Environmental


The CPWL Environmental Team is responsible for implementing, managing, and monitoring CPWL’s resource consents to ensure CPWL maintains the legislative and operational requirements to deliver and operate CPWL.

Sustainability

CPWL has been designed to replace the use of environmentally sensitive groundwater in the area with a more sustainable surface water scheme, supported by water storage. For CPWL sustainability is about ensuring that the Central Plains Water Enhancement Scheme (CPWES) is viable and contributes lasting benefits to society through consideration of social, environmental, ethical, and economic aspects in all that it does.

Water Quality

Key to the establishment of CPWL was the desire to protect Canterbury’s water quality and quantity, including switching land users from groundwater abstraction to low nutrient alpine sourced water. CPWL’s development was closely aligned with the vision of the Canterbury Water Management Strategy (CWMS) and CPWL is a primary contributor towards the success of the CWMS Outcomes. CPWL has the potential to deliver widespread environmental benefits by leading shareholders towards more sustainable and efficient farm practices with its proposed collective approach to managing nutrients and on-farm management.

Environmental Benefits

CPWL strives to be an environmental leader that sets the benchmark for water use as part of sustainable land use practice. CPWL’s key Environmental Benefits to the Region are:

  • Recharged Aquifers (groundwater).
  • Increased flows in Selwyn River and Lowland Streams.
  • Management of Nutrients via Farm Environment Plans (FEP), Farm Environment Plan Audits and Water Use Agreement.
  • Biodiversity and Ecosystem Enhancement – Environmental Management Fund, Te Waihora Environmental Management Fund and contributing to the cost of opening Te Waihora/Lake Ellesmere.
  • Groundwater and Surface Water Monitoring.

Environmentally Sustainable

CPWL want to be recognised environmentally as a world leader in environmental and sustainable practice. We will achieve this goal by protecting and enhancing the surrounding waterways. Just like farmers, we are caretakers protecting the quality of our land. The two key ways we will achieve this are:

  1. Protecting the aquifers. By taking low nutrient alpine water from the Rakaia River in a controlled way, as provided for by the Water Conservation Order, CPWL is protecting the aquifers. Farmers no longer have to abstract water from groundwater wells and artesian supplies. This water can now be left in the aquifers.
  2. Controlling and reducing use of nutrients. Every farm must have a Farm Environment Plan (FEP) which is independently audited. Nutrient levels on farms in the CPWL scheme are monitored and audited, and the reduction in nutrients is one of the key environmental pillars on which the scheme is built. In the long term, our nutrient discharge levels will be lower in 2022 than they were at the commencement of the scheme because of the advancement of new management practices and consent requirements.

In the first year of all stages (Stage 1, 2 and Sheffield) only 17% of the annual groundwater volume held by our shareholders was used. In 2014/2015 over 100 million cubic metres (m3) of the consented volume, which is over 200 million m3, was used by our shareholders, this decreased to 35 million m3 in 2018/2019 irrigation season.

CPWL has implemented Farm Environment Management Plans (FEPs) for all Shareholders to ensure that farmers are carrying out good management practices on their farm.

At the end of 2019/2020 irrigation season, all CPWL farms will have completed two FEP audits with some having completed their third FEP audit. The FEPs are the prescribed tool required to ensure nitrogen and phosphorous losses, resulting from farming activities, are reduced to allow water quality to improve over time. CPWL has a significant responsibility to ensure water quality goals are achieved and to develop processes and systems to ensure that CPWL can manage and monitor results. To date 93% of CPWL’s farms have received an A or B grade in their latest Farm Environment Plan audit.

Over the four year construction phase, CPWL achieved almost 100% compliance with the Resource Consents. CPWL has enabled farmers to switch from groundwater to surface water irrigation, reducing the demand on groundwater aquifers and allowing them to refill. This improves the flow in streams that are linked to one of New Zealand’s most important lakes – Lake Ellesmere/Te Waihora achieving a key outcome of the Canterbury Water Management Strategy.

Between 2014 and 2020, 29 river and stream sites and 20 groundwater monitoring bores were installed, ranging in depth from 40m to 100m. This enables the accurate monitoring of water quality and quantity across the scheme with accurate data collection imperative to enable CPWL and environmental regulators to track performance over time.

Additional benefits that CPWL provides include:

  • 20 connection points to supply water for FENZ fire fighting
  • Supply of Water to Water Treatment plants
  • Supply of water for stockwater, and
  • Development of a website that shows Potential Evapotranspiration across the scheme area.

Water Sources

CPWL originally intended to deliver run of river water from both the Waimakariri and Rakaia rivers via a 56 kilometre long headrace canal and approximately 400 kilometres of open channel reticulation system.

However, plans altered considerably from the concept designs developed for the original consent applications process.  Farms within the Stage 1 & 2 area are supplied from the Rakaia River via a 17 kilometre long headrace.  Water is then distributed across both the Stage 1 and 2 areas, predominantly under gravity through an underground pipe network. This underground pipe network means that leakage from the scheme is minimal.

Conditions of resource consents on the Rakaia River authorising the taking of water, are subject to minimum flow conditions which require the rate of abstraction to progressively reduce as river flows decline. Figure 1 illustrates the controls governing abstraction of water from the Rakaia River under the Rakaia River Water Conservation Order (WCO).

The WCO establishes a minimum flow at Rakaia Gorge which varies depending on the month between 90 cubic metres per second (cumecs) in September and 139 cumecs in December. When flows are below the minimum flow, no water can be taken from the river. When flows are higher than the minimum flow, water can be taken from the river by resource consents assigned to 5 allocation ‘Bands’ on a 1:1 basis. Under these allocation bands for every 2 cumecs of flow above the minimum, 1 cumec can be taken from the river. Minimum flows increase from Band 1 to Band 5, decreasing the period of time water can be taken.

The bulk of allocation held by CPWL is assigned to Band 5. This band has the lowest reliability (i.e. it is cut-off first as river flows fall) and allows water to be taken when flows are between 70 and 140 cumecs higher than the WCO minimum flow (so the full allocation of 70 cumecs can only be taken when flows are at least 140 cumecs higher than the minimum flow). As a result, the full volume of water allowed by the CPWL consents can only be abstracted from the river around 63 percent of the time (on average) during the irrigation season. Irrigation requires a reliable supply of water during the growing season.

Due to the frequency of abstraction being cut-off, the original Scheme included provision for a large water storage dam in the Waianiwaniwa valley. During consent hearings CPWL withdrew the applications for construction of this water storage and subsequently entered into an agreement with TrustPower Ltd to access water stored in Lake Coleridge.

Figure 1 - Rakaia River Water Allocation and Restriction Bands

Farming Requirements in Selwyn Waihora

What happens behind the farm gate is important in maintaining and enhancing water quality. Farms under CPWL are required to meet good farm management practices and complete mandatory Farm Environment Plans. These plans are subject to an audit, which is carried out by an independent assessor. Any non-compliance must be rectified within a specified period. If not rectified, the supply of water to the offending user will be turned off.

By 2022, farms within CPWL will have to have reduced their nitrogen/nitrate loss. Dairy farms are required to reduce by 30 per cent and dairy support by 22 per cent, Irrigated sheep and beef farmers must reduce by five per cent and arable by seven per cent. Even with the conversion to new irrigation by 2022, CPWL will have achieved reductions of 413 tonnes, and be under the pre CPWL catchment load.

Further measures that were recommendations in the Selwyn Waihora Solutions Package have been formally adopted by Environment Canterbury via Plan Change 1 to the Canterbury Land and Water Regional Plan (LWRP) these include:

  1. Prohibiting new takes in over-allocated water management zones and reducing the total volume of water allocated within the Zone.
  2. Prohibiting the transfer of any part of an existing Groundwater Consent (other than to successors in title to the land currently having the benefit of those Groundwater Consents and where the location of the take and use of water does not change).
  3. Revised surface water allocation limits to deliver ecological and cultural flows, particularly in lowland streams.
  4. Introduction of a fixed allocation or “cap” on nitrogen losses in the catchment (including the Scheme).
  5. Progressive reductions in cumulative nitrogen losses are required over time.
  6. A requirement for all farming properties to prepare a Farm Environment Plan (FEP) and implement a range of good management practices. This includes specific requirements for individual landholdings to reduce nitrogen leaching losses by specific amounts (depending on land use type) by 2022.
  7. A reduction in legacy phosphorus in Te Waihora/Lake Ellesmere by 50 percent and improved management of lake-level and opening.