HOW EXTREME WAS THE DROUGHT

In 1993/94 a severe drought on the North Island of New Zealand caused water shortage in the Auckland metropolis. How extreme was the drought ? This paper presents comparisons of frequencies of the 1993/94 drough t in four North Island regions using different indicators of drought a nd including both streamflow and rainfall data. With regard to streamf low deficit volume and duration the exceedance probabilities ranged fr om 1 to 25%; however, the 7-day annual minimum flows in 1993/94 were l ess extreme with non-exceedance probabilities from 10 to 34%. With reg ard to rainfall the drought in the Auckland region was most extreme (o n average 2% exceedance probability) when annual rainfall totals were analysed, compared to seasonal totals (on average 6% exceedance probab ility for half-annual totals and 13-38% for three-month totals). Thus, the conclusion was that the 1993/94 drought was extreme because of it s duration rather than its magnitude.