ILLINOIS WATER AND CLIMATE SUMMARY

Transcription

1 ILLINOIS WATER AND CLIMATE SUMMARY July 2009 Illinois State Water Survey 2204 Griffith Drive, Champaign, IL Tel (217) Fax (217) July 2009 Overview (Bob Scott) Temperatures in Illinois during July were well below average, yielding the coldest July on record since Precipitation was above average. Soil moisture within the top 40 inches of soil was above the long-term statewide average. Mean streamflows were above long-term median values. Shallow groundwater levels were above long-term average depths. Temperatures across Illinois (Figure 1) for July were well below average (a -5.3-degree departure). Crop Reporting District (CRD) temperatures ranged from 4.4 degrees below average (southwest and southeast) to 6.3 degrees below average (northwest). Based on preliminary data, this was the coldest July on record since 1895 in Illinois and within each CRD. Precipitation amounts for Illinois in July were above normal (Figure 1). The statewide average of 4.88 inches represented a 1.06-inch surplus or 128 percent of normal for the month. The northeast CRD received the least amount of rainfall, 3.04 inches (81 percent of normal), while the southeast CRD recorded the greatest rainfall total with 7.32 inches (199 percent of normal). Based on preliminary data, this was the 20 th wettest July, 12 th wettest May July (three months), 3 rd wettest February July (six months), and 3 rd wettest August July (12 months) since Soil moisture in the 0- to 40-inch (0- to 100-centimeter) layer at the end of July was above normal near the surface, except in northeastern Illinois, and largely above normal in deeper layers. Overall, soil moisture in Illinois at month s end was above normal for this time of year (Figure 1). Mean provisional streamflow statewide was above the median flow in July, 200 percent of median (Figure 1). Rivers throughout Illinois recorded monthly mean discharges ranging from normal to much above normal. Portions of the lower Illinois River were above local flood stages at the beginning of July. Water surface levels at the end of July were below the normal pool/target operating level at 10 of 29 reporting reservoirs. At the end of July, Rend Lake was 3.7 feet above spillway level, Carlyle Lake was 4.3 feet above seasonal target operating level, and Lake Shelbyville was 9.6 feet above its seasonal target operating level. Lake Michigan s mean level remains below the long-term average. Statewide, shallow groundwater levels were above normal with an average departure of +1.9 feet. Combined with the change in normal monthly groundwater levels between June and July, a 0.3-foot increase in departures from last month was observed (Figure 1). Levels averaged 0.4 feet lower than June levels and were approximately 0.6 feet below July levels of last year. Figure 1. Statewide departures from normal Note: The WARM Network maps and extended network descriptions appear in the January and July issues. Water and Atmospheric Resources Monitoring Program Illinois State Water Survey Institute of Natural Resource Sustainability University of Illinois at Urbana-Champaign Contact Bob Scott: (217) , rwscott1@illinois.edu

2 Weather/Climate Information (Jim Angel and Bob Scott) Temperatures across Illinois for July were well below normal (Figure 2 and Table 1). The highest temperature for the month was reported at Kaskaskia, 95 F on July 10, and the lowest for the month occurred at Wheaton, 44 F on July 5. Based on preliminary data, the statewide average of 70.3 F was the coldest July on record in Illinois since 1895, breaking the 71.5 F record average in Conversely, July of 1936 was the warmest of any month in Illinois since 1895 with a value of 83.1 F. July had 33 reports of record daily minimum temperatures as well as 218 reports of record low maximum temperatures. Precipitation for July was above normal statewide (Figure 2 and Table 1). Du Quoin (Perry County) reported the highest one-day precipitation of 4.88 inches on July 11, and St. David (Fulton County) reported the highest monthly total of 9.04 inches. Severe weather was minimal in July with six reports of tornadoes. On July 1, two tornadoes were reported in Boone County, causing no significant damage. On July 8, a tornado was spotted in both Peoria and Mason Counties with no reported damage. On July 16, a tornado struck near Iuka (Marion County) and destroyed two barns. On July 24, a tornado struck near Princeton (Bureau County) and caused damage to crops, trees, vehicles, and buildings on one farm. The National Weather Service rated it as an EF1 event. Also on this day, numerous reports of hail and wind damage were submitted throughout Illinois. Illinois Climate Network (ICN) Data. Average daily wind speeds across Illinois for July (Figure 3) ranged from 2.8 mph at Dixon Springs to 7 mph at Stelle. The highest value for the month was recorded at Fairfield with a 51-mph gust on July 16. The prevailing wind direction was west-southwesterly to northwesterly across the state. Wind speeds in excess of 8 mph varied from 19 hours at Kilbourne to 253 hours at Stelle. (July has 744 hours.) Average air temperatures ranged from 66 F at DeKalb to 73 F at Carbondale. Solar radiation totals in July fell slightly from June and ranged from 563 Mega-Joules per meter squared (MJ/m 2 ) at Freeport to near 682 MJ/m 2 at Kilbourne. Potential evapotranspiration observations were near a seasonal maximum, varying from 3.0 inches at Freeport to nearly 3.9 inches at Kilbourne. Soil temperatures in Illinois ranged from 64 F at Big Bend to 79 F at Dixon Springs (4-inch level) and from 68 F at DeKalb to 79 F at Dixon Springs (8-inch level). Extended climate outlooks issued by the U.S. Department of Commerce, National Oceanic and Atmospheric Administration, Climate Prediction Center for August call for below normal temperatures and above normal precipitation across Illinois. Outlooks for August through October call for a slight chance of above normal temperatures in northern Illinois and equal chances of above, below, and normal precipitation statewide. Figure 2. Illinois temperature and precipitation during July

3 Crop Reporting District Table 1. Illinois Precipitation (inches) and Temperature (ºF) by Crop Reporting District Jul 09 Amount Last Month Last 3 Months Last 6 Months Last 12 Months % Temp May 09- % Temp Feb 09- % Temp Aug 08- % Avg Dev Jul 09 Avg Dev Jul 09 Avg Dev Jul 09 Avg Northwest Northeast West Central East West-southwest East-southeast Southwest Southeast State Average Note: Data are provisional. Complete, quality-controlled data are available about six months after a given month. Temp Dev Additional Information: Illinois temperature and precipitation data included in these monthly reports are from measurements taken at selected sites within the Cooperative Observer Network of the National Weather Service (NWS), an agency of the National Oceanic and Atmospheric Administration (NOAA), U.S. Department of Commerce (USDOC). Near real-time data are received by the Midwestern Regional Climate Center (MRCC) at the Illinois State Water Survey (ISWS). These data are provisional. Complete, quality-controlled data are received at MRCC from the National Climatic Data Center (NCDC, NOAA, USDOC) about three months after the data are collected. The Illinois Climate Network (ICN) is a 19-site array of automated weather stations scattered across Illinois, operated and maintained by ISWS staff. The network provides enhanced temporal weather observations on numerous weather and climate variables, including atmospheric pressure, air temperature, relative humidity, wind speed and direction, solar radiation, and precipitation. Values of potential evapotranspiration and dew point temperatures are computed and added to the data set. Other direct observations of weather-related variables include soil temperatures and moisture data at various depths and shallow water table levels. ICN sites are located primarily at university agricultural experimental farms and community colleges within the state. Most sensors are polled automatically every 10 seconds and averaged by hour and day. Hourly and daily extremes and times of occurrence for some variables are recorded as well. All data are downloaded to an ISWS computer once a day. The daily maximum and minimum temperature and precipitation data are added to the MRCC records. ICN data provide valuable information on extreme and usual weather events, as well as short- and long-term trends in climate data, which may have direct future impacts on other water resources of Illinois. Extended climate outlooks are produced on a monthly and seasonal basis by the Climate Prediction Center (CPC, NOAA, USDOC) based on extensive sources of timely climate information. The outlooks for Illinois are extracted from the CPC records and are provided in this report as a service to readers. Soil Moisture Information (Bob Scott) Precipitation in Illinois during July was above normal. By the end of July, above normal soil moisture was observed near the surface across Illinois, except in northeastern counties (Figure 4). In the 0- to 6-inch layer, values ranged from 31 percent of normal at Stelle and 78 percent at Champaign to more than 200 percent at Peoria. Conditions in the 6- to 20-inch layer were similarly variable, ranging from 36 percent at Springfield and Rend Lake to greater than 200 percent at Freeport and Carbondale. Soil moisture in the 20- to 40-inch layer ranged from 76 percent at Springfield to more than 200 percent at Freeport. Values in the 40- to 72-inch layer ranged from 77 percent at Champaign to 182 percent at Rend Lake. Overall, soil moisture in Illinois at the end of July continued to be above normal (Figure 1). Compared to conditions at the end of June, soil moisture at the end of July in Illinois increased at many sites (Table 2). Moisture in the 0- to 6-inch layer increased by about 50 percent at Rend Lake and Dixon Springs and by 135 percent at Carbondale, but decreased by 27 percent at Stelle. Changes in the 6- to 20-inch layer increased by 3

4 Figure 3. July monthly averages and totals as collected by the Illinois Climate Network 4

5 Figure 4. August 1 observed percent-of-normal soil moisture based on mean 5

6 Location Table 2. Soil Moisture in Various Layers on August 1, 2009 Aug (inches) Change from Jul 1 (%) Aug (inches) Change from Jul 1 (%) Aug (inches) Change from Jul 1 (%) Freeport (NW) DeKalb (NE) Monmouth (W) East Peoria (C) Stelle (E) Champaign (E) Bondville (E) Perry (WSW) Springfield (WSW) Brownstown (ESE) Olney (ESE) Belleville (SW) Carbondale (SW) Ina (SE) Fairfield (SE) Dixon Springs (SE) percent at Freeport, but decreased by percent across much of central Illinois. In the 20- to 40-inch layer, soil moisture decreased by 11 percent at Carbondale, but changed by no more than 7 percent elsewhere. Additional Information: Soil moisture monitoring is co-located with ICN locations. Historic data were collected manually from site visits twice a month during the growing season (March to October) and once monthly during the remainder of the year. All sites now use automatic readings, which are downloaded nightly within the ICN data stream. These data aid in pinpointing areas and extents of unusual soil moisture levels, their impacts on Illinois agriculture, and insight into potential pending stresses on other water resources of the state. The information becomes especially important during prolonged periods of precipitation drought. The two newest sites, St. Charles and Big Bend, have data histories that are too short to be included here. Surface Water Information (Bill Saylor and Vern Knapp) River and stream discharge and stage data are obtained from gaging stations operated by the U.S. Geological Survey (USGS) or the U.S. Army Corps of Engineers (USACE). The USGS gaging station network is supported, in part, by the Illinois Department of Natural Resources Office of Water Resources, ISWS, and the USACE. Provisional discharge data are obtained from the USGS. Table 3 lists the provisional peak stage for the current month compared to flood stage at selected streamgaging stations located on the Illinois, Mississippi, and Ohio Rivers. The peak stage is determined from the daily morning readings posted by the NWS and/or the USACE. Portions of the lower Illinois River from Havana downstream remained above local flood stages through about the first week of July. Provisional monthly mean flows for 26 streamgaging stations located throughout Illinois are shown in Table 4. Mean values posted by the USGS are listed if available; otherwise, daily mean discharge data posted by the USGS are used to estimate the mean flow for the month. Long-term mean flows for each month are published by the USGS. The month s median flow for each station listed in Table 4 was determined by ranking the July mean flow for each year of record, and selecting the middle value, 50 percent exceedence probability. The statewide percent of historical mean flow and percent of historical median flow are calculated by dividing the sum of the average flows this month at stations in Table 4 by the sum of the historical mean and median flows calculated for the month, respectively, at the same stations. This method is intended to weight individual 6

7 River Station River Illinois mile* Table 3. Peak Stages for Major Rivers during July 2009 Flood stage (feet)* Peak stage (feet)** Date Morris La Salle Peoria Havana Beardstown Hardin Mississippi Dubuque Keokuk Quincy Grafton St. Louis Chester Thebes Ohio Cairo Notes: * River mile and flood stage from River Stages in Illinois: Flood and Damage Data, Illinois Department of Natural Resources, Office of Water Resources, August 2004 (and Addendum, February 2007). ** Peak stage based on daily a.m. readings, not instantaneous peak. Stage data obtained from U.S. Army Corps of Engineers. observations proportionately in the aggregate comparison. (The Illinois River and Rock River stations are excluded from the statewide calculation because other rivers listed in Table 4 contribute to their flow.) Mean provisional flow statewide was above the median value for July (200 percent of the median) and above the long-term mean for the month (130 percent of the mean). Mean streamflow conditions throughout Illinois ranged from normal to much above normal in July. Water-Supply Lakes and Major Reservoirs. Table 5 lists reservoirs in Illinois, their normal pool or target water surface elevation, and other data related to observed variations in water surface elevations. Reservoir levels are obtained from a network of cooperating reservoir operators who are contacted each month by ISWS staff for the current water levels. Reservoir levels are reported in terms of their difference from normal pool (or target level). The average of the month-end readings for the period of record is reported in terms of the difference from normal pool or target level (column 6 of Table 5), and the number of years of record for each reservoir also is given (column 7). Most reservoirs serve as public water supplies, with the exceptions noted in the last column. Compared to end-of-june water levels at 29 reservoirs, end-of-july water levels were higher at three reservoirs, the same as at the end of last month at 16 reservoirs, and lower at 10 reservoirs. For the 29 reservoirs with observations reported at the end of July, water levels at 10 reservoirs were below normal pool (or target operating level), nine reservoirs were above normal pool, and 10 reservoirs were at normal pool or spillway level. Major Reservoirs. Compared to water levels at the end of June, Rend Lake level was about the same at the end of July, Carlyle Lake level was 0.4 feet higher, and Lake Shelbyville was 5.3 feet lower. At the end of July, Rend Lake was 3.7 feet above spillway level, Carlyle Lake was 4.3 feet above seasonal target operating level, and Lake Shelbyville was 9.6 feet above its summer target operating level. Great Lakes. Current month mean and end-of-month values are provisional and are relative to International Great Lakes Datum The July mean level for Lake Michigan was feet, compared to a mean level of feet in July The long-term average lake level for July is feet, based on data. Historically, the lowest mean level for Lake Michigan in July occurred in 1964 at feet, and the highest level occurred in 1986 at feet. The month-end level of Lake Michigan was feet. Additional information: River stage observations are obtained from gaging stations operated by the U.S. Army Corps of Engineers (USACE). Stage observations are reported at 14 locations along the Illinois, Mississippi, and 7

8 Table 4. Provisional Mean Flows, July 2009 Drainage Years 2009 Long-term flows Percent Days of area of mean flow Mean* Median chance of data this Station (sq mi) record (cfs) (cfs) (cfs) Flow condition exceedence month Rock River at Rockton above normal Rock River near Joslin above normal Pecatonica River at Freeport above normal Green River near Geneseo much above normal 7 31 Edwards River near New Boston much above normal 7 31 Kankakee River at Momence normal Iroquois River near Chebanse normal Fox River at Dayton above normal Vermilion River at Pontiac normal Spoon River at Seville much above normal LaMoine River at Ripley normal Bear Creek near Marceline normal Mackinaw River near Congerville normal Salt Creek near Greenview above normal Sangamon River at Monticello normal South Fork Sangamon near Rochester normal Illinois River at Valley City 26, ,500 21,040 18,650 above normal Macoupin Creek near Kane above normal Vermilion River near Danville normal Kaskaskia River at Vandalia much above normal 8 31 Shoal Creek near Breese above normal Embarras River at Ste. Marie above normal Skillet Fork at Wayne City N/A N/A N/A 16 Little Wabash below Clay City normal Big Muddy at Plumfield much above normal 3 31 Cache River at Forman above normal Notes: Source streamflow data is obtained from the U.S. Geological Survey. N/A = not available. Much below normal flow = % chance of exceedence. Below normal flow = 70-90% chance of exceedence. Normal flow = 30-70% chance of exceedence. Above normal flow = 10-30% chance of exceedence. Much above normal flow = 0-10% chance of exceedence. *As reported in U.S. Geological Survey (USGS) Water Resources Data, Illinois, Water Year

9 Table 5. Reservoir Levels in Illinois, July 2009 Current level Average June Normal pool difference from Monthly difference from Years reported or target normal or target change normal or target of pumpage Reservoir County level (feet) (feet) (feet) (feet) record (million gallons) Altamont Effingham N/A N/A N/A Bloomington McLean No pumpage Canton Fulton Carlinville Macoupin Carlyle (1) Clinton N/A Coulterville Randolph N/A N/A N/A Decatur (1,3) Macon ,045.5 Evergreen (4) Woodford Glenn Shoals (2) Montgomery w/hillsboro Greenfield Greene Highland Madison Hillsboro (2) Montgomery Jacksonville (2) Morgan N/A N/A w/mauvaise Terre Kinkaid Jackson Lake of Egypt Williamson N/A Mattoon Coles w/paradise Mauvaise Terre (2) Morgan N/A N/A no meter Mt. Olive (new) Macoupin N/A N/A w/mt. Olive (old) Mt. Olive (old) Macoupin Nashville (3) Washington N/A N/A Pana Christian N/A Paradise Coles Paris (east) Edgar Paris (west) Edgar w/paris (east) Pinckneyville Perry N/A N/A Pittsfield Pike Raccoon (1) Marion N/A N/A Rend Franklin N/A Salem (3) Marion Shelbyville (1) Shelby Not PWS Sparta (3) Randolph Spring (4) McDonough N/A Springfield (1,3) Sangamon Taylorville Christian Vermilion (4) Vermilion Virginia Cass Not PWS Notes: Normal pool and target level datum is NGVD Current levels reported represent water surface levels at the end of the month, not the monthly average. Average difference from normal or target level is the arithmetic average of reported month-end values for the period of record indicated. Years of record = total number of monthly readings included in month-end average. Total period of record may be longer. Not PWS = not a public water supply. N/A = not available. (1) Target operating level may vary. Seasonal target levels this month represent August 1 values. (2) Instrumentation not available to measure height of water elevation above spillway. (3) Natural inflow can be supplemented by other sources. (4) Normal pool elevations have changed during period of record reported. 9

10 Ohio Rivers. River stage is the observed water surface level at the gage location relative to the gage s own datum, or zero mark. The elevation of gage zero for each site is chosen arbitrarily, and varies from station to station. Stage is not equivalent to the depth to the river bottom. Flood stage is a specified stage value, typically describing the approximate level at which a river goes out of its banks at or near the gage location. Flood stage designations vary from station to station, and apply locally. Stage may be converted to an elevation (relative to mean sea level) by adding the stage value to the gage datum elevation, as reported in a common vertical datum (e.g., National Geodetic Vertical Datum 1929). Streamflow data are obtained for 26 stations along selected Illinois streams and rivers from long-term monthly means published by the U.S. Geological Survey (USGS). The USGS gaging station network is supported in part by the Illinois Department of Natural Resources Office of Water Resources, the Illinois State Water Survey (ISWS), and the USACE. Provisional discharge data are obtained from the USGS. Monthly median flow is determined by ranking the monthly mean flows for the same month for each year of record, and selecting the middle value, to determine a 50 percent exceedence probability. The current month s flow condition at each station is classified from much above normal to much below normal by a comparison of the mean flow for the current month relative to the monthly mean flow statistics during the period of record for the same month. With very few exceptions, the median flow for a particular month will be less than the mean flow. The current month s flow as a percent of the median in nearly every case will be higher than the percent of the mean. Reservoir levels are obtained from a network of cooperating reservoir operators who are contacted each month by ISWS staff. The current month s average month-end water surface level for each reservoir is the arithmetic average of the month-end levels for the period of record of reports to ISWS. Most of the reservoirs polled serve their local communities as public water supply reservoirs. The ISWS began collecting month-end water surface elevations at reservoirs in Groundwater Information (Ken Hlinka) Comparison to Average Levels. Shallow groundwater levels in 16 observation wells, which are remote from pumping centers, were above average for the month. July levels were 1.9 feet above normal and ranged from 0.4 feet below to 6.4 feet above normal levels (Table 6). Comparison to Previous Month. Shallow groundwater levels were below those of last month. Levels averaged 0.4 feet below and ranged from 3.8 feet below to 2.7 feet above levels of last month. Comparison to Same Month, Previous Year. Shallow groundwater levels in July were below levels measured one year ago. Levels averaged 0.6 feet below and ranged from 10.3 feet below to 2.6 feet higher than during July Additional Information. Shallow groundwater well monitoring is conducted at 17 locations in Illinois sited in rural areas to measure water table conditions under natural conditions remote from pumping stations. Wells are installed with on-site recording devices and downloaded during monthly site visits. These data enable ISWS staff to assess short- and long-term trends in water table levels to enhance our understanding of the impacts and extents of phenomena such as droughts and floods in Illinois. In particular, these data become important to monitor the lingering effects of periods of deficit precipitation on the shallow groundwater resources of the state. 10

11 Table 6. Month-End Shallow Groundwater Level Data Sites, July 2009 Number Well name County Well depth (feet) This month s reading (depth to water, feet) 15-year avg. level (feet) Deviation from Period of record avg. (feet) Previous month (feet) Previous year (feet) 1 Galena JoDaviess Mt. Morris Ogle Crystal Lake McHenry Cambridge Henry *12.80 N/A N/A N/A N/A 5 Fermi Lab DuPage Good Hope McDonough Snicarte Mason Coffman Pike N/A Greenfield Greene Janesville Cumberland St. Peter Fayette SWS #2 St. Clair Boyleston Wayne Sparta Randolph SE College Saline Dixon Springs Pope Bondville Champaign Notes: * Data not used in analysis N/A - Data not available. Averages Addendum (Nancy Westcott) Imperial Valley Precipitation. Precipitation for July 2009 was again above average and variable. Monthly gage totals were greatest in the south-central region, and precipitation was lightest in the southwestern and northeastern corners of the network. Individual gage amounts ranged from 9.80 inches at Site #21 to 2.57 inches at Site #18. The 30-year, , average precipitation amounts for July at Havana and Mason City are 3.87 and 4.04 inches, respectively. The July 2009 network average of 5.16 inches is about 135 percent of the 16-year ( ) IVWA July network average of 3.82 inches. Cook County Precipitation. July 2009 precipitation amounts were generally light. The greatest precipitation was found in the far south and north-central regions of the county, and the lightest precipitation was in the northern and southwestern portions of the network. Precipitation values ranged from 3.53 inches at Site #25 (Chicago Heights) to 0.78 inches at Site #1 (Northbrook). The July 2009 network average of 1.79 inches is about 50 percent of the 19-year ( ) July network average of 3.56 inches. Additional Information: The addendum presents reports on two small, regional, long-term precipitation networks in Illinois. The Imperial Valley Precipitation Network is a 20-site weighing-bucket rain gauge array operated by ISWS for the Imperial Valley Water Authority since The network is located in Mason and Tazewell Counties of Illinois within the most heavily irrigated region of the state. Soils here are thick sand and gravel deposits associated with the confluence of two major ancient river valleys, the Mississippi and the Mahomet- Teays. The precipitation data help to determine the rate of groundwater drawdown in dry periods and during the growing season, and the rate at which the aquifer recharges. The Cook County Precipitation Network is a 25-site weighing-bucket rain gauge array operated by the ISWS for the U. S. Army Corps of Engineers since The network is located in the Lake Michigan and Des Plaines River watersheds of Cook County to provide accurate precipitation measurements for modeling storm runoff, a crucial parameter used to compute the amount of water diverted from Lake Michigan. 11

12 a. Imperial Valley b. Cook County Figure 5. Long-term raingage network precipitation totals (inches) for July 2009 Data sources for information in this publication include the following: CPC - Climate Predication Center, ISWS - Illinois State Water Survey, MRCC - Midwestern Regional Climate Center, NCDC - National Climate Data Center, NWS - National Weather Service, USACE - U.S. Army Corp of Engineers, USGS - U.S. Geological Survey, WARM - Water and Atmospheric Resources Monitoring Program, 12

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14 Mt. Olive (new) 14