ALCOM Working Paper No. 16

ALCOMGCP/RAF/277/BEL
Aquatic Resource Management for Local Community Development Programme
Cover
The Watershed Database for Sub-equatorial Africa, Structure and User Interface

by
Lieven Verheust
Fisheries and Data Management Officer, ALCOM
and
Gayle Johnson
GIS and Database Assistant, ALCOM

Funding Agencies:
BELGIAN ADMINISTRATION FOR DEVELOPMENT CO-OPERATION WORLD WIDE FUND FOR NATURE

Executing Agency:
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Harare, 1998

Table of Contents



The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries.

Verheust, L; Johnson, G.
The watershed database for sub-equatorial Africa, structure and user interface.
ALCOM Working Paper No 16.Harare, ALCOM/FAO. 1998. 21 p.
ABSTRACT
The watershed delineation for sub-equatorial Africa was done in 1997 based on a digital elevation model and the river layer of the Digital Chart of the World. All subwatersheds were subsequently named and ordered in a transparent database. The watershed database was developed for users who do not have access to high-end GIS packages and can be used as a standalone cellular database or in combination with simple mapping packages. A user interface which was developed for a specific database package in combination with freely available mapping software is also explained.

Preface

This paper accompanies the digital dataset of the watershed model for sub-equatorial Africa. The watershed model was developed with the purpose of delineating exactly the different drainage regions of sub-equatorial Africa across country borders. Delineating drainage regions also means delineating potential boundaries for aquatic species - be they plants or animals - which was the original goal of the development of the watershed model.

ALCOM is a regional aquatic resource management programme of the FAO (Food and Agriculture Organization of the United Nations), based in Harare, Zimbabwe. It covers all the mainland member-countries of SADC before 1998 (Angola, Botswana, Lesotho, Malawi, Mozambique, Namibia, South Africa, Swaziland, Tanzania, Zambia and Zimbabwe).

The aim of ALCOM is to assist member-countries improve the living standards of rural populations through the practice of improved water resource management. Toward this end, pilot activities are conducted in member-countries to demonstrate new techniques, technologies or methodologies.

The information service plays a very important role in ALCOM to disseminate information and to make information available to all those interested in water resource management for local communities. It is in this framework that the following paper was realised.

For more information or to obtain the latest digital watershed data contact ALCOM at:
 
Mailing address:P.O. Box 3730 Harare, Zimbabwe
Physical address:National Parks Complex, Sandringham Drive Harare, Zimbabwe
Telephone:263-4-724985/734797
FAX:263-4-792782
E-Mail:[email protected]
Homepage:http://www.zamnet.zm/zamnet/alcom/alcom.htm

Cover graphic: Watershed delineation of sub-equatorial Africa


Hyperlinks to non-FAO Internet sites do not imply any official endorsement of or responsibility for the opinions, ideas, data or products presented at these locations, or guarantee the validity of the information provided. The sole purpose of links to non-FAO sites is to indicate further information available on related topics.

This electronic document has been scanned using optical character recognition (OCR) software. FAO declines all responsibility for any discrepancies that may exist between the present document and its original printed version.


Table of Contents

List of Acronyms and Abbreviations

1.   INTRODUCTION

2.   INSTALLATION INSTRUCTIONS

2.1.   Required software

2.2.   Installation steps

2.3.   Directory structure

3.   DEVELOPMENT OF THE DATABASE

3.1.   Manual ordering and naming

3.2.   Generation of downstream sequence

3.3.   Generation of upstream sequence

3.4.   Generation of level and megabasin name

3.5.   Colour assignment to megawatersheds

3.6.   Combination of downstream ID'S

3.7.   Calculation of surface area

4.   DATABASE STRUCTURE

4.1.   Fields and linking

4.2.   File and directory structure

5.   INTERFACE

5.1.   Database interface

5.1.1.   Map selected areas as a part of the complete watershed map

5.1.2.   Extract selected areas from the complete watershed map BNA file

5.1.3.   Determination of upstream and downstream basins

5.2.   Mapping software

5.2.1.   Mapviewer

5.2.2.   Windisp

5.3.   Custom written software

5.4.   Modifications in macros, maps and batch files with regard to the directory structure

5.4.1.   Macros

5.4.2.   Map files

5.4.3.   Batch files

References

Appendix I:   Files included on the base disks

Appendix II:   Processing Summary for Joint ALCOM/WWF SADC Watershed Model

Appendix III:   Summary statistics for all megabasins in the database

Appendix IV:   Main watersheds in sub-equatorial Africa

Appendix V:   Program listing of WS_SELEC.BAS