Allocation and Irrigation

Parts of eastern and southern Marlborough are amongst the driest regions in New Zealand and symptomatic of this is the location of the Lake Grassmere saltworks near Ward.

In these areas it is necessary to irrigate crops over summer to supplement the low rainfall and offset the naturally high evapotranspiration rate. Even the small volumes of water needed for drinking or stock supply can be scarce during some seasons.

In some catchments such as the Southern Valleys along the southern flank of the Wairau Plain, surface flows dry up in summer with groundwater representing the only viable source of water.

Marlborough District Council is the regulatory authority that issues resource consents to take and use water for commercial purposes based on the sustainable limits in the Marlborough Environment Plan (MEP).

In most Marlborough catchments the quantum of water available for allocation is now approaching or has reached sustainable limits, although there are still high surface water flows for storage available in some catchments.

The Southern Valleys Catchments are currently overallocated with the Omaka, Brancott and Benmorven Aquifers undergoing a formal reconciliation process to bring allocation into line with safe limits in the MEP.

River catchments are now referred to under central government legislation as Freshwater Management Units (FMU’s).

The influence of climate change is becoming more evident with time. For example, Wairau Plain grape harvests are earlier due to higher air temperatures while irrigation of dairy pasture in the relatively high rainfall Marlborough Sounds catchments has become normal practice. Coastal groundwater levels are rising in response to sea-level rise at Rarangi and overall, the district’s weather is more volatile.

With more dynamic weather patterns affecting water demand and recharge patterns, there is a need for more frequent reviews of MEP water allocation limits.

For example, based on MDC state of the environment monitoring aquifer results beneath the Cloudy Bay coast and a greater understanding of river-groundwater exchange processes, the MEP limits for the Riverlands Aquifer and Wairau Aquifer are being reviewed.

The accompanying photographs show a travelling type pasture irrigator in the Wairau Valley and a standard post and wire vineyard support system used in most Marlborough vineyards.

For further information on the process of applying for a water permit to take and use water for irrigation
Go to the resource consents webpage

Allocation and Irrigation

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