Consented freshwater takes

  • River flow is the quantity of water passing a point over a certain time. Each river has natural patterns of high and low flows that influence how much water is available for irrigation, drinking water, hydroelectricity generation, and recreational activities. River flows also influence physical habitat and ecological processes like migration, spawning, food supply for aquatic life, and removal of nuisance algae. We report on two indicators of the pressure on our river flows. The first outlines key variables regulated through consents to take water, including the location, use, source, maximum allowable instantaneous rate, and maximum allowable annual volume. The second is the potential impact of consented freshwater takes on river flows across New Zealand.

    We classified Consented freshwater takes as a national indicator.

    Key findings

    Excluding hydroelectricity consents, irrigation was the largest consented consumptive use of water (65.9 percent of consents) in the 2013–14 water reporting year (July 2013 to June 2014).

    • Excluding hydroelectricity consents, national consents for irrigation use had the largest:
      • summed instantaneous rate (the maximum rate at which abstraction may occur), with a summed maximum instantaneous rate of 63.4 percent of consented rate
      • summed annual volume, with a summed maximum annual volume of 51.1 percent of total consented volume.
    • Groundwater irrigation consents were largely concentrated in Canterbury, while surface water irrigation consents were more evenly distributed across the country.
    • There were more consents to take groundwater (10,857) than there were for surface water (5,064), but the summed annual volume and summed maximum instantaneous rate were higher by 48.1 percent and 24.9 percent, respectively, for surface water takes than for groundwater takes.
    • The largest potential impact on freshwater flows of consented takes is in small rivers where there is a combined effect of a large number of consents, each allowing moderate volumes of water to be taken from the same small river.
    • Irrigation has potentially the most widespread impact on river flows across the country; however, consents to take water for hydroelectricity, industrial, and drinking uses were important in some catchments.

    Figure 1

    Note: ‘Other’ use comprises consents for stock, frost protection, combined/mix, not specified, or other. Hydroelectricity is excluded on the assumption that it is generally non-consumptive.

    Figure 2

    Note: ‘Other’ use comprises consents for stock, frost protection, combined/mix, not specified, or other. Hydroelectricity is excluded on the assumption that it is generally non-consumptive.

    Figure 3

    Note: ‘Other’ use comprises consents for stock, frost protection, combined/mix, not specified, or other. Hydroelectricity is excluded on the assumption that it is generally non-consumptive.

    Figure 4

    Figure 5

    Definition and methodology

    All 16 regional and unitary councils supplied consent information on water takes. Consent information includes location of the take, maximum instantaneous rate (maximum rate at which abstraction may occur), maximum annual volume (maximum volume of water that can be abstracted in a year), whether it is groundwater or surface water take, and primary use (eg for irrigation or drinking water). Only ‘active’ consents (ie consents not expired) at 14 February 2014 were used because this date falls near the likely peak of the irrigation season for the water reporting year 2013–14.

    NIWA mapped the location of each water take onto a digital representation of New Zealand’s river network, called the River Environment Classification (version 1). They proportioned each groundwater take between its assigned river segments (ie individual portions of a river of equal length) as a function of distance and river low flow.

    NIWA calculated the reduction in river flows as a result of all upstream consented takes for each river segment in New Zealand (Booker et al, 2016). This represented the potential impact on river flows, calculated by summing instantaneous rates of all upstream consented takes and then dividing by the estimated long-term natural median flow. Negative values indicate potential for flow to be augmented due to a consented flow diversion. This sometimes occurs when hydroelectric schemes take water and then return it to a different river location after use.

    These indicators do not represent actual water takes or actual flow reductions. Maximum potential flow alteration from all consented takes is represented by using consent information (rather than actual takes). All groundwater takes were assumed to influence river flows. The effects of non-consumptive hydroelectric operations (at dams) and takes for permitted activities, such as for stock water, are not included. Some consent conditions require takes to cease or be restricted during times of low flow or during other environmental conditions. We did not include the effects of these restrictions on takes in this analysis due to lack of nationwide data availability.

    Data quality 

    Topic Classification   Relevance Accuracy 
     Resource use and management, and other human activities  National indicator

    Image, Direct relevance.

    Direct 

     Image, High accuracy.

    High

    See Data quality information for more detail.

    References

    Booker, D, Henderson, R, & Whitehead, A (2016). National water allocation statistics for environmental reporting. Prepared for the Ministry for the Environment. NIWA Client Report no. 2017065CH. Retrieved from www.mfe.govt.nz.

    Published 27 April 2017

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