Applications of GIS toWater Resources Engineering

Francisco OliveraDepartment of Civil Engineering

Texas A&M University

Texas A&M UniversityDepartment of Civil Engineering - SeminarSeptember 12, 2001 – College Station, Texas

Geographic Information Systems

The Problem

To analyze hydrologic processes in a non-uniform landscape.

Non-uniformity of the terrain involves the topography, land use and soils, and consequently affects the hydrologic properties of the flow paths.

Watershed divide

Watershed point

Flow path

Watershed outlet

Opportunity

The Solutions

Lumped models: Easy to implement, but do not account for terrain variability.

Spatially-distributed models: Require sophisticated tools to implement, but account for terrain variability.

Overview

Soil Water Balance

Flow Routing Methods

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 – Niger Basin

February May

August November

Period between storms: 3 days.

Monthly Surplus – Niger Basin

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.

Overview

Soil Water Balance

Flow Routing Methods

Results

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.

With this resolution, 69 cells were defined.

Low Resolution River Network

Low resolution river networks determined from high resolution hydrographic data.

B

C

D

1 2

3A

4

Low Resolution River Network

High resolution flow directions (1-Km DEM cells) are used to define low resolution river network (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

B

C

D

1 2

3A

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.

Delineated Streams

Guadalquivir Basin

HMS Schematic of theGuadalquivir 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

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.

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

Pure translation

Translation, flow attenuation, dispersion and decay

Qsink = Qi = [Ii(t) *

Ui(t)]

Source - i

Flow-path - i Sink(t)

Ui(t)

t t

(t)

t

(t)

Ui(t)

t

Ui(t)

Overview

Soil Water Balance

Flow Routing Methods

Results

Global Monthly Surplus

Animation prepared by Kwabena Asante

Global River Network

Hydrographs - Congo River

Runoff Flow

Hydrographs - Amazon River

Runoff Flow

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

0 10 20 30 40 50 60 70

Time (days)

Flo

w (

m3 /s

)

C

B

A

Watershed Geomorphology

V = 1 m/sD = 150 m2/s

Niger River Basin: A = 2’260,000 Km2, B = 226 Km2, and C = 22,600 m2.

Flooding t.u. Campus

Animation prepared by Esteban Azagra

Flooding t.u. Campus

Animation prepared by Esteban Azagra