Outlook for water resources January-March 2004

Outlook for water resources January–March 2004

Average summer air temperatures are expected in many areas, with average or above average temperatures likely in eastern areas of both islands. More anticyclones than usual are expected across the North Island, and more westerlies across the South Island. Settled weather, especially if warm, is likely to create the sort of stable, strongly stratified and warm conditions that favour algal bloom development in North Island lakes, similar to the blooms of autumn 2002. If the predicted weather pattern develops, the risk of cyanobacterial blooms developing is above average for this summer.

Normal or below normal rainfall is likely in most areas. Groundwater levels are likely to be normal to below normal. Soil moisture levels and river flows are predicted to be below normal for the east of the country and the Nelson- Marlborough region, and normal or below normal for the north of the North Island. Normal soil moisture levels and river flows are predicted elsewhere. As a result, summer inflows into the major hydroelectricity reservoirs are likely to be near normal. However, the dry conditions in the east of New Zealand that developed in December are likely to continue. Canterbury and Otago currently have an increased risk of below normal groundwater levels over summer. With low flows and warmer temperatures in the lowland streams of eastern New Zealand there is an increased risk of nuisance periphyton growth.