DAMS & WATER STORAGE
Dams are like
loaded guns Water flowing over concrete spillway at Spioenkop Dam on the Tugela River
The Dam Safety Office (DSO), a division of the Department of Water and Sanitation (DWS), is responsible for safeguarding the people, properties and infrastructure downstream of dams. By Kirsten Kelly
L
ike a loaded gun, a dam has the potential to cause serious harm. A loaded gun must never be left unattended, and must be owned by someone with a licence. Dams also require licences and only qualified people can design, build and assess them. One cannot own a dam without conducting regular assessments and maintenance,” explains Wally Ramokopa, director: Dam Safety Regulation, DWS. Classification of dams A dam with a safety risk contains, or can store more than, 50 000 m³ of water and has a wall with a vertical height of more than 5 m. All dams with a safety risk, regardless of who owns them (public or private), must be registered with the DSO and comply with legislation. Any structure capable of diverting or storing water is classified as a dam, and so the dam safety register also includes, for example, mine tailings dumps, pollution control dams, and potable water reservoirs that fit the classification. In exceptional cases, the Minister of the DWS may also declare a dam as having a safety risk even if it falls outside the
Wally Ramokopa, director: Dam Safety Regulation, Department of Water and Sanitation
TABLE 1 Size classification of dams with a safety risk Size Small Medium Large
Maximum wall height <12 m but <30 m 30 m
conventional registration parameters. Once the registration information of the dam is received, the DSO then classifies the dam into one of three categories that determine the required level of control at that particular dam. The classification is based on the size and hazard potential rating of a dam. The hazard potential of a dam is based on an assessment of the potential loss of life, potential economic loss with respect to downstream development, as well as the potential adverse impact on resource quality that may result from the failure of a dam.
Geographic information system (GIS) technology is used so that the DSO can see the position of any dam on a computer screen or on a 1:50 000 map and on satellite images in different years. Google Earth is also used. This helps the DSO assess a dam’s hazard potential by evaluating the households, property and infrastructure downstream that could be impacted should the dam fail. The size of the dam and its hazard potential rating is used in allocating a category classification to the dam. “There are many instances where
TABLE 2 Hazard potential of dams with a safety risk Hazard potential rating
Potential loss of life
Potential economic loss
Low Significant High
None ≤10 >10
Minimal Significant Great
Potential adverse impact on resource quality Low Significant Severe
M A R/ A P R 2022
53
