Supported by CFAR-SRI IT

TOPOGRAPHIC ANALYSIS AND HYDROLOGIC MODELING FOR PRECISION FARMING

http://www2.gis.uiuc.edu:2280/modviz/pfarm/farm1.html

Helena Mitasova, Bill Brown, Diane Tomlin, Lubos Mitas, Doug Johnston

Computed with GRASS5.0

Field 14

DEM and topographic parameters

• Elevation, given site data and tile
• Slope
• Aspect
• Profile curvature (accelerated/decelerated flow)
• Tangential curvature (convergent/divergent flow)
• Mean curvature (pc+tc)/2

Water and sediment flow analysis

• Simple index based on terrain geometry
• Upslope contributing area A (overland steady state water flow)
• Wetness index (ln(A/tan(slope)), used in older versions of TOPMODEL
• Process based simulation for 9mm/hr rainfall excess, surface rougness with Manning's n=0.05 (results from SIMWE model, without tile)
• Water depth during a brief event before water reaches steady state (300 iterations)
• Water depth for a longer event but still before water reaches steady state (500 iterations)
• Water depth at steady state (5000 iterations)
• Water depth at steady state with highly diffusive flow - this seems to be close to corn yields (5000 iterations)
• net erosion deposition during a brief event (300 iterations, net erosion/deposition is very low)
• net erosion deposition for a longer event (500 iterations, erosion rates typical for gullies start to occure in some areas of concentrated flow and then disappear as the terrain flattens)
• Process based simulation for an extreme event with 36mm/hr rainfall excess (results from SIMWE model, without tile)
• Steady state water depth (low roughness with Mannings n=0.02, water flow is concentrated: forms quickly rills and gullies (increased diffusion starts at 40cm depth))
• Steady state water depth (higher roughness with Mannings n=0.05, water flow is dispersive (prevailing sheet flow, increased diffusion starts at 10cm water depth))
• net erosion deposition for the extreme event

Selected soil chemical properties

• Om : Organic Matter
• K
• P

Yield data

• Corn yields data displayed as point symbols
• Cut through the corn yields data displayed as point symbols
• Smoothed corn draped over 50x exagerrated elevation
• Smoothed corn draped over water depth simulated by SIMWE 
• Bean draped over 50x exagerrated elevation
• Smoothed Bean draped over 50x exagerrated elevation

Conclusion

Fields 26 and 35

DEM (10-30 times exagerrated), selected topographic parameters and wetness index:

• Elevation and given site data
• Slope
• Aspect
• Mean curvature (pc+tc)/2
• Upslope contributing area A
• Wetness index (ln(A/tan(slope))
• Soil conductivity

Water flow analysis

• Water depth after 2 min
• Water depth after 11 minutes with tile network draped over it
• Water depth after 11 minutes (shown as an exagerrated surface)
• Water depth after 47 minutes with tile network
• Water depth after 47 minutes (shown as an exagerrated surface)

• water depths after 10min rain
• water depths after 60 min rain
• water depths 4 hours after rain stops
• water depths 24 hours after rain stops
• water depths 48 hours after rain
• water depths 72 hours after rain.
• animation showing the development of water depths during and shortly after 1in/1hr rainfall lasting for 1 hour and water then draining for 7.5 minutes: movie in mpg format or movie in avi format

Methods/tools under development

Simulation of impact of an open channel on drainage of a small depression using SIMWE:
 

• water depth without a channel in a watershed with small depression
• water depth for the same rainfall with channel (1cell(2m) wide, with 2% slope)

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