Kwabena Asante

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Continental Scale River Flow Routing

• presented by
• Kwabena Asante
• Dr David Maidment
• Dr Jay Famiglietti
• Dr Francisco Olivera

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Acknowledgements
National Science Foundation EROS Data Center of
the USGS GIS Hydro Research Group Global
Hydrology Group Dissertation Committee
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Outline

• General Introduction
• Database Construction
• Conceptual Basin Models
• Implementing the Models
• Comparing the Models
• Conclusions

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GIS Hydro 99 Digital Atlas
Digital Atlas of the World Water Balance
www.crwr.utexas.edu
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1500 Major Drainage Basins
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Conceptual Models of a River Basin
Cell-to-Cell
CTC
Watershed Based
HMS
Source-to-Sink
STS
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Developing a HMS model

• Delineate stream and watersheds
• Define routing parameters
• Calculate attributes
• Compute network connectivity
• Create and Edit Basin file
• Route by Muskingum Method

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Developing a STS model

• Define sinks
• Delineate drainage basins
• Define sources
• Calculate attributes of sources
• Create input file for routing code
• Route by Diffusion Wave Method

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The Congo Basin
Area 3.78 million km2 Mean flow 45 000 m3/s 8
Countries
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STS and HMS models of the Congo
Delineation Threshold 1000 km2 Number
of Subbasins/Reaches 1791
Modeling Unit Size 30 (60 x 60 km) Number
of Sources 1378
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Reason for the 3 day delay?
HMS Watershed lag time taken as the larger of
(0.6 longest flow time) and (3.5 routing
time step) 1550 out of 1791 watersheds
Average watershed flow time 1004.1
minutes Average HMS enforced lag time 5273.8
minutes The difference 4269.7
minutes 2.965 days
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Longitudinal Decomposability in HMS
reach length 162,000 m flow velocity 0.3
m/s muskingum K 0.3
n 4
n 5
n 6
n 7
n 8
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Longitudinal Decomposability in HMS
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Longitudinal Decomposability in STS
2000 km
1000 km
1200 km
800 km
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Longitudinal Decomposability in STS
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Effect of STS Modeling Unit Size
Source size 30 (60 x 60 km)
Source size 10 (20 x 20 km)
Source size 5 (10 x 10 km)
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The Nile Basin
Area 3.25 million km2 Mean flow 2,500 m3/s
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Effect of Spatially Distributed Parameters (
Velocity Dispersion Coefficient)
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Conclusions

• STS model can be used to represent the hydrologic
  processes represented in a watershed based model
• STS model incorporating dispersion is
  longitudinally decomposable, hence the STS model
  is scale independent
• Spatially variable velocity and dispersion
  coefficients do make a difference and should be
  taken into account if variable parameter zones
  exist
• HMS imposed restrictions on parameters should be
  reviewed to establish a more scientific basis for
  imposition