Wetlands are unique ecosystems in the landscape that play an essential role in the functioning of the hydrological cycle (Department of Water Affairs (DWA), 2014; Bredin et al., 2019). They occur at positions in the landscape where climate, geology, topography and biology create suitable hydrologic conditions (Job & le Roux, 2019). Depending on the nature of the landscape in which they occur, they vary in their biophysical characteristics and environmental role. Different types of wetlands require different management and protection actions, and exhibit different levels of vulnerability to impacts and resilience to environmental change (DWA, 2014; Ramsar Convention on Wetlands, 2018). Wetlands are prime examples of ecosystems that lie at the heart of sustainable development, and despite their provision of important ecosystem services, have been extensively impacted by a range of anthropogenic activities (MEA 2005; TEEB 2010; DWS, 2014; Ramsar Convention on Wetlands, 2018; Kotze et al., 2020). As a result, there is a clear challenge in achieving the balance between development and sustainable wetland management.

Hydropedology is an interdisciplinary research field that focuses on the interactive relationship between soils and water. According to van Tol et al. (2017; 2018), hydrological processes play an important role in the formation of soil morphological properties such as colour, mottles, macropores and carbonate accumulations. While hydrological mechanisms and processes are very difficult to observe in the field, due to their dynamic nature with strong temporal and spatial variation, soil morphological properties are not dynamic in nature and their spatial variation is not random (van Tol, 2020). One of the major contributions of hydropedology in the management of ecosystems, including wetlands, is the ability to conceptualise hydrological processes. This is achieved through accurate mapping and the interpretation of soil morphological properties, which can be used to conceptualise and characterise hydrological processes, including water flowpaths, storage mechanisms, and the connectivity between different flowpaths. This allows for a more holistic understanding of the hydrological functioning of landscapes at different scales (i.e. catchments and /or hillslopes).

The Institute of Natural Resources NPC (INR), the University of the Free State, and the South African Biodiversity Institute have begun working on a three-year Water Research Commission (WRC) project, which aims to integrate hydropedology into wetlands management and development authorization at catchment and site scales. The project will build on a recent WRC project which developed a useful set of guidelines to apply hydropedology to interpret the relative contribution of wetland-catchment hillslopes to enable informed decision-making around addressing impacts to wetlands from activities within the catchment. While the guidelines themselves provide a sufficiently robust step by step approach to conceptualising hydropedological influences on wetlands, the following limitations are worth noting:

• The conceptualisations of hydrological behaviour are mostly qualitative, with only limited quantification of fluxes in research catchments; and
• The most recent guidelines (Van Tol et al., 2021) conclude with a semi-quantitative impact characterization of a development on flowpaths, streamflow, and wetland water regimes, but provide little guidance on the impact on wetland functioning and services.

In addition, while decision-makers have had an initial introduction to the guidelines, it is acknowledged that this is an emerging field of work and there is more collaborative learning needed to improve the guidelines and their uptake. It is also acknowledged that practitioners generally are not applying the guidelines satisfactorily.

The WRC project referred to above aims to address some of these limitations through the development of an improved set of guidelines, which maximise the benefits of integrating hydropedology into wetlands management and development authorization. This will be undertaken through the use of urban, forestry, and mining development case studies. For more information please contact Ian Bredin at the INR (ibredin@inr.org.za).

References:

Bredin, I.P., Awuah, A., Pringle, C., Quayle, L., Kotze, D.C. and Marneweck, G.C., 2019. A procedure to develop and monitor wetland resource quality objectives. WRC Report No TT 795/19. Water Research Commission, Pretoria.

DWA, 2014. Assessing the Impact of Land-based Activities on Water Resources: User Manual for the Automated Land-based Activity Risk Assessment Method. Version 1.01. Directorate: Water Resources Information Programmes, Department of Water Affairs, South Africa. Report No: WP 10255.

Job, N.M. and le Roux, P.A.L., 2019. Developing wetland distribution and transfer functions from land type data as a basis for the critical evaluation of wetland delineation guidelines by inclusion of soil water flow dynamics in catchment areas. Volume 2: preliminary guidelines to apply hydropedology in support of wetland assessment and reserve determination. Water Research Commission. WRC Report No. 2461/2/18

Kotze, D.C., Macfarlane, D.M. and Edwards, R., 2020. WET-EcoServices (Version 2) – A technique for rapidly assessing ecosystem services supplied by wetlands and riparian areas. Water Research Commission, WRC Project K5/2737.

Millennium Ecosystem Assessment (MEA), 2005. Ecosystems and Human Well-being: Synthesis. Island Press, Washington DC.

Ramsar Convention on Wetlands, 2018. Global Wetland Outlook: State of the World’s Wetlands and their Services to People. Gland, Switzerland: Ramsar Convention Secretariat.

The Economics of Ecosystems and Biodiversity (TEEB), 2010. The Economics of Ecosystems and Biodiversity: Ecological and Economic Foundations. Editor: Kumar P. Earthscan, London and Washington.

Van Tol, J.J., 2020. Hydropedology in South Africa: advances, applications and research opportunities. South African Journal of Plant and Soil. https://doi.org/10.1080/02571862.2019. 1640300

Van Tol, J.J., Bouwer, D. & Le Roux, P.A.L., 2021. Guideline for Hydropedological Assessments and Minimum Requirements. Department of Water and Sanitation, South Africa.

Van Tol, J.J., Lorentz, S.A. & Le Roux, P.A.L., 2017. The science of hydropedology – linking soil morphology with hydrological processes. Water Research Commission, The Water Wheel May/June 2017, 20-22.

Van Tol, J.J., Lorentz, S.A., van Zijl, G.M. & Le Roux, P.A.L., 2018. The contribution of hydropedological assessments to the availability and sustainable water, for all (SDG#6). In Lal, R., Horn, R. & Kosaki, T. (eds). Soil and Sustainable Development Goals. Catena-Schweizerbart, Stuttgart. 102 – 117.