The development of a pre-mining groundwater monitoring network for open pit mines in South Africa

[摘要] English: After the discovery of minerals mining formed the backbone of the South African economy formore than a century. The contribution that mining had on the economy is probably best reflectedwhen the country's currency was changed to the Rand (which refers to the gold deposits of theWitwatersrand) in 1961.Although there have been a down scaling in production of some minerals over the last couple ofdecades the country is still a large producer of numerous commodities and dispose of mineraldeposits matched by only a small number of countries. Without a doubt mining will still prevail asa pillar of the economy in the years to come.Although the mineral industry in South Africa consumes a relatively small quantity of groundwaterabstracted (13 percent) the use of water at mining operations has the potential to affect the qualityof surface as well as groundwater. The abstraction of groundwater to ensure safe mine activitiesat especially open pit mines have a negative impact on the surrounding water sources.Groundwater play an essential role in South Africa as two thirds of the country's rural populationis depended on groundwater for their domestic needs while it is also an important source of waterfor numerous towns. The management and protection of the country's water resources cannot bestressed enough as South Africa is ranked as the 30th driest country in the world.The protection of the country's water resources gain momentum in the late 1990's when a numberof Acts, the important ones from a water resource point being the National EnvironmentalManagement Act (NEMA); Act 107 of 1998 and the National Water Act, Act 36 of 1998 werepromulgated that placed strong emphasis on equitable access for all residents to the country'swater resources.In the mining sector groundwater monitoring are usually done for two reasons, the one to obtainthe necessary data/information needed to develop the water management and monitoringprogrammes for the mining operation to effective protect and manage the groundwater resourcesin the area they operate within and the other to comply with the environmental and water licenceregulatory requirements.The literature review and in particular the first-hand experience as documented and described inthe case study form the corner stone of the guideline developed for the set-up of a pre-mininggroundwater monitoring network for open pit mines. The different phases for the set-up of themonitoring network is discussed in detail in the dissertation and can be summarized as follow: Monitoring objectives - For any monitoring programme to be successful clear objectivesmust be set on what exactly needs to be achieved with the focus on efficiency andpracticality. A thorough understanding of the hydrogeological characteristics of theaquifers must be gained that informed decisions can be taken to effectively protect andmanage the water resources.�?Desktop study �?A desktop study must be performed in order that all available geologicaland hydrogeological reports, data and information of the area are sourced that aconceptual model of the area can be formalized. This is vital in the planning of thefieldwork to obtain the necessary hydrogeological information needed to fully characterizethe water resources in the study area.�?Planning of hydrocensus �?Evaluation of the data sourced during the desktop study willgive guidance in demarcating the area that needed to be surveyed during thehydrocensus and also provide a good indication what to expect during the census.Effective and good communication with land owners regarding the hydrocensus is ofcardinal importance as this will determine right from the start the success of thehydrocensus and the co-operation from the land owners.�?Data acquisition during hydrocensus �?During a hydrocensus not only water level datamust be obtained but all available information regarding the boreholes for example thewater strikes and depths, yield and usage, geology and water quality. Other data such asrainfall and information on the water infrastructure network and the number of stockdependant on a watering point is also important and must also be noted during thehydrocensus survey.�?Set-up of a monitoring network - The exact number of monitoring points for a specificmonitoring programme is always debateable. The monitoring objectives together with thehydrogeological conditions plays the major role in determining the number and positionof the monitoring points while the site specific conditions (accessibility and topography)must also be taken into account when designing the monitoring programme.�?Evaluation and analysing of data �?Evaluation and analysing of the monitoring data isindispensable in understanding the hydrogeological characteristics of the aquifers in anarea and to update and adjust the conceptual model as outlined during the desktop study.Interested and affected parties �?The efficiency and success of a monitoringprogramme will greatly depend on the relationship between the mining company and theland owners. It is necessary that an Environmental Forum be established that can beused as a platform for communication between the parties to ensure that theenvironmental aspects of which water is usually the main discussing point can beadministered and managed in an effective manner that will be beneficial to both parties.�?Validation of monitoring network �?The monitoring network needs to be validated on acontinuous base to ensure that it still complies with the monitoring objectives as forexample changes in the mine's water usages or modifications in the environmentallegislation will necessitate that the monitoring objectives be adjusted accordingly.�?Review and update of monitoring network - The evaluation and analysing of themonitoring data will indicate areas where additional data is needed or whereexcessiveness of data is present. In data scarce areas it might be necessary forboreholes to be drilled or that the monitoring area be expanded to include boreholes fromadjacent areas while in areas where there is excessive data the monitoring points canbe decreased or the intervals between the monitoring periods can be lengthened.The set-up and development of a monitoring network is not a once off occasion but an iterativeprocess that must be evaluated at least once a year and the necessary changes implementedwhere necessary to ensure that the monitoring programme give a true reflection on the behaviourof the groundwater resources that are monitored otherwise it will not be possible to protect andmanage the groundwater resources in a responsible and effective way.Taking in account that every mining activity and its site conditions is unique it must be bear inmind that some of the guidelines described in the dissertation for the set-up of the monitoringnetwork might not be practical or applicable and will need to be adjusted to fit the specific siteconditions.

[发布机构] University of the Free State