Top Banner
Flux to the Flux to the Upper Upper Mississippi Mississippi River – River – Approach and Approach and application to application to nutrient nutrient understanding understanding
31

True confessions….

Mar 19, 2016

Download

Documents

Groundwater Flux to the Upper Mississippi River – Approach and application to nutrient understanding. True confessions…. The “Upper Mississippi River” has a mix of geologic terrains and associated groundwater flow systems This talk focuses on the unglaciated areas - PowerPoint PPT Presentation
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: True confessions….

Groundwater Flux Groundwater Flux to the Upper to the Upper Mississippi River – Mississippi River – Approach and Approach and application to application to nutrient nutrient understandingunderstanding

Page 2: True confessions….

True confessions….The “Upper Mississippi River” has a mix of

geologic terrains and associated groundwater flow systems

This talk focuses on the unglaciated areas However, approaches/insights gained are

applicable to larger systemWork presented here was team effort

Page 3: True confessions….

La Crosse Areas covered by Study

Coon Valley Watershed

Pool 8 of Mississippi River(Rick Hooper $)

City of La Crosse

La Crosse County

Page 4: True confessions….

Present objectives Characterize regional groundwater flow system Quantify groundwater flow into Pool 8 and

estimate importance for nitrate loading Identify the area that contributes water to each

municipal well Investigate virus occurrence in municipal wells Evaluate the effects of changing land use

(primarily ag practices) on groundwater resources

Page 5: True confessions….

Project ApproachDevelop a simple regional groundwater

flow model for greater La Crosse area Cut out smaller models from regional

model (Pool 8, La Crosse County, Coon Valley)

Perform project objectives on smaller models

Page 6: True confessions….

La Crosse Area Projects

Regional ModelPool 8 ModelLa Crosse County ModelCoon Valley ModelLa Crosse Virus study

Page 7: True confessions….

How groundwater models work:

Plumber’s RuleScotty’s RuleNumerical equations representing real

world entered into the computerAllows us to quantify system and forms

the basis for predictionData requirements can be large

Page 8: True confessions….

Conceptual modelM

issi

ssip

pi R

iver

Lem

on W

eir

Riv

er

La

Cro

sse

Riv

er

Page 9: True confessions….

Miss. River

Regional Area Covered by the GFLOW AE Model

La Crosse

Black River

La Crosse

Kick-apooCoonRoot

175 miles

Black River @ Neilsville

simulated areas outside of watershed of interest

Page 10: True confessions….

Potential ProblemsGaging station data sets may not

overlap in time Large basins have long-term gaging

stations, but also may have confounding factors (e.g., dams)

Definition of baseflow = ?Average baseflow may not be stationary

in time

Page 11: True confessions….

“Average baseflow” may not be stationary in time…

Changes in Q50 flows over time at Four Gaging Stations

0

200

400

600

800

1000

1200

Q50

of K

icka

poo

and

La C

ross

e R

iver

(cfs

)

0

20

40

60

80

100

120

140

160

180

Black nr GalesvilleRoot nr HoustonKickapoo @ La FargeLaCrosse @ Sparta

1938 to 1976 1992 to 2000 1997 to 20001938 to 2000

Q50

of B

lack

and

Roo

t Riv

er (c

fs)

Page 12: True confessions….

Results 1999 Q50 baseflow

0

200

400

600

800

1000

1200Q

50 B

asef

low

(cfs

)

Root River @Houston

Black @Galesville

La X @ Sparta Kickapoo @ LaFarge

Coon @ CoonValley

Measured Simulated

Page 13: True confessions….

R rates needed to match flux targets

5

6

7

8

9

10

11

12

Bas

in R

rate

(in/

yr)

9.1

8.0 8.2

6.4

R_Black R_Lax R_Kickapoo R_Coon

Optimized R rates (1999 Q50 targets, base=500)

NE to SW

Page 14: True confessions….

Okay, complete results

5

6

7

8

9

10

11

12

Bas

in R

rate

(in/

yr)

11.7

R_Root

9.1

8.0 8.2

6.4

R_Black R_Lax R_Kickapoo R_Coon

Optimized R rates (1999 Q50 targets, base=500)

NE to SW

Page 15: True confessions….

Digression: What is going on in the Root River? Root River (using 1999 target) is higher than

expected, with R rate higher than we’d expect to see in the NE parts of Wisconsin!

If we used the entire record (from 1909 until the present) the Root River has the lowest R rate of all basins

Upstream gage knocked out and not replaced Suggests lack in our understanding,and a

problem with our handling of the 1999 measured target

Need to monitor the tributaries if you want to simulate the larger system

Page 16: True confessions….

Looking at the Pool as a whole under baseflow conditions…

Source of Water to Pool 8

93.1%

6.4%

0.5%

Pool 7 inflow

Tributary inflow

Direct GW discharge

Page 17: True confessions….

Being that simulated streams at baseflow = “indirect gw dischg”…

93%

0%

7% Pool 7 inflow

Surface water

Groundwater

(indirect and direct)

Page 18: True confessions….

Not to say there is no event water…Estimated Total Flow using Sartz (1977)

91%

2%7%

Pool 7StormflowBaseflow

Page 19: True confessions….

Geologic sectionM

issi

ssip

pi R

iver

Lem

on W

eir

Riv

er

La

Cro

sse

Riv

er

Eau Claire Confining Unit

Hole in Confining Unit

Page 20: True confessions….

Well Logs compiled by WGNHS

Page 21: True confessions….

Top of Mt. Simon

Page 22: True confessions….

Top of Eau Claire(blue=sh/slt or ss w/ much sh; green=ss w/ some sh)

Northern part of Pool 8

Page 23: True confessions….

Top of Bedrock or Land Surface

Page 24: True confessions….

Add Fluvial Sediments

Page 25: True confessions….

Add Surface Water features

Page 26: True confessions….

Note how similar model is to conceptual model in cross section

Page 27: True confessions….

Plan view Pool 8 model domain extracted from AE 2D model

Pool 7

Pool 8

City of La Crosse

Area of strong upward gradients (artesian wells)

E-W cross section near Goose Island

E-W cross section near Goose Island

Page 28: True confessions….

2D and 3D Regional Model Results

2D AE Source of Water to Pool 8

93.1%

6.4%

0.5%

Pool 7 inflow

Tributary inflow

Groundwater

93.1%

6.5%

0.4%

3D FD Source of Water to Pool 8

Page 29: True confessions….

Distribution of Flux from FD model

**Preliminary Results

River cell flux, ft3/d

2.7 – 0.05 0.05 – 0.020.02 – 0.0070.007 – 0.0050.005-0.0040.004 – 0.0030.003 – 0.0Recharge 0 – 2.6

River Cell Flux (ft/d)

Page 30: True confessions….

Nitrogen Data from BRD

**Preliminary Results

River cell flux, ft3/d

2.7 – 0.05 0.05 – 0.020.02 – 0.0070.007 – 0.0050.005-0.0040.004 – 0.0030.003 – 0.0Recharge 0 – 2.6

River Cell Flux (ft/d)

Max NO3= 16 mg/l as NMax NH4= 0.4 mg/l as N

Max NO3= 13 mg/l as NMax NH4= 0.3 mg/l as N

Max NO3= 6 mg/l as NMax NH4= 7 mg/l as N

Max NO3= 3 mg/l as NMax NH4= 15 mg/l as N

Page 31: True confessions….

Take Home Points We have gw-sw modeling tools that can cover

large areas (Mississippi Pool scale) 2D models performed well for:

Calculating boundaries for 3D inset models Pool 8 water balance information

3D model performed well for: representing best available knowledge Time of travel, vertical gradients, distribution of flow

into pool Direct GW discharge to Pool 8 was small %

Distribution important for other research questions Would be dominant if gw included discharge to tribs