Municipalities poisoning water bodies
URBAN local authorities are the biggest polluters of natural water bodies, with the Harare City Council and surrounding towns the major culprits, the Environmental Management Authority says.
Tributaries of rivers that pass through major towns and cities such as Harare, Bulawayo, Gweru, Chitungwiza, Marondera, Kadoma, Chinhoyi and Norton show higher levels of pollution relative to those in rural areas.
Scum and invasive weeds in lakes Chivero and Manyame, EMA adds, show signs of a “high-nutrient load coming from sewer discharges”.
EMA communications officer Ms Joyce Chapungu told The Sunday Mail recently that, “The pollution is emanating from discharges of untreated and poorly treated sewage from the local authorities’ sewer collection and treatment facilities.
“Examples of such rivers include Mukuvisi, Marimba Nyatsime and Ruwa River in Upper Manyame Catchment, Mazai, Matsheamhlope and Umguza River in Gwai Catchment, as well as Sebakwe and Kwekwe River in Sanyati Catchment.
High phosphates and manganese concentrations and low dissolved oxygen levels have been found to be the major contaminants in water bodies in and around urban areas, according to the agency.
“The algal blooms (green-coloured scum) on the surface in lakes Chivero and Manyame and the infestation of water weeds such as water hyacinth are evidence of the eutrophic (plant conducive) conditions of the lakes caused by high nutrient load coming from sewer discharges,” explained Mrs Chapungu. Sanyati, Save and Mazowe catchments are considered the least polluted. However, Yellow Jacket River in Mazowe is contaminated with high concentrations of heavy metals such as iron and manganese as a result of acid mine drainage effects from mining operations in that area.
Last year, EMA flagged mining operations across Zimbabwe as major surface-water polluters through toxic chemicals such as mercury, which often end up in dams and rivers.
EMA says it will push Government to set aside funds for rehabilitation and upgrade of the national sewer infrastructure.