DH Environmental contracted to assess value of TMDL approach for managing South African catchments

14 December 2012

DH Environmental Consulting has been awarded a two-year Water Research Commission contract to assess the value of the Total Maximum Daily Load (TMDL) approach for use in South Africa.  TMDLs are written plans or protocols which may be employed to address the management of any aspect of water quality but, in particular, they are mostly used for setting achievable goals for attenuating nutrient pollution.  The ‘daily load’ aspect addresses variations in loading resulting from individual pollution practices and the related hydrological characteristics.  TMDLs are also applied, for example, to specific toxicants or for maintaining levels of dissolved oxygen necessary to sustain aquaculture operations.

In essence, TMDLs involve the allocation of responsibility among different pollutant sources, including point and nonpoint sources, to reduce their aggregate pollutant production. The TMDL process can distinguish between places that need more pollutant control, from places that need less pollutant control. TMDLs do this by identifying more or less vulnerable areas of watersheds, in terms of both sensitivity to pollutant inputs (e.g., fish spawning areas at different times of the year) and risk of pollutant discharges (e.g. soils that are high in selenium or very erosive). The allocations can reflect this information by allocating pollutant reduction responsibilities to the places where it will do the most good (spatial disaggregation). Secondly, the TMDL process provides an analytical forum for considering and weighing stakeholder values, interests, and capabilities. If local stakeholders are able to negotiate local allocation packages that meet TMDLs, it increases the likelihood that solutions will be implemented.

Importantly, the TMDL framework can provide for tradeoffs (and pollutant trading) between different pollutant sources to help support more cost-effective solutions. The successful in brokering of tradeoffs between point sources and nonpoint sources could result in a meaningful infusion of much-needed cash to support implementation of BMPs to address polluted runoff from agricultural lands, and more cost-effective overall approaches to water quality protection.

DH Environmental has previously undertaken WRC commissions to develop guidelines for catchment management, the formulation of a eutrophication assessment model (NEAP) and the preliminary determination of annual loads (TMALs) for key South African dams.  The outcomes of this prior work are already being used to determine load reductions for the Department of Water Affairs’ Waste Discharge: Charge System.

The project will commence in April 2013 and will focus on specific test cases.

Leave a Reply

Your email address will not be published. Required fields are marked *