ALCOM GCP/RAF/277/BELALCOM GCP/RAF/277/BEL Aquatic Resource Management for Local Community Development Programme ALCOM Working Paper No. 16 The Watershed Database for Sub-equatorial

ALCOM GCP/RAF/277/BELAquatic Resource Management for Local Community Development Programme

ALCOM Working Paper No. 16

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

Table of Contents

List of Acronyms and Abbreviations v1. INTRODUCTION 12. INSTALLATION INSTRUCTIONS 2 2.1. Required software 2 2.2. Installation steps 2 2.3. Directory structure 23. DEVELOPMENT OF THE DATABASE 3 3.1. Manual ordering and naming 3 3.2. Generation of downstream sequence 3 3.3. Generation of upstream sequence 3 3.4. Generation of level and megabasin name 4 3.5. Colour assignment to megawatersheds 4 3.6 Combination of downstream ID'S 4 3.7. Calculation of surface area 44. DATABASE STRUCTURE 5 4.1. Fields and linking 5 4.2. File and directory structure 55. INTERFACE 6 5.1. Database interface 6 5.1.1 Map selected areas as a part of the complete watershed map 6 5.1.2.. Extract selected areas from the complete watershed map BNA file 6 5.1.3. Determination of upstream and downstream basins 6 5.2. Mapping software 7 5.2.1. Mapviewer 7 5.2.2. Windisp 7 5.3. Custom written software 8 5.4. Modifications in macros, maps and batch files with regard to the directory

structure 9 5.4.1. Macros 9 5.4.2. Map files 9 5.4.3. Batch files 10

References 11

Appendix I: Files included on the base disk 12Appendix II; Processing Summary for Joint ALCOM/WWF SADC Watershed Model 13Appendix III: Summary statistics for all megabasins in the database 17Appendix IV: Main watersheds in sub-equatorial Africa 20Appendix V: Program listing of WS SELEC.BAS 21

List of Acronyms and Abbreviations

ALCOM Aquatic Resource Management for Local Community Development ProgrammeBADC Belgian Agency for Development Cooperation BNA Atlas GIS file mapping format DCW Digital Chart of the World DEM Digital Elevation Model DMA Defense Mapping Agency FAO Food and Agriculture Organization of the United Nations GIS Geographic Information System GSM Golden Software Map IWQS Institute for Water Quality Studies (Dpt. of Water Affairs and Forestry, ZA) ONC Operational Navigation Chart RRSP Regional Remote Sensing Project SADC Southern African Development Community USAID United States Agency for International Development USFS United States Forestry Service USGS United States Geological Survey WRD Water Resource Database WWF World Wide Fund for Nature WWW World Wide Web

1. INTRODUCTION The initial idea for the creation of the Watershed Database for sub-equatorial Africa was based on ALCOM's need for digital fish species distribution maps. Digital fish species distribution maps allow assessment of what fish are potentially present in a certain catchment and therefore what species can be recommended for stocking of dams. The Watershed Database and the complete Water Resource Database (WRD) have however developed into a much more versatile tool for general water resource management. The first practical work on the Watershed Database started beginning 1997 when a consultant (J. Dooley) was approached for the delineation of watersheds in the mainland SADC region. When WWF offered to co-fund the delineation and species distribution work, the first watershed model was created in April 1997. The delineation, naming and ordering of the watersheds was examined and commented thoroughly by several experts from different countries and formed the basis for a major revision which came out in September. The delineation procedure is explained in a separate report by the consultant and is included in this document as appendix II.

The current watershed model holds 1157 watershed polygons, starting 40 minutes South of the Equator and including all current mainland SADC countries. All subwatersheds were ordered and named. Surface areas were calculated and are included in the database. Summary statistics for all megabasins in the database are provided in appendix III and show that the largest watersheds in the region are the Zaire, Zambezi, Orange, Okavango and Limpopo basins.

ALCOM developed an interface for the watershed model which does not require the use of a major GIS software package. The interface combines regular database software with a simple mapping program and allows visualisation of upstream and downstream watersheds, calculation of surface areas of catchments and calculation of other catchment statistics based on raster images. It also enables the user to "cut out" selected watersheds or groups of watersheds from the main watershed polygon file to work with selected areas only. Visualisation of changes in elevation throughout the course of a watershed are simple and straightforward.

The currently developed interface needs Lotus Approach (Lotus Development Corporation©) and Mapviewer (Golden Software©) or alternatively Windisp3 (Map and image display system by E. Pfirman and J. Hogue with support from many organisations such as FAO, USAID, USFS, USGS and SADC/RRSP). It is planned to develop alternative interfaces for MS Access and Dbase (Contact ALCOM for the latest updates).

The presented database and interface are only a part of the much broader SADC Water Resource Database which was developed by ALCOM (Verheust, 1997; Verheust, in press; Verheust and Johnson, in prep). The SADC WRD holds various data on surface water bodies, rivers, fish species, bibliographic records, a mailing list and much more water resource related information.

This working paper explains the development and structure of the current watershed database as well as the developed interface. Best use can be made of this document in combination with the digital watershed model which can be obtained in digital format from ALCOM.

2. INSTALLATION INSTRUCTIONS 2.1 Required software To use the full interface, you should have the following software running under Windows 3.0 or higher with preferably 8 MB of RAM:

Lotus Approach 3 or higher Commercial database software Windisp3 version 980223 or higher Freely available mapping and GIS software Mapviewer 2 or higher Commercial mapping software Qbasic 1.1 or higher Basic programming software (comes with MS-DOS)

The Lotus Approach interface can be replaced by an interface in other database software such as MS Access, Oracle or Dbase as explained further in the document.

2.2. Installation steps

1. Run install.bat from your floppy drive to copy all files to C:\ If you want to install to another drive, unzip both disks manually and modify mapping project files, batch files and approach interface accordingly (cf. 5.4.)

2. Windisp3 should be installed under C:\Windisp3\ to be able to call the map project files automatically. If Windisp3 is installed under a different directory, please modify the Approach macros accordingly (cf. 5.4.)

3. Mapviewer should be installed and the GSM extension in Windows should be associated with the program to be able to open GSM map files from Lotus Approach

4. Qbasic exe should be located in a directory that is included in the DOS path statement, otherwise the program has to be copied to c:\alcomwrd\ws\dbase\ which is done automatically by the installation batch file

5. List separator in Windows should be a comma, if necessary this can be modified in the "International" settings of Windows. List separators are used in the determination of downstream subwatersheds.

6. If all above software is installed, add the C:\ALCOMWRD\DBASE\WS_SADC.APR file as a new program item in Windows (either program manager or Win 95 shortcut) and choose C:\ALCOMWRD\DBASE\WS SADC.ICO as an icon.

Contact ALCOM for the availability of other database interfaces if you do not have Lotus Approach.

2.3. Directory structure

The directory structure was conceived as part of the larger ALCOM Water Resource Database: \ALC0MWRD ALCOM Water Resource Database \ALC0M\WS Watershed Database \ALCOM\WS \DBASE Holds all database and related files \ALCOM\WS \DOC Holds all document files \ALCOM\WS \MAP Holds all mapping files including map manipulation software

3. DEVELOPMENT OF THE DATABASE Based on the delineation of watersheds at different pixel levels (cf. appendix II), ALCOM developed the database that accompanies the watershed polygon file. The different steps in the development of this database include: ordering, naming, downstream and upstream sequence generation, assignment of colours for mapping and calculation of surface areas.

3.1. Manual ordering and naming A database with four fields was created based on manual ordering. Most names were based on a map for Central and Southern Africa from J. Bartholomew & Son LTD at a 1:5000000 scale from 1988. Names for the South Africa watersheds were based on the digital river map from the IWQS (Roodeplaat, ZA). Some names were taken from national maps, preferably the most recent hydrological maps when available. In certain cases the Operational Navigation Charts from the US Defense Mapping Agency provided supplementary information on river names.

Database fields from the first step of ordering and naming:

1. WS _ ID Integer Identifier for the watershed, as in WS_SADC.BNA. 2. NAME_1 Name of the main river in the watershed (coastal drainage if no

unique outflowing river) 3. NAME 2 Name(s) of secondary rivers in the watershed 4. D1 Identifier of the watershed just below this watershed

3.2. Generation of downstream sequence The identifiers of all downstream basins (D2 to D39) were generated automatically by repetitive linking of field 4 with field 1. This resulted in the database file WS_D.DBF. A maximum sequence of 39 watersheds was found in the generated database.

3.3. Generation of upstream sequence Based on the created downstream basins, the watershed was built up again from the lowest basin in each mega-watershed. In most cases this was the ocean (with identifier 0) but it could also be an internal basin (with identifier 9999) or an edge basin (identifier 8888). This was done by aligning all cells to the right with a macro in a spreadsheet program. The result of this process was stored in:

fields UP37 to UPO with: UP0 ID of the drainage of the lowest basin (e.g. 0 for the ocean, 9999 for internal

drainage, 8888 for edge basin) UP1 ID of the lowest watershed in the megabasin (after which the whole basin is

named) UP39 ID of the highest basin in the watershed

The UP(i) fields were stored in WS_UP DBF

3.4. Generation of level and megabasin name Based on the former classification the following fields were generated:

LEVEL level of the basin: no of watersheds above lowest watershed in the megabasin

MEGABASIN name of the megabasin: typically the name of the lowest watershed

These fields were stored in the core database, WS_SADC.DBF together with the fields that were created in the first step (of. 2.1).

3.5. Colour assignment to megawatersheds Colour codes were assigned to megawatersheds in order to make sure that two adjacent megabasins would have different colours. A small colour code database determines what colours were used for mapping. These data are stored in WS_CLR.DBF and CLR_CODE.DBF.

3.6. Combination of downstream ID'S All the downstream ID's (D1 to D39) were combined in one text string, delimited by commas in order to allow combined searching for these watersheds in a database. This was done by concatenating D1 to D39. The result was stored in WS_DOWN.DBF. The exact purpose of this string is explained in part 4.

3.7. Calculation of surface area Surface areas (in km2) were calculated in Idrisi 2.0 for Windows and linked to the main database file. This field is called AREA. It allows to calculate total surface areas for megawatersheds or upstream watersheds.

4. DATABASE STRUCTURE 4.1. Fields and linking

The complete database holds the following fields:

NAME TYPE WIDTH DESCRIPTION WS ID text 4 numeric identifier in text format NAME_1 text 30 name of major outflowing river NAME_2 text 100 name of secondary river(s) LEVEL integer 3 level (distance from final sink in number of

basins) MEGABASIN text 30 name of megabasin AREA real 15 surface area in km2

COLOR_CODE integer 1 colour coding (numerical) COLOR text 9 colour DOWN ALL text 180 combined string of all downstream basin ID's D1...D39 text 4 downstream basin ID's UP0..UP39 text 4 upstream basin ID's

Figure 1: Linking of the separate database files is done as follows:

4.2. File and directory structure An installation file (install bat) file has been provided on disk for automatic installation on the C: drive only. Files will then be expanded to the C:\ALCOMWRD\WS\ directory with specific subdirectories for each type of file. The \DBASE, \DOC and \MAP subdirectories respectively hold database files (extension DBF and APR), document files (DOC and TXT) and mapping files (BNA, GSM, PRJ, CUR, BAS and BAT). The complete interface will be available only for users who have Lotus approach by opening the WS_SADC.APR file but a similar interface in other database packages can be developed rather easily following the instructions in this document on the interface.

5. INTERFACE The database can be used to determine and map upstream and downstream basins, or megabasins as well as catchment surface areas. To enable this, an interface was developed based on a database package (in this case Lotus Approach) which is steering external programs through simple macro's (Verheust, in prep.). Screen movies to illustrate the procedures have been developed in Lotus Screencam and can be requested from ALCOM. Lotus Screencam player can be downloaded freely from the Lotus homepage on the WWW.

5.1. Database interface The database package links all database files (in Dbase IV format) as explained in figure 1. Based on this linking, queries can be executed and subsequently mapped through simple macro's:

5.1.1. Map selected areas as a part of the complete watershed map This macro executes the following commands:

• Export a comma delimited ASCII text file (WS_SELEC.TXT) holding: WS_ID NAME_1 MEGABASIN COLOR

• Start up the mapping software and load a specific mapping file

• This mapping file will then load WS_SELEC.TXT colouring only the selected subwatersheds

5.1.2. Extract selected areas from the complete watershed map BNA file This macro executes the following commands:

• Export a comma delimited ASCII text file (WS_SELEC.TXT) holding: WS_ID NAME_1 MEGABASIN COLOR

• Start up the custom written QBASIC software (of. Appendix V)

• This QBASIC software package will load WS_SELEC.TXT to produce a WS_SELEC.BNA file holding the selected watersheds based on the complete watershed map BNA file (WS_SADC.BNA)

5.1.3. Determination of upstream and downstream basins To determine upstream basins, one should query in the UP(i) field for the WS_ID of the respective basin, where "i" is the level of the respective basin. Downstream basins can be determined in the D1-D39 fields or in the DOWN_ALL field which allow a query for all the downstream watersheds. Macro's in the currently developed interface then export the WS_ID's and subsequently map the selected watersheds. Note that all WS_ID's are stored in text format in the DBF files. This is to allow export of identifiers in text format (between quotes) which is used by most mapping programs that use BNA files. An example of the approach template is included for users that have Lotus approach (of, fig. 2).

Figure 2: Main form of the database interface with mapping macro buttons

5.2. Mapping software Two mapping programs are currently used by ALCOM and were integrated in the interface: Mapviewer (version 2) and Windisp (version 3),

5.2.1. Mapviewer Mapviewer is a commercially developed software package which allows fast vector mapping, and advanced mapping of features. A demo version of the program can be downloaded from the Golden Software website (http://www.golden.com). The package is relatively cheap and user friendly. Mapviewer 2 has the advantage over Windisp3 that it is faster in display and identifiers can be easily copied to the database by double clicking and CTRL-C.

A Mapviewer file (WS_SADC.GSM) has been included which loads the WS_SELEC.TXT file, colouring only the watersheds which were selected in the database and exported in the data file. This is done through the hatch map feature from Mapviewer. Mapviewer files incorporate all map items but update external data files in order to display colours or labels.

5.2.2. Windisp Windisp3 is a program which was developed through the coordination of many organisations such as FAO, USAID, USFS, USGS and SADC/RRSP. It is freely available and can be downloaded from WWW at http://ag.arizona.edu/~epfirman/windisp3.html. Windisp was mainly developed to visualise and analyse raster maps but also has advanced vector mapping features. It is a bit slower in vector mapping than Mapviewer since it redraws all maps based on the original components but allows also simple GIS analyses such as calculation of statistics for vector objects based on raster maps.

Two Windisp3 project files (WS_SADC.PRJ and WS_SELEC.PRJ) and a Windisp3 colour table (WS_SADC.CLR) are included (cf. fig. 3) together with a SADC country

layer (DC_NAT.BNA) which allow mapping and colouring of the watersheds if one has the windisp3 software installed (RRSP, 1998). The Windisp project file will load the watershed map together with the WS_SELEC.TXT file which will colour the selected watersheds.

Figure 3: Example of display in Windisp3 indicating Zambezi and Orange basins

5.3. Custom written software A custom made Qbasic program allows export of selected watersheds based on a text file (WS_SELEC.TXT) with the identifiers of these watersheds. The program (WS_SELEC.BAS) is left in source code and should be kept in the same directory as WS_SADC.BNA. Before running the program, the WS_SELEC.TXT should be modified to contain the selected WS_ID's and names. In the current interface, this is done through a macro that exports a comma delimited text file with the WS_ID, NAME1, MEGABASIN and COLOR_CODE. The program can be executed through the batch file (WS_SELEC.BAT) if qbasic.exe is copied to the database subdirectory or directory listed in the DOS path command. A program listing of WS_SELEC.BAS is included in Appendix V.

5.4. Modifications in macros, maps and batch files with regard to the directory structure The interface was developed for a fairly strict directory structure. Windisp3 should be installed in the default directory C:\WTNDISP3, all database and map files should be installed on C:\ALCOMWRD and QBASIC.EXE should be installed in a path directory. If this is not the case, macros, maps and batch files might have to be modified in order to reflect this difference in directory or path structure.

5.4.1. Macros The current database interface holds 5 different macros which can be modified through the Approach Macro/Edit command when needed. If needed, changes can be made to the directories or drives in the macro commands. In case Windisp is located in a different directory (e.g. a server drive), macro 3 and 4 will have to be changed to reflect the correct programme location. In case the main database directory or drive has been changed, all macros will need to be modified.

Macro 1: Create map worksheet Exports c:\alcomwrd\ws\map\ws_selec.txt

Macro 2: Extract bna for selection Runs macro 1 (create map worksheet) Runs c:\alcomwrd\ws\map\ws_select.bat

Macro 3: View extracted watersheds Opens c:\windisp3\windisp3.exe file open project, "c:\alcomwrd\ws\map\ws_selec.prj, 1,1"

Macro 4: View selected watersheds Runs macro 1 (create map worksheet) Opens c:\windisp3\windisp3.exe file open project, "c:\alcomwrd\ws\map\ws_sadc.prj, 1,1"

Macro 5: View selected watersheds in mapviewer Runs macro 1 (create map worksheet) Opens c:\alcomwrd\ws\map\ws_sadc.gsm

5.4.2. Map files Mapviewer map files will read data from a specific directory or from the same directory as the map. Since the developed mapviewer map loads the data from the \MAP\ directory, there is no need to change mapviewer map files with regard to a change in directory structure. The GSM extension for the mapviewer maps has to be associated in Windows with the mapviewer programme in order to automatically open the map files.

Windips project files are drive and directory specific and need to be changed in case the whole database is installed on a different drive or directory. Windisp project files are in ASCII format and can be changed in notepad or most word processors.

Listing of the WS_SADC project file is as follows:

[Parameters] Junk, Elevation," " Allow zoom,File Retrieve Image,"C:\ALCOMWRD\WS\MAP\BLANK.IML,,C:\ALCOMWRD\WS\MAP\ZOOM.CLR, 0, 0, 30, 35" Elevation,File Retrieve Image,"C:\ALCOMWRD\WS\MAP\DEM100.IML,,C:\ALCOMWRD\WS\MAP\DEM100.CLR, 0,8,320,400"

Junk,Watersheds (WS), " " Watersheds uncoloured,File Retrieve Map, "c:\ALCOMWRD\WS\MAP\WS_sadc.BNA, 0, 0, 6, 1, , , " WS selection coloured,File Retrieve Map,"c:\ALCOMWRD\WS\MAP\ws_sadc.BNA, 0, 0, 6, 1 , C:\ALCOMWRD\WS\MAP\WS_SELEC.TXT,COLOR_CODE, C

:\ALCOMWRD\WS\MAP\WS_SADC.CLR" WS all coloured,File Retrieve Map,"c:\ALCOMWRD\WS\MAP\ws_sadc.BNA, 0, 0, 6, 1,C:\ALCOMWRD\WS\MAP\WS_ALL.TXT,COLOR_CODE, C: \ALCOMWRD\WS\MAP\WS_SADC.CLR"

Junk, Countries, " " SADC Countries,File Retrieve Map,"c:\ALCOMWRD\WS\MAP\DC_NAT.BNA, 12, 0, 6, 1,,,"

[Variables] [Settings] [Window1] Allow Zoom, Y, DEM, N, WS uncoloured, N, WS selection coloured, Y, WS all coloured, N, SADC Countries, Y,

When the drive or directory structure is changed, this should be reflected in all directory statements in the project file as listed above. The second project file, WS_SELEC. PRJ which displays the watersheds that were cut out can be modified in an analogue manner.

5.4.3. Batch files

Only one batch file (WS_SELEC BAT in the map directory) is currently used to cut out the selected watersheds from the main watershed BNA file. If the whole database is installed on a different drive or directory this batch file needs to be modified as well. Batch files are in ASCII format and can be changed in notepad or most word processors. Listing of the batch file is as follows:

qbasic/run c:\alcomwrd\ws\map\ws_selec.bas

Both the directory for the BAS file as for the qbasic program should be changed in this line if necessary.

References RRSP, 1998. The Database of the SADC Regional Remote Sensing Project, Version 1.0. RRSP Working Paper No. 6, SADC-RRSP, Harare, Zimbabwe

Verheust, 1997. ALCOM's Surface Water Body Database for SADC, more than just a list of dams, lakes and swamps. The FAO Aquaculture Newsletter April 1997, No. 15 (12-17).

Verheust, in press. Obtaining basic information for the enhancement of small water body fisheries: a regional project viewpoint pp. 183-203. In Petr, T. (ed.). Inland Fishery Enhancements. FAO Fisheries Technical Paper, 374, Rome, FAO.

Verheust, in prep. A simple watershed ordering system for regular database packages, case of the ALCOM watershed model for SADC.

Verheust and Johnson, in prep. The SADC Water Resource Database: contents, data structure and user interface. ALCOM Working Paper No. 14. Harare, ALCOM/FAO.

Appendix I: Files included on the base disks

README TXT TXT Disk contents INSTALL.BAT BATCH Installation batch file PKUNZIP.EXE Program Decompressing software WS_SADC1.ZIP ZIP Compressed archive 1 WS_SADC2.ZIP ZIP Compressed archive 2

The compressed archives include the following files:

Files prepared by the consultant, Joe Dooley: WS_DOOLE.DOC Word 6.0 Explains procedure how the polygons were created WS_SADCBNA BNA 5,000 cell accumulation model, modified by ALCOM

DOCUMENT FILES by ALCOM

TOR WS.DOC Word 6.0 Terms Of Reference for the consultant WS_SADC.DOC Word 6.0 This document

DATABASE FILES by ALCOM:

WS_SADC.DBF DBase IV Core watershed database file WS_CLR.DBF DBase IV Colour coding to colour megabasins CLR_CODE DBF DBase IV Colours used to print the WS map WS_DOWN DBF DBase IV Combined downstream WS_ID's WS_D.DBF DBase IV Separate downstream WS_ID's WS_UP DBF DBase IV Separate upstream WS_ID'S WS_SADC.APR Approach 3 Approach template to work with DBF files

PROGRAM and GRAPHIC FILES by ALCOM:

WS_SELEC.BAT DOS Batch Batch file to run qbasic program WS_SELEC BAS QBasic prog QBasic program to extract Watersheds from BNA WS_SADC BMP Bitmap Bitmap file representing small watershed map WS_SADC.ICO Icon Icon representing small watershed map

MAP FILES BY ALCOM AND SADC-RRSP

WS_SADC.PRJ Windisp3 Project file for Windisp3 to display coloured watersheds

WS_SELEC.PRJ Windisp3 Project file for Windisp3 to display extracted watersheds

WS_SADC.CLR Windisp3 Colour table for Windisp3 to colour watersheds DEM100.IML Windisp3 Elevation image by SADC RRSP DEM100.CLR Windisp3 Colour table for elevation image BLANK.IML Windisp3 Blank image to allow zooming in Windisp3 BLANK.CLR Windisp3 Colour table zooming image WS_SADC.GSM Mapviewer Base Mapviewer file displaying all watersheds basedDC_NAT.BNA BNA National boundaries for SADC in BNA format WS_SELEC.TXT DOS Text Example text file to run WS_SELEC program but

which is also loaded by Windisp and Mapviewer for display

WS_ALL.TXT DOS Text Text file as above but holding info on all watersheds WS_SELEC.BNA BNA Example of an extracted watershed BNA file

Appendix II: Processing Summary for Joint ALCOM/WWF SADC Watershed Model by Joe Dooley RS/G1S Consultant c/o USAID/Zimbabwe P.O. Box 6988, Harare 1 Pascoe Ave, Beilravia Harare, Zimbabwe

Overview In February of 1997 the above consultant was hired under a joint project between the ALCOM/FAO SADC Regional Fisheries project and WWF Zimbabwe to develop a digital watershed model for the SADC region This model was to be derived from the 30 arc second digital elevation model (DEM) of Africa1, and was to include watersheds for up to third order rivers which ultimately flowed into the Atlantic or Indian Oceans.

Processing Details The 1DR1SI formatted DEM was translated into Arclnfo grid format for processing using the Spatial Analyst module of Arc View 3 0 (AVSA); note: to retain the integer format of these data required a intermediate translation of the data into a ERDAS G1S format. Using the hydrologic extension functions to AVSA the DEM was. first "filled" to smooth out areas of no drainage, then the flow direction of each cell was calculated, and next the accumulation of upslope cells flowing to each cell was derived Next a processing mask for the region was developed using the coastlines from the DCW to exclude oceans and islands from the delineation of watersheds; a mask which included major inland waterbodics and pans as well was also developed but later discarded based on unsatisfactory determination of watershed boundaries. Both of these masks extended from 1 ] 25e,0s to 41 25e,35.25s. Additionally, the extent of processing was limited to a rectangle extending from 11.5e,0.75s and 41e,35s to limit any edge processing errors; this later proved unnecessary but unfortunately the northern boundary of the analysis was never extended back to teach the equator.

Using the above datasets, boundaries for watersheds at various cell accumulations were next calculated Boundaries for watersheds which had a minimum of 250,000, 100,000, 50,000; 35,000; 10,000, 5,000 and 1,000 cells flowing into them were delineated, the 0 0084 cell size of the source DEM was retined throughout processing. The watersheds determined based on the 5,000 cell accumulation were selected as the basis for further processing after consultations with ALCOM This 5,000 cell 'resolution' delineated basically 4th order watersheds, while at the same time effectively capturing coastal lake and ocean watersheds. It also resulted in only 'irregular' discrepancies between the DCW rivers data layer, i.e. rivers flowing up hill across watersheds, rather than the 'gross' inconsistencies which resulted from processing at a lower cell accumulation. During these consultations it was also determined that the results of the 5,000 cell delineation would only be corrected based on other DCW layers where the results were totally inadequate, e.g. the Okavango Delta, Etosha Pan, and the confluences of major rivers and coastal areas; the decision to carry out only limited editing was later to prove overly optimistic.

The grided results of the 5,000 cell accumulation watershed model were next vectorized into the Arc View Shapefile file format. It was only after this vectorization process, that a realistic estimate of the manual editing which would be necessary could be determined.

The grid model, which had delineated 1101 watersheds, had produced 1891 unique polygons when vectorized; many of these additional polygons were simple one to two cell polygon primitives which often happen during raster/vector conversion. However, while reviewing the amount of actual editing which would be needed, versus automated aggregation or elimination to remove these primitives, the true extent of the discrepancies between the DEM derived watersheds and the DCW drainage layers became evident. While it was anticipated that many pour points would not match the confluences of streams, rivers, and coastlines; it was not anticipated that over 40% of them would need major adjustments. Nor was it realized that whole stream and river networks would be flowing across or "up to" the wrong basin/direction as depicted on the ONC source or other smaller scale maps. Also, while the basins delineated in the model did correspond well with a drainage network derived from the DEM, this network compared poorly with the DCW drainage layer. As it was assumed that the contour and drainage layers for the ONC were likely to have been based on the same or similar sources, the consultant decided it was better to correct the basin boundaries favoring the DCW drainage layers rather than the DCW/DTED derived DEM.

Due to the massive amount of editing which would be needed, and after initial attempts at line editing/corrections in ArcView proved cumbersome due to almost constant screen updating, it was decided to translate the watershed boundaries into Arc-Dbase and from there into Intergraph/Bentley's CAD package MicroStation for further editing. Here the almost 5,000 lines delineating watershed boundaries were joined with the DCW coastlines and major inland waterbodies, and edited against a backdrop of the DCW drainage layers. Other than retaining coding for the joined DCW data and lines depicting the northern extent of the model, the editing in MicroStation yielded three line types:

1) Lines derived from the watershed analysis which required only minor editing of pour points, and/or line densification based in two points straddling a stream but not capturing the top or bends in a stream. While this editing did correct for the tops and bends of streams crossing watersheds, it could still be described as cosmetic 'enhancement' of the lines. {1900 lines}

2) Lines derived from the analysis but requiring extensive editing to pour points, and/or the location of the line itself because it allowed the DCW drainage network to impossibly flow across a drainage boundary or boundaries. Some of these lines were edited so extensively that they could have been classified as new or added lines. Edited lines tended to follow or conform to the nearest DCW drainage feature. {1210 lines}

3) Lines which were added by hand because the derived lines were grossly incomparable with the DCW drainage layer, or lines which were added because a needed line was missing and no drainage boundary had been delineated. Every effort was taken to ensure that lines added were based on a visual interpretation of the DEM, the ONC source maps where available, or other source maps where the ONC charts were not. However, even with these efforts, these lines can perhaps best be described as conformal questimates based on the DCW drainage layer. {260 lines}

The types of editing listed above arc described in order to emphasize that while the model may be derived from the DEM of Africa, it now would more closely depict any errors in the DCW Drainage layer rather than those in DEM. Basically other than the 841 lines derived from adding the DCW coastlines and waterbodies, and the extent of the analysis boundaries, each of the remaining 3370 original lines have been edited in one

way or another; and over 1500 lines were deleted from the original dataset. Any inland DCW waterbodies which were wholly contained within a single watershed were also deleted from the dataset. After editing in MicroStation the line and label/text data were translated back into Arc-Dbase where topology was constructed for the 1113 resulting watershed boundaries. The Arc-Dbase coverage was then translated into Atlas BNA polygon format specified by ALCOM as a deliverable. The primary and secondary attributes used in the translation were the User_ID value and a field called Basin_Name. In the BNA dataset the Basin_Name contains only three different labels. These are: "Coastal Drainage", used for all single basin stream networks which flow directly into a major lake or ocean, "Edge Drainage", used for all basin polygons which were truncated by the northern extent of the analysis boundary and are not part of a basin network which originates or continues from/into the interior of the model; and lastly, "Unknown Basin", used for the majority of the basins until naming and basin order conventions are developed by ALCOM/WWF.

Attribution of the Model Once ALCOM/WWF codify basin order and naming conventions, each of the individual basins will need to be given a primary name --possibly using the Bartholomew 1:5,000,000 Map of Central and Southern Africa as a source -- and attributed as to their membership in any larger basin orders. It is likely that, although many basins delineated are not 'fourth order', each will need to be coded to this or at least a third order level. An example of fourth order attribution using the Sanyati River Network originating in Zimbabwe could be:

Sanyati River Network as part of the Zambezi Mega Basin First Order Zambezi Zambezi Zambezi Zambezi Zambezi Second Order Zambezi Zambezi Sanyati Sanyati Sanyati Third Order Zambezi Zambezi Munyati Munyati Umfuli Fourth Order Zambezi Lake Kariba Sebakwe Umniate/Ngezi Urnfuli

However, this example highlights some of the problems which will need to be addressed in basin order convention and attribution; in this case what to do with Lake Kariba. The Sanyati actually flows into Lake Kariba, but the Zambezi actually flows into/through/out-of the lake. In effect, Lake Kariba is the Zambezi River. One could add a fifth order here, although this could lead to greater redundancy and possibly confusion; in fact Lake Kariba could be dropped as a fourth order itself.

To aid in classifying each basin the grided data from the 250,000; 100,000; 50,000; and 35,000 cell accumulations were also vectorized to shape-file and then BNA format. ALCOM/WWF will use these as possible guides to help in attributing the membership of each basin in larger basin networks. Unfortunately, coding and naming these larger basin delineations, and then simply overlaying them with the 5,000 cell basin model to attribute the model, would yield too many inaccuracies based on the extent of editing which took place in the model. It was decided that ALCOM/WWF would use and expand the Dbase file listed below, which contains the USER_ID and BASIN_NAME fields, as the basis for their attribution. This Dbase file will then be returned to the consultant who will then produce aggregated basins which reflect the edits made to individual basin delineations. Additionally, using the model the consultant will generate a coding scheme for the each order of basin, calculate the maximum, minimum, and mode elevations for each basin, as well as equal area measurements of each basin's hectarage. The coding, statistics, and measurements will also be present in any first, second, or third order

basin aggregations requested by ALCOM/WWF.

Limitations of the Basin Model Based on the 1:1,000,000 source used to derive most of the DEM, the basin model could be used for analyses at a scale of 1:1,000,000; although analyses at a scale of 1:750,000 should also yield satisfactory results. At no time should the model be used for larger scale analyses than 1:500,000. In terms of the positional accuracy of the edited basin boundaries all DCW and type 1) lines described above should be between 3 and 5 pixels, or roughly 3 to 5 kilometers. Line types 2) and 3), also described above, should be recognized as having a positional accuracy of between 5 to 10 pixels, or 5-10 kilometers.

Files delivered to ALCOM/WWF

File Name Size WS_5000.BNA -> 2,819,436 5,000 cell accumulation model WS_5000.DBF -> 40,198 Dbase file for Attribution of basins WS._35000.BNA -> 606,356* 35,000 cell accumulation, unedited WS_50000.BNA -> 578,609* 50,000 cell accumulation, unedited W_100000.BNA -> 402,394 100,000 cell accumulation, unedited W_250000.BNA -> 209,699 250,000 cell accumulation, unedited DIRCLINE.BNA -> 3,452 Lines showing direction of flow in certain

problem areas or basins. *These basin bna files were modified by ALCOM to eliminate the artificial tie lines which connected Africa mainland with Islands in the oceans. 1 The DEM of Africa used had been developed by U.S and other international cooperators at the USGS EROS Data

Center in Sioux falls,SD.USA This DEM was based primarily on elevation data taken from the Digital Chart of the World (DCW) which had been digitized from the 1:1.000,000 Operational Navigation Charts by the Environmental Systems Research Institute (ESRI) for the U.S. Defence Mapping Agency (DMA). Where incomplete elevation data were indicated on the ONC Charts courser resolution data from ihe DTED DEM, also from the DMA, were used to fill elevation gaps in the USGS DEM. The interpolated resolution of the DEM of Africa corresponds to 0 0084 decimal degrees which equates to roughly one square kilometer pixels. The DEM provided by the FAO/FSTAU to ALCOM for the project was in 1DR1S1 format.

Appendix III: Summary statistics for all megabasins in the database Note that surface areas for edge basins (e.g. Nile, Zaire) represent only surface area within the boundaries of the model (South of 40' S)

Megabasin Name TOTAL AREA (km2)

Number of watersheds

Maximum LEVEL

ANIB 6 738 1 1 BAHU SWAMP 27 056 1 1 BALBOL AMBUSSEL 11 334 1 1 BALBOL AMBUSSEL 2 1 018 1 1 BALOMBO 4 544 1 1 BENGO 11 365 1 1 BLACK UMBULUZI 6 674 1 1 13REE 12 246 1 1 BUFFELS 10 801 1 1 BUSCBUSC 808 1 1 BUZI 28 844 5 3 CAPOROLA 15 595 1 1 CARUNJAMBA 7 070 1 1 CATUMBELA 16 572 3 2 COASTAL DRAINAGE 377 679 76 2 COASTAL RIVER 11 737 3 2 COROCA 19 682 1 1 CUACUA 19 193 3 3 CUANZA (Kwanza) 151 241 21 9 CUBAL 16 658 2 1 CUNENE 112 328 17 9 CUVO 23 124 1 1 DANDE 11 871 1 1 EMUGUR ORETATI 6 127 1 1 ETOSHA PAN 161 170 9 3 GA.LANA 48 331 5 3 GAMTOOS 34 284 5 3 GIRAUL 5 252 1 1 GORONGOSA 9 808 1 1 GOURITS 45 487 9 4 GROEN 4 367 1 1 GROOT-BERG 7 886 2 2 GROOT-KEI 20 525 3 2 GROOT-VIS 30 464 3 2 GURURO 17 223 1 1 HOANIB 16 130 1 1 HOARUSIB 15 910 1 1

HUAB 17 846 3 2 INCOMATI 46 569 8 4 KASHA GURGURDA (waterhole) 688 1 1 KOICHAB 15 596 2 1 KUISEB 18 197 1 1 LAC YOUBI 1 725 1 1 LAKE BANAMANA 4015 1 1 LAKE BURUNGI 11 786 3 2 LAKE CHILWA 8 780 1 1 LAKE EYASI 63 655 12 6 LAKE JIPE 2 826 1 1 LAKE MAGADI 8 564 2 2 LAKE MANYARA 4 912 2 2 LAKE NAIVASHA 751 1 1 LAKE NATRON 21 040 5 3 LAKE RUKWA 73 328 14 4 LAKE ST. LUCIA 9 128 2 2 LARDE 3 858 1 1 LICUNGO 23 260 3 2 LIGONHA 15 263 1 1 LIMPOPO 421 683 56 17 LOGE 11 838 1 1 LONGA 22 596 3 2 LUKULEDI 6 467 1 1 LURIO 61606 3 2 MAPUTO 30 827 5 3 MATANDU 14 732 1 1 MBASHE 6 119 1 1 MBWENKURU 17718 1 1 MEBRIGEDE 18 176 1 1 MEGARUMA 5 403 1 1 MELELA 8 609 1 1 MELULI 9 445 1 1 MESSALO 25 100 1 1 MFOLOZI 10 226 1 1 MGENI 4411 1 1 MINU 262 1 1 MKOMAZI 4 520 1 1 MLIGASI 3 007 1 1 MNGAZI RUVU 17 791 1 1 MOCUBURI 10 257 1 1 MOLOCUE 6413 1 1

MONAPO 8 431 1 1 MONTEPUEZ 9 357 1 1 MSANGASI 4 224 1 1 MUCARAU 3 291 1 1 MZIMKHULU 6 846 1 1 MZ1MVUBU 772 1 1 NA.MACURRA 3 544 1 1 NGORONGORO CRATER 608 2 2 N1AR1 61 555 5 3 NILE 180 398 22 6 NTPIODE 9 806 1 1 NUMEROUS SMALL PANS 430 1 1 NYANGA 10 064 2 2 OGOOUE 63 843 13 4 OKAVANGO DELTA 694 686 50 10 OLIFANTS 47218 11 4 OMARURU 12 503 1 1 ORANGE 977 553 145 23 PANGANI 34 833 7 5 PUNGOE 32 126 7 5 ROVUMA (Ruvuma) 153 796 16 6 RUFIJI 183 208 22 7 RUTSHURU 7 466 2 2 SAVE 105 812 14 5 SEMBO 4 474 1 1 SONDAGS 21 467 1 1 SONGA 6 252 1 1 SWAKOP 30 536 3 2 TANA 62 764 6 2 TSARIS 8 197 1 1 TSAUCHAB (pan) 7 554 1 1 TSONDAB 8 932 1 1 TUGELA 29 323 3 2 UGAB 29 930 1 1 UMBA 8 388 1 1 UMZIMVUBU 18 981 2 2 UNIAB 4 893 1 1 WAMI 41 441 6 5 ZAIRE 2233 479 294 39 ZAMBEZI 1374 030 168 26 Total 8899 145 1157 39

Appendix IV: Main watersheds in sub-equatorial Africa

Appendix V: Program listing of WS_SELEC.BAS

REM REM qbasic program to create BNA file with selected objects based on ID1 REM PROCEDURE: REM Read a data file which holds ID1 and ID2 of selected objects REM Store ID1 and ID2 in an array REM Read through the complete bna file, one object at a time REM Check if ID1 of this object was present in the datafile REM If present write ID1 and ID2 from the datafile to a new BNA file REM REM written by Lieven Verheust on 12/6/97

OPEN "c:\alcomwrd\ws\map\ws_sadc.bna" FOR INPUT AS #1 OPEN "c:\alcomwrd\ws\map\ws_selec.txt" FOR INPUT AS #2 OPEN "c:\alcomwrd\ws\map\ws_selec.bna" FOR OUTPUT AS #3

DIM id$(1201) DIM na$(1201)

CLS INPUT #2, w$, w$, w$, c

j = 0 10 IF EOF(2) THEN GOTO 20

j=j + l INPUT #2, id$(j), na$(j), w$, c m=j

GOTO 10

20 PRINT m;" objects found in data file" PRINT "now processing bna file, please be patient, this might take some time"

30 IF EOF(l) THEN PRINT m;" objects processed, ws_selec.bna was created" IF EOF(l) THEN SYSTEM INPUT #l,a$, b$, n

FORj = 1 TO m p = 0 IF id$(j) = a$ THEN p = 1 IF id$(j) = a$ THEN GOTO 40

NEXT j

40 IF p = 1 THEN WRITE #3, a$, na$(j), n IF p = 1 THEN PRINT "processing object"; a$;""; na$(j)

FOR k = 1 TO n INPUT #l,x,y IF p = 1 THEN WRITE #3, x, y

NEXT k GOTO 30