The following steps were executed to merge data from the different sources. The hardcopy list of dams from the Dam Safety Office was used as a base file since it was the largest inventory with 3592 dams, and according to the originators also one of the most reliable ones.
All the records from the Dam Safety Office (DSO) were scanned into text files. These were edited first in a word processor, by inserting tabs to define field separations and then imported as tab delimited files in a spreadsheet. Further editing was done to ensure entries appeared in the correct fields and an attempt was made to correct spelling errors caused by the scanning process. Some of these may still exist.
A database file was created from the DSO spreadsheet file and this was used as the base file to check which records still needed to be added to the existing inventory from AGLW/FAO. A manual search was done first using data from the DWAF Hydrological Service (government records) and a number of the smaller dams were added. This also included some natural water bodies such as Nsezi lake.
A third search was manually carried out using records from the DWAF Hydrographical Survey Service. There were few outstanding data and these were added to the base file.
A list of South African isolated coastal lakes and coastal lake systems was taken from a report published by the Department of Environmental Affairs and Tourism, ‘Wetlands of South Africa’, SA Wetlands Conservation Programme Series, 1995. The majority of these records were new and were added to the existing inventory. Where the records already existed, for example from the DWAF Hydrological Service, the records were merged and the various sources recorded.
The newly created database (steps 1–4) was linked to the existing older database (mainly from AGLW/FAO), first based on co-ordinates (latitude, longitude) and then by using names. Where there were duplicate records the data entries were merged to preserve all the data from the various fields. Where there were discrepancies, data from the DSO was given priority, except in the instance where co-ordinates from another source were more precise. A small number of dams in the old database were not present in the new one and these were added accordingly.
Hydrozones were derived from the index number. The first number and letter of the index figure was taken to be the hydrozone at the primary level.
SADC Identifiers (unique identifiers used in the complete SADC SWB database) are added as sequential numbers according to the time of entry in the database. This results in lower ID's for the water bodies that were already present in the original older database. The locality number was entered as the national index number and as a unique national identifier.
