trends in iowa water run-off
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Trends in Iowa Water Run-off . Rick Cruse, Greg Brenneman, and Matt Helmers Iowa Water Center and Iowa State University Extension. For a Given Water Application Rate - Runoff Caused By. Surface of sponge restricting water infiltration – paper towel covering sponge - PowerPoint PPT PresentationTRANSCRIPT
Trends in Iowa Water Run-off Rick Cruse, Greg Brenneman, and Matt
HelmersIowa Water Center and Iowa State University Extension
For a Given Water Application Rate - Runoff Caused By
Surface of sponge restricting water infiltration – paper towel covering sponge
Sponge full of water – nowhere for water to go
For a Given Sponge Condition – Runoff Caused byIncreased water application rate
InfiltrationInfiltration – entry of water into the soil.
Influenced by: Physical characteristics of the soil (e.g. soil texture and soil structure) Soil moisture Cover on the soil and management of the soil Rainfall intensity
Impacts of Land Use on Infiltration
Source: Bharati et. al., 2002Source: Bharati et. al., 2002
Landuse Example Pochohantas Co. Watershed
2002 Landuse
Grassland/herbaceous (6%)Pasture/hay (3%)Cultivated crops (78%)Other (13%)
1940 Landuse
Grassland/herbaceous (25%)Pasture/hay (26%)Corn (29%)Small grains (20%)
Changes in Iowa Farmland
1930 1970 20100
5,000
10,000
15,000
20,000
25,000
30,000
oatshaysoybeansCorn
Acr
es o
f Cro
p - t
hous
ands
Land Cover TrendsMore row cropsRow crops have lower infiltration rates
Tile DrainageRemoves water from saturated ‘sponge’Creates storage space for subsequent rainfallReduces runoff for repetitive storms when
soil profile is full or nearly full
Cum
ulat
ive
surfa
ce ru
noff
(in a
cre-1
)
0
1
2
3
4
5
6
100% Row-crop10% Perennial Cover at Toe Slope10% Perennial Cover in Contour Strips20% Perennial Cover in Contour Strips
Date
Cum
ulat
ive
sedi
men
t exp
ort (
lb a
cre-1
)
0
5000
10000
15000
20000
100% Row-crop10% Perennial Cover at Toe Slope10% Perennial Cover in Contour Strips20% Perennial Cover in Contour Strips
Trends in Precipitation
Groisman, Pavel Ya., Richard W. Knight, David R. Easterling, Thomas R. Karl,Gabriele C. Hegerl, and Vyacheslav N. Razuvaev. 2005. Trends in intense precipitation in the climate record. J. of Climate. 18:1326-1350.
Cedar River Annual Flow Cedar Rapids
1880 1900 1920 1940 1960 1980 2000 20200
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
Ann
ual F
low
- C
FS
Cedar River Peak Flow Rates
Iowa River Peak Flow Rates
Iowa River Peak Flows - Marengo
Concluding CommentsLoss of continuous living cover, increased soil
disturbance, and limited use of conservation practices can increase runoffImpacts are greater for smaller events and dryer soilsMuch smaller impacts for larger events or wet soils
Removal of water from soil profile (evapotransporation, tile drainage) reduces runoff
Water runs off concrete, asphalt, and building roofsExtreme rainfall event frequencies have increasedHigh production and increased water infiltration
(10% perennial cover) may coexist