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
ALCOM Working Paper No. 16
| ALCOM | GCP/RAF/277/BEL |
| Aquatic Resource Management for Local Community Development Programme | |
| 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
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.
List of Acronyms and Abbreviations
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
4.2. File and directory structure
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
5.4. Modifications in macros, maps and batch files with regard to the directory structure
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