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Global Hydrology

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19th ESRI International User Conference GIS Hydro 99 - Introduction to GIS Hydrology July 25, 1999 - San Diego, California Global Hydrology Francisco Olivera – PowerPoint PPT presentation

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Title: Global Hydrology


1
Global Hydrology
19th ESRI International User Conference GIS Hydro
99 - Introduction to GIS HydrologyJuly 25, 1999
- San Diego, California
  • Francisco Olivera
  • Center for Research in Water Resources
  • University of Texas at Austin

2
The Team
  • Kwabena Asante
  • Marcia Branstetter
  • James Famiglietti
  • Mary Lear
  • David Maidment
  • Francisco Olivera

Researchers celebrating after the successful run
of an Avenue script. (Picture taken from Ajax
Amsterdam The Official Web Site).
3
Overview
  • Soil water balance
  • GIS-based data development.
  • Externally run soil water balance model.
  • GIS-based presentation of results.
  • Flow routing
  • GIS-based terrain and topologic data development.
  • Externally run flow routing model.
  • External presentation of results.

4
Soil Water Balance Model
5
Soil Water Balance Model
Evaporation
Given wfc soil field capacity (mm) wpwp soil
permanent wilting point (mm) P precipitation
(mm) T temperature (C) Rn net radiation
(W/m2)
Soil moisture and surplus
Calculated w actual soil moisture (mm) S
water surplus (mm) E actual evaporation (mm) Ep
potential evaporation (mm)
6
Global Data
Precipitation (Jan.)
Temperature (Jan.)
Net Radiation (Jan.)
Soil Water Holding Capacity
Precipitation and temperature data, at 0.5
resolution, by D. Legates and C. Willmott of the
University of Delaware. Net radiation data, at
2.5 resolution, by the Earth Radiation Budget
Experiment (ERBR). Soil water holding capacity,
at a 0.5 resolution, by Dunne and Willmott.
7
Monthly Surplus
Period between storms 3 days.
8
Monthly Surplus
Effect of disaggregation of monthly precipitation
into multiple storms.
9
Flow Routing Models
Cell
Cell
  • Cell-to-cell
  • Element-to-element
  • Source to sink

Sub-Basin
Reach
Junction
Sink
10
Cell-to-Cell Model
  • Sets a mesh of cells on the terrain and
    establishes their connectivity.
  • Represents each cell as a linear reservoir
    (outflow proportional to storage). One parameter
    per cell residence time in the cell.
  • Flow is routed from cell-to-cell and hydrographs
    are calculated at each cell.

11
Mesh of Cells
  • Congo River basin subdivided into cells by a
    2.8125 ? 2.8125 mesh (T42).
  • With this resolution, 69 cells were defined.

12
Low Resolution Flow Direction
1
2
  • Low resolution flow directions determined from
    high resolution flow directions.
  • The algorithm supports
  • Cells that are not aligned with the DEM.
  • Through-the-side and through-the-corner flow
    directions.

B
A
FAc1
FAc2
3
4
C
FAc3
D
FAc4
13
Low Resolution Stream Network
  • High resolution flow directions (1 Km DEM cells)
    are used to define low resolution flow directions
    (0.5 cells).
  • Niger River Basin stream network based on low
    resolution flow directions (0.5 cells).

14
Cell Length
1
2
  • The cell length is calculated as the length of
    the flow path that runs from the cell outlet to
    the receiving cell outlet.

B
A
FAc1
FAc2
3
4
C
FAc3
D
FAc4
15
Element-to-Element Model
  • Defines hydrologic elements (basins, reaches,
    junctions, reservoirs, diversions, sources and
    sinks) and their topology.
  • Elements are attributed with hydrologic
    parameters extracted from GIS spatial data.
  • Flow is routed from element-to-element and
    hydrographs are calculated at all elements.
  • Different flow routing options are available for
    each hydrologic element type.

16
Sub-Basins and Reaches
  • Congo River basin subdivided into sub-basins and
    reaches.
  • Sub-basins and reaches delineated from digital
    elevation models (1 Km resolution).
  • Streams drain more than 50,000 Km2. Sub-basin
    were defined for each stream segment.

17
Hydrologic System Schematic
  • Hydrologic system schematic of the Congo River
    basin as displayed by HEC-HMS.

18
Hydrologic System Schematic
  • Detail of the schematic of the Congo River basin.

19
Source-to-Sink Model
  • Defines sources where surplus enters the surface
    water system, and sinks where surplus leaves the
    surface water system.
  • Flow is routed from the sources directly to the
    sinks, and hydrographs are calculated at the
    sinks only.
  • A response function is used to represent the
    motion of water from the sources to the sinks.

Source
Flow-path
Source
Sink
Flow-path
20
Sinks
  • Sinks are defined at the continental margin and
    at the pour points of the inland catchments.
  • Using a 3x3 mesh, 132 sinks were identified for
    the African continent (including inland
    catchments like Lake Chad).

21
Drainage Area of the Sinks
  • The drainage area of each sink is delineated
    using raster-based GIS functions applied to a
    1-Km DEM (GTOPO30).

GTOPO30 has been developed by the EROS Data
Center of the USGS, Sioux Falls, ND.
22
Land Boxes
  • Land boxes capture the geomorphology of the
    hydrologic system.
  • A 0.5x0.5 mesh is used to subdivide the terrain
    into land boxes.
  • For the Congo River basin, 1379 land boxes were
    identified.

23
Surplus Boxes (T42 Data)
  • Surplus boxes are associated to a surplus time
    series.
  • Surplus data has been calculated using NCARs
    CCM3.2 GCM model over a 2.8125 x 2.8125 mesh
    (T42).
  • For the Congo River basin, 69 surplus boxes were
    identified.

24
Sources
  • Sources are obtained by intersecting
  • drainage area of the sinks
  • land boxes
  • surplus boxes
  • Number of sources
  • Congo River basin 1,954
  • African continent 19,170

25
Response Function
Ssource
Sink
Flow-path
Qsource
Source
Qsource
Ssource
  • Advection(pure translation)
  • Advection and dispersion (translation and flow
    attenuation)

t
t
Qsource
Ssource
t
t
Qsink S Qsource
26
Source-to-Sink vs. Cell-to-Cell
  • Congo River at the Atlantic Ocean
  • Surplus from NCARs CCM3.2 GCM model
  • v 0.3 m/s

Source-to-sink
Cell-to-cell
27
Source-to-Sink vs.Element-to-Element
  • Congo River at the Atlantic Ocean
  • Instantaneous and uniform surplus of 0.01 m
  • v 0.3 m/s and D 2000 m2/s

Source-to-sink
Cell-to-cell
28
Nerd Stuff
  • Accounting of spatial distribution of flow
    velocities and flow attenuation coefficients.
  • Accounting for losses due to infiltration and
    evaporation.
  • Accounting for controlled and uncontrolled
    reservoirs, and floodplain storage.
  • Relative importance of hydrodynamic dispersion
    (flow attenuation) vs. advection (pure
    translation).
  • Relative importance of hydrodynamic dispersion
    vs. geomorphologic dispersion in large hydrologic
    systems.
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