The World of GIS Hydro ‘98 David R. Maidment University of Texas at Austin Presented by:

GISHydrologic Modeling Environmental descriptionProcess representation Data Input Model Results Synthesis of GIS and Modeling

Linking Data and Models Integrated Spatial Database GIS Hydro ‘98 Models Watershed Characterization Runoff & Routing Hydraulics Water Quality Atmosphere & Soil Water

Traditional approach Spatial Hydrology Process Representation Environmental Description Process-based Modeling Map-based Modeling Hydrologic Modeling

Users Hydrologic simulation Time series data Spatial hydrologic model Spatial data Real World Spatial Hydrologic Modeling Concept

t t t I Q t  Continuous time hourly, daily  Steady state mean annual  Seasonal monthly  Single event Dealing with Time Variation

Two tasks: I. Environmental description using a map II. Process representation using equations Modeling Procedure

Environmental description Process representation  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 Ten Step Procedure for Modeling

 Objectives of the study?  Range and subdivision of the spatial domain?  Duration and subdivision of the time horizon?  Variables to be computed? Step 1. Study Design

Computational effort ~ LMN LMN < 10,000,000 for execution within ArcView Number of: Spatial units = L Variables computed = M Time intervals = N Time Variables Space N M L Space, Time, and Process Variables

Mean annual flow and transport on a raster grid Time Variables Space N=1 M L Time-Averaged Modeling

Land Characterization (Land use, Soils, Climate, Terrain) Water Characterization (water yield, flooding, groundwater, pollution, sediment) Relationships between land type and water characteristics Land and Water Interaction

Land Characterization (Land use, Soils, Climate, Terrain) Non Point Source Pollution (mean annual flows and pollutant loads) Adapt Water to the Land System Water Characterization (water yield, flooding, pollution, sediment)

Land Characterization (Land use, Soils, Climate, Terrain) Water Characterization (water yield, flooding, pollution, sediment) CRWR-PrePro (GIS Preprocessor for HEC-HMS flood hydrograph simulation) Adapt Land to the Water System

CRWR-PrePro: HMS Preprocessor Geographic DataSchematic Diagram Increasing Scale  Increasing Complexity

Digital Elevation Model (DEM)

 Vector representation as points, lines and areas  Raster representation on a grid of DEM cells Vector Raster OutletStreamWatershed Raster-Vector Equivalence

+ =  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 “Burning In” the Streams

 Begin with an elevation grid  Flow in direction of steepest descent Eight-Direction Pour Point Model

ElevationFlow direction grid Flow Direction Grid

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

Flow direction grid Implied network between cell centers Grid Network

Number of upstream cells Classification of flow accumulation Number of cells > 6 = stream 0 cells = watershed boundary Flow Accumulation Grid

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

Types of Outlets and Nodes Stream junction node Stream headwater node System outlet node User-defined node Sub-basin Stream

Stream Segmentation u 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.

Watershed Delineation u The drainage area of each stream segment is delineated.

 What DEM cell size to use?  Cell size = Region area / 1,000,000  What size watershed to delineate?  Watershed > 1000 cells Thousand-Million Rule

Cell Size Watershed Area (km 2 ) Typical Application 1” (~ 30 m) 3” (~ 100 m) 15” (~ 500 m) 30” (~ 1 km) 3’ (~ 5 km) 5’ (~ 10km) , ,000 Urban watersheds Rural watersheds River basins, States Nations Continental Global Application of Digital Elevation Models

Raster to Vector Conversion u Streams and watersheds are converted from raster to vector format.

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

Watershed Parameters Flow length upstream and downstream Average Curve Number Slope and length of the longest flow-path Identification of the longest flow-path Lag-time SCS Unit Hydrograph

 distance downstream to outlet Flow-Length Function in ArcView  distance to upstream divide

Flow Length Downstream to the Watershed Outlet

Flow Length Upstream to the Watershed Divide

Longest Flow-Path Total flow length = upstream length + downstream length

V 21 V 11 V 41 V 31 V 61 V 51 V 32 V 12 V 22 V 42 V 52 V 62 V 23 V 13 V 33 V 53 V 43 V 24 V 16 V 15 V 14 V 63 V 34 V 44 V 54 V 64 V 25 V 35 V 45 V 55 V 65 V 26 V 36 V 46 V 56 V 66 Velocity magnitudeVelocity direction V = aS b S = slope a,b = land cover coefficients Velocity Field

 time to outlet (weighted flow length) Time = Distance x 1 Velocity Flow Time Computation

Isolation of a Sub-System

Connection to HEC-HMS HMS SchematicParameter Transfer HMS Basin File Ferdi’s code

Upper Mississippi Flood Study

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)

CRWR-Prepro Schematic Network Inlets Mississippi River Missouri River Outlet (Mississippi R. at Thebes, Ill)

HEC-Hydrologic Modeling System HMS Basin file CRWR-PrePro HEC-HMS Model Schematic

Land Characterization (Land use, Soils, Climate, Terrain) Non Point Source Pollution (mean annual flows and pollutant loads) Adapt Water to the Land System Water Characterization (water yield, flooding, pollution, sediment)

Possible Land-Water Transform Coefficients Water Land

Map-Based Surface Water Runoff Runoff, Q (mm/yr) Precipitation, P (mm/yr) Accumulated Runoff (cfs) P Q Runoff Coefficient C = Q/P

Water Quality: Pollution Loading Module DEM Precip. Runoff LandUse EMC Table Concentration Load Accumulated Load Load [Mass/Time] = Runoff [Vol/Time] x Concentration [Mass/Vol]

Expected Mean Concentration Land Use EMC Table derived from USGS water quality monitoring sites

Total Constituent Loads Input for Water Quality Model Water Quality: Land Surface -Water Body Connection Bay Water Quality

Flood Hydraulics u Given the flood discharge (HEC-HMS), what is the water surface elevation (HEC- RAS, River Analysis System) u How to draw flood plain maps? HEC-RAS AVRAS Cross-section mapping

Flood Hydraulics: Stream Geometry Data l Determine cross-section elevations from TIN terrain data l HEC-RAS pre- and post-processing using avRAS (ArcView) or HEC AMLs (Arc/Info) l Visualize floodplain TINs with ArcView’s 3D Analyst extension as flood rises

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

GIS - River Analysis System (AVRAS) Pre Processor (Avenue) GIS GIS RAS Import RAS 2.0 GIS RAS Export Post Processor (Avenue) GIS Hydraulic Input Dean Djokic & Zichuan Ye (ESRI)

Stream Bed Shape in ArcView Cross-sections

Flood Plain in HEC-RAS

Floodplain in ArcView

Floodplain in ArcView 3-D Analyst

Spatial Hydrology Virtual Campus Courses u ESRI Virtual Campus course on Spatial Hydrology ( u University of Texas GIS in Water Resources online course during Fall 1998 (limited enrollment) (

DHI: Hydraulic & Water Resources Engineering MIKE SHE MIKE BASIN MIKE 11 MOUSE DHI Models Pipe Networks River Basin Networks 1-D River Modeling Hydrologic Modeling Danish Hydraulic Institute

BYU: Surface and Groundwater Flow Integrates digital terrain models with standard runoff models such as HEC-1, TR-20, TR-55. Subsurface Representation and Model Interface for Groundwater Simulation: MODFLOW, MT3D, MODPATH, SEEP2D, and FEMWATER. Two-Dimensional Surface Water Model Interface for RMA2, RMA4, RMA10, HIVEL2D, FLO2DH (FESWMS), ADCIRC, CGWAVE, WSPRO, SED2D- WES, and DAMBRK. Brigham Young University

EPA: Water Quality TOXIROUTE NPSMQUAL2E US Environmental Protection Agency ArcView Preprocessor for Water Quality Models