global hydrology francisco olivera center for research in water resources university of texas at...
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Global Hydrology
Francisco OliveraCenter for Research in Water
ResourcesUniversity of Texas at Austin
19th ESRI International User ConferenceGIS Hydro 99 - Introduction to GIS HydrologyJuly 25, 1999 - San Diego, California
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).
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.
Soil Water Balance Model
Precipitation: PEvaporation: E
Soil moisture: w
Surplus: S
Temperature: TNet Radiation:
Rn
Soil Water Balance Model
Given:wfc : soil field capacity (mm)wpwp : soil permanent wilting point (mm)P : precipitation (mm)T : temperature (°C)Rn : net radiation (W/m2)
pwpfc
pwpiinipi ww
ww)R,T(EE
Evaporation:
iii1i EPw
0SandPwwE,wwwIf
0SandwwwIf
wSandwwwIf
iipwpiipwp1ipwp1i
i1i1i*
1ipwp
*1ii
*1i
*1i
Soil moisture and surplus: Calculated:w : actual soil moisture (mm)S : water surplus (mm)E : actual evaporation (mm)Ep : potential evaporation (mm)
pwpfc* www
Global Data
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.
Precipitation (Jan.) Temperature (Jan.)
Net Radiation (Jan.) Soil Water Holding Capacity
Monthly Surplus
February May
August November
Period between storms: 3 days.
Monthly Surplus
10 days between storms
1 day between storms 3 days between storms
30 days between storms
Effect of disaggregation of monthly precipitation into multiple storms.
Flow Routing Models
Cell-to-cell
Element-to-element
Source to sinkSource
Flow-path Sink
Cell Cell
Sub-Basin
Junction
Reach
Sink
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.
K1 K2 K3 K4 K5
Mesh of Cells
Congo River basin subdivided into cells by a 2.8125° 2.8125° mesh (T42).
With this resolution, 69 cells were defined.
Low Resolution Flow Direction
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.
FAc3
FAc4
B
C
D
1 2
3
FAc1 A FAc2
4
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).
Cell Length
The cell length is calculated as the length of the flow path that runs from the cell outlet to the receiving cell outlet.
CDL
BCL
ACL
3
2
1
FAc3
FAc4
B
C
D
1 2
3
FAc1 A FAc2
4
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.
Sub-Basin
JunctionReach Sink
Sub-Basin
Sub-Basin
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.
Hydrologic System Schematic
Hydrologic system schematic of the Congo River basin as displayed by HEC-HMS.
Hydrologic System Schematic
Detail of the schematic of the Congo River basin.
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
Sink
SourceFlow-path
Sinks
Sinks are defined at the continental margin and at the pour points of the inland catchments.
Using a 3°x3° mesh, 132 sinks were identified for the African continent (including inland catchments like Lake Chad).
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.
Land Boxes
Land boxes capture the geomorphology of the hydrologic system.
A 0.5°x0.5° mesh is used to subdivide the terrain into land boxes.
For the Congo River basin, 1379 land boxes were identified.
Surplus Boxes (T42 Data)
Surplus boxes are associated to a surplus time series.
Surplus data has been calculated using NCAR’s CCM3.2 GCM model over a 2.8125° x 2.8125° mesh (T42).
For the Congo River basin, 69 surplus boxes were identified.
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
Response Function
Advection(pure translation)
Advection and dispersion (translation and flow attenuation)
Source
Flow-path Sink
t
t
t
t
Qsink = Qsource
Ssource
Qsource
Ssource
Ssource
Qsource
Qsource
Source-to-Sink vs. Cell-to-Cell
Source-to-sink
Cell-to-cell
Congo River at the Atlantic Ocean
Surplus from NCAR’s CCM3.2 GCM model
v = 0.3 m/s
Source-to-Sink vs.Element-to-Element
Source-to-sink
Cell-to-cell
Congo River at the Atlantic Ocean
Instantaneous and uniform surplus of 0.01 m
v = 0.3 m/s and D = 2000 m2/s
0
10,000
20,000
30,000
40,000
50,000
60,000
0 30 60 90 120 150 180 210 240
Time (days)
Flo
w (
m3/s
)
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.