TOWARDS THE RESOURCE DIRECTED MEASURES: GOUNDWATER COMPONENT
REPORT NO: 1090-2/1/03
The National Water Act of 1998 places an emphasis on the protection of water resources for their sustainable utilisation. This is reflected in the subsequent development of Resource Directed Measures (RDM), which consists of three important aspects, namely: classification; the reserve; and resource quality objectives.
The purpose of the Version 1.1 report is to provide the technical reader with the best available information regarding an approach for determination of the groundwater component of the RDM as required for issuing licenses for water use.
As a core concept of the RDM, the Reserve covers both Basic Human Needs (BHN) and Ecological Reserve (ER). Since October 1ST, 1999, a Reserve determination of the total water resource should be undertaken if a license application for water allocation is processed. Determination of the Reserve for aquatic ecosystems entails investigation of the relationship of major interactive components of the hydrologic cycle, namely groundwater and surface water bodies including rivers, lakes and estuaries. Depending upon the current stress on the resource in question, the Reserve determination required may be a rapid or intermediate estimate, or a comprehensive evaluation.As part of the RDM, this draft of the final report is based on the research findings of programme entitled "Groundwater Reserve Determination", sponsored by the Water Research Commission (WRC). The Programme started on January 1ST, 1999 and is completed by the end of 2001.
This documentation presents a recommended approach to classify groundwater resources under the NWA, and set the Reserve and Resource Quality Objectives.
For purpose of groundwater protection, all three' mechanisms of the RDM, namely Classification, Setting of the Reserve and Resource Quality Objectives, should be used.
It is generally accepted that groundwater plays a role in the ecological Reserve determination if there is a direct hydraulic connection between groundwater and surface water bodies that jointly sustains the aquatic ecosystems. In such situations the often complex role of groundwater (in terms of water level, volume, and water quality), in supporting the ecosystem and human population, has to be ascertained, so that groundwater is not subsequently misallocated. Where aquifers have minimal connection with the aquatic ecosystems, the groundwater component of Reserve would refer to the Basic Human Needs component (25 l/d/person multiplied by the number of people using the groundwater supply in the area).
The broader environmental role of groundwater in supporting important terrestrial ecosystems and hypogean life, particularly in the large semi-arid parts of South Africa, is resource quality objectives.
Once the groundwater component of the RDM has been determined, its role must be sustainable. This is to be achieved through an optimal balancing of competing uses, ensuring that long-term deterioration of the entire groundwater system is minimised. Monitoring and periodic review of allocations is central to this process. The attributes of sustainable development of groundwater resources, such as aquifer physical integrity, deteriorating water quality, etc., will have to be accommodated within the provisions of the National Water Act.
The classification system prescribed under the National Water Act (NWA) will provide guidelines on how to set appropriate levels of protection for water resources. This chapter outlines guidelines for classification of groundwater resources under the NWA.
The application of this classification system will delineate a groundwater management unit within a significant aquifer resource classed as either Protected, Good, Fair or Severely Modified. These four classes imply different levels of protection and impact acceptable to the stakeholders of the resource. They provide a frame of reference for the implementation of groundwater protection, use and management plans for that groundwater management unit.
This document presents recommendations for a groundwater RDM classification system. It focuses on the role of the groundwater specialist and their technical and scientific input to the process. That role will have to be performed in parallel to surface water specialists and a stakeholder participation process.
The following sections outline guidelines and procedures for groundwater specialists contribute to the Classification of groundwater resources. These follow the generic Classification outline described in the NWRS. For each stage of the generic procedure, the following is described:
Where relevant, parallel processes which underpin the validity of the procedure will be highlighted. These may include, for example, stakeholder participation or the characterisation of surface water resources.
A summary of the tasks to be performed by the groundwater specialist can be outlined as follows:
Groundwater management units will be defined as areas of the catchment, which requires consistent management actions to maintain the desired level of use and protection of groundwater. Their delineation and classification according to a level of impact acceptable to the stakeholders, will be the final outcome of the Classification process. The groundwater specialist has a key role to play in terms of informing stakeholders and other water resource management decision makers.
Groundwater Interaction with Surface Water Bodies
Understanding groundwater interaction with surface water bodies is prerequisite for determination of groundwater component of the Reserve. However this is a poorly understood area in South Africa at present. Geohydrologsts were familiar with analysing streams solely in order to gain a better understanding of recharge mechanisms. South Africa is no exception to this rule (Vegter, 1997). Similarly, hydrologists are not experienced in determining the groundwater fed component of baseflow to rivers in typical South African settings. However, the scope of interaction between surface water bodies and groundwater is being broadened through a process of the ecological Reserve determination, as it includes analyses of the water exchange between the two, especially the floodplain and stream channel.
A summary of current understanding of groundwater interaction with surface water is outlined. A hydrogeomorphologic approach to quantification of groundwater contribution is developed. The proposed new method has improved the Herold method adopted in the WR90 study. Typical riverine, wetland and coastal groundwater environments of South Africa should also be examined. In addition, issues relating to groundwater-dependence of ecosystems and their ability to adjust to changing conditions are important, which are discussed in a separate report.
Setting of the Reserve
The "Reserve" defined in the National Water Act of 1998 can be interpreted as the quantity and quality of groundwater required:
The basic human needs Reserve provides for the minimum living requirements of individuals served by the water resource in question, and includes water for essential uses such as drinking, food preparation and personal hygiene (set, for the time being, at 25 l/d/person). The ecological Reserve is largely reliant upon expert judgement and set at a value so as to ensure that the aquatic ecosystem of the identified area is maintained or improved, depending on the Management Class set. The Reserve (i.e. basic human needs and ecological requirements) is defined as both the quantity and quality of the whole water resource, and will vary depending on the class of the resource. The Minister is required to determine the Reserve for all or part of any significant water resource.
The key steps required for such determination are outlined as follows:
Resource Quality Objectives
RQOs provide goals within the management class. They are set by the Minister during the process of classification of significant water resources. They may be seen as goals to aim for, if the management class represents an improvement on an impacted resource, or thresholds or safety nets which represent the limit of acceptable impact. They may be numeric or descriptive.
RQOs are seen as being particularly important for groundwater as they are not restricted to aquatic ecosystems and may therefore represent the important role of aquifers to the wider environment.
It is proposed that a functional approach should be adopted, considering the functions and importance of groundwater use by humans and the environment. The potential functions of aquifers in the environment could be summarised as providing: sources or sinks for water; sources or sinks for nutrients; habitats. Once the various uses have been identified, objectives should be formulated to safeguard those functions. The objectives should be practically measurable and preferably summarised as key indicators. A range of hydraulic (e.g. groundwater gradients, water table levels), hydrochemical (e.g. total dissolved solids, nitrate) and biotic indicators (e.g. thriving vegetation communities, hypogean fauna) could be selected to indicate that aquifers are effectively fulfilling their important uses. It is envisaged that the functions and indicators should be identified by specialists and the importance of those functions and levels of RQOs (based on the risk of impacting on that function) should be set by informed stakeholders. However the reader must note that more information on RQOs will still come from a separate RQOs project.
Conclusion and Recommendation
The RDM determination may be a rapid, intermediate or comprehensive evaluation. The latter may be achieved through improvement and upgrading of the former into a more comprehensive and accurate Reserve assessment as more information becomes available. We have been convinced through case studies that a single approach should be used for the determination of the groundwater component of the RDM with confidence levels ranging from rapid to comprehensive.
Although the monitoring is out of scope of the research programme, it is realised that the follow-up monitoring process plays a vital role in verification and improvement of RDM determinations.
The proposed approaches were variably applied in three case studies: (1) the Pienaars River catchment; (2) the Kammanassie area and (3) Mutshindudi River catchment. The case studies showed that the conceptualisation of the aquifer system is a key to successful application of the methodology.
Potential problems tend to stem from the lack of existing long-term observation data sets relating to groundwater quality, piezometric levels, etc. This presented a problem throughout and made it particularly difficult to infer reference conditions from present day conditions at the site.