the path to studying tile drainage

Size: px

Start display at page:

Download "the path to studying tile drainage"

Leon Mitchell
5 years ago
Views:

Fingerprinting Sources of Suspended Sediments Mean 210 Pb Flux (pci/cm 2 /yr) 2.5 2 1.5 1 0.5 Sagatagan Kreighle Henderson George Long Diamond Duck Stahl Reference Lakes y = 0.65 + 4.8x R 2 = 0.

1 Fingerprinting Sources of Suspended Sediments Mean 210 Pb Flux (pci/cm 2 /yr) Sagatagan Kreighle Henderson George Long Diamond Duck Stahl Reference Lakes y = x R 2 = 0.58 Hook Fish Dunns Beaver Conventional Tillage Be Fe Pb Cs Hg Be Fe Pb Cs Hg Streambank Bass George Be Fe Pb Cs Hg Richardson Minimum Tillage Be Fe Pb Cs Hg Tile Drainage Avg Sed Rate inorg. (g/cm 2 /yr) Pasture Be Fe Pb Cs Hg Sand Creek Suspended Sediment the path to studying tile drainage Shawn Schottler, Dan Engstrom and Dylan Blumentritt St. Croix Watershed Research Station--Department of the Science Museum of Minnesota

Lake Pepin Sediment Accumulation History Core Top 10 3 tons/yr 0 200 400 600 800 2008 1990 1970 Hey, Brain what are we going to do today Same thing we do every day Pinky try to figure out where the

2 Lake Pepin Sediment Accumulation History Core Top 10 3 tons/yr Hey, Brain what are we going to do today Same thing we do every day Pinky try to figure out where the sediment comes from, and why it changes Down Core - 10 X faster than pre-settlement mucho 133 dump trucks/day - Records erosion history of Minnesota s ag lands

MN Watershed Bay City I Maiden Rock N W E II S km J III Lake

3 Lake Pepin: Integrator of watershed scale erosion processes Sediment cores = window to the past Record erosion history of MN Watershed Bay City I Maiden Rock N W E II S km J III Lake Pepin Lake City IV Pepin V MN River watershed, ~85% cultivated

4 What is the source of the sediment? Lake Pepin Sediment Accumulation History Field Erosion Non-field

5 So What. Sediment a serious pollutant Ag Fields assumed to be major source Spend many $$$$ to keep soil on fields BMP s designed for fields Can t solve the problem unless we understand the problem??

6 Why does it change over time? Lake Pepin Sediment Accumulation Rate Core Top tons/yr -It s possible the reasons are related -Why does the rate change the way it does? - Do the sources also change? Down Core We can t solve the problem until we understand what is causing the changes.

7 Fingerprinting Sediment Sources with 210 Pb Constant Exposure to Atmosphere and Rain Pb-210 Cultivated Field Suspended Sediment Activity (bq/g) Non-field Erosion 0 Minimal Exposure to Atmosp. and Rain

8 Relative Contribution of Fields to Riverine Sediment 24% 31% S. Fork Crow = 25% 31% 26% Lake Pepin = 14% 28% 20% 16% 27% 30% 15% 14%

9 Redwood R. Chippewa R. Upper Carver Cr. S. Fork Crow R. Watonwan R. Upper LeSueur R. Cottonwood R. Carver Cr Bevens Cr High Island Blue Earth R. LeSueur R Field vs Non-field Sediment Loads Field Load Non-field Load Between Watersheds: - Non-field vary by: 400,000 - Field Load Vary only: 20,000 - Non-field highly variable! Load (1000's tons/yr)

10 Redwood R. Chippewa R. Upper Carver Cr. S. Fork Crow R. Watonwan R. Cottonwood R. Carver Cr Bevens Cr High Island Blue Earth R. LeSueur R Yields--- Field Yield Non field Yield Steeply Incised Watersheds Less Incised Field Yield Vary by 60 kg/ha Non-field Vary by 500 kg/ha Yield (kg/ha-yr)

11 From Hudak and Hajc, 2005

12 ..and now for Lake Pepin (= field + non-field) Field Non-field % 75% % 72% % 65% % 30% Neat-O, but why does it change

13 Non-field if you express loading as is loading, increasing. some sources not really changing 6 Lake Pepin Sediment Loading 5 Field Non-Field Field load ~ constant Non-field accelerating & is now 6X natural rate Load (g/cm 2 -yr) Prairie Ag

14 So % Sediment from non-field sources Ravens Creek = 70% Kasota Pond & integrator sites = 60-80% Lake Pepin = 65% Event TSS samples = >70% and

15 Symbols of the L. Pepin Sed. Accumulation Rate tons/yr Sed Rate is 10X pre-settlement >65% of sed is non-field Therefore RATE of non-field is not natural

16 why change: A hypothesis that needs testing Rate due to artificial drainage + precip Rate due to loss of perennial cover tons/yr (inorganic sed.) % prairie gone Intensification of tile-drainage (& increasing precip) Natural Rate Begin plowing prairie

17 Blue Earth County, slide from MPCA

18 Given that: Non-field inputs are significant and increasing Hypothesize that: changes in riverine hydrology are mechanism for non-field inputs.? Has tile drainage changed riverine hydrologic conditions? Are changes in precipitation responsible These two are linked--how do we disentangle them?

19 Compare watersheds with and without drainage Hydrologic Changes -over time -between watersheds -link to amount/density of drainage - normalize to climate Relate magnitude and timing of: -- hydrologic changes -- installation of drainage to Pepin sedimentation rate changes

20 Disentangling effects of climate from artificial drainage Preliminary data--a hint at what we might find 800 Elk River (minimal tile drainage) LeSueur River (intense tile drainage) R 2 = 0 p = 0.71 R 2 = 0.17 p= Runoff Ratio -May Runoff Ratio = flow/precipition (normalizes flow to rainfall)

21 Examine 14 other hydrologic parameters (monthly and seasonally) e.g. runoff ratio, peak frequency, maximum flow, max flow duration, rate of increase, rate of decrease, flow:pdhi - do they change over time - how do watersheds compare - are changes coincident with drainage, or climate - how much can be explained by drainage v. climate -Has drainage changed hydrologic conditions? Model 2 Waterhsheds ( 1with, 1 without ) Swat model: -calibrate to compare model predictions to actual

22 Summary WHY? Not natural Why has non-field sediment loading increased How much is related to intensification of artificial drainage and/or increased precipitation?

2006 70% 1964 67% 1950 50% 1940 40% Sediment

24 Redwood River Reservoir---different river, same story Glacial Lake Agassiz Non-Field % % % % Sediment Rate Field Non-field

25 Climate is getting Wetter 8 Palmer Hydrologic Drought Index Avg. PHDI April - August y = x R 2 = 0.09 y = x R 2 = 0.08 Region 8 Region

26 Sedimentation Rate and Climate? Avg. PHDI April - August Palmer Hydrologic Drought Index y = 9.8-0x R 2 = 0 y = x R 2 = 0 Region 8 Region kg m -2 yr t yr -1 2X

27 Trends in Sediment Accumulation Rates-- in Different Systems Factor Increase 10 Increase in Sed. Rate since Settlement Pepin Reference Lakes Riverine systems Field + Non-Field Field Source Only Neat-O, but why are they different? 2 0 pre

28 Effect of artificial drainage on flow and non-field erosion?? 800 Elk River (near Big Lake MN) Runoff Ratio Since 1940 Q/P - May y = x R 2 = 0 p = Le Sueur River Runoff Ratio Since 1940 y = x R 2 = 0.17 p= Watershed with minimal artificial drainage Need to quantify and understand this difference Q/P - May Watershed with dense artificial drainage

29 Lake Pepin Sediment Accumulation Rate Core Top tons/yr (inorganic sed.) Hey, Brain what are we going to do today Same thing we do every day Pinky, Try to figure out where the sediment comes from, and why it changes Down Core

Tracing Sediment Sources with Radioisotope Fingerprints. 1. 210 Pb and 137 Cs are deposited by rain 2. Different Sources = Different Concentrations 3.

30 Tracing Sediment Sources with Radioisotope Fingerprints Pb and 137 Cs are deposited by rain 2. Different Sources = Different Concentrations 3. Fields have high concentrations why am I singing and what does it have to do with fingerprinting 4. Non-fields sources have ~ 0 Ravines, Streambanks, Bluffs Gullies 5. Suspended Sediment combination 6. Measure suspended sed. and compare to Source Fingerprints

Patrick Baskfield. Scott Matteson. Minnesota Pollution Control Agency. Minnesota State University Water Resource Center

Patrick Baskfield. Scott Matteson. Minnesota Pollution Control Agency. Minnesota State University Water Resource Center Regression Analysis of Total Suspended Solids Concentrations to Estimate Streambank, Upland Field, and Classic Gully Sediment Contributions to Minnesota River Tributaries Patrick Baskfield Minnesota Pollution