Quantifying the Hydrological Effect of Permitted Water Abstractions across Spatial Scales

Area of Science:

• Environmental Science
• Hydrology
• Ecology

Background:

• Water abstraction alters freshwater flow regimes, impacting ecosystem health and services.
• Balancing economic benefits of abstraction with ecological consequences is crucial.
• New Zealand legislation mandates water resource limits to manage cumulative abstraction impacts.

Purpose of the Study:

• To develop and apply a national method for calculating total water allocation limits.
• To assess the extent of water resource over-allocation across New Zealand catchments.
• To identify catchments requiring reduced water abstraction.

Main Methods:

• Collated a national database of water abstraction consents.
• Applied a replicable method to calculate total allocation at national, catchment, and reach scales.
• Mapped Weighted Allocation Impact to integrate abstraction magnitude and spread.

Main Results:

• Existing water abstraction consents have led to over-allocation in several New Zealand catchments.
• The Weighted Allocation Impact index quantified the spatial distribution of over-allocation.
• Identified specific catchments where abstraction reduction is necessary.

Conclusions:

• Current water allocation practices in New Zealand have resulted in significant over-allocation.
• The developed method provides a transferable tool for assessing water resource management.
• Urgent strategies are needed to reduce abstraction in over-allocated freshwater systems.