The precipitation distribution in the lake pukaki catchment

A 1971-2000 average annual precipitation distribution has been prepared for the Lake Pukaki catchment using a combination of new and historical precipitation observations. The distribution was prepared using repeatable objective interpolation and is able to be updated as new precipitation observations are made. With inclusion of undercatch assessments, the distribution indicates over 15 m of precipitation falls in the north west region of the catchment. The new distribution leads to a catchment-wide 1971-2000 mean annual precipitation of 3400 mm yr which is within the error range of the water-balance derived precipitation estimate of 3600 +/- 500 mm yr. A strong horizontal gradient of precipitation exists over the catchment, similar to, but not as steep, as a previous 1951-1980 distribution estimate. The new observations with which this distribution was constrained in the upper catchment gave mean annual precipitation estimates in excess of any previous measurements made in an east coast New Zealand catchment, and are equivalent to the highest precipitation observations made anywhere in New Zealand.