sediment delivery to the watonwan river 2000-2002
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Sediment Delivery to the Watonwan River 2000-2002
What Are Total Suspended Solids (TSS)
• Solid material that is suspended in the water column– Clay and Silt– Organic matter
0
100
200
300
400
500
600
700
800
900
1,000
Ch
ipp
ew
a
Ye
llo
w B
an
k
La
q Q
ue
Pa
rle
Ye
llo
w M
ed
icin
e
Ha
wk
Re
dw
oo
d
Co
tto
nw
oo
d
Lit
tle
Co
tto
nw
oo
d
Du
tch
Wa
ton
wa
n
Le
Su
eu
r
Blu
e E
art
h
Se
ve
n M
ile
Hig
h I
sla
nd
Be
ve
ns
Sa
nd
Ca
rve
r
Blu
ff
Ril
ey
Cre
dit
Wil
low
Nin
e M
ile
TS
S F
WM
C (
mg
/L)
2000 TSS 2001 TSS 2002 TSS TSS Standard (66 mg/l)
Monitoring Season Total Suspended Solids (TSS) Flow-Weighted Mean Concentration
###
##
WO
WSF
WMS3
WMS1
WMS2Madelia
St. James
Mountain Lake
Truman
SampleshedsWMS1 - Watonwan Mainstem by Sveadahl (WT5)WMS2 - North Fork of the Watonwan by LaSalle (WS1)WMS3 - St James and Butterfield Creeks (WT4)WO - Watonwan River Outlet by Garden City (WP1+WT3+WT1)WSF - South Fork of the Watonwan River by Madelia (WT6+WT2)
# Monitoring Site LocationsCitiesRivers and Tributaries
N
EW
S
Watonwan River Samplesheds
Major Storms and Sediment Loads
WMS3
216,000 acres
Watonwan River Site WMS3 Runoff
0.00
2.00
4.00
6.00
8.00
10.00
12.00
2000 2001 2002
Year
Ru
no
ff (
inc
he
s)
15 Year Average
0
0.5
1
1.5
2
4/19
4/30
5/11
5/22 6/2
6/13
6/24 7/5
7/16
7/27 8/7
8/18
8/29 9/9
9/20
10/1
10/1
2
10/2
3
Date
Da
ily
Ra
infa
ll (
in)
0
50
100
150
200
250
300
350
Dis
ch
arg
e (
cfs
)
Daily Rainfall (in)
Discharge (cfs)
Sample Collected
WMS3 2000 Daily Average Flow and Rainfall
4 Storms accounted for 78% of the sediment load
2000 WMS3 Maximum 1 Hour Rainfall Intensities
0
0.5
1
1.5
2
4/18 5/9 5/30 6/20 7/11 8/1 8/22 9/12 10/3 10/24
Date
Ma
x. R
ain
fall In
ten
sit
y (
in/h
r)
0
50
100
150
200
250
300
350
Dis
ch
arg
e (
cfs
)
largest daily 1 hrintensityDischarge (cfs)
Sample Collected
4 events accounted for 78% of the sediment load
Event 1 25% of loadInt - 0.63 in/15min
Event 432% of loadInt - 0.94 in/15min
2000 Summary
• 17 rain events over 0.5”• 4 events accounted for most of the flow
and sediment • All had rainfall intensities greater than 0.5”/hr
• Timing is important - After the crop canopy is closed, runoff and erosion from tillable acres appears to be substantially reduced
WMS3 2002 Daily Average Flow and Rainfall
3 Storms accounted for 71% of the TSS Load
0
0.5
1
1.5
2
2.5
3
3.5
4
3/29 4/19 5/10 5/31 6/21 7/12 8/2 8/23 9/13 10/4 10/25
Date
Da
ily
Ra
infa
ll (
in)
0
50
100
150
200
250
300
350
400
450
Dis
ch
arg
e (
cfs
)
Green < 25NTU'sRed > 25 NTU's
Early through Mid-spring Late Spring through Mid-Summer Period
Late Summer Period-Crop Canopy Closed
WMS3 2002 Daily Average Flow and Maximum 1 hr. Rainfall
Intensities0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
3/29 4/19 5/10 5/31 6/21 7/12 8/2 8/23 9/13 10/4
Date
Da
ily
Ra
infa
ll (
in)
0
50
100
150
200
250
300
350
400
450
Dis
ch
arg
e (
cfs
)
Green < 25NTU'sRed > 25 NTU's
Early through Mid-Spring Pre-Planting Period
Mid-Spring Through Mid-Summer Period
Post-Planting Pre-Canopy
Mid-Summer Through Fall Post-Canopy Period
2002 Summary
• Early Spring – little overland flow• Low intensity storms/residue
• Early through midsummer – 2 storms alone accounted for 58% of the sediment load but only 25% of the flow• High Intensity storms, minimal residue,
altered soil structure
• Late summer – canopy closed• erosion and runoff reduced
Watonwan 2001 – Flood Year
WMS3 2001 Daily Average Flow and Rainfall
0
0.5
1
1.5
2
2.5
3
4/10 5/1 5/22 6/12 7/3 7/24 8/14 9/4 9/25 10/16
Date
Da
ily
Ra
infa
ll (
in)
0
500
1000
1500
2000
2500
3000
3500
4000
Dis
ch
arg
e (
cfs
)
Rain (in)
Dly Ave Flow (cfs)
Sample Collected
32% of load
20% of load
25% of load 14% of total flow
5% of load
Green < 25 NTU'sRed > 25 NTU's
WMS3 2001 Daily Average Flow and Rainfall – Flood Flows Excluded
One storm accounted for 58% of the TSS load
0
0.5
1
1.5
2
2.5
3
3.5
4
5/18 6/8 6/29 7/20 8/10 8/31 9/21 10/12
Date
Da
ily
Ra
infa
ll (
in)
0
200
400
600
800
1000
1200
1400
1600
Dis
ch
arg
e (
cfs
)
Rain (in)
Dly Ave Flow (cfs)
Sample Collected
11% of load
14% of load
58% of load
Green < 25 NTU's Red > 25 NTU's
Watonwan River TSS Flow Weighted Mean Concentrations
0
20
40
60
80
100
120
140
160
180
2000 2001 2002 2003
Year
TS
S F
low
We
igh
ted
Me
an
C
on
ce
ntr
ati
on
s (
mg
/L)
Potential Sediment Sources
Overland flow Runoff from construction sites
Storm water runoffStream bank erosion
2000 Watonwan Storms
2000 Watonwan Storms
Open Tile Intakes
Result
What Can Be Done to Reduce The Amount of Sediment Delivered to
the Watonwan River?• Best Management Practices
– Urban – Stormwater and Construction BMP’s
– Rural – agricultural BMP’s• Continue existing BMP’s: residue
management; conservation tillage; environmentally sensitive land retirements
• Increased: buffers; wetland restorations (water storage); grass waterways; alternate tile intakes
Agricultural BMP’s
Conclusions• High intensity storms of large aerial
coverage occurring during the post-planting pre-canopy period delivered the majority of the total suspended solids loads to Watonwan River site WMS3 during 2000 and 2002
• The TSS load delivered with the flood flows of 2001 was a significant proportion of the seasonal sediment load. However, the TSS flow weighted mean concentration was the lowest of the four monitoring seasons
Conclusions cont.• It appears current BMP’s succeed in reducing sediment
delivery to the Watonwan River during the pre-planting period.
• Runoff and sediment delivery during the closed-canopy period is less than the during the post-planting/pre-canopy period
• Additional BMP’s are needed to address sediment loads and concentrations delivered to the river during the post-planting/pre-canopy period– Wetland restorations– Buffer strips– Grass waterways– Alternatives to open tile intakes
Mid-Spring Through Mid-Summer Period
Post-Planting Pre-Canopy
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