IRMA Standard for Responsible Mining (Draft 2.0)
Chapter 3.2 Water Quantity

This chapter has been flagged. IRMA is seeking feedback during this comment period on the potential application of a risk-based approach to the protection of water quantity, including examples of where such an approach has been used effectively. Please see Chapter 3.1, Approach C, for a risk-based approach to water quality protection.



Mines are often a large water user for their locale, even if not over a large region.  The impacts of the quantity of water used by a mining project are highly location-specific, depending critically on the local climate as well as on competition for water for uses other than mining.  In arid regions water scarcity may be a critical concern, whereas in high rainfall regions challenges arise from the need to divert water in order to develop a mine. The depletion of groundwater by dewatering operations and the presence of large mine facilities can take decades to replenish after mining ceases, and in some instances, groundwater levels and flow directions can be altered indefinitely.

Key aspects of responsible mining in relation to water use include the efficient use of production water, the withdrawal and disposal of mine dewatering water, stormwater, and floodwater in ways that minimize harm to surrounding water users and environmental resources, and ensuring that total withdrawals maintain environmental flows in nearby streams, springs, lakes, wetlands and any other surface water resource. Responsible mining operations can also clean up previously impacted water to make them usable, and in some cases might provide a water supply from an alternative source. Responsible mining protects water resources by reducing the amount used for processing and by minimizing the need for dewatering or efficiently using the dewatering water.  Responsible groundwater use will protect other groundwater users by not causing unreasonable groundwater drawdown.


To maximize efficiency of water-use and minimize off-site impacts to the environment through the adoption of leading water management strategies and practices throughout the full mine life cycle.

Scope of Application

Chapter Relevance:  This chapter is applicable to all mines applying for IRMA certification.

Existing legal water rights regimes may supersede the implementation of certain aspects of the IRMA requirements.


  • Major reorganization with the addition of supplemental explanatory text to add clarity.
  • Previous criterion related to Underground Mines, which addressed backfilling, was removed because it is adequately covered in Chapter 4.2 Reclamation and Closure, criterion 4.2.5.
  • The means of verification (MOV) have been removed from this version of the draft IRMA Standard. If you would prefer to review and comment on a version of the draft Standard that has the means of verification, you can download a pdf version of the Standard with MOV.

Water Quantity Requirements

3.2.1.  General Requirements  To the extent practicable the operating company shall maximize the use of water efficient processes.  Mine surface or groundwater water use shall not:

a. Decrease the flow from a spring by more than 50%;

b. Change stream base flows to rates less than required for passby flows;

c. Cause significant negative impacts to:

i. Community or individual water supplies;

ii. Aquatic life or wildlife;

iii. Rare / endangered species; or

iv. The ecological or amenity value of water bodies within protected areas.  The operating company shall identify all relevant water users potentially affected by the mine, regardless of whether their water rights are recognized by a government.

3.2.2.  Mitigation  If not resolved by other means, issues arising around ground or surface water impacts shall be discussed and resolved through the operational-level grievance mechanism (see IRMA Chapter 2.13).  For significant impacts on ground or surface waters in protected areas or on protected waters, mitigation other than prevention or avoidance shall not be an alternative.

3.2.3.  Planning, Monitoring, and Modeling  The operating company shall complete a suitable groundwater analysis for existing mines, and in advance of an Environmental (and Social) Impact Assessment for a new mine, to estimate the potential for the mine to affect groundwater resources, including both groundwater quantity and quality.  A suitable analysis includes:

a. A Conceptual Flow Model (CFM), or its functional equivalent, including:

i. A quantitative analysis of baseline conditions for recharge to the aquifers;

ii. Discharges from the aquifer; and

iii. Flow pathways and aquifer properties controlling the flow between recharge and discharge.

b. The mine plan will be imposed on the CFM, or its equivalent, to estimate significant impacts including, but not limited to, the following:

i. Whether dewatering will be required;

ii. Whether production water is available and the impacts of using it; and

iii. The effect of the mine voids (underground and/or open pit) during the various project phases, including whether a pit lake will form, its volume, or the estimated inflow and void volume for underground workings.  If the Conceptual Flow Model indicates that there could be impacts, a numerical streamflow and/or groundwater model shall be developed by the operating company to quantify the impacts and help to plan mitigation and mine water management (see section

a. The numerical model will be developed to industry standards,[1]  including use of the appropriate code, model structure including discretization and boundaries, proper model calibration and verification, and appropriate assumptions for the mine;

b. The numerical model will be used to predict the impacts of pumping, dewatering, seepage, and any other significant mine-related groundwater impacts including, but not limited to:

i. The amount of water removed, and the extent of groundwater drawdown caused by mine dewatering and by the development of mine production water, both from open pits and underground mine voids; and

ii. The impacts on streams and springs including, the amount of water drawn from springs and streams and the time until impacts are felt at the stream.

c. The numerical model shall be verified at least every five years during mine operations and closure, to assess whether it accurately predicted impacts of the mine and to improve calibration for continued predictions.  A mine water management plan shall be developed, and include:

a. A water management strategy designed to estimate the needed water for each aspect and phase of mining and where that water will be obtained. The operating company shall demonstrate through its water management strategy that it will use water efficiently and minimize the mining impacts on surface and groundwater resources. This includes:

i. Minimizing the impacts of mine dewatering;

ii. Placing production wells so that the effects do not reach surface in less than 30 days; and

iii. Using production water most efficiently.

b. A surface water and groundwater monitoring strategy (which may also incorporate/include other monitoring requirements);

c. A surface water and groundwater impact mitigation strategy (which may also incorporate/include other mitigation requirements);

d. A strategy to mitigate aspects of mine water use and dewatering that could affect water quality.  This includes the development of acid generating and/or metals leaching conditions as a result of oxygen reaching the dewatered aquifer or due to leaching caused by disposal of the dewatering water; and

e. A review at least every five years, or when there is a significant change to mining-related activities or the mining operation.  If monitoring data do not support the estimates:

a. The model shall be revised until monitoring data support the estimates; and

b. The water management plan shall be amended in response to the revised model.  The operating company shall provide an accurate mine-site water balance accounting for its operations:

a. The accounting shall identify the sources of water to be stored onsite, consumptively used, and discharged; and

b. Any discharge location shall be listed and mapped in a monitoring plan.  All groundwater and surface water hydrology data and reports shall be publicly available.

3.2.4.  Surface Water Passby Flows  The operating company shall establish passby flows for sites affected by surface water withdrawals from the mining project.[2]  Passby flows shall be based on the flow maintenance goals of the natural flow regime method.[3]  Unless the operating company can justify different requirements that account for habitat, in-stream flow, and channel-building flow, the following specified passby flows shall be met:

a. If the watershed area exceeds 130 square kilometres (50 square miles) the passby flow shall be Q75 for winter/spring months and Q60 for the summer months.

b. If the watershed area is less than 130 square kilometres (50 square miles) the Q60 value shall apply all year.

c. If withdrawals are higher or passby flows lower than those specified above, the operating company shall demonstrate, using an appropriate in-stream habitat methodology, that habitat will be protected for the aquatic and terrestrial life present at the site. The operating company shall:

a. Estimate the exceedance flows (Q60, Q75) using the best available data and/or methodology

b. Document its justification for its data analysis and/or choice of methodology; and

c. Review and update exceedance flow estimates at least every five years on the basis of river flow gauging data and analysis.  The operating company shall establish a river flow gauging station[4]  at the withdrawal site(s), and monitor such site(s) to verify that withdrawals stay within the prescribed values.  In regions where legal water rights regimes control passby flow, the legal permit/entitlement/allocation shall be considered the minimum obligation for passby flows.

3.2.5.  Groundwater Use  If there is potential to affect off-site groundwater uses or users, the operating company shall not use groundwater in excess of the rate of replenishment (groundwater mining).  Exceptions can be made for:

a. Mine dewatering, or

b. Providing initial production water, if that usage will not cause deleterious effects to surrounding groundwater-dependent resources.  In arid regions where groundwater is isolated from the surface water and there is effectively no local recharge to the aquifer, groundwater may be used for production or other mine-related activities for the life of the mine.  The operator shall:

a. Implement water conservation activities to minimize the use of this isolated groundwater; and

b. Provide evidence that the groundwater is isolated, which includes evidence that indicates that using this isolated water will not affect surface water sources for a minimum of 100 years.

3.2.6.  Mine Dewatering  The operating company shall reduce the impact of mine dewatering on water quality or quantities by:

a. Using the dewatering water as production water;

b. Providing the dewatering water to other local water users to replace their pumpage;

c. Returning the water to the same aquifer it was removed from; or,

d. Returning the water to same local basin.

e. In areas where precipitation exceeds evaporation, mine dewatering water may be discharged to streams so long as it will not exacerbate flooding, cause erosion, and meets the protection of water quality requirements as specified in Chapter 3.1.[5]

3.2.7.  Pit Lakes and Mine Workings  In areas in which evaporation exceeds precipitation, and where the pit lake shape will be altered by partial backfilling or other means, the final shape of the pit lake shall be designed to minimize evaporative loss.  The operating company shall plan, whenever safe and possible, to provide for long-term usage of the pit lake water, providing for beneficial uses that are consistent with long-term water quality and safety.  In areas where the final mine void water balance indicates a risk of pit lake overflow, the operating company shall design to avoid or control any overflow discharge to surface waters.

3.2.8.  Water Quantity Monitoring  Groundwater and surface water monitoring locations shall be informed by the Conceptual Flow Model.  Monitoring of groundwater levels and surface water flows shall commence prior to mining operations and continue as the final void (open cut or underground) fills.  Monitoring shall inform the mitigation and management strategies during operations and closure.


The requirements of the IRMA Water Quantity chapter attempt to protect surface and groundwater beneficial uses – aquatic organisms (surface waters), drinking water, human health, irrigation, agriculture and livestock.

Groundwater Use
The effect of using groundwater for mine production depends on the source of groundwater, whether it is a large or small aquifer, and whether it is connected to a nearby surface water source.  The IRMA standard is to show that pumping will not affect streamflow for 30 days, with the alternative to show the water is not being drawn from the alluvium underneath the stream within a broader subterranean channel, attempts to create a balance between surface and groundwater rights while also acknowledging that most groundwater pumping will eventually be drawn from surface water sources. 

Surface Water Use
A passby flow is a prescribed flow rate that must be allowed to pass an intake when a withdrawal is occurring, which is the same as a low flow condition during which no water can be withdrawn.  If too low, specified passby flows can allow significant damage to occur to streams, especially small streams.

Cross Reference to Other Chapters



1.1—Legal Compliance As per Chapter 1.1, if there are host country laws that pertain specifically to the topics addressed in any IRMA chapter, the company is required to abide by those laws. If IRMA requirements are more stringent than host country law, the company is required to also meet the IRMA requirement, as long as complying with it would not require the operating company to break the host country law.

Existing legal water rights regimes in host countries may conflict with IRMA requirements, and therefore supersede the implementation of certain aspects of the IRMA requirements.
2.13—Grievance Mechanism and Access to Other Remedy Requirement refers to potential disputes over ground or surface water withdrawal. These disputes may be addressed through the operational-level grievance mechanism or some other means.
3.1—Water Quality Chapter 3.1 has requirements related to pit lakes (e.g., that may be relevant to 3.2.7.
3.7—Protected Areas Requirements and refer to conditions that apply to Protected Areas.  See Chapter 3.7 for identification of, and requirements related to mines operating in and adjacent to protected areas.
4.1—Environmental and Social Impact Assessment requires that a Conceptual Flow Model (CFM), or its functional equivalent, be utilized as part of the groundwater analysis in an Environmental and Social Impact Assessment, and provides details on how the CFM is to be utilized in this analysis.
4.2—Reclamation and Closure Chapter 4.2 has requirements related to pit lakes (e.g., 4.2.3) that may be relevant to 3.2.7.



1. (E.g., See Anderson, Woessner and Hunt. 2015. Applied Groundwater Modeling: Simulation of Flow and Advective Transport. Second Edition. Academic Press.)

2. Passby flows are not necessary if there are no surface or groundwater withdrawals; or if the existing water rights regime prevents the use of specified passby flows.
3. Poff et al. 1997. The Natural Flow Regime. BioScience. Vol. 47, No. 11.

4.  Gauging station: A site at which surface flows can be measured.  For IRMA, it is primarily used for the maintenance of passby flows or monitoring the effects of groundwater withdrawals on surface water.  At a minimum, it is a staff gauge with well-defined stage discharge relationship.  If it is part of a monitoring plan, it should include a continuous recording water level measurement device.

5.  See Chapter 3.1, requirement 3.1.1 in Approaches A and B, and 3.1.11 in Approach C.