Lake Decatur Watershed 15-year Monitoring: Nitrates and Trends

Transcription

1 Lake Decatur Watershed 15-year Monitoring: Nitrates and Trends Laura L. Keefer, Erin Bauer & Momcilo Markus Illinois State Water Survey Prairie Research Institute University of Illinois Champaign, Illinois

2 Acknowledgements City of Decatur, Keith Alexander ISWS Staff Field staff Data processing Lab analysis Louis Arighi Ben Bromiel Sue Bachman Bill Bogner Brian Chaille Saada Hamdy Kevin Rennels Brad Chapin Troy Foster Amy Russell Robert Gardner Sofia Lazovski Susan Shaw Sandy Jones Matt Lowell James Slowikowski David Preston RuthAnn Nicols Josh Stevens Mary Richardson Todd Peters Marguerite Tan Amy Russell Lavany Reddy Ryan Williams Susan Shaw Lauren Sievers Loretta Skowron Kay Surratt Dan Webb

3 Overview Watershed background Historical nitrate-n levels in Lake Decatur Change in land cover Summary of 15-year monitoring data Spatial and temporal observations Nitrate-N trends

4 Lake Decatur Watershed

5 Lake Decatur Nitrate Levels ( ) ISWS Monitoring Period

6 Lake Decatur Nitrate Levels ( ) Nitrate-N Concentration (mg/l) 18 Annual Maximum Concentration Annual Mean Concentration 16 Annual Minimum Concentration MCL Water Year

7 Watershed Land Use/Cover Acres ( x 1) All Acres Corn and Beans 6 Corn Soybeans Small Grains 5 Watershed Area = 592, acres 4 Monitoring Period Year Illinois Agriculture Statistics for Lake Decatur watershed ( )

8 Watershed Land Use/Cover Acres ( x 1) All Acres Corn and Beans 6 Corn Soybeans Small Grains 5 Watershed Area = 592, acres 4 Monitoring Period Year Change in percent watershed Illinois Agriculture area by Statistics NASS land for cover Lake categories Decatur watershed ( ) between 1999 & 28

9 FISHER!< Gibson City MCLEAN DEWITT!< GOOSE CREEK Sangamon River!. 112!. 16!< Rantoul BIG DITCH Location and monitoring period of stations!< Clinton MACON FRIENDS CREEK Decatur!<!.!< 11 Lake Decatur 13!.! !.!<!. Monticello 12 Sangamon River PIATT BIG/LONG CREEK!. 15!< CAMP CREEK CHAMPAIGN Urbana!< ± Sub-watershed Boundary Major Stream!. Stream Monitoring Station!< Precipitation Station 11: WY : WY : WY : WY : WY : WY : WY : WY Miles

10 Nitrate Concentration (mg/l) Nitrate-N Concentrations 2 15 Long Creek Friends Creek Sangamon River at Monticello Lake Decatur a) Minimum Concentration 1 MCL b) Mean Concentration 1 MCL 5 2 c) Maximum Concentration 15 1 MCL Water Year

11 Annual Nitrate-N Load ( lb/acre) Annual Nitrate-N Load (lb/acre) Annual Nitrate-N Load ( lb/acre) Ann Nitrate Loads (lb/acre) Long Creek Friends Creek Monticello Camp Creek 55 + Data only during May Sept Figure??. Annual nitrate-n load for tributary stations during Water Year WYannualNO3Tribs.grf

12 Annual Runoff (inches) and Nitrate-N Yield (lb/acre/year) Flow Weighted Average Nitrate-N Concentration (mg/l) Flow-weighted Nitrate-N Concentrations Runoff: Long Creek Runoff: Friends Creek Runoff: Sangamon River Load per acre: Long Creek Load per acre: Friends Creek Load per acre: Sangamon River Flow-weighted Concentration: Long Creek Flow-weighted Concentration: Friends Creek Flow-weighted Concentration: Sangamon River Water Year

13 Project & long-term data period investigation Sangamon River At Oakford: WY Project Stations: WY Illinois River Oakford Sangamon River Friends Creek Salt Creek Monticello Lake Decatur Watershed Sangamon River At Oakford: WY Sangamon River Watershed Long Creek Miles

14 Nitrate-N Concentration (mg/l) Annual Average nitrate-n concentrations 12 1 Long Creek WY Friends Creek WY Sangamon River at Monticello WY Sangamon River at Oakford WY Water Year Figure 3. Annual average nitrate-n concentrations at project and regional stations

15 Nitrate-N Yield (lbs/acre) Runoff (inches) Average Monthly Nitrate Runoff and Yield Long Creek WY Friends Creek WY Sangamon River at Monticello WY Sangamon River at Oakford WY Sangamon River at Oakford WY Runoff.5. OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP Month Long Creek WY Friends Creek WY Sangamon River at Monticello WY Sangamon River at Oakford WY Sangamon River at Oakford WY Load 2 1 OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP Month

16 Precipitation (inches) Monitoring Period Annual and Moving Average Precipitation a) ILLINOIS Annual Total Precipitation 5-year Moving Average 11-year Moving Average Year

17 Precipitation (inches) Monitoring Period Annual and Moving Average Precipitation 65 6 b) DECATUR Annual Total Precipitation 5-year Moving Average 11-year Moving Average Year

18 Discharge, Concentration, & Yield Trends Significant Trends Based on Kendall-Tau Test (Orange), T-Test (Blue), and Hotelling-Pabst Test (Grey), for Variable Confidence Levels

19 Observations Monitoring period was wet: 8 of 15 years above 3-yr mean annual precipitation Monticello 1-yr streamflow record shows 4 of top 11 total annual discharges occurred during monitoring Nitrate-N Concentrations decreased as drainage area increased Loads were disperse around watershed and varied from year to year Project stations had no significant trends in discharge and yields Based on trends during project and long-term data analysis, possible no significant change in nitrate yields for Lake Decatur watershed since 1975

20 Thank you! CR/ISWSCR21-7.pdf