The Case StudyDeveloping new ways to reduce the negative impact of our plantations on water flow in South Africa
Over the past eight years, research teams from the Council for Scientific and Industrial Research (CSIR) and the University of KwaZulu-Natal have conducted experiments at Two Streams catchment in one of Mondi's South African forests providing information that could help to reduce the impact of our plantations on water flow in future.
Funding and resources for the experiments were provided by CSIR, the Water Research Commission (WRC), Department of Water Affairs and Forestry, the Working for Water public programme and Mondi; the experiments were reported in a Water Research Commission report, which explains methodology and initial findings.
The Two Streams experiments to study the impact of plantation trees on soil hydrological processes have been carried out in Mondi's Seven Oaks forest, near Greytown in KwaZulu-Natal. The Two Streams catchment is one of the few remaining small-scale catchment research areas in South Africa.
The research teams first started to gauge streamflow at Two Streams in 1999 in a mature stand of wattle trees. Following a short period during which measurements were calibrated, all the trees in the riparian zone, designated B Zone were cleared in July 2000. The trees in the rest of the catchment were removed later in 2004/2005 and the entire area under examination lay fallow until replanting in 2006.
The detailed hydrological monitoring carried out across the catchment during this extended period gave researchers the opportunity to study the impact of newly planted crops on the water balance.
The Two Streams WRC Project is expected to improve Mondi's understanding of the impacts of deep rooted plants on low water flows, verify previous observations which suggest that annual evaporation can at times exceed annual rainfall, and also produce data concerning the impact of repeated crop rotations of deep rooted trees on soil water reserves. The project should also produce an accurate technique for measuring soil water using Time
For Mondi and other participants in the project, one thing seems very clear: following the clearing of trees from the riparian area in 2000, water flow continued unabated despite some very dry conditions. This finding provides more justification for our decision to remove commercial trees from riparian areas across all our South African plantations in order to minimise our impact on water supplies.