The World of GIS Hydro 98

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The World of GIS Hydro 98
Presented by
David R. Maidment University of Texas at Austin
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Synthesis of GIS and Modeling
GIS
Hydrologic Modeling
Environmental description
Process representation
Input
Data
Model
Results
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Linking Data and Models
Integrated Spatial Database
GIS Hydro 98 Models
Watershed Characterization
Atmosphere Soil Water
Runoff Routing
Hydraulics
Water Quality
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Hydrologic Modeling
Traditional approach
Spatial Hydrology
Process Representation
Environmental Description
Process-based Modeling
Map-based Modeling
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Spatial Hydrologic Modeling Concept
Hydrologic simulation
Time series data
Users
Real World
Spatial hydrologic model
Spatial data
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Dealing with Time Variation
? Continuous time hourly, daily
t
? Steady state mean annual
t
? Seasonal monthly
t
Q
I
? Single event
t
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Modeling Procedure
I. Environmental description using a map
Two tasks
II. Process representation using equations
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Ten Step Procedure for Modeling
? 1. Study design ? 2. Terrain analysis ?
3. Land surface description ? 4. Subsurface
description ? 5. Hydrologic data
representation ? 6. Soil water balance ? 7.
Water flow ? 8. Constituent transport ? 9.
Impact of water utilization ? 10. Presentation of
results
Environmental description
Process representation
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Step 1. Study Design
? Objectives of the study? ? Range and
subdivision of the spatial domain? ? Duration
and subdivision of the time horizon? ?
Variables to be computed?
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Space, Time, and Process Variables
Number of Spatial units L Variables computed
M Time intervals N
Time
Variables
N
Computational effort LMN
M
Space
LMN lt 10,000,000 for execution within ArcView
L
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Time-Averaged Modeling
Mean annual flow and transport on a raster grid
Time
Variables
M
L
N1
Space
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Land and Water Interaction
Water Characterization (water yield, flooding,
groundwater, pollution, sediment)
Land Characterization (Land use, Soils, Climate, T
errain)
Relationships between land type and water
characteristics
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Adapt Water to the Land System
Water Characterization (water yield, flooding,
pollution, sediment)
Land Characterization (Land use, Soils, Climate, T
errain)
Non Point Source Pollution (mean annual flows and
pollutant loads)
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Adapt Land to the Water System
Water Characterization (water yield, flooding,
pollution, sediment)
Land Characterization (Land use, Soils, Climate, T
errain)
CRWR-PrePro (GIS Preprocessor for HEC-HMS
flood hydrograph simulation)
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CRWR-PrePro HMS Preprocessor
Geographic Data
Schematic Diagram
Increasing Scale ? Increasing Complexity
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Digital Elevation Model (DEM)
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Raster-Vector Equivalence
? Vector representation as points, lines and
areas ? Raster representation on a grid of DEM
cells
Vector
Outlet
Stream
Watershed
Raster
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Burning In the Streams
? Take a mapped stream network and a DEM ? Make a
grid of the streams ? Raise the off-stream DEM
cells by an arbitrary elevation increment ?
Produces "burned in" DEM streams mapped streams


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Eight-Direction Pour Point Model
? Begin with an elevation grid ? Flow in
direction of steepest descent
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Flow Direction Grid
Elevation
Flow direction grid
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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 of eight possible
  values.

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Grid Network
Implied network between cell centers
Flow direction grid
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Flow Accumulation Grid
Number of upstream cells
Classification of flow accumulation
Number of cells gt 6 stream 0 cells watershed
boundary
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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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Types of Outlets and Nodes
Stream junction node Stream headwater
node System outlet node User-defined node
Sub-basin Stream
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Stream Segmentation

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

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Watershed Delineation

• The drainage area of each stream segment is
  delineated.

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Thousand-Million Rule
? What DEM cell size to use? ? Cell size Region
area / 1,000,000 ? What size watershed to
delineate? ? Watershed gt 1000 cells
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Application of Digital Elevation Models
Watershed Area (km2)
Typical Application
Cell Size
1 ( 30 m) 3 ( 100 m) 15 ( 500 m) 30
( 1 km) 3 ( 5 km) 5 ( 10km)
5 40 1000 4000 150,000 400,000
Urban watersheds Rural watersheds River basins,
States Nations Continental Global
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Raster to Vector Conversion

• Streams and watersheds are converted from raster
  to vector format.

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Dissolving Spurious Polygons

• Cells connected to the main watershed polygon
  through a corner are defined as a separate
  polygon (spurious polygon).
• These polygons are dissolved into the main
  polygon.

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Watershed Parameters
Flow length upstream and downstream
AverageCurve Number
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Flow-Length Function in ArcView
? distance downstream to outlet
? distance to upstream divide
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Flow Length Downstream to the Watershed Outlet
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Flow Length Upstream to the Watershed Divide
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Longest Flow-Path
Total flow length upstream length downstream
length
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Velocity Field
Velocity magnitude
Velocity direction
V aSb S slope a,b land cover
coefficients
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Flow Time Computation
? time to outlet (weighted flow length)
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Isolation of a Sub-System
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Connection to HEC-HMS
HMS Schematic
Parameter Transfer
Ferdis code
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Upper Mississippi Flood Study
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Streams and Subwatersheds
162 subwatersheds each with a USGS gage at the
outlet defined using 15 (500m) DEM
Rivers defined by EPA River Reach File 1 (RF1)
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CRWR-Prepro Schematic Network
Mississippi River
Missouri River
Outlet (Mississippi R. at Thebes, Ill)
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HEC-Hydrologic Modeling System
HEC-HMS Model Schematic
CRWR-PrePro
HMS Basin file
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Adapt Water to the Land System
Water Characterization (water yield, flooding,
pollution, sediment)
Land Characterization (Land use, Soils, Climate, T
errain)
Non Point Source Pollution (mean annual flows and
pollutant loads)
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Possible Land-Water Transform Coefficients
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Map-Based Surface Water Runoff
Estimating the surface water yield by using a
rainfall-runoff function
Runoff, Q (mm/yr)
Q
P
Runoff Coefficient C Q/P
Accumulated Runoff (cfs)
Precipitation, P (mm/yr)
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Water Quality Pollution Loading Module
Load Mass/Time Runoff Vol/Time x
Concentration Mass/Vol
Precip.
Runoff
DEM
LandUse
Accumulated Load
EMC Table
Load
Concentration
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Expected Mean Concentration
Land Use
EMC
Table derived from USGS water quality monitoring
sites
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Water Quality Land Surface -Water Body Connection
Bay Water Quality
Total Constituent Loads
Input for Water Quality Model
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Flood Hydraulics

• Given the flood discharge (HEC-HMS), what is the
  water surface elevation (HEC-RAS, River Analysis
  System)
• How to draw flood plain maps?

AVRAS
HEC-RAS
Cross-section mapping
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Flood Hydraulics Stream Geometry Data

• Determine cross-section elevations from TIN
  terrain data
• HEC-RAS pre- and post-processing using avRAS
  (ArcView) or HEC AMLs (Arc/Info)
• Visualize floodplain TINs with ArcViews 3D
  Analyst extension

as flood rises
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Hydraulics RAS Stream Geometry Data

• Digital orthophoto serves as a base map upon
  which to digitize the stream
• Avenue scripts create an ArcView cross-section
  table from the HEC-RAS output text file
• Link cross-section table records to cross-section
  locations on the digitized stream

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GIS - River Analysis System (AVRAS)
GIS
Hydraulic Input
Pre Processor (Avenue)
GIS RAS Import
RAS 2.0
GIS RAS Export
Dean Djokic Zichuan Ye (ESRI)
Post Processor (Avenue)
GIS
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Stream Bed Shape in ArcView
Cross-sections
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Flood Plain in HEC-RAS
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Floodplain in ArcView
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Floodplain in ArcView 3-D Analyst
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Spatial Hydrology Virtual Campus Courses

• ESRI Virtual Campus course on Spatial Hydrology
  (http//campus.esri.com/campus/home/home.cfm)
• University of Texas GIS in Water Resources online
  course during Fall 1998 (limited enrollment)
  (http//www.ce.utexas.edu/prof/maidment)

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DHI Hydraulic Water Resources Engineering
Danish Hydraulic Institute
MIKE 11
MOUSE
Pipe Networks
River Basin Networks
1-D River Modeling
Hydrologic Modeling
MIKE SHE
MIKE BASIN
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BYU Surface and Groundwater Flow
Brigham Young University
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EPA Water Quality
US Environmental Protection Agency
NPSM
QUAL2E
ArcView Preprocessor for Water Quality Models
TOXIROUTE