Winter Rainfall Update
With only a few days to go and not much rain forecast, August will fall short of normal rainfall totals, Marlborough District Council’s Environmental Scientist - Hydrology, Val Wadsworth told today’s Environment Committee.
“Only two months in 2020 - May and June - recorded above average rainfall across the district.”
“Annual totals for the year to date are generally about 60% to 75% for most of Marlborough, with a few sites in the Sounds and Te Hoiere/Pelorus areas up to 90% of the year-to-date (YTD) total.”
Val said the July and August totals are about 45% to 65% of normal in Eastern and Southern Marlborough, and 65% to 75% of normal in Northern and Western Marlborough (see table attached).
“The rainfall over the last few days will be very beneficial for early spring pasture growth. Despite this more rainfall is needed in spring to further replenish soil moisture and river base flows for the coming summer.”
“Evapotranspiration exceeds average rainfall in East Coast areas from September onwards. This means above average rainfall will be required to further reduce soil moisture deficits.”
“Pastoral farmers will be the first to feel the pinch if moisture levels don’t produce sufficient spring growth to carry into summer. Irrigators will also be affected if river flows fall to below cut-off levels early or for prolonged periods,” he said.
“Snow cover in the Marlborough high country is a significant contributor to summer flows; this week’s snow will be beneficial. Good Wairau River flows are a key part of the recharge mechanism for the steadily declining Wairau aquifer.”
“Of concern is the inland Wairau aquifer and Riverlands aquifers. However the Southern Valleys aquifers are relatively full.”
“Most of our river flows are also below average for this time of year - the Awatere is at 75% of normal and the Wairau at 60% to 70%.”
“NIWA is predicting the next two months rainfall to be about normal. There is still time for some good spring rainfall and nature does sometimes tend to balance itself out, but it is not a given.”
“Marlborough is one of the driest regions in New Zealand - we are only ever six to eight dry weeks away from water shortage issues.”