The Integration of Hydropedology, Wetland Ecology and Aquatic Assessments- The Way to GO!

Posted on 10 Mar 2021

“By integrating hydropedology, wetland and aquatic assessments for each proposed development the overall influence of the landcover change on the downstream catchment area can be quantified and adequate mitigation and/or rehabilitation measures proposed in accordance with the mitigation hierarchy. These tools are available to practitioners and should be utilised to ensure that the precious water resources of SA are conserved and rehabilitated to ensure that sustainable growth can be achieved”.

 

The landscape within South Africa and globally is becoming increasingly urbanised and developed into the infrastructure required for the various economic sectors. The development of previously open space, and thus relatively undisturbed land has an impact on the previously unquantified relationship between the soil-hydrology interface downslope and resultantly the wetland and/or river environments typically situated at the valley-bottom within the landscape. The wetlands and rivers that are at-risk of being impacted on by the ever-increasing developments are treated as isolated systems within the methodologies and techniques that currently used to assess these ecosystems. The broader catchment areas from which the wetlands and rivers are fed have not yet been considered in the conservation and management of these valuable water resources. The field of hydropedology aims to define and utilise the soil-hydrology flow paths within the terrestrial component of the upslope wetland and river catchment areas to aid in the conservation and management of these previously isolated systems. This tool should be utilised in conjunction with the existing wetland and aquatic assessment indices, such as the updated WET-Health and existing aquatic indices, to determine the overall influence of a proposed development on the receiving aquatic environment.

 

Hydropedology is not a new science, but has recently acquired national attention as its value is being realised at various spheres within government, specifically within the Department of Human Settlements, Water and Sanitation (DHSWS). The Water Research Commission (WRC) (2019) defines hydropedology as the study of the hydrological interaction of water with soil and the fractured rock zone. Its application essentially makes it possible to identify water resources and flow paths within the hillslope of a wetland/river from crest to the pinnacle, which is the wetland or stream itself.

 

Until recently, the procedure for undertaking hydropedology assessments in South Africa (SA) had not been standardised. However, the Department of Water and Sanitation (DWS) recently released the ‘guideline for hydropedological assessment and minimum requirements’ (Van Tol et al., 2021) to guide the assessment process. The guideline was divided into four (4) steps, each applicable to certain levels of assessment. These steps include; 1) Identification of dominant hillslopes, 2) Conceptualising hillslope hydropedological responses, 3) Quantification of hydraulic properties and flowrates and 4) Quantification of hydropedological fluxes. The first two steps are applicable to any impact assessment requiring a hydropedology study, whereas steps 3 and 4 will typically only be required where largescale changes to landcover will occur (e.g. open-pit mines and large developments). This clarity provides guidance and a standard method to be utilised, which can be coupled with other forms of assessment including wetland indices.

 

Like the recent developments in the field of hydropedology in SA, movement on the techniques and methodologies used to identify and assessed wetlands has also occurred. Until the recent update of the WET-health (Version 2.0) methodology (Macfarlane et al. 2020), wetland ecology has focused purely on the wetland systems in isolation from the broader catchment area. The updated methodology recognises the influence of the upstream catchment and changes thereof on the overall health and functionality of the downstream wetlands. In addition to this, the updated tool has undergone a comprehensive revision of the geomorphology module, which now clearly differentiates between impacts to geomorphic processes and impacts on geomorphic structures, as well as added a water quality module to the overall assessment. These additions have improved the integration potential of the wetland assessment techniques with the standardised hydropedology technique.

 

Although no new standard methodologies/tools have recently been developed in the SA aquatic science field, the existing suite of indices such as SASS5, IHAS, MIRAI, VEGRAI, FRAI and IHIA have proven to be robust at an international scale. These indices focus directly on the assessed reach of a specific river system, but when coupled with aspects such as spatial and temporal water quality indices, such as chemical, diatom and toxicity analyses, the influence of the upstream catchment area can to some degree be quantified. The primary objective of utilising these indices is to determine the Ecostatus, or Present Ecological State (PES) of various components of a river system. The results of which ultimately assist the practitioner to ascertain what impacts may have altered the integrity of the river from a presumed natural, or reference state. This provides guidance on the mitigation and/or rehabilitation measures may need to be implemented to rectify the identified negative impacts and improve the integrity of the system to the Recommended Ecological Category (REC).

 

By integrating hydropedology, wetland and aquatic assessments for each proposed development the overall influence of the landcover change on the downstream catchment area can be quantified and adequate mitigation and/or rehabilitation measures proposed in accordance with the mitigation hierarchy. These tools are available to practitioners and should be utilised to ensure that the precious water resources of SA are conserved and rehabilitated to ensure that sustainable growth can be achieved.

 

The highly qualified specialist team at Environmental Assurance (Pty) Ltd. (ENVASS) have the internal capabilities to conduct all the hydropedology, wetland and aquatic assessments that our clients may require. If ever the need arises, please do not hesitate to contact ENVASS for detailed assessments applicable to various stages of development. You can contact us on 012 460 9768, or email us at info@envass.co.za. We look forward to hearing from you!