Christie Terrell
Growing awareness around the importance of wetlands is prompting the Department of Water and Sanitation (DWS) to request specialist hydropedological studies from companies applying for water use licences under certain conditions.
Hydropedology – the study of the interaction between soils and water – provides insights into interflow processes in the sub-surface area between surface water and groundwater.
SRK Consulting water resources senior scientist Christie Terrell says the field helps to understand the flow drivers contributing to wetlands and water courses that may be impacted by the activities of the water licence holder.
“By understanding the flow drivers, developers can make better decisions about which mitigation measures need to be in place for a project,” she points out.
The DWS may request hydropedological studies in accordance with its guidelines in terms of sections 21(c) and 21(i) of the National Water Act, says SRK Consulting bioresource engineer Roanne Sutcliffe. These sections refer to the two water uses most commonly linked to wetlands.
“Any development or operation within a 500 m buffer zone of a wetland will fall within the ambit of these sections and will trigger the requirement for a hydropedological study,” explains Sutcliffe.
Terrell highlights that, whenever a surface water or groundwater study is required, companies also need to consider whether a hydropedological study may be required in their context. Such a study will investigate features like hill slopes and soil properties around a wetland or water source and how these features interact with hydrological elements.
“A hydropedological study will include an exploration of how water will flow through the soil on a hill slope,” she says.
“Traditionally, a wetland study will focus on the wetland itself and its buffer zones – but not really on how those wetlands are being sustained, including the hill slopes and flows in the area that affect how they are fed.”
She notes that a better understanding of interflows is important, not just in terms of environmental-impact mitigation and rehabilitation, but in terms of how sub-surface water could directly endanger a construction or mining project.
“If a development is planned on a hill slope that has a significant interflow component, the client may be dealing with a lot more water than originally anticipated.
“Project planning needs to be informed by how soils will react,” she notes.
Sutcliffe emphasises that different soils will have different flow components, so they will respond differently to water flowing through the sub-surface area.
To its benefit, South Africa has been involved in numerous research projects regarding hill slope hydrology and the discipline of hydropedology has evolved globally over the past two decades, with South African researchers providing valuable direction in the development of the discipline.
The local academic community includes a number of specialists in this field, including Dr Simon Lorentz, a principal hydrologist at SRK, and an honorary associate professor at the School of Bio-Resources Engineering and Environmental Hydrology at the University of KwaZulu-Natal.
“While there has been pioneering research conducted in the field of hydropedology in South Africa, it has only recently started being applied by industry.
“The new focus by DWS on hydropedological studies is likely to see this application increasing sharply,” says Sutcliffe.