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By Daniel Collins

In the Christchurch Press today there is an article about the race to irrigate Canterbury. In it is the following statement:

“Canterbury had 70 per cent of New Zealand’s fresh water resource, and 34 per cent of its hydro-generation capacity.”

Unfortunately the 70% is an error that has appeared in the past and it is timely to make a correction and provide some other statistics that describe water resources in Canterbury more generally.

Canterbury has about 12% of New Zealand’s freshwater. This number is obtained from a Statistics NZ report, written by NIWA, on the water stock accounts of New Zealand.

To check for yourself, download the two Excel files from the Statistics NZ website, calculate the annual average of “Outflow to sea and net abstraction” for both Canterbury and the country as a whole, and divide one by the other.

This error has already been noted by the Christchurch Press in an article from March 2010.

For a fuller picture, here are some more useful statistics, from the Ministry of the Environment’s 2010 water allocation snapshot compiled by Aqualinc Research:

    Canterbury’s percent of national water consents (number): 30%
    Canterbury’s percent of national irrigation consents (number): 35%
    Canterbury’s percent of national annual consumptive allocation (m3/yr): 19%
    Canterbury’s percent of national annual consumptive allocation, discounting Southland’s Manapouri hydro scheme (m3/yr): 46%
    Canterbury’s percent of national irrigation allocation (m3/yr): 62%
    Canterbury’s percent of national consented irrigated area (ha): 63%

And from the Canterbury Water Management Strategy:

    Canterbury’s percent of national water allocation (m3/yr): 58%
    Canterbury’s percent of national irrigated area (ha): 70%