Economic valuation of the averted degradation of the Vyeboom Wetland in the Theewaterskloof Dam catchment, South Africa

  • Daniel Marais Prevision, Postnet 225, Private Bag X17, Weltevreden Park 1715, Johannesburg, South Africa
  • Theo Fischer EScience Associates (Pty) Ltd, PO Box 2950, Saxonwold 2132, Johannesburg, South Africa
  • Donovan Kotze Centre for Water Resources Research, University of KwaZulu-Natal, Durban, South Africa
  • Bennie Haasbroek EScience Associates (Pty) Ltd, PO Box 2950, Saxonwold 2132, Johannesburg, South Africa
  • Malin Govender EScience Associates (Pty) Ltd, PO Box 2950, Saxonwold 2132, Johannesburg, South Africa
  • James Pugin EScience Associates (Pty) Ltd, PO Box 2950, Saxonwold 2132, Johannesburg, South Africa
  • Annabel Horn Department of Environmental Affairs and Development Planning, Western Cape Government, Cape Town, South Africa
Keywords: ecosystem services, wetland rehabilitation, water quality, valuation, Breede Catchment

Abstract

Wetlands within the catchments of water supply dams have potential to make important contributions to water-related ecosystem services, particularly water quality enhancement. Wetlands are facing growing threats and continuing degradation. There have been limited attempts at evaluating the contribution of South African wetlands, and their rehabilitation, for water quality enhancement and other water-related ecosystem services. A comprehensive and integrated wetland services economic assessment determined the value of the Vyeboom Wetland in the catchment of the Theewaterskloof Dam. The water of this dam is a significant contributor to the City of Cape Town’s water supply. The economic valuation model integrates hydrological, catchment status and economic models, with a long-term (80-year monthly) wetland water balance from a calibrated hydrological model as a driver for the nutrient removal aspect. The economic valuation builds on a water quality enhancement model, based on the minimisation of indirect use replacement cost principle, supplemented by a sediment retention and carbon storage assessment. The capability of the economic valuation model is illustrated by assessing the rehabilitation of a 25-ha area in the Vyeboom Wetland, which is currently intact, but is under threat of being severely degraded by the advancing erosion headcut. It was assumed that the current state of the Vyeboom Wetland is almost pristine (only 1 ha degraded), but that a further 24 ha would degrade over a period of 50 years, following spatial changes over time. By balancing the total investment in offsetting the potential loss in benefits, it is evident that an amount of 2.5 million ZAR could be afforded for rehabilitation. If, instead of a logistic degradation profile, the wetland is assumed to already be in a state of accelerated deterioration, the rehabilitation project budget for Vyeboom Wetland will increase once the other intrinsic benefits described are considered in the analysis.

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Published
2021-01-28
Section
Research paper