THE IMPACT OF URBANISATION ON THE WATER QUALITY OF LAKE CHIVERO, ZIMBABWE

This study quantified concentrations of nitrogen and phosphorus in the Lake Chivero catchment area, Zimbabwe. The results showed that sewage effluent is the major source of nutrients in the lake. The lake is hypertrophic, and it was concluded that the current situation is not sustainable. The Vollenweider model was used to predict the acceptable inflow phosphorus concentrations based upon oligotrophic conditions. The predicted value of 10 t/year total phosphorus was considered to be unattainable under the current situation because it is already lower than that from non-point sources. A 1970s value of 75 t/year total phosphorus is recommended as a starting point because it excludes sewage effluent and, for the long-term, it is recommended that pollution prevention and water re-use should be adopted in combination with the recycling of nutrients in controlled urban agriculture.