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.