Review of Mine Water Reports in the Hotazel, Kathu and Postmasburg Areas, Northern Cape
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Review of mine water reports in the Hotazel, Kathu and Postmasburg areas, Northern Cape Dr. Kevin Pietersen with contributions from Zaheed Gaffoor Reviewer: Dr. Hans Beekman Client: Agri Northern Cape November 2017 Final Report Review of mine water reports in the Hotazel, Kathu and Postmasburg areas, Northern Cape EXECUTIVE SUMMARY Since the 1930s there have been numerous investigations to better understand the hydrogeology of the Hotazel, Kathu (Sishen) and Postmasburg areas in the Northern Cape. There have been concerns about the dewatering operations of the Sishen Iron Mine but there has been limited consideration in the studies of the cumulative dewatering impact of all water users: agriculture, mining, (proposed) solar power generation facilities and water supply, in the region – so called cumulative management. This has led to concerns about the sustainability of groundwater abstractions in the region. This study was a desk-top review of groundwater literature with the aim to understand the issues in more detail. The most significant impact of the mines in the region has been the dewatering of the aquifers. The sources of water for dewatering are the banded iron formations (BIF) and dolomites of the Ghaap Group. To predict changes in hydrogeological conditions resulting from mine dewatering, the mines have constructed groundwater models at a local scale with limited consideration of a broader perspective, i.e. a regional and holistic approach. A regional and holistic approach allows for the assessment and evaluation of the combined effect of abstractions of all stakeholders on the groundwater resources and ultimately allows for appropriate groundwater management interventions. Note that the groundwater modelling studies in the area were commissioned by the mines and are not easily available in the public domain. The extent of the dewatering zones of the Sishen Iron Ore Mine has been investigated extensively, whilst for the other mines in the region there were no such detailed investigations accessible. Groundwater discharge processes include evaporation and transpiration of groundwater, and groundwater flow to the surface (seepage), including discharge to wetlands and rivers and subsurface drainage. In semi-arid areas with relatively low rainfall, quantification of groundwater recharge is complex because its rate is only a very small fraction of the water balance (usually less than 5% of the average annual rainfall). Recharge events in such environments are predominantly episodic or intermittent. This means that rainfall is percolating to the water table only during extreme (surplus) rainfall events. The dewatering of the aquifer systems means that flowing springs disappear and i baseflow is absent, giving rise to dry river beds (e.g. the Gamagara River). There seems to be no major visible discharge areas in the aquifer systems except for possible discharge zones in the Skeifontein Spruit. The natural groundwater drainage is from the eastern catchment boundary (recharge area) in the east (Kuruman Hills) towards the outflow area at Dibeng. Recharge can be local and indirect and is also induced as a result of the dewatering activities. The Gamagara River is a gaining river outside the zone of dewatering. Inside the dewatered zone (Moria to Demaneng and Demaneng to Mokaning), the Gamagara River is a losing stream (recharging the aquifer). The aquifer is over-exploited (abstraction from the aquifer exceeds sustainable rates). Discharge areas are difficult to identify as the compartments are dewatered so the open pits are sinks to groundwater flow in the region. The absence of a holistic and integrated regional study makes it difficult to evaluate the implications of large-scale groundwater abstraction on competing users. There are concerns from stakeholders that water use licenses are issued without due regard of the cumulative impact of these abstractions on the groundwater resources. The catchments are water stressed (see reserve determinations). The water (consumption) footprint is dominated by demand from the mining sector, followed by Local Municipalities, agricultural sector and power generation. The challenge remains not only the provision of adequate volumes of water for local economic development but also taking into account spatial and temporal requirements. Only few studies have been conducted to understand the cumulative implications of mine dewatering and large-scale abstraction on competing groundwater users. The decision-making framework developed by Seyler et al. [1] together with the groundwater governance frameworks developed by Pietersen et al. [2,3] was used as a basis for analysis of the sustainability of the resource. The analysis revealed the following: The current use of groundwater is unsustainable. In the catchments there are competing demands for groundwater consumption, i.e. water supply for domestic and industrial use and for agricultural purposes. Inspections and investigations by Department of Water and Sanitation (DWS) indicated that a number of mines in the region are operating without the needed water use authorizations. The management of the groundwater resources must take into consideration not only technical issues but also social and environmental aspects. The framework categories identified in the table below were adapted to the local situation to analyse the sustainability provisions for groundwater management in the region. In undertaking the analysis, any areas where parts of the sustainability provisions are not addressed represent a ‘gap’. The analysis reflected in the table is based on ii numerous sources of information being provided and which were compiled, reviewed, and mined using a framework analysis. Each of the identified gaps was categorised and colour-coded to reflect the magnitude of the gap: (a) green (3) – criteria are met; (b) amber (2) – criteria partially met; (c) red (1) – significant gap or absent. Table: Framework for analysis of sustainability provisions. Capacity Criterion Context Gap Technical Basic hydrogeological maps For identification of groundwater 3 resources Groundwater body/aquifer delineation With classification of typology 3 Availability of aquifer numerical At least preliminary for strategic critical 3 ‘management models’ aquifers Change in natural discharge Detection of change in water table 2 towards discharge point Assessment of discharge 2 Flow in discharge-receiving 2 environment Chemical composition of discharge- 1 receiving environment Change in pre-abstraction recharge Detection of change in water table 2 towards recharge zone Direct detection of change in water 2 table in recharge zone Indirect detection of change in water 1 table in recharge zone Assessment of surface water flows in 2 recharge zone Chemical tracer for recharge source 1 Increased recharge 2 Change in storage Detection of change in water table 2 Response time/status of aquifer Age of water 1 towards new dynamic equilibrium Quantification of the relationship The shape, gradient and scales of the between increasing abstraction and curves will vary for each system 2 reducing discharge and other aquifer flows Recovery assessment If this is very long, then the flows at a reasonable water supply planning and 1 environmental timescale should be determined Legal and Water well drilling permits & For large users, with interests of small 2 institutional groundwater use rights users noted Instruments to reduce groundwater Water well closure/constraint in critical 1 abstraction areas Instruments to prevent water well In overexploited or polluted areas 1 construction Sanction for illegal water well Penalizing excessive pumping above 1 operation permit Groundwater abstraction & use ‘Resource charge’ on larger users 1 charging Land use control on potentially Prohibition or restriction since 2 polluting activities groundwater hazard Levies on generation/discharge of Providing incentives for pollution 1 potential pollutants prevention Government agency as ‘groundwater Empowered to act on cross-sectoral 2 resource guardian’ basis Community aquifer management Mobilising and formalising community 2 organisations participation Cross-Sector Coordination with agricultural, mineral Ensuring ‘real water saving’ and 2 Policy and social development pollution control Coordination Groundwater based urban/industrial To conserve and protect groundwater 2 planning resources Compensation for groundwater Related to constraints on land-use 2 protection activities iii Capacity Criterion Context Gap Operational Public participation in groundwater Effective in control of exploitation and 1 management pollution Existence of groundwater With measures and instruments 2 management action plan agreed This analysis has highlighted gaps that need to be addressed to support sustainable development of groundwater resources in the region. The indicators which are not met focus on priority interventions. An approach similar to a strategic environmental assessment is required to analyse the cumulative impact of large-scale groundwater dewatering and abstraction on groundwater users and environment. The groundwater resources and particularly the dolomite aquifers are at risk of being dewatered unless regulations are enforced. Based on the evaluation of numerous reports and the gap analysis, I would recommend to: Establish a groundwater monitoring network that takes into account monitoring of recharge and discharge areas; Establish a standardised regional digital relational database that combines data from all water