The influence of urbanization on pans on the East Rand (Johannesburg, South Africa)

Pans are naturally occuring depressions or closed basins. Thousands of pans characterize the southern African landscape. Many pans form an integral part of the natural and cultivated landscape and some are found in the urbanized East Rand to the east of the metropolis of Johannesburg. Little research has been conducted on how humans have influenced the pans occurring in this urban environment, how these pans are frequently misused and mismanaged, and to what extent they may form an asset by complementing the open areas in urban environments. The aims of this research were to investigate the negative influences that aspects of urbanization have had on pans of the East Rand, and to supply some recommendations as to how these pans could be properly utilized for the benefit of the urban environment. Textural analyses of the pan floor sediments revealed that the sand fraction varies between 15.6% and 43.1%. For lower values, the pan water is hydrologically isolated from the underlying groundwater table; higher values pose a real threat to groundwater pollution from contaminated pan water percolating downwards. Chemical analyses of the pan water showed that the pH range from 6.0 to 9.0 (as compared with pH 6.8 under ‘natural’ conditions), and that nitrate and ammonia concentrations vary from 1 ppm for slightly polluted to 17 ppm for severely polluted pans. These values clearly indicate the positive or negative influence of humans on the pan. It is recommended that every pan should be considered as a natural feature of the landscape within the urban environment. Residents should get involved in preserving the pan, and the establishment of residential areas next to the pan should be avoided.