Algae-free irrigation systems to save money for farmers

5th August 2016

By: Simon Sonnekus



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The Council for Scientific and Industrial Research (CSIR) has estimated the rand value of the impact of algae pollution in the Berg river, near Stellenbosch, in the Western Cape. The calculation enables farmers to compare different ways of managing the problem in the area.

A ‘Water SA’ report estimated the monetary value of the impacts of filamentous green algae on commercial agriculture. Results from two case studies in different geographical areas published last month point out that farmers within the region of the Dwars river (a tributary of the Berg river) could spend up to R600 000 a year ridding their irrigation system of algae.

Co-author of the report and CSIR senior economist Dr Willem de Lange says farmers included in the study could spend up to R1 887 ha/y on problems involving algae in irrigation systems. He adds that the incorporation of pollution mitigation strategies could increase the production cost of agricultural produce in the area.

The model used to estimate the cost implications of algae pollution was built in close collaboration with farmers, noting that each farmer manages the impacts slightly differently.

Fellow co-authors, Stellenbosch University Department of Genetics professor Anna-Maria Botha and CSIR limnologist Dr Paul Oberholster, state that, although filamentous green algae poses no direct threat to crops, it affects the operational efficiency of irrigation systems and, therefore, affects the operation and maintenance costs of irrigation infrastructure.

De Lange notes that the natural flow of the river allows for a self-cleansing effect, decreasing algae downstream.

It also notes that although pollution loads vary throughout the year, algae growth is a year-round phenomenon and impacts most significantly on agriculture during the irrigation season.

De Lange says algae not only obstructs and clogs strainers, intake valves and manifolds but also places a higher load on impellers and bearings of pumps, while decreasing the volume delivered per pump hour.

By using information obtained from the databases of, for example, the horticultural industry knowledge group Hortgro, the South African Wine Industry Information and Systems, viticulture service organisation VINPRO, agrichemicals company Nulandis and agricultural input supplier Kaap-Agri, De Lange calculated the additional cost of heavier-than-usual algae loads on farm profitability.


The work informed further research on the development of a tradable water pollution permit system, which is a market-based approach to manage pollution – a first of its kind for South Africa.

The CSIR report notes that the permit system aims to impose a cost on polluters or generates reward for pollution abatement. This enables individual participants to trade within the constraints set by the rules of the market to not only their mutual advantage but also the benefit of the ecological functioning of the river.

“Although the transfer of permits is referred to as ‘trade’, in effect, the buyer of a permit pays for the right to pollute, while the seller receives compensation by letting go of such right. Thus, in theory, those who can reduce pollution most cheaply will do so, achieving pollution reduction at the lowest cost, given the cost structure of the two parties,” the report notes.

It further mentions that a pollution permit scheme usually makes pollution a more expensive activity, which will create incentives to reduce pollution directly and to adopt cleaner production and consumption activities.

It also tends to lower pollution regulation costs, as the polluter has to decide how to reduce pollution. This is based on the assumption that polluters will choose the most cost-effective way to mitigate pollution regulation, but this is not always the case.

“Pollution in effect becomes a tradable commodity. This mechanism uses the marketplace to distribute pollution impacts more evenly to support the self-cleansing capability of rivers. The permit is not a system to make the problem go away, but is a tool to avoid extreme events,” De Lange notes.

The work presents some of the fundamental conditions and requirements for a water pollution permit system along with some of the processes that will facilitate implementation for South African river systems. De Lange notes that, “the workings of such a system are quite complex and involve the design of the tradable permit itself, the specification of the terms and conditions, the transactional protocol for transactions and the design of a suitable monitoring and managerial system”.

He further points out that, “these . . . need to be piloted and the political acceptability of such a system should be tested along with a process geared towards facilitating acceptance among those affected”.

A similar system is also being investigated at the Loskop irrigation area in Groblersdal, in Limpopo.

Edited by Zandile Mavuso
Creamer Media Senior Deputy Editor: Features


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