Large volumes of mine water need to be managed, or treated at great cost. However, many mine waters are suitable for irrigation, a consumptive use of water, and large tracts of rehabilitated land are often in close proximity to these water sources. In addition, off-site environmental impact of mine water irrigation may be expected to be less when irrigating rehabilitated land compared to unmined land, as return flows will report to old pit voids below irrigated fields. Furthermore, productively irrigating with suitable mine water on appropriately rehabilitated land will promote agricultural activity, improve food security and the livelihoods and well-being of surrounding local communities, thereby making an important contribution towards the Just Energy Transition. Guidance is needed on the characteristics of rehabilitated land that will make it irrigable, and not just arable.

Irrigation of rehabilitated land is a relatively new approach to mine water management, and no guidance is available on the requirements for rehabilitated land to be considered irrigable. Such guidelines are presented here.

Primary factors rendering rehabilitated land unsuitable for irrigation include inappropriate topography (surface drainage and erosion risk) micro-relief (subsidence), incorrect use of soil materials, compaction, poor surface infiltration and subsurface drainage, and insufficient rooting depth. Therefore, the focus of the guidelines is on physical properties that include hydrological position in the landscape, slope and micro-relief, and soil physical factors that affect infiltrability, permeability, water holding capacity and internal drainage. Although chemical limitations to crop production are important, these are more easily remedied than physical limitations, and are thus not considered as part of the irrigability assessment criteria. Guidance is given on the successful rehabilitation of open-cast mined land to irrigable standards, the assessment of the irrigation potential of such rehabilitated mine land, and the remediation of sub-optimal areas in such fields, should these be present.

The guidelines will support the rehabilitation of mined land to irrigable standard, assist with selection of areas of rehabilitation for irrigation, and provide guidance for the remediation of areas of rehabilitation that cannot currently be irrigated sustainably and profitably.

The right volume of water, at the right quality, at the right time is essential for sustaining both aquatic and riparian ecosystems. The same can be said of mining operations. However, mining activities can negatively affect water resources by degrading land, altering watercourses, and exposing water to ore and tailings. Surface water in West Africa is an essential resource for both natural systems and local communities affected by mining. To minimise environmental consequences and balance the mine’s water requirements with those of the surrounding environment, a comprehensive understanding of these competing needs was developed during the mine planning stage of this project.

The mining area is located between several watercourses, which transition from fresh water in the upper reaches to estuarine in the lower reaches, incorporating a complex combination of wetland, peat and mangrove habitats. Geochemical modelling undertaken indicated that acid rock drainage can be expected. This paper presents the multi-disciplinary approach adopted for the determination of the Ecological Flow requirements of the surrounding watercourses both in terms of water quantity and quality. A web of interdependencies between the individual specialist fields and the mine planning team was developed prior to project commencement. Roles and interdependencies were defined in an optimised, integrated approach. The focus was on the development of a dynamic, daily time-step model, in GoldSim, which integrated the mine water balance, salt balance, streamflow and in-stream water quality for the mine and the associated catchment. The model included a stochastic rainfall generator to enable probabilistic estimates of streamflow and mine water make, calibrated against flow and water quality data from the local environment and a similar local mining operation. The model was utilised as an interfacing tool between mine planning and the Ecological Flow teams, assessing mining scenarios and mitigation of environmental effects.

A holistic assessment facilitated the development of a balanced mine design that is expected to effectively mitigate the environmental effect on water resources to an acceptable level. Ecological Flow requirements for both water quantity and quality are therefore likely to be met. Concomitantly, the design supports the mine’s operational- and financial imperatives.

This study underscores the value of a detailed and integrated hydrological model in mine planning and the management of environmental effects on water resources. With a multi-disciplinary team, ongoing engagement and a co-operative relationship between the engineering and environmental teams, it is possible to achieve outcomes that satisfy both mining and environmental objectives.

Hydrogeological studies are essential during the exploration phase of mining operations to ensure sustainable water management, especially in the case of phosphate mining in Morocco, where the risks extend beyond water scarcity for mining operations to the management of significant volumes of water that at least partially or completely submerge phosphate layers, notably in the Beni Amir deposit, where high evaporation exacerbates water shortages.

By integrating geological, hydrogeological, and geophysical data into both two-dimensional and three-dimensional models, the study introduces a new approach for identifying both submerged and dry phosphate layers. This advancement addresses a critical knowledge gap regarding hydrogeological conditions in sedimentary rock mining regions, offering a novel tool for assessing and managing groundwater-related challenges. This modeling effort is particularly groundbreaking given the lack of research on hydrogeological processes in North African phosphate deposits, especially in complex mining environments.

The study followed a multi-step process. First, geological and hydrogeological data were collected and analyzed to develop a hydro-stratigraphic conceptual model, which detailed the interaction between phosphate layers and the water table. This model was based on data from 692 boreholes across the study area. A delineation map was then created to identify the saturated zones, where phosphate layers are submerged, as well as the dry areas. The findings showed that approximately 73% of the Beni Amir deposit is at least partially submerged by the aquifer, while the remaining 27% constitutes dry zones. These results guided the placement of geophysical profiles and surveys to refine the initial results and characterize water-bearing geological formations. This geophysical assessment helped determine hydrogeological parameters and quantify water content using a combination of Electrical Resistivity Tomography (ERT) and Magnetic Resonance Sounding (MRS).

The combined ERT and MRS results identified multiple aquifers within distinct geological formations. The Lutetian and Danian-Thanetian formations exhibited higher water content and permeability, while the Maastrichtian formations showed moderate permeability with variable water content. The Senonian formations were highly heterogeneous. Strong correlations between MRS and ERT results were validated by piezometric levels. MRS estimates of permeability and transmissivity also demonstrated minimal uncertainty (1.74%) compared to pumping well data, indicating high accuracy.

This comprehensive understanding of groundwater dynamics at the mine site is crucial for developing effective strategies to mitigate water-related hazards, ensuring the safety of mining operations, and protecting valuable water resources.

Large Open Pit mines in Chile currently operate below the natural groundwater level, leading the operations to deal with big challenges related to groundwater, as could be obtaining field data measurements and perform hydraulic test, or controlling the seepage that flows into the pit slopes, among other relevant issues. These challenges are usually investigated by different consultants to help the mining operation, sometimes with different scopes, as could be regional groundwater modeling for environmental studies, or mine-scale models for slope stability analysis.

The continuity and duration of studies for specific hydrogeological topics is always different and depends on the scopes, but some tasks and works are repeated year after year, like data gathering, or modelling processes for Five Year Plan evaluation. Sometimes in these processes the consultants leading those works are changed for different reasons, as could be economic reasons. When this happens and a new consult starts from zero, there is a knowledge that is lost, and a new learning curve starts. In this case after five years working as hydrogeological consultants for one of these Large Open Pit mines, different lessons have been learned and are presented in this paper.

One of the main lessons is that critical data review must be performed every time, even for repeated tasks when the same data is received from the mine staff, it must be reviewed carefully because it could have different values for old data, indicating inconsistencies that should be raised before starting to work with it. Another relevant matter that helps both mine operation and consultant companies is the constant Peer Review processes, that allow to highlight improvement opportunities to the work that has been done, and from a third-party eye, issues and new ideas for field work, conceptual model and numerical model are obtained to achieve robust hydrogeological study.

Finally, this knowledge obtained after five years of constant work with the mine staff leads to a better understanding of the hydrogeological conditions in the study area and allows us to help the client with additional topics like the knowledge sharing for new staff or new consultants. It also generates a high standard hydrogeology area inside the mining company that can deal with technical issues and uncertainty for the future of the mine site.

Irrigation has been proposed as a cost-effective, long-term option for managing mining-influenced waters in the Witwatersrand Goldfields. However, there are concerns about the suitability of these waters for crop production as well as the safety of the produce for consumption. To address these concerns, A glasshouse pot trial was established where crops were irrigated with untreated and HDS-treated mine water from the Eastern, Central and Western Basins of the Witwatersrand Goldfields. The findings of this study indicate that crops that are safe to consume can successfully be produced with treated mine waters from the Witwatersrand Goldfields. Furthermore, the findings suggest that untreated mine waters from these goldfields can be utilized for irrigation if soils are strategically limed.