This document discusses climate change, agricultural drainage, and water storage in Minnesota. It notes that precipitation in Minnesota has become more variable and extreme rainfall events have increased in size. This challenges the assumption of stationarity used for drainage system design. The document explores how increased precipitation interacts with fixed geology to potentially enlarge drainage pathways and change channel forms. It also discusses Minnesota statutes related to adequate drainage outlets and maintaining water quality and storage. The question is posed of whether both improved agricultural drainage and water storage can be accomplished with increased precipitation under climate change.

1. Climate Change, Ag-
Drainage & Water
Storage in Minnesota
JOE MAGNER*, GARY SANDS*, & JOHN KOLB^
*BIOPRODUCTS & BIOSYSTEMS ENGINEERING, UNIVERSITY OF MINNESOTA, ST. PAUL , MN
^RINKE NOONAN LAW FIRM, ST. CLOUD, MINNESOTA

2. What are today’s Ag-
drainage needs?

3. Field scale blow-out Photo credit ISG

4. Embeddedness
None [5] 5 to 15% Light 25-50% [3] 14
Moderate 50-75%
Severe 75-100% [-
1]
No coarse
substrate [0]
Percent to which
coarse substrates
are surrounded by
by or covered with
fine sediments
throughout the
reach. A few
scattered coarse
particles
surrounded by
sands not rated.
Check if coarse
substrates are
overlain with fine
substrates.

5. MN Statutes Chapter 103E
MN Law requires an Adequate Outlet
An inadequate outlet allows for downstream environmental and aquatic damage
Excessive sediment and nutrient transport leading to eutrophication and the loss of habitat.
Channel enlargement – bank and bed erosion
Sediment deposition in spawning riffles and filling of pools

6. MPCA’s Watershed Program
Ten-year rotating 8-HUC watershed size
Biological - Index of Biological Integrity (IBI)
Chemical - DO, pH, Temp, Pesticides, TSS,
Nutrients
Physical – Habitat, Altered Drainage
Watershed Restoration and Protection Strategy
(WRAPS) Report & One Watershed One Plan

7. Channel
Evolution
Model
Simon and
Hupp (1986)

8. Ditch Channel Adjustment Photo credit Magner

9. Natural
Channel
Adjustment?
Photo credit MNDNR

10. “the river is the carpenter of
its own edifice” (Leopold, 1994)
I S T H E R E A R E L A T I O N S H I P B E T W E E N
C H A N N E L F O R M A N D D R A I N A G E A R E A ?

11. Southwestern Minnesota Regional Curve
y = 3.1194x0.7073
R2
= 0.9875
1
10
100
1000
0.1 1 10 100 1000 10000
Drainage Area (Sq Mi)
Cross-Sectional
Area
(Sq
Ft)
from, Magner & Steffen (2000)

12. Quasi-dynamic equilibrium
There is a direct relationship between Drainage Area (DA) and Channel Cross-
Sectional Area (X-SA).
For a given climate, geology, land use a channel X-SA will adjust to find quasi-
dynamic equilibrium with respect to the contributing DA.
So, we know the climate is changing, what about geology?

13. Geology is
Fixed!
Adding more water
upon fixed geology will
create new pathways of
water movement!
OR…enlarge existing
pathways.

14. 9/14/2022 14
2
3
4
5
6
7
8
9
10
11
1916
1920
1924
1928
1932
1936
1940
1944
1948
1952
1956
1960
1964
1968
1972
1976
1980
1984
1988
1992
1996
2000
2004
2008
2012
2016
Max
Rainfall
size
(inches)
39-station max rainfall by year
Heaviest rain in state often larger, more variable

16. A loss of
Stationarity?

17. We measure Precipitation using
30-year moving averages
Technical Term = STATIONARITY
The statistical
◦ mean,
◦ variance, and
◦ covariance stay constant.
An example: Background noise of the universe,
Non-example: Daily stock market

19. Photo credit Unknown
Major flooding: but that is not the focus of 103F.05

20. MN Statutes 103F.05
“Water quality and storage practices" means those practices that sustain or improve water quality via surface
water rate and volume and ecological management, including but not limited to:
1) retention structures and basins;
2) acquisition of flowage rights;
3) soil and substrate infiltration;
4) wetland restoration, creation, or enhancement;
5) channel restoration or enhancement; and
6) floodplain restoration or enhancement.

21. Can both improved Ag-
drainage and Water storage
be accomplished with
increased precipitation?