measurable Precipitation at Harrisburg, Illinois, 1901-2001 Average winter snowfall at Harrisburg is 12.5 inches, but there is great year-to-year variability. The most snowfall during anyone winter in Harrisburg was 54.5 inches during the 1977-1978 winter, whereas the least amount of snow was reported during the winters of 1922-1923 (O.O'inches). Snowfall from the 1901-1902 winter season through the 2000-2001 season is shown in Figure 12. Snowfall was high before 1920 to much 18 lower amounts through 1960. Snowfall was generally higher in the 1960s and 1970s . before returning to earlier low levels since 1980. 60 50 ',' ~ c 40 :.:. :i1! 30 ~ o· ~I .:5 20 • I" :-- ~ ~ I 10 fJI rd. v:- Y VJI Vl ~ o V 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Figure 12. Annual Snowfall at Harrisburg, Illinois, Winters 1901-1902 to 2000-2001 Figure 13 shows the number of days each winter with snowfall, from 1901-1902 through 2000-2001. The number ofdays with snow per year has a pattern very similar to total snowfall. A daily snowfall ofmore than 6 inches occurs about once every other year. Snow cover is frequently experienced at Harrisburg, typically lasting from a few days at a time to as long as 45 days (January 12,1978 to February 25, 1978). 25 ~ 20 11: 0 c . Ul 15 ..c: "i- A, .Ii .. 10 tI I > A ...., c rtl!.. ~A ...'" 1/\ IVY II 1'1 A, IA 0 5 'It ""V ' V~ o 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Figure 13. Annual Number ofDays with Measurable Snowfall at Harrisburg, Illinois, Winters 1901-1902 to 2000-2001 19 ------Precipitation Deficits and Excesses Following are the driest years in Harrisburg, starting with the driest: 1930 (25.33"), 1936 (27.11"), and 1963 (28.14"). Driest summer seasons (June, July, and August) in the basin include: 1936 (2.75"), 1930 (3.05"), and 1913 (4.58"). The three wettest years in Harrisburg are 1950 (71.84"), 1957 (64.78"), and 1927 (61.02"). Severe Weather Tornadoes Although tornadoes are not uncommon in Illinois, most people do not expect to be affected directly, even if they live in the state for a lifetime. This is because tornadoes are generally only one-quarter mile in diameter, travel at roughly 30 miles per hour for only 15-20 minutes, and then dissipate, directly affecting a total area less than 2 square miles. Since Illinois observes an average of28 tornadoes a year (though the actual number varies from fewer than ten to about 100 during the last 35 years), the total area directly affected by tornadoes annually is only about 55 square miles, 0.1 % the total area of the state. Even with 107 tornadoes reported in Illinois in 1974 (the greatest number reported in the last 30 years), the affected area was only about 0.3% the total area of the state. These numbers do not diminish the effect on those experiencing property damage, injury, or worse, but they demonstrate the extremely low probability ofdirect impact at any given location. The most recent study on tornadoes in Illinois (Wendland and Guinan, 1988) examined events from 1955 to 1986 and found no apparent trend in tornado frequency or intensity. The six counties located in the Shawnee Assessment Area (Hardin, Gallatin, Saline, Johnson, Pope, and Massac) experienced 35 reported tornado touchdowns between 1950 and 2001. A majority of these were too weak or short-lived to cause damage or injuries. Hail Hail events are somewhat rare and typically affect a very small area (from a single farm field up to a few square miles). Unfortunately, very few NWS Coop sites measure hail. The combination of small, infrequent events being measured by a sparse climate network makes for very few reliable, long-tenn records ofthese events, particularly for large areas. Based on Changnon (1995), the Shawnee Assessment Area experiences 2.6 hail days per year, with the actual number of hail days varying greatly from year to year. The years with the most hail days were 1907, 1917, 1927, 1945, and 1970, all with seven. There are no indications of trends in hail.days, based on the records from Marion, illinois from 1901 to 1994. 20 Thunderstorms The Shawnee Assessment Area experiences an average of 56 days with thunderstorms each year. The annual number ofdays with thunder over the Shawnee Assessment Area since 1901 is shown in Figure 14, which is composed of data from Paducah, Kentucky (1901-2001). There is substantial year-to-year variation in thunderstorm days, ranging from as many as 79 in 1927 to as few as 33 in 1976. A new automated surface observation system (ASaS) was commissioned in August 1995, replacing the human observers. Therefore, it may be difficult to compare the data after 1995 with data before 1995. The number ofdays with thunder declined through 1980. Recent years have seen some increase in the frequency. 90 ~ 80 -0 C A ~ 70 I z:. I .A 'i 60 '\\ VI V rl ~ III V f'J IN ,NV\A ' ~ 50 c ...o 40 \ J ~ " 30 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Figure 14. Annual Number ofDays with Thunderstorms at Paducah, Kentucky 1901-2001. Missing data occurredfrom 1965 to 1969 andfrom 1982 to 1984 Summary Mean annual temperatures at Harrisburg show gradual warming from 1900 to 1930, followed by a gradual cooling trend through 2001. Days with temperatures at or above 900 P show higher values through 1930, followed by a decline through 2001. Days with temperatures equal to or below 32°F show a slight decline through 1920, followed by a slight increase through 1960, before leveling off through 2001. Days with temperatures equal to or below O°F shows a decline through 1930, followed by an increase through 1980, before declining once again through the 2000-2001 winter. 21 Precipitation has shown no trend over the course ofthe record from 1901 to 2001. The number ofdays with measurable precipitation showed a decrease through the 1930s before returning to higher levels. Winter snowfall amounts were high before 1920, declined through 1960, reached a second high in the 1960s and 1970s, before dropping once again. The number ofdays with snow shows a pattern ofchange similar to total snowfall. Records extending back to 1901.show no clear trends in hail events. Similarly, there are no apparent trends in tornado events, although reliable records date only to 1950. The number ofdays with thunderstorms has been recorded since 190I with a downward trend through 1980 before showing some recovery. 22 ,-,- -~ Streamflow and Trends in Streamflow Surface water resources are an essential component of any ecosystem because they provide different types ofhabitats for aquatic and terrestrial biota. In addition to their natural functions, they are sources ofwater supply for domestic, industrial, and agricultural use. Changes in natural and human factors, such as climate, land and water use, and hydrologic modifications, can greatly affect the quantity, quality, and distribution (both in space and time) of surface waters in a river basin. There are about 1,168 miles ofrivers and streams in the Shawnee Assessment Area. The status ofthese rivers and streams is monitored by streamgaging stations, which measure the flow ofwater over a period oftime, providing infonnation on the amount and distribution of surface water passing the station. Since it is not feasible to monitor all streams in a basin, gaging stations ar.e established at selected locations, and the data collected are transferred to other parts ofthe watershed by applying hydrologic principles. Streamgaging Records The U.S. Geological Survey (USGS) has operated five continuous-discharge streamgages in the Shawnee Assessment Area. Table 8 lists these stations, and Figure 15 gives their locations. Only one ofthe gages in the assessinent area is currently active, that being for the Lusk gage near Eddyville. Also listed in Table 8 is the gaging record for the Cache River near Fonnan, which is used in this report to evaluate long-tenn hydrologic conditions in the assessment area. Table 8. USGS Continuous Discharge Stations in the Shawnee Assessment Area Drainage RL* Period USGS ill Station name area (mi') (years) ofrecord Continuous Discharge Records 03384450 Lusk Creek near Eddyville 42.9 33 1967-present 03385000 Hayes Creek at Glendale 19.1 26 1949-1975 03385500 Lake Glendale Inlet near Dixon Springs 1.0 9 1954-1963 03386000 Lake Glendale Outlet near Dixon Springs 2.0 8 1955-1963 03386500 Sugar Creek near Dixon Springs 9.9 21 1950-1971 03612000 Cache River near Forman 244.0 78 I922-present Note: * RL =record length 23 • U.S.G.S. Gaging Stations - Streams - Boundary N t Scale 1:500,000 5~"""'!l_.~O~~~5__iiiiiiiiil10 Miles Figure 15. Location of Streamgages in the Shawnee Assessment Area. 24 Human Impacts on Streamflows in the Assessment Area The characteristics of streamflow in any moderately developed watershed will, over time, vary from earlier conditions because ofa combination ofclimate variability and the cumulative effect of human activities in the region. Most ofthe streamgaging records in this region are less than 60 years old, and thus represent hydrologic conditions related to the region's landscape in the late 20th Century. The two potential land use factors that are the most likely to have affected flow conditions in the streams are reforestation and changes in agricultural practices. Water use in the area is smalI, and thus is not expected to have much impact on streams. A number ofsmalI reservoirs have been built, which are expected to have limited impact on streamflows except for local effects on flood discharge. Climate variability also influences the changes in streamflows from year to year and decade to decade. The major changes to the climate during this century are assumed to occur from natural climatic variability. However, with recent research focusing on global climate change, it is possible that these changes may be shown also to result from human influences. Variability in Annual Streamflows The average annual amount ofprecipitation in the Shawnee Assessment Area is approximately 48 inches. Of this water, about 65 percent eventualIy returns to the atmosphere through evapotranspiration. Most ofthe remaining 35 percent ultimately flows to streams by way ofrunoffafter precipitation events or from the more gradual seepage of water stored in the soil and shalIow groundwater. The average amount of streamflow during the last half of this century has been approximately 17 inches. This represents an average flow rate ofapproximately 1.25 cubic feet per second (cfs) per square mile of drainage area. Figure 16 shows the annual series of average streamflow for the four longest gaging records in and near the assessment area: Sugar Creek near Dixon Springs. Hayes Creek at Glendale,.Lusk Creek near Eddyville, and the Cache River at Forman. Flows are presented in units ofinches ofrunoffover each gage's subwatershed. These plots show that average streamflow in the watershed can vary greatly from year to year. Figure 16 shows a considerable similarity in the total annual flows for different locations in the assessment area. The gage on Lusk Creek near Eddyville typicaIly shows a slightly higher annual runoff rate than the other gages. Statistical Trend Analysis Trend correlation statistics were estimated for the annual flow records of the four gaging stations having records greater than 20 years. These correlation statistics are presented in Table 9. The KendaIl trend statistic was used to provide an indicator of the increase or decrease in the flow values. A KendaIl correlation of 1.0 indicates that there is an absolute increasing trend, with each year having a higher flow than the previous year. A KendaIl correlation of -1.0 indicates an absolute decreasing trend, and a correlation of 25 50 --.-Cache River at Forman -+- Lusk Creek near Edd~iIIe 45 --*-Hayes Creek at Glen ale --.-Sugar Creek near Dixon Springs 40 , ~ ~~ ~ ~ ~ 'I!j 10 c.J. j. Ii 5 o 1920 1930 1940 1950 1960 1970 1980 1990 2000 Figure 16. Average Annual Streamflowfor the Gages in and near the Shawnee Assessment Area 0.0 indicates no trend. The statistical significance ofa trend correlation depends in part on the length ofthe record being analyzed. With a 60-year record, correlation values greater than 0.14 or less than -0.14 indicate that there exists a statistically significant trend, one that can be declared with 90% level ofconfidence. The level ofconfidence with which a trend can be declared increases as the absolute value ofthe correlation increases. To establish statistical significance, shorter records require a higher correlation value and longer records do not need as high a correlation value. The trend correlations given in Table 9 indicate that none ofthe long-tenn gaging records have a statistically-significant change in average flow conditions. Table 9. Trend Correlations for Annual Flows Stream aging location Period ofrecord Trend correlation Lusk Creek near Eddyville 1967-2000 -0.074 Hayes Creek at Glendale 1949-1975 0.052 Sugar Creek near Dixon Springs 1950-1971 0.029 Cache River near Forman 1922-2000 0.007 26 Daily and Seasonal Variation in Flows Figure 17 plots the flow duration curves for the four longer gaging records in and near the assessment area. The flow duration curve provides an estimate of the frequency with which the given flows are exceeded. As described earlier, the flow duration represents the percentage of time at which the flow is greater than a given rate; for example, the 90% flow is exceeded 90% of the time for the period of record, and thus represents the expected low flow conditions in the stream. The magnitude ofthe flows at each gaging location are different because of varying watershed size. For example, the flows for Lusk Creek near Eddyville convey the runoff for a 43 square-mile watershed, and thus flows are over twice as much as the flows measured for the 19 square-mile watershed for Hayes Creek at Glendale. Variations in the overall shapes of the flow duration curves often point to either regional differences in the hydrology ofthe streams or human impacts on streamflows. As can be seen in figure 17, the flow duration curves for most of the gaging records have a very similar shape and plot as nearly parallel lines. The gradient in the flow duration curve is somewhat steeper for smaller streams than for larger rivers, which is typical for any region, and several of the smaller streams (Hayes Creek and Sugar Creek) have zero flow during dry periods ofmost years. 10000 r----'------;::===:::;==~=~=====~---, ~ cache River at Forrran ~ Lusk Creek near 8:::ldyville __ Hayes Q-eek at Glendale 1000 -0- Sugar Qeek near Dixon Springs 100 '0 ui ~ 10 u Ul is 0.1 0.01 .L---c------...,..,.--=-=--=-----\=---=-:\~-::_::_----''<---__::--' 10 20 30 50 70 80 90 99 FB Figure 17. Flow Duration Curves (Discharge Versus Probability) for Gages in and near the Shawnee Assessment Area 27 As with all other locations in Illinois, streams in the Shawnee Assessment Area display a well-defined seasonal cycle. Figure 18 shows the monthly probability ·offlows for the Lusk Creek near Eddyville. Three levels of flow probability are given: 50% flow (medium flow), 10% flow (high flow), and 90% flow (low flow). The 10% flow is exceeded only 10% of the time during that month. In contrast, the 90% flow is exceeded 90% of the time, and thus represents the expected low flow conditions in the stream. This figure shows that the average flow in any month can vary considerably from the long-term median condition. For example, the highest 10% of the flows can be more than 10 times the median flow for any month. Flows are normally expected to be greatest during the spring months, March-April, and then decline until the lowest flow conditions in or around September. 1000,------...., __90% -B-SO% -e-10% tl uj C!l ?i:r: '-' o'" 1 . 0.1 . 0.01 +--~--~--_-_---,--~--...,.->,-_--_-+--,-----l Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 18. Monthly Flow Probabilitiesfor Lusk Creek near Eddyville Flooding and High Flows Figure 19 shows the annual series of peakflows for three gaging records: Lusk Creek near Eddyville, Hayes Creek at Glendale, and Cache River near Forman. The flood ofrecord for both Lusk Creek and Hayes Creek occurred on August 24,1985. Since 1985, the annual peakflows for all stations have been slightly below the long~term average, however an examination ofFigure 19 does not show any noticeable long-term trends in peakflows for any of the gaging records. I I 28 I I ,I 100000 ,------'~----___, -.-cache River near Forrran __ Lusk Creek near Eddyville -0-Hayes O'eek near Glendale 10000 ----- 1000 100 ~---_---_---_-_-_-_-_-_-_----j 1930 1940 1950 1960 1970 1980 1990 2000 Figure 19. Annual Peakflows for the Selected Gaging Records Trend Assessment Results ofthe statistical trend analysis ofthe peakflow records are given in Table 10 for the Lusk Creek, Hayes Creek, and Cache River gaging records. The analysis indicates that there is little or no trendin peakflows over the period ofrecord at the three gages. Table 10. Trend Correlations for Peakflows Streamgaging Location Period ofrecord Trend correlation Lusk Creek near Eddyville 1967-2000 -0.004 Hayes Creek at Glendale· 1949-2000 -0.049 Cache River near Forman 1922-2000 -0.042 Seasonal Distribution of Flood Events Table 11 presents the monthly distribution ofthe occurrence ofthe top 25 annual peakflows for the Lusk Creek, Hayes Creek, and Cache River gages. Note that this table only includes annual peaks, and does not include significant flood events that are not part ofthe annual maximum event. The values in Table II indicate that over 80% of all floods happen during the 6-month period from December through May. Summer flood events happen occasionally on smaller streams, and are responsible for the floods of record for both the Lusk Creek and Hayes Creek gages. But summer floods are very 29 Table 11. Monthly Distribution of Top 25 Flood Events at Selected Stations Month Jan Feb Mar Jun lui Aug Se Oct Nov Dec Lusk Creek near 5 0 5 6 3 I 2 I 0 0 I I Eddyville Hayes Creek at 5 I 6 3 4 I 2 0 0 I I Glendale Cache River near 6 2 8 3 3 0 0 0 0 0 2 Forman uncommon for larger streams such as the Cache River. The month with the most common occurrence of flooding in the assessment area is March, with floods in January and April also being common. Low Flows and Drought Minimum flows during droughts and dry periods are usually defined by the average flow experienced during a critical period oflow streamflow. The average flow experienced during a short critical period, such as with a I-day or 7-day low flow, is useful for evaluating short-term impacts oflow streamflow on water quality, aquatic habitat, and direct water withdrawals from streams. The average flow experienced during a long critical period, ranging from 18 to 42 months in duration, is useful in analyzing drought impacts on water supplies. Seven-Day Low Flows The 7-day low flow (Q7) is used herein to describe the minimum streamflows expected during a drought or dry period. The Q7 for a particular year is defined as the minimum average flow experienced during aseven-day period within that year. This minimum flow is useful for evaluating the effect ofdry periods on aquatic life, navigation, and other instream uses of flow on the streams. The 7-day, 10-year low flow is the lowest Q7 that would be expected to occur on average only once in ten years, and is commonly used for defining the minimum amount ofdilution for streams receiving treatment effluents. Figure 20 shows the annual series of 7-day low flows for the Lusk Creek and Cache River gages. All of the other gaging stations have zero low flows for most years. All streams in the Saline Assessment Area (with the exception ofthe Ohio River) are expected to have zero flows during very dry conditions such as the ten-year low flow. Table 12 shows the correlation coefficients associated with a trend analysis oflow flows at the Lusk Creek and Cache River gages. The trend coefficients suggest there may be a slight increasing trend in low flows, however the trend is insignificant at a 90% level of confidence. 30 100 --e- Lusk Creek near Eddyville __ Cache River near Forrren 10 ~ ,. ~ 7~ tai ~ ~ y A G I~ \, If , 0.1 j:' l'f 0.01 0.001 1920 1930 1940 1950 1960 1970 1980 1990 2000 Figure 20. Annual 7-Day Low Flows for the Lusk Creek and Cache River Gages Table 12. Trend Correlations for Low Flows Stream a in Station Period of record Trend correlation Lusk Creek near Eddyville 1967-2000 0.155 Cache River near Forman 1922-2000 0.103 Muiti-Year Drought Flows Table 13 lists the average flows during the most severe droughts on record for the Cache River near Fonnan. Although the Cache River is located outside of the Shawnee Assessment Area, it provides the longest gaging record in the region for analysis of drought frequency. Flows in Table 13 are computed for several drought durations. These values illustrate that the severity of a drought can vary over time. The drought in the mid-1950s was the most severe drought both in persistence, having dry conditions that lasted for several years. In contrast, the 1964 drought had the lowest flow conditions over a shorter 6 month period. All severe droughts impacting the Cache River have produced periods ofzero flows. 31 F Table 13. Drought Flows for the Cache River uear Forman, 1914-2000; Average Flow (in cfs) over the Specified Critical Period Duration of critical period Drou ht ears 7-da 6-month 18-month 3D-month 54-month 1930-1931 0.0 7.8 46 133 201 1939-1941 0.0 5.8 38 83 166 1953-1956 0.0 6.7 54 75 123 1963-1965 0.0 2.6 ~ 123 168 1980-1981 0.0 7.9 126 155 242 1987-1989 0.0 12.3 85 124 216 1999-2001 0.2 3.7 112 158 166 Summary Long-tenn hydrologic records indicate that there has been little or no !Jverall trend in average, low, and high flow conditions in flow conditions in the Shawnee Assessment Area. Streamflows in the assessment area may be impacted to a certain extent by reforestation and changes in agriculture practices, but it is difficult in this short analysis to detect the extent ofthese impacts ifthey exist. In general, the flows in the assessment area also have negligible impact from water use and water resource projects such as reservOirs. I l 32 Erosion and Sedimentation Instream Sediment Load Instream sediment load is the component of soil eroded in the watershed and from the streambanks that is transported to and measured at a gaging station. It indicates the actual amount of soil generated upstream ofthe gaging station and eventually transported to downstream reaches ofthe river. Given the complex dynamic process of soil erosion, sediment transport, and deposition, it is very difficult to quantify how much ofthe soil eroded from uplands and streambanks actually moves to downstream reaches. The sediment transported by a stream is a relatively small percentage ofthe total erosion in the watershed. However, the amount of sediment transported by a stream is the most reliable measure ofthe cumulative results of soil erosion, bank erosion, and sedimentation in the watershed upstream ofa monitoring station. There is one gaging station in the ShaWnee Assessment Area where instream sediment was monitored for some time. As shown in Figure 21, the station is located on the Lusk Creek near Eddyville. Table 14 summarizes information about this station. Table 14. Suspended Sediment Monitoring Stations within the Shawnee Assessment Area USGS station Drainage area Station name number (sq. mi.) Period ofrecord Lusk Creek near Eddyville 03384450 42.9 Jan. 1980-Sept. 1981 At the Lusk Creek near Eddyville, the U.S. Geological Survey (USGS) monitored sediment yield for less than two water 'years (1980-1981). Data collected by the USGS were reported as daily average concentrations. Therefore, daily and annual sediment loads at the station can be calculated. Figures 22 shows daily sediment concentrations and loads for the station monitored.. The figures show the variability ofstreamflow (Qw), suspended sediment concentration (Cs), and suspended sediment load (Qs). Water years start on October 1 and end on September 30. For the Lusk Creek near Eddyville (Figure 21), concentrations varied from a low of 1 milligram per liter (mg/I) to a high of299 mg/I measured by the USGS during the period ofJanuary 1980 to September J981. Higher concentrations occurred in the winter (January) and the spring (May). 33 I ~ .. Sediment Monitoring Stations - Streams - Boundary N t Scale 1:500,000 5~~iiiiiiiiiiO~~~~5iiiiiiiiiiiiiiiiiiiOi10 Miles Figure 21. Sediment Monitoring Stations in the Shawnee Assessment Area. 34 ------F 1600 ~------, 03384450 Lusk Creek near Eddyville 1200 '- . 400 ow..l...ll~~b[;!2:..:."'-..-AI1J-,--,--l---'---L----'-~~~.c.i.:.!!.1A....J1...... o-I 1000 .------~-___, ~ 100 ~ U'" 10 IL,--,--,w.h.JJIL..c.LllIJ1IIl.JL..JIlLLJJWUlWU 10000 ~------, '""' 1000 ~ ~ g0: 100 CI'" 10 IL---,---,-.wJ..-,--..w..wJ--,--,-JL--,---,--'---,--,--,----'-'lUJ.....n1JWJl.'IJll..WJJWL-L--J 10/1179 1011180 101 liS I Date Figure 22. Variabilities ofDaily Discharge and Suspended Sediment Concentration and Load for Lusk Creek near Eddyville (data collected by the USGS) 35 ------'------~-- To provide values in tons per day, sediment load was computed by multiplying the daily water discharge by the instantaneous sediment concentrations and applying the proper unit conversion factors. For the Lusk Creek near Eddyville, the average daily sediment load measured by the USGS varied from 0.01 tons per day to 2,340 tons per day. Annual sediment load can be calculated for the Lusk Creek near Eddyville for water years from 1980 to 1981. As shown in Table IS, annual sediment load at the Lusk Creek near Eddyville varied from a low of 1,586 tons in 1980 to a high of 12,267 tons in 1981. It should be noted that the 1980 load for the Lusk Creek near Eddyville was only for a period ofnine months. " The corresponding sediment yield per square mile ranged from 37 tons per square mile in 1980 to 286 tons per square mile in 1981 for the Lusk Creek near Eddyville. Table 15. Annual SedimentLoad for tbe Sbawnee Assessment Area Station name Water ear Water dischar e cfs) Sediment load tons Lusk Creek near Eddyville 1980 16,906 1,586* 1981 15,864 12,267 Note: *Represents a nine-month total. Sedimentation Sedimentation is the process by which eroded soil is deposited in stream channels, lakes, wetlands, and floodplains. In natural systems that have achieved dynamic equilibrium, the rates of erosion and sedimentation are' in balance over a long period oftime. This results in a stable system, at least until disrupted by extreme events. However, in ecosystems where there are significant human activities such as farming, construction, and hydraulic modifications, the dynamic equilibrium is disturbed, resulting in increased rates oferosion in some areas and a corresponding increased rate of sedimentation in other areas. Erosion rates are measured by estimating soil loss in upland areas and measuring streambank and bed erosion along drainageways. These measurements are generally not very accurate and thus are estimated indirectly, most often through evaluation of sediment transport rates based on instream sediment measurements and empirical" equations. Similarly, measurement ofsedimentation rates in stream channels is very difficult and expensive. Lake sedimentation surveys provide the most reliable sedimentation measurements. Since lakes are typically created by constructing dams across rivers, creating a stagnant or slow-moving body of water, they trap most ofthe sediment that flows into them. The 36 continuous accumulation oferoded soils in lakebeds provides a good measure of how much soil has been eroded in the watershed upstream of the lake. Lake sedimentation rates for one lake surveyed in the Shawnee Assessment Area are presented in Table 16. The Vienna Correctional Center Lake was constructed in 1964 to serve as the raw water source for the Vienna Correctional Center, a minimum security facility. The Shawnee Correctional Center, a medium security facility, was built in 1985. Table 16. Lake Sedimentation Surveys in the Shawnee Assessment Area Watershed Surveyed Loss rate volume for period Lake name (acre-feet) % er ear Vienna Correctional Center Lake 1.25 76.7 1,160 1996 1,080 0.22 Constructed 1965 37 F Water Use and Availability Statewide, water use has increased a modest 27% since 1965 (Illinois Department of Energy and Natural Resources, 1994). Most of that increase is in power generation. Public water supply (PWS) use has risen only about 7% during that time, less than the concurrent percentage increase in population. The number ofpublic ground-water supply facilities in Illinois has risen significantly during that time, yet the total amount supplied by ground-water remains near 25%. A dependable, adequate source of water is essential to meeting existing and potential population demands and industrial uses in Illinois. Modifications to and practical management ofboth surface and ground-water use have helped make Illinois' water resources reliable. As individual facilities experience increases in water use, innovative alternative approaches to developing adequate water supplies must be developed, such as use ofboth surface and ground-waters. Major metropolitan centers such as the Chicago area, Peoria, and Decatur, as well as smaller communities, have already developed surface and ground-water sources to meet their development needs and to sustain growth. The construction of impounding reservoirs has become and will remain economically and environmentally expensive, making it a less common approach. Proper management of water resources is also necessary to ensure a reliable, high quality supply for the population. Water conservation practices will become increasingly important to reduce total demand and avoid exceeding available supplies. Both our ground-water resources and surface reservoir storage must be preserved to maintain reliable sources for future generations. Ground-Water Resources Ground-water provides approximately one-third of Illinois' population with drinking water. The sources of this water can be broken down into three major. units: 1) sand and gravel, 2) shallow bedrock, and 3) deep bedrock. Most ground-water resources are centered in the northern two-thirds of Illinois. Sand-and-gravel aquifers are found along many of the major rivers and streams across the state and also within "buried bedrock valley" systems created by complex glacial and interglacial episodes of surface erosion. There are also many instances of thin sand-and gravel deposits in the unconsolidated materials above bedrock. These thin deposits are used throughout Illinois to meet the water needs of small towns. Shallow bedrock units are more commonly used in the northern third of Illinois, whereas the deep bedrock units are most widely used in the northeastern quarter (in and around the Chicago area). The variety of uses and the volume of water used vary widely throughout the state. This section describes ground-water availability and use in the Shawnee Assessment Area. 39 r Data Sources Private Well Information The Illinois State Water Survey (ISWS) has maintained well construction reports since the late 1890s. Selected information from these documents has been computerized and is maintained in the Private Well Database. These data are easily queiied and summarized for specific needs and form the basis of well distribution studies in the area. Public Well Information Public Water Supply (PWS) well information has been maintained at the ISWS since the late 1890s. Municipal well books (or files) have been created for virtually all of the reported surface and ground-water PWS facilities in Illinois. Details from these files are assembled in the Public-Industrial-Commercial Database, which was created to house water well and water use information collected by the ISWS. Ground-water Use Information The water use data given in this report come from the records compiled by the ISWS' Illinois Water Inventory Program (IWIP). This Program was developed to document and facilitate planning and management of existing water resources in Illinois. Information for this program is collected through an annual water use summary mailed directly to each PWS facility. Data Limitations Several limitations must be taken into consideration when interpreting these data: 1. Information is reported by drillers and by each PWS facility. 2. Data measuring devices are generally not very accurate. 3. Participation in the IWIP is voluntary. Information assembled from well construction reports and from the IWIP is considered "reported" information~ This means that the data are as accurate as the reliability of the individual reporting or as mechanical devices dictate. The quality ofthe reported information depends upon the skill or budget of the driller or facility, respectively. Moreover, the ISWS estimates that only one-third to one-half of the wells in the state are on file at the Survey, mainly due to the lack of reporting regulations prior to 1976. In general, water use measuring devices, such as the meters used by PWS facilities, are not very accurate. In fact, errors of as much as 10% are not uncommon. Much of the information reported in the IWIP is estimated by the water operator or by program staff. Participation in the program is not required by the State ofIl1inois, and each facility voluntarily reports its information through a yearly survey. However, not all facilities know ofor respond to the water use questionnaire. After several mail and telephone attempts have been made to gather this information, estimates are made using various 40 techniques. To help reduce errors associated with the program, reported water use information is checked against usage from previous years to identify any large-scale reporting errors. Ground-Water Availability The Shawnee Assessment Area encompasses portions of six counties: Gallatin, Hardin, Johnson, Massac, Pope, and Saline. The portions of each county within the assessment area range from less than one percent (Gallatin Co.) up to ninety-five percent in Hardin Co. This section summarizes ground-water availability within the assessment area, taking into consideration·only the portions ofeach county that are actually within the assessment area. Domestic and Farm Wells The available regional information indicates that ground-water for most domestic and farm use in the assessment area is mainly obtained from small-diameter drilled wells tapping the underlying bedrock formations. These wells are finished in thin sandstone and creviced limestone beds in the underlying Pennsylvanian- and Mississippian-aged bedrock. The chances of developing a domestic well from these units is fair. Regional information also indicates that there are some large-diameter bored wells finished with the unconsolidated materials above bedrock. These wells tap stringers or lenses of silt, sand or gravel only a few inches thick contained in the unconsolidated materials above bedrock. These wells have been constructed in areas where the water-yielding Pennsylvanian- and Mississippian-aged bedrock was not encountered. Table 17 summarizes the number ofreported private wells in the watershed by county and depth. Table 17. Number of Reported Private Wells in the Shawnee Assessment Area (Source: ISWS Private Well Database) De th ran e, feet Coun <50 <100 <150 <200 <250 <300 <350 <400. >400 Total Gallatin 0 0 0 0 0 0 0 0 0 0 Hardin 114 67 84 65 64 28 27 21 27 497 Johnson 100 11 9 9 14 8 3 2 4 160 Massac I 2 0 I 3 2 0 I I 11 Pope 216 69 42 41 27 20 12 11 29 467 Saline 4 5 5 0 I I I 0 I 18 Total 435 154 140 116 109 59 43 35 62 1153 Public Water Supply Wells Information from the ISWS Public-Industrial-Commercial-Survey (PICS) database indicates ground-water is obtained by 2 facilities that tap the underlying Mississippian 41 / aged limestone beds at depths ranging from 396 to 700 feet below land surface. Three facilities purchase water from other ground-water users outside the assessment area and one facility, the Vienna Correctional Center, uses its own lake as the source oftheir water. 2000 Ground-Water Use Ground-water use in the assessment area makes up 21 percent of this areas' total reported water use. Total ground-water use within the area is estimated to be 0.81 million gallons per day (mgd). Public Water Supplies withdraw 0.19 mgd, self-supplied-industries withdraw 0.00 mgd, rural/domestic withdrawals are estimated at 0.01 mgd, and livestock watering is estimated to use 0.61 mgd. Public Water Supply In 2000, residential use for 2 facilities using ground-water is reported to be 0.19 mgd, serving a reported population of 1,954. The average per capita use ofthese facilities is reported to be 88.5 gallons per day. Self-Supplied Industry Self-supplied-industries are defined as those facilities that provide all or a portion oftheir water needs from their own sources. Within the Shawnee Assessment Area, we have no reported facilities that use ground-water within this category. Rural/Domestic There is no direct method for determining rural/domestic water use within the basin. In order to get a rough estimate ofthis water use in this area, several assumptions were made using existing information. Reported population served and number of services from PWS facilities were used to calculate an average population per service for all the· PWS facilities within the assessment area. This number was then used as an estimate of population per reported domestic well within the assessment area. The average PWS per capita use was then used as a multiplier to detemline total rural/domestic water use from each well. Since there are 1,153 reported wells within the ISWS Private Well Database within the assessment area (Table 17) and an average of2.5 people per service (well) and an average of 88.5 gallons per day per person, the total rural/domestic water use was estimated to be less than 0.01 mgd. Livestock Watering Water withdrawals for livestock use in 2000 were estimated to be 0.61 mgd. The water use estimates for livestock are based on a fixed amount ofwater use per head for each type of animal. Percentages ofthe total animal population (Illinois Dept. OfAgriculture, et aI., 2000) for the major livestock (cattle and hogs) in the counties were calculated based upon the percentage of county acres within the Shawnee Assessment Area. Daily 42 r------ consumption rates (beef cattle = 12 gpd, all other cattle = 35 gpd, and hogs = 4 gpd) provided the basis for these calculations. Ground-Water Use Trends Overall groundcwater use within the assessment area had remained relatively constant from 1990 through 1994. In 1994, the closure of a fluorspar mine brought a noticeable change in water use within the summary period. Total ground-water use within the Shawnee Assessment Area has averaged 1.13 mgd and has ranged from 0.14 to 2.63 mgd. Public Water Supply (PWS) ground-water use has averaged 0.18 mgd and has ranged from 0.09 to 0.25 mgd over the years. Self-Supplied-Industry (SSI) has averaged 0.94 mgd and has ranged from less than 0.01 mgd to 2.54 mgd. Table 18 shows the individual totals per year for 1990 through 2000. Table 18. Ground-Water Use Trends in the Shawnee Assessment Area (in million gallons per day, mgd) Year PWS SSI Total 1990 0.14 0.94 1.08 1991 0.09 2.54 2.63 1992 0.14 2.33 2.47 1993 0.25 2.30 2.55 1994 0.25 2.27 2.52 1995 0.14 0.00 0.14 1996 0.21 0.00 0.21 1997 0.21 0.00 0.21 1998 0.21 0.00 0.21 1999 0.20 0.00 0.20 2000 0.19 0.00 0.19 Average 0.18 0.94 1.13 Surface Water Resources The rivers, streams, and lakes ofthe Shawnee Assessment Area ~erve valuable uses for recreation, aesthetics, and habitat for aquatic life. Minor uses include the use of streamflows for water supply, stormwater drainage, and wastewater assimilation. The primary focus ofthis section is the potential use ofsurface waters in the assessment area for supplying public and/or industrial water systems. There are two existing public water supplies in the Shawnee Assessment Area that use surface water sources. The town ofRosiclare withdrawals water from the Ohio River for its water supply, and the Vienna State Correctional Center has a lake that provides its water supply. In 1995, the average water use from these two facilities was 0.63 million gallons per day (mgd). 43 Potential for Development of Additional Surface Water Supplies Water supply systems generally obtain surface water in one of three manners: I) direct withdrawal from a river or stream, 2) impoundment ofa stream to create a storage reservoir, and 3) creation of an off-channel (side~channel) storage reservoir into which stream water is pumped. Direct Withdrawals from Streams For a stream or river to support a continuous direct withdrawal of water, it must have sufficient sustained flow during extreme drought.conditions. For the Shawnee Assessment Area, only the Ohio River provides the sustained flow needed for water supply. The flow in the Ohio River is sufficiently abundant so that withdrawals should not cause any conflicts with instream flow needs, such as water needed for water quality concerns or aquatic habitat. Impounding Reservoirs, Roberts et al. (1957) describe 16 potential reservoir sites that are located in the Shawnee Assessment Area. The locations of these potential sites are shown in Figure 23. Given the favorable terrain, a number ofthese reservoirs could store significant amounts of water, with yields in excess of 5 mgd, far surpassing the currently water use needs of the entire assessment area. However, the construction of impounding reservoirs may be a less likely option for waier supply in this region, because of environmental concerns for the unique'and valuable ecological character ofthe region's streams. Side-Channel Reservoirs Off-channel storage reservoirs, also called side-channel reservoirs, can be a viable water supply for communities requiring a relatively small water use. The construction of side channel reservoirs is generally not limited by local topography and, depending on the desired yield, may be a water-supply option along many streams in the area. The amount ofwater supply that off-channel storage can provide is limited primarily by the temporal distribution of flow in the nearby stream, the size of the storage reservoir, and the amount ofwater that is reserved in the stream for instream flow considerations. 44 _ Reservoirs Boundary N t Scale 1:500,000 5 0 5 10 Miles ; Figure 23. Potential Reservoir Sites in the Shawnee Assessment Area. 45 r Ground-Water Quality This section examines ground-water quality records to detennine temporal trends and to provide baseline water quality parameters within the Shawnee Assessment Area. Increasingly, ground-water contamination is discussed in the news media, and it may seem that the entire ground-water resource has been affected. However, these contamination events are often localized and may not represent widespread degradation of the ground-water resource. By examining the temporal trends in ground-water quality within the area, it may be possible to detennine whether large-scale degradation of the ground-water resource has occurred. . . The general tenn "ground-water quality" refers to the chemical composition of ground water. Ground-water originates as precipitation that filters into the ground. As the water infiltrates the soil, it begins to change chemically due to reactions with air in the soil and with the earth materials through which it flows. Human-induced chemical changes can also occur. In fact, contamination of ground-water is generally the result ofhurnan induced chemical changes and not naturally occurring processes. As a general rule, local ground-water quality tends to remain nearly constant under natural conditions because of long ground-water travel times. Therefore, significant changes in ground-water quality can often indicate degradation of the ground-water resource. Data Sources The ground-water quality data that are used in this report come from two sources: private wells and municipal wells. The private well water quality data are compiled by the Chemistry Division of the Illinois State Water Survey (ISWS) as part ofits water testing program and are maintained by the Ground-water Infonnation group in a water quality database. The municipal well data come from ISWS analyses and from the Illinois Environmental Protection Agency (IEPA) laboratories. The combined database now contains more than 50,000 records of chemical analyses from samples analyzed at the ISWS and IEPA laboratories. Some of these analyses date to the early part of the century, but most are from 1970 to the present. Before 1987, most analyses addressed inorganic compounds and physical parameters. Since then, many organic analyses have been added to the database from theIEPA Safe Drinking Water Act compliance monitoring program. This report presents infonnation for only a portion ofthe chemical parameters within the ISWS database. 47 Data Limitations Several limitations must be understood before meaningful interpretation of the water quality data can begin: I. Representativeness of the sample 2. Location information 3. Data quality (checked by charge balance) 4. Extrapolation to larger areas Private well samples are likely not completely representative of regional ground-water quality. In most cases, private well owners submit samples for analysis only when they believe there may be a problem such as high iron or an odd odor or taste. This suggests that while one or more constituents may not be representative, in general the remainder of the chemical information will be accurate and useful. As a result, the composite data may be skewed toward analyses with higher than normal concentrations. On the other hand, private well information probably gives a better picture ofthe spatial distribution of chemical ground-water quality than municipal well information because of the larger number of samples spread over a large area. Recent IEPA data from municipal wells will not be skewed because each well is sampled and analyzed on a regular basis. While this produces a much more representative sample overall, samples are generally limited to specific areas where municipalities are located. Therefore, these data may not be good indicators of regional ground-water quality. Much ofthe location information for the private wells is based solely on the location provided by the driller at the time the well was constructed. Generally, locations are given to the nearest lO-acre plot ofland. For this discussion, that degree of resolution is adequate. However, it is not uncommon for a given location to be in error by as much as 6 miles. To circumvent possible location errors, this report presents results on an assessment area basis. The validity of water quality data was not checked for this report. However, previous charge balance checking ofthese data was conducted for a similar statewide project (Illinois Department of Energy and Natural Resources, 1994). Charge balance is a simple measure ofthe accuracy of a water quality analysis. It measures the deviation from the constraint ofelectrical neutrality of the water by comparing total cations (positively charged ions) with total anions (negatively charged ions). Because many of the early analyses were performed for specific chemical constituents, a complete chemical analysis is not always available from which to calculate a charge balance. The statewide study searched the water quality database for analyses with sufficient chemical constituents to perform an ion balance. The charge balance checking of those data found that more than 98% ofthe analyses produced acceptable mass balance, which suggests that the chemical analyses are accurate within the database. Using that assumption for this report, we feel confident that most of the analyses used are accurate 48 and give representative water quality parameters for the Shawnee Assessment Area. However, this may be true only for large samples, a factor that should be considered when reviewing the results, as this report presents data from ten decades and a wide range of sample sizes. The question ofextrapolation ofpoint value (a well water sample) to a regional description of ground-water quality is difficult and theoretically beyond the scope ofthis report. However, none ofthe data provide a uniform spatial coverage. Therefore, it seems best to summarize the data on an assessment area basis to ensure an adequate number ofvalues. The private well analyses are more numerous and wi11likely provide better spatial coverage than the municipal well data, which are concentrated in isolated locations. Chemical Comp,onents Selected for Trend Analysis 'In many cases, ground-water contamination involves the introduction into ground-water ofindustrial or agricultural chemicals such as organic solvents, heavy metals, fertilizers, and pesticides. However, recent evidence suggests that many ofthese contamination occurrences are localized and form finite plumes that extend down gradient from the source. Much ofthis information is relatively recent, dating back a few decades, but long-term records at anyone site are rare. As mentioned earlier, changes in the concentrations ofnaturally occurring chemical elements such as chloride, sulfate, or nitrate also can indicate contamination. For instance, increasing chloride concentrations may indicate contamination from road salt or oil field brine, while increasing sulfate concentrations may be from acid wastes such as metal pickling, and increasing nitrate concentrations may result from fertilizer application, feed-lot runoff, or leaking septic tanks. These naturally occurring substances are the major components ofmineral quality in ground-water and are routinely included in ground-water quality analyses. Fortunately, the ISWS has maintained records of routine water quality analyses of private and commercial wells that extend as far back as the 1890s. After examination ofthese records, six chemical constituents were chosen for trend analyses based on the large number ofavailable analyses and because they may be indicators ofhuman-induced degradation of ground-water quality. These components are iron (Fe), total dissolved solids (TDS), sulfate (S04), nitrate (N03), chloride (CI), and hardness (as CaC03). Aquifer Unit Analysis Ground-water occurs in many types ofgeological materials and at various depths below the land surface. This variability results in significant differences ofnatural ground water quality from one part ofIllinois to another and from one aquifer to the next even at the same location. For the purpose ofthis trend analysis, wells that were finished within 49 the unconsolidated sand and gravel units were grouped together, as were wells finished within the bedrock units. The bedrock aquifer systems are the most used within the Shawnee Assessment Area. From the water quality analyses within the ISWS water quality database, 84 (74%) of the 113 well analyses for the area, indicated that the water for the sample came from the bedrock units, whereas, 29 (26%) came from wells finished within the unconsolidated materials above bedrock. Discussion and Results Temporal trends in the six chemical constituents from unconsolidated and bedrock materials are sununarized in this section. Tables 19 and 20 present the results ofdata points and the maximum, minimum, mean, and median ofthe decade analyses for each of the six chemical constituents for unconsolidated and bedrock materials, respectively. Median values are given in the tables by decade, beginning with 1930-1939 (Decade 3), 1940-1949 (Decade 4) and so on through the 1990s (Decade 9) for Table 19. Table 20 begins with Decade 2 (1920-1929) through Decade 9. Decades with only one sample were included in Table 19 and should be used cautiously in any analysis ofmedian values. Each decade covers the corresponding ten-year period. Median concentrations are given per decade so that temporal trends can be identified within the data set. Median values are the midpoints of a set ofdata, above which lie half the data points and below which is found the remaining half. These values are used to look at the central tendency ofthe data set. Although the arithmetic mean would also look at this statistic, it incorporates all data points into its analysis, which can move the mean value in one direction or another based upon maximum or minimum values. In many data sets, outliers occur. These are extreme values that tend to stand alone from the central values ofthe data set. They may lead to a false interpretation ofthe data set, whereas the median values are true values that are central to the data set. By looking at the median we can determine trends in the central portions ofthe data. However, for data sets with a small number of samples, the median may not necessarily be representative of the water quality in the area. The median values for decades where only one sample was analyzed were not included in the median range analysis so as not to skew the interpretation. It is important to recognize that the values included in these tables are reported values. While every attempt to verify the values was made, the validity of each value with regard to method error, etc. is not known. For this reason, the tables include every analysis within the database and all analysis results regardless ofwhether a value seems excessive and regardless ofthe sample size in the decade. 50 Table 19. Chemical Constituents Selected for Trend Analysis, Unconsolidated Aquifer Systems Decade Chemical constituent 3 4 5 6 7 8 9 Iron (Fe) Sample size (N) 12 2 5 I 4 I I Minimum (mg/L) 0.0 0.9 2.0 2.1 0.0 2.6 0.1 Maximum (mg/L) 6.0 25.4 35.0 2.1 3.1 2.6 0.1 Mean (mg/L) 1.3 13.1 23.1 2.1 1.7 2.6 0.1 Median (mg/L) 0.2 13.1 25.0 2.1 1.8 2.6 0.1 TDS Sample size (N) 15 2 5 I 4 I I Minimum (mg/L) 70.0 306.0 228.0 460.0 378.0 483.0 669.0 Maximum (mg/I) 702.0 307.0 539.0 460.0 448.0 483.0 669.0 Mean (mg/l) 313.3 306.5 310.8 460.0 421.2 483.0 669.0 Median (mg/I) 272.0 306.5 258.0 460.0 429.5 483.0 669.0 Sulfate (S04) Sample size (N) 15 2 2 0 3 I I Minimum (mg/I) 3.0 53.0 171.0 0.0 32.0 65.0 314.0 Maximum (mg/I) 270.0 184.0 174.0 0.0 80.0 65.0 314.0 Mean (mg/l) 51.7 118.5 172.5 0.0 58.0 65.0 314.0 Median (mg/I) 24.0 118.5 172.5 0.0 62.0 65.0 314.0 Nitrate (NO,) Sample size (N) 12 2 2 1 4 0 0 Minimum (mg/I) 0.8 1.5 0.0 0.9 0.0 0.0 0.0 Maximum (mgll) 159.2 1.5 0.0 0.9 0.4 0.0 0.0 Mean (mg/I) 28.6 1.5 0.0 0.9 0.2 0.0 0.0 Median (mg/I) 11.2 1.5 0.0 0.9 0.3 0.0 0.0 Chloride (CI) Sample size (N) 15 2 5 I 4 1 I Minimum (mg/I) 3.0 5.0 4.0 15.0 4.0 14.0 8.1 Maximum (mg/I) 92.0 9.0 9.0 15.0 15.0 14.0 8.1 Mean (mg/I) 29.5 7.0 6.6 15.0 9.8 14.0 8.1 Median (mg/I) 21.0 7.0 7.0 15.0 10.0 14.0 8.1 Hardness (as CaCO,) Sample size (N) 12 2 5 I 4 1 1 Minimum (mg/l) 12.0 166.0 169.0 210.0 283.0 383.0 570.0 Maximum (mgll) 490.0 216.0 ·398.0 210.0 390.0 383.0 570.0 Mean (mg/I) 203.5 191.0 222.8 210.0 344.2 383.0 570.0 Median (mgll) 197.5 19.1.0 184.0 210.0 352.0 383.0 570.0 Note: Decade 3~1930-1939, Decade 4=1940-1949, and so on. 51 Table 20. Chemical Constituents Selected for Trend Analysis, Bedrock Aquifer Systems Decade Chemical constituent 2 3 4 5 6 7 8 9 Iron (Fe) Sample size (N) 2 18 5 4 10 31 7 4 Minimum (mg/L) 0.0 0.0 0.1 0.2 0.2 0.0 0.1 0.1 Maximum (mg/L) 15.0 14.0 5.1 11.0 29.0 38.0 1.0 1.3 Mean (mg/L) 7.5 2.3 2.0 4.8 5.2 2.6 0.3 0.4 Median (mg/L) 7.5 0.8 2.0 4.0 1.7 0.2 0.1 0.1 TDS Sample size (N) 2 19 6 4 10 30 6 4 Minimum (mgll 403.0 166.0 207.0 272.0 142.0 195.0 348.0 383.0 Maximum (mg/I) 457.0 2562.0 3048.0 546.0 2135.0 1584.0 409.0 418.0 Mean (mgll) 430.0 678.1 842.3 415.5 695.0 426.3 376.8 406.8 Median (mg/I) 430.0 528.0 391.5 422.0 361.0 355.5 373.0 413.0 Sulfate (S04) Sample size (N) 2 19 3 0 3 17 7 4 Minimum (mg/I) 42.0 0.0 29.0 0.0 21.0 5.0 15.0 22.0 Maximum (mg/I) 60.0 584.0 1810.0 0.0 1376.0 240.0 40.0 36.0 Mean (mgll) 51.0 151.9 626.0 0.0 496.0 56.2 31.3 26.8 Median (mg/I) 51.0 37.0 39.0 0.0 91.0 31.0 38.0 24.6 Nitrate (NO,) Sample size (N) 2 17 I 3 9 23 0 0 Minimum (mg/I) 1.2 0.0 2.7 0.7 0.8 0.0 0.0 0.0 Maximum (mg/I) 31.0 38.9 2.7 1.5 51.0 14.9 0.0 0.0 Mean (mg/L) 16.1 5.0 2.7 1.1 8.6 6.1 0.0 0.0 Median (mg/I) 16.1 2.2 2.7 1.0 2.7 7.1 0.0 0.0 Chloride (CI) Sample size (N) 2 19 6 4 10 30 7 4 Minimum (mg/I) 11.0 4.0 6.0 4.0 4.0 2.0 7.3 10.0 Maximum (mg/I) 31.0 1265.0 34.0 19.0 70.0 42.0 27.0 16.0 Mean (mg/I) 21.0 92.4 16.2 12.5 28.9 11.3 15.7 12.2 Median (mg/I) 21.0 26.0 9.0 13.5 26.0 8.0 19.0 1l.5 Hardness (as CaCO,) Sample size (N) 2 19 6 4 10 29 4 2 Minimum (mg/I) 348.0 25.0 138.0 44.0 84.0 20.0 297.0 324.0 Maximum (mg/I) 349.0 942.0 1872.0 342.0 1390.0 1080.0 336.0 334.0 Mean (mg/I) 348.5 358.9 530.0 206.8 468.3 306.3 321.8 329.0 Median (mgll) 348.5 271.0 271.5 220.5 291.0 280.0 327.0 329.0 Note: Decade 2=1920-1929, Decade 3~1930-1939, and so on.· 52 r Iron (Fe) Iron in ground-water occurs naturally in the soluble (ferrous) state. However, when exposed to air, iron becomes oxidized into the ferric state and forms fine to fluffy reddish-brown particles that will settle to the bottom ofa container ifallowed to sit long enough. The presence of iron in quantities much greater than 0.1 to 0.3 milligrams per liter (mg/l) usually causes reddish-brown stains on porcelain fixtures and laundry. The drinking water standards recommend a maximum limit of0.3 mg/l iron to avoid staining (Gibb, 1973). Unconsolidated Aquifer Systems Iron concentrations for unconsolidated aquifer systems in the assessment area are given in Table 19. Minimum and maximum concentrations for the seven decades are 0.0 and 35.0 mg/I, respectively. The median values range from 0.2 to 25.0 mg/I for these decades. The 25.0 mg/I iron concentration would likely necessitate the use of a commercial treatment system. Concentrations above 1.8 mg/I begin to taste metallic (Fetter, 1980) and would need to be treated in any use of the water. Concentrations greater than 0.3 mg/I would also cause staining of porcelain fixtures, but generally poses no threat to human health. Table 19 suggests no trend in iron concentrations in the area but suggests there may be elevated levels ofiron potentially due to the mining activities that have been a part of this area for many years. Bedrock Aquifer Systems Iron concentrations for bedrock aquifer systems in the assessment area are given in Table 20. Minimum and maximum concentrations are 0.0 and 38.0 mg/I, respectively. The median values range from 0.1 to 7.5 mg/I for all eight decades. These median values could cause staining ofporcelain fixtures (greater than 0.3 mg/I), but generally pose no threat to human health. Table 20 suggests no trend in iron concentrations in the area: Total Dissolved Solids (TDS) The TDS content ofground-water is a measure of the mineral solutes in the water. Water with a high mineral content may taste salty or brackish depending on the types of minerals in solution and their concentrations. In general, water containing more than 500 mg/I TDS will taste slightly mineralized. However, the general public can become accustomed to the taste ofwater with concentrations ofup to 2,000 mg/I. Water containing more than 3,000 mg/I TDS generally is not acceptable for domestic use, and at 5,000 to 6,000 mg/I, livestock may not drink the water. Because TDS concentration is a lumped measure of the total amount of dissolved chemical constituents in the water, it will not be a sensitive indicator of trace-level contamination. However, it is a good indicator of major inputs of ions or cations to ground-water. Unconsolidated Aquifer Systems TDS concentrations within the unconsolidated aquifer systems in the assessment area are given for the seven decades in Table 19. Minimum and maximum concentrations are 53 ...~ reported to be 70.0 and 702.0 mg/I, respectively. The median values for these analyses range from 258.0 to 429.5 mg/1. There are no significant trends in TDS concentrations i indicated within these aquifer systems in the assessment area. Bedrock Aquifer Systems TDS concentrations for bedrock aquifer systems in the assessment area are reported in Table 20. Minimum and maximum concentrations are 142.0 and 3,048 mg/I, respectively. Median values range from 355.5 to 528.0 mg/I. The data indicate no significant trends in TDS. Water with high sulfate concentrations often has a medicinal taste and a pronounced laxative effect on those not accustomed to it. Sulfates generally are present in aquifer systems in one ofthree fonns: as magnesium sulfate (sometimes called Epsom salt); as sodium sulfate (Glauber's salt); or as calcium sulfate (gypsum). They also occur in earth materials in a soluble fonn that is the source for natural concentrations ofthis compound. Human sources similar to those for chloride also can contribute locally to sulfate concentrations. Coal mining operations particularly are a common source of sulfate pollution, as are industrial wastes. Drinking water standards recommend an upper limit of 250 mg/l for sulfates. Trends in sulfate concentrations can suggest potential ground water pollution. Unconsolidated Aquifer Systems Sulfate concentrations for unconsolidated aquifer systems in the assessment area are reported in Table 19. Minimum and maximum concentrations for these decades are 3.0 and 314.0 mg/l, respectively. The median values for the seven decades range from 24.0 to 172.5 mg/1. The table suggests no trends for these decades. Bedrock Aquifer Systems Sulfate concentrations for bedrock aquifer systems in the assessment area are reported in Table 20. Minimum and maximum concentrations are 0.0 and 1,810.0 mg/l, respectively. The maximum concentration (1,810.0) is a reported value; however, it should be viewed as an outlier ofthe dataset, and not as representative ofthe water quality in the area. Median values range from 24.6 to 91.0 mg/l for these decades. Table 20 indicates no significant trend in sulfate concentrations within the assessment area from these aquifer units. Nitrates are considered harmful to fetuses and children under the age ofone when concentrations in drinking water supplies exceed 45 mg/l (as N03), or the approximate equivalent of 10 mg/l nitrogen (N). Excessive nitrate concentrations in water may cause "blue baby" syndrome (methmoglobinemia) when such water is used in the preparation ofinfant feeding fonnulas. Inorganic nitrogen fertilizer has proven to be a source of nitrate pollution in some shallow aquifers, and may become an even more significant 54 r ! source in the future as ever increasing quantities are applied to Illinois fannlands. Trends in concentrations ofnitrate may be a good indication that farm practices in the area are affecting the ground-water environment. Unconsolidated Aquifer Systems Nitrate concentrations for unconsolidated aquifer systems in the assessment area are reported in Table 19. Minimum and maximum concentrations are 0.0 and 159.2 mg/I, respectively. Median values are all below the drinking water standards, and range from 0.3 to 11.2 mg/I for these decades. The ISWS has documented numerous cases of elevated nitrate levels associated with rural private wells (Wilson et aI., 1992). The evidence suggests that rural well contamination is associated more with fannstead contamination ofthe local ground-water or well than with regional contamination of major portions ofan aquifer from land application of fertilizers. This topic continues to be actively studied. Bedrock Aquifer Systems Nitrate concentrations for bedrock aquifer systems in the assessment area are reported in Table 20. Minimum and maximum concentrations are 0.0 and 51.0 mg/I, respectively. Median values are well below the drinking water standards, and range from 1.0 to 16.1 mg/l. The data reported indicates no trends in nitrate concentrations within the assessment area. Chloride Chloride is generally present in aquifer systems as sodium chloride or calcium chloride. Concentrations greater than about 250 mg/l usually cause the water to taste salty. Chloride occurs in earth materials in a soluble form that is the source for normal concentrations ofthis mineral in water. Ofthe constituents examined in this report, chloride is one of the most likely to indicate the impacts ofanthropogenic activity on ground-water. Increasing chloride concentrations may indicate contamination from road salt or oil field brine. The drinking water standards recommend an upper limit of250 mg/I for chloride. In sand and gravel aquifers throughout most of the state, chloride concentrations are usually less than 10 mg/l. Unconsolidated Aquifer Systems Chloride concentrations for unconsolidated aquifer systems in the assessment area are reported in Table 19. Minimum and maximum concentrations are 3.0 and 92.0 mgll, respectively. The median values for these analyses range from 7.0 to 21.0, well below the recommended drinking water standard. Bedrock Aquifer Systems Chloride concentrations for bedrock aquifer systems in the assessment area are reported in Table 20. Minimum and maximum concentrations are 2.0 and 1,265.0 mg/I, respectively. The maximum concentration (1,265.0) is a reported value; however, it should be viewed as an outlier of the dataset, and not as representative of the water 55 r I quality in the area. Median values range from 8.0 to 26.0 mg/I. Table 20 indicates no Significant trend within the assessment area. Hardness (as CaC03) . Hardness in water is caused by calcium and magnesium. These hardness-forming minerals generally are of major importance to users since they affect the consumption of soap and soap products and produce scale in water heaters, pipes, and other parts ofthe water system. The drinking water standards do not recommend an upper limit for hardness. The distinction between hard and soft water is relative, depending on the type of water a person is accustomed to. The ISWS categorizes water from 0 to 75 mg/l as soft, 75 to 125 mg/l as fairly soft, 125 to 250 mg/l as moderately hard, 250 to 400 mg/l as hard, and over 400 mg/l as very hard. Unconsolidated Aquifer Systems Hardness concentrations for unconsolidated aquifer systems in the assessment area are reported in Table 19. Minimum and maximum concentrations are 12.0 and 570.0 mg/l, respectively. The median values for these analyses range from 184.0 to 352.0 mg/I, indicating moderately hard to hard ground-water from the unconsolidated aquifer systems in this area. Bedrock Aquifer Systems Hardness concentrations for bedrock aquifer systems in the assessment area are reported in Table 20. Minimum and maximum concentrations are 20.0 and 1,872.0 mg/I, respectively. Median values range from 220.5 to 348.5 mg/l for these decades. Waters with these concentrations are considered moderately hard to hard. No trends are observed in hardness concentrations from the bedrock in this area. Summary This work was undertaken to examine long-term temporal trends in ground-water quality within the Shawnee Assessment Area. Data from private and municipal wells were the primary sources ofinformation used to show the trends in six chemical constituents of ground-water within the area. The data pertaining to those constituents selected for analysis, demonstrate that on the assessment area scale, ground-water has not been degraded with respect to these chemicals examined. Fluctuations from one decade to the next are more likely related to data limitations than to any inherent changes in ground water quality. It is also evident that the sample size within each decade can playa role in trend analysis. The summarized data reported in Tables 19 and 20 indicated variability, but no significant trend in any of the constituents selected for analysis. Much ofthe contamination ofIllinois' ground-water is localized. Nonetheless, this contamination can render a private or municipal ground-water supply unusable. Once contaminated, ground-water is very difficult and expensive to clean, and clean-up may take many years to complete. Clearly it is in the best interests ofthe people ofIllinois to 56 r protect their ground-water resource through prevention of contamination. The information presented in this report can now be used as a reference in looking at ground water quality in future studies to see whether this resource is remaining stable or degrading. . 57 References Introduction Allen, J.S. 1970. Pope County Surface Water Resources. Illinois Department of Conservation, Division of Fisheries. Allen, J.S. 1971a. Hardin County Surface Water Resources. Illinois Department of Conservation, Division of Fisheries. Allen, J.S. 1971b. Johnson County Surface Water Resources. Illinois Department of gonse~~t!Q!1,J?ivis~n_QfI!!~herie~:.. ~__ ,----- ...- ______Healey, R.W. 1979. River Mileages and Drainage Areas for Illinois Streams, Volume 2: Illinois River Basin. U.S. Geological Survey Water Resources Investigations 79 111. Illinois Department of Commerce and Community Affairs (IDCCA). 2001. Illinois Census 2000. htto://www.state.il.us/2000census Illinois Department ofNatural Resources. 1996. Illinois Land Cover, An Atlas, Illinois Department ofNatural Resources, Springfield, IL, IDNR/EEA-96/05, 157 p. Leighton, M.M., G.E. Ekblaw, and L. Horberg. 1948. Physiographic Divisions of Illinois. Illinois State Geological Survey Report ofInvestigation 129. Mattingly, R.L., and E.E. Herricks. 1991. Channelization of Streams and Rivers in Illinois: Procedural Review and Selected Case Studies. Illinois Department of Natural Resources Report ILENR/RE-WR-91/01. Runge, E.C.A., L.E. Tyler, and S.G. Carmer. 1969. Soil Type Acreages for Illinois. University of Illinois at Urbana-Champaign, College of Agriculture, Agricultural Experiment Station Bulletin 735. Suloway, L., and M. Hubbell. 1994. Wetland Resources of Illinois: An Analysis and Atlas. Illinois Natural History Survey Special Publication 15. Climate and Trends in Climate Changnon, S.A., Jr. 1984. Climate Fluctuations in Illinois: 1901-1980. Illinois State Water Survey Bulletin 68. Changnon, S.A., Jr. 1995. Temporal Fluctuations of Hail in Illinois. Illinois State Water Survey Miscellaneous Publication 167. Illinois Department ofEnergy and Natural Resources. 1994. The Changing Illinois Environment: Critical Trends. Volume 1: Air Resources. ILENR/RE-EA 94/05(1), Springfield IL. Wendland, W.M., and Guinan, P. 1988. A Tornado and Severe Weather Climatology for Illinois: 1955-1986. Transactions of the Illinois Academy of Science 81 (1&2):131-146. 59 Water Use Availability Illinois Department ofEnergy and Natnral Resources. 1994. The Changing Illinois Environment: Critical Trends. Volume 2: Water Resources. ILENRIRE-EA 94/05(2), Springfield, IL. Illinois Department of Agriculture and United States Department of Agriculture, 2000. Illinois Agricultural Statistics, 2000. Illinois Agricultural Statistics Service Bulletin 00-1, Springfield, IL. Roberts, W.J., R. Hanson, F.A. Huff, S.A. Changnon, Jr., and T.E. Larson. 1957. Potential Water Resources of Southern Illinois. Illinois State Water Survey Report ofInvestigation 31. Ground-Water Quality Fetter, C.W. Jr., 1980. Applied Hydrogeology. Charles E. Merrill Publishing Co. Columbus, Ohio. Gibb, J.P. 1973. Water Quality and Treatment ofDomestic Ground-water Supplies. Illinois State Water Survey Circular 118. Illinois Department of Energy and Natural Resources. 1994. The Changing Illinois Environment: Critical Trends. Volume 2: Water Resources ILENRIRE-EA 94/05(2), Springfield, IL. Wilson, S.D., K.J. Hlinka, J.M. Shafer, J.R. Kamy, and K.A. Panczak. 1992. "Agricultural chemical contamination of shallow-bored and dug wells." In Research on Agricultural Chemicals in Illinois Ground-water: Status and Future Directions II. Proceedings of the second annual conference, Illinois Ground-water Consortium, Southern Illinois University, Carbondale, IL. 60