Appendix 2: Existing Approaches to Ecological Flows

Northland Regional Council

(Operative plan)

Design minimum flow is set at MALF for streams with MALF  300 L/s. Otherwise, it is set at Q5 unless the water body has a high ecological value; then MALF becomes the design minimum flow.

Flow correlation method used to estimate design minimum flow (Q5) in catchments with no long-term record.

In all instances, lower minimum flows can be set if the adverse effects of the take can be demonstrated to be avoided.

The schedule in the Regional Plan specifies aquifers with high actual / potential demand.

In some sensitive aquifers, groundwater level triggers for reducing takes are imposed.

Auckland Regional Council

(Proposed plan)

Regional plan provides for the setting of minimum flows in high-use rivers and streams.

No minimum flows are scheduled in the regional plan. However, ARC uses key documents to set minimum flow requirements: Flow guidelines for instream values (MfE 1998) and Guidelines for setting stream flow regimes in the Auckland Region – draft (ARC 2000).

The plan also uses the WAIORA (Water Allocation Impacts on River Abstraction) modelling tool to identify the effect of actions to meet its objectives.

Regional plan provides for the setting of aquifer levels and water availability in high-use aquifers.

Schedule 2 includes water availability (m3/year) for 22 aquifers and groundwater levels in three aquifers.

Takes are restricted where Schedule 2 groundwater levels drop below the set level.

Environment Waikato

(Proposed water allocation variation notified October 2006)

The proposed plan variation establishes more policies to prioritise water allocation and restrictions on water takes.

Minimum flow trigger is a percentage of Q5, but will be assessed on a case-by-case basis for specified catchments.

Allocatable flows are 5% of Q5 for upland catchments, and 5–30% of Q5 for others.

Proposed plan variation establishes sustainable yields for aquifers and prioritises restrictions on water takes. No specific method is stated for establishing sustainable yields.

Environment Bay of Plenty

(Proposed plan)

Minimum flows are determined through IFIM and RHYHABSIM¹³ to protect specific ecological values.

The plan also uses Flow guidelines for instream values (MfE 1998) for other values.

Otherwise, the default instream minimum flow requirement is 90% of the Q5 seven-day low flow, with a default allocation limit of 5% of the Q5 seven-day low flow.

Aquifers are being mapped to assist in developing sustainable yields.

Gisborne District Council

(Operative plan)

Minimum flows are set based on a minimum level at a river gauging site at the northern areas that are irrigated. When the level drops, monitoring begins.

Triggers are on large aquifers.

Taranaki Regional Council

(Operative plan)

Default minimum flow will provide two-thirds of the habitat at MALF. It is a guideline only – flow will go under or over it, depending on the values and community. This method was found to be the most robust method for the region and is based on scientific work.

The water plan seeks to limit the taking of groundwater to the sustainable yield of the aquifer.

Manawatu Wanganui (Horizons) Regional Council

(Draft plan, replaces previous operative plan)

Decisions made on a case-by-case basis, considering habitat requirements and chemical parameters. It is an integrated approach, using IFIM.

The default primary allocation is 20% of MALF.

The allocation is supplementary when the river is above its median flow and no more than 10% of the flow taken at any one time.

A ‘default’ minimum is still under consideration.

Guidance regarding the sustainable yield is provided in the Council’s technical publication Groundwater allocation methodology: Horowhenua and Manawatu (Horizons Regional Council 2004). The sustainable yield is based on 50% of the land surface recharge.

Hawkes Bay Regional Council

(Operative plan)

Minimum flows are established on a case-by-case basis for surface water takes. The Council uses IFIM.

It has used New Zealand-derived habitat curves for native fish and is collaboratively developing an East Coast-specific habitat curve for trout.

The plan does not have developed sustainable yields or volumes of allocation for any aquifer systems.

Greater Wellington

(Operative plan)

Fourteen rivers in the region have comprehensive management regimes that set minimum flows.

A case-by-case assessment of minimum flow requirements is carried out. Guidance states that historical flow methods can be used in rivers with a MALF 1000 L/s, and IFIM can be used in bigger rivers. Allocation is primarily habitat-based (two-thirds habitat protection).

The water plan specifies safe yields for all aquifers. It states that ‘daily safe yields are based on the estimated sustainable yield of the aquifer system which are calculated from annual water balance information. These yields are, therefore, conservative estimates based on the precautionary approach’.

A conceptual model of aquifers is being developed to help refine the assessment of availability.

A detailed hydrogeological model has been developed for the Lower Hutt groundwater system, to set a sustainable yield and minimum water level. For other aquifers, where there is no detailed model or the recharge mechanism is well understood, the sustainable yield is based on the water balance approach or calculated aquifer throughflow.

Marlborough District Council

(Operative plan)

Sustainable flow regimes are set for rivers in the Plan.

No specific information is available on how minimum flows are set.

A throughflow approach was used to set sustainable yield limits. Models exist for some aquifers.

Nelson City Council

(Operative plan)

Surface water default allocation limits are used.

For specified rivers, this is 10% of the one-in-five-year mean low flow for rivers with high ecological values.

33% of the one-in-five-year mean low flow is used for rivers from which water is abstracted.

For unspecified rivers, the limit is 10% of the one-in-five-year mean low flow.

There are no aquifers within Nelson City.

Tasman District Council

(Operative plan)

The Plan is to have regard to Flow guidelines for instream values (MfE 1998) when establishing minimum flow regimes.

Integrated surface and groundwater models are used where required to establish links, and modified IFIM methods are used for surface water triggers. An allocation limit based on a 1:10-year security of supply standard (35% reduction in a one-in-ten-year drought) forms part of how allocation limits are set.

Minimum flows and triggers for rationing of water takes are specified for high-use catchments based on the previous paragraph.

For smaller rivers where there is insufficient information or where abstractive pressures are less, the established thresholds for abstractive allocation are based on the five-year, seven-day low flow and the significance of the rivers or streams.

Water plan seeks to establish the sustainable yield of aquifers.

Detailed integrated hydrogeological models including river interactions where applicable have been used to determine limits of abstraction for key groundwater systems on the same security of supply standard as river systems where applicable.

The five-year, seven-day low flow is the default as a trigger for other river / aquifer interrelated systems.

West Coast Regional Council

(Proposed plan)

Where more than 20% of any stream has been allocated, a minimum flow will be applied to any new consent for taking water.

In the absence of detailed hydrological information, a minimum flow based on 75% of the MALF will apply.

Lower minimum flows can be set if the adverse effects of the take can be demonstrated to be avoided.

The plan does not have sustainable yields or volumes of allocation for any aquifer systems.

Environment Canterbury

(Operative catchment regional plans)

(Water Conservation orders)

(Proposed plan NRRP)

Three operative catchment regional plans. Each apply different methods to set flow and allocation (generally have included IFIM approach).

Flow and allocation regimes included in three water conservation orders. Waitaki Regional Plan recognises allocation and minimum flow provisions of the Ahuriri WCO. NRRP recognises Rakaia WCO and is to be amended to recognise the Rangitata WCO (finalised since the NRRP was notified).

Some flow and allocation regimes are set in the NRRP and more are being introduced into NRRP via variations following specific catchment investigations and consultation. Flow requirements are determined for different values and judgement applied to establish overall water management regime including flow and allocation. IFIM approach often used also expert panel approach. Guided by Flow Guidelines for Instream Values (MFE 1998).

Where water management regime has not been developed, a default ‘A’ allocation limit set by flow equalled or exceeded 85% in January / February less the minimum flow. Supplementary or ‘B’ allocation – guidance given that ‘B’ allocation can start once river flows exceed an amount equal to minimum flow plus half the ‘A’ allocation. The minimum flow used in the default situation is that which has been established in the catchment to date via the resource consent process.

Proposed plan contains interim limits. Variation 4 sets allocation limits as annual volumes in the NRRP. Initial estimate is 50% of the annual average land-surface recharge or, if insufficient information is available, then 15% of the average annual rainfall is used. Once limits have been calculated using these formulas, adjustments have been made to them based on other available information (eg, required low land stream inflows).

Otago Regional Council

(Operative plan)

Site and catchment-specific scientific approach – predominantly IFIM – for all rivers.

Catchment Specific Allocation limits are set in schedule 2A of the water plan. Where no specific limit is set a default primary allocation of 50% of seven-day MALF or the consented seven-day take as at February 1998 less any consented surrendered, lapsed or not replaced after 28 February 1998 is used.

Further allocation is available as Supplementary allocation and is based on 50/50 flow sharing. Supplementary minimum flows are set to allow water harvesting at moderate to high flows.

An aquifer-specific approach is used. Allocation limits are set using different methods for each aquifer.

There are restriction levels on key reference bores within some aquifers. There are 25%, 50% and 100% restrictions on groundwater use within seven aquifers.

Environment Southland

(Proposed plan)

The plan groups rivers using the ‘Source of Flow’ level in the River Environment Classification (REC). For each group of rivers, critical values are identified that are used as the basis for determining minimum flows and levels. The concept of critical values is that by providing sufficient flow to sustain the most flow-sensitive value, the other significant values will also be sustained.

The Plan contains a staged management approach to surface water allocation as follows:

• where less than 10% of the mean annual low flow is allocated, the default minimum flow is the mean annual low flow and the take or diversion is a restricted discretionary activity

• where 10% to 30% of the mean annual low flow is allocated, a minimum flow derived from generalised habitat models for the critical value species applies and the take or diversion is a discretionary activity

• where greater than 30% of the mean annual low flow is allocated, a minimum flow derived from an instream habitat analysis for the critical value species applies and the take or diversion is a non-complying activity.

Incorporates a staged management approach to various aquifer types based on the level of risk of adverse environmental effects.

The level of risk is directly related to the sensitivity of the hydrological setting to adverse effects and the level of resource development expressed as a percentage of annual land-surface recharge.

Riparian or terrace aquifer: 25% of the mean annual land surface recharge (stage 1).

Confined aquifer: pumping results in no more than a 25% reduction in the potentiometric head at a distance 250 metres from the bore (stage 1).

Riparian or terrace aquifer: greater than 50% of the mean annual land surface recharge (stage 3).

Lowland aquifer: greater than 15% of the mean annual land surface recharge.

Confined aquifer: pumping results in greater than a 50% reduction in the potentiometric head at a distance 250 metres from the bore.