From GIS to HMS

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From GIS to HMS

• U.S. Army Corps of EngineersHydrologic
  Engineering Center
• University of Texas at AustinCenter for Research
  in Water Resources
• Francisco OliveraAubrey DuggerDavid
  MaidmentEdward Holley

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Overview
Digital Elevation Model (DEM)
Hydrologic Parameters
Precipitation Data
GIS to HMS
HMS
Hydrograph
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Digital Elevation Model (DEM)

• DEM of the Upper Cedar River in Iowa.
• Cell size 500 m

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Flow Direction

• Water flows to one of its neighbor cells
  according to the direction of the steepest
  descent.
• Flow direction takes one out eight possible
  values.

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Flow Accumulation

• Flow accumulation is an indirect way of measuring
  drainage areas (in units of grid cells).

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Stream Definition

• All grid cells draining more than 250 cells (62.5
  Km2) are part of the stream network.

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Stream Segmentation

• Stream segments (links) are the sections of a
  stream channel connecting two successive
  junctions, a junction and the outlet, or a
  junction and the drainage divide.

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Watershed Delineation

• All grid cells flowing towards a specific stream
  segment (link) constitute its watershed or
  drainage area.
• The watershed grid is then converted from raster
  into vector.

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Dissolving Watershed Polygons

• Dangling polygons should be dissolved into any of
  its adjacent (through the side) polygons.

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Watershed Parameters

• Length of main channel L (ft)
• Slope of main channel s ()
• Average curve number
• Lag time tc (min) (SCS 1973)

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Watershed Parameters
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Stream Parameters

• Muskingum steps
• Muskingum K
• Muskingum X

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Stream Parameters
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HMS Basin File

• The output of HECPREPRO is a text file that
  serves as the HMS Basin File (input).

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Hydrologic Elements Structure

• Hydrologic elements structure showing subbasins,
  reaches, junctions and sinks.

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Hydrologic Elements Structure

• Detail of the hydrologic element structure.

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Theissen Polygons

• A Theissen polygon is defined for each
  precipitation station.

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Theissen and Subbasin Polygons

• Theissen polygons intersected with subbasin
  polygons.
• Each polygon of the resulting coverage belongs to
  only one Theissen polygon and only one subbasin
  polygon.

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Theissen and Subbasin Polygons

• Attributes of the subbasins are attached to the
  resulting coverage by joining the attribute
  tables.

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Watershed Precipitation

• The watershed precipitation is the weighted
  average (according to the Theissen polygons) of
  the precipitation recorded at the neighbor
  stations.

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GageWts.precip file for HMS
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Precipitation Input Filefor HMS in DSS Format
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HMS - Basin Hydrograph
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HMS - Reach Hydrograph
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Observed vs. Compared
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Observed vs. Compared
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Conclusions

• The connection between GIS and HMS has been
  developed.
• Sub-basin attributes can be transferred.
• Problems transferring reach attributes.
• Model calibration necessary to estimate
  hydrologic parameters.