Current drought may go on

Ian Blair is an ex MAF and Wrightson consultant who now specialises in forecasting long-term pasture growth. A key difference between his and other forecasts is the emphasis he puts on soil moisture. He also takes account of existing pasture cover.

Earlier this month he talked to Federated Farmers South Canterbury annual meeting and had a chilling message for delegates from the drought struck region: analysis of soil moisture trends over the decades suggest the dry will impact next season’s production too.

“I warned them that the spring will be bad if we continue with this current weather cycle, the summer will be similar and the autumn will be bad too,” he told Rural News after the event.

That warning holds true for most of the currently dry areas of New Zealand, he added.

While rain in April renewed growth in many areas it’s only skin deep and soil moisture reserves are still well below field capacity with time for winter recharge running out.

“The trend is for below normal soil moisture and if you don’t get a winter top-up in the next 30 days you’re not likely to get enough water to replenish those soil reserves.

“And if you don’t get the rain, you’re not going to get the stream flows and there’s a fair chance you’ll be into irrigation restrictions again pretty quickly.”

For alpine-fed irrigation schemes, such as Morven-Glenavy in Canterbury’s far south, Rangitata South, the various schemes off the Rangitata Diversion Race, or Central Plains Water, that shouldn’t be a problem but for the likes of the Opuha, which ran dry in February this year for the first time in its 16-year history, Blair’s message is bleak.

South Canterbury Feds’ newly elected president, Fairlie sheep and beef farmer Mark Adams, recognises the risk. “A lot of people are relying on Lake Opuha to be full come spring but we’ve seen it in the past when it’s not filled up over winter.”

Previously spring rain’s saved the day but if El Nino digs in that’s less likely. Adams says he found Blair’s presentation compelling and is keen to get him back to the region to talk to a wider audience. “He’d analysed a lot of data to try to predict what would unfold.”

He sees Blair’s presentation as a “heads up” to be careful with spring planning and have contingencies in case of another big dry.

El Nino or not?

Australia's Bureau of Meteorology last week announced  El Niño thresholds in the tropical Pacific were reached for the first time since March 2010 but New Zealand’s NIWA says it’s not El Nino yet.

“There’s an 80% likelihood that within the next three months we’ll be in El Nino,” principal scientist Chris Brandolino told Rural News. “We’d like to see some of the other indicators hold for a bit longer before we declare a full El Nino.”

Metservice’s Georgina Griffiths said El Nino ocean and atmosphere conditions are in place but it is too early to tell whether it will become a strong El Nino.

“The most obvious impact El Nino brings to New Zealand is an increase in southerly to southwest winds over winter and spring.”
That means cooler winters in all areas but rain response is more complicated, depending on season and region.

“The chances of a relatively dry winter increase during El Nino for the western North Island (Northland, Auckland, Waikato, Waitomo, Taumarunui and Taranaki), as well as for Nelson and Marlborough. But… we may not notice this effect very much from day to day, since winter usually yields more than enough rain.”

However, come spring El Nino may really “flex its muscles” with a stormy, often extremely cold, windy spring. In the west and south of the South Island it’s usually wetter than normal too, but the western North Island, Nelson and Marlborough, tend to be drier.

Canterbury and the eastern North Island often turn drier than normal in summer.