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Drought check

https://www.gw.govt.nz/drought-check

Drought check

Updated 13 September 2021 2:54pm

This webpage provides a brief summary of climate and hydrological conditions in the region. This service is only updated during periods in which closer monitoring is required (regardless of time of the year), in recognition that there is potential for dry spells, or irregular hydrological recharging. It does not define an official council position on drought or drought declaration.

Situation Statement

Updated 13 September 2021
Next update due when there is a significant change of conditions, as the situation evolves 

Background

After a predominantly dry summer and autumn in the Wairarapa, a significant winter recharge (400 plus mm around Long bush) provided some welcome relief to the dry conditions.

Winter 2021 was the wettest since 2008 for both Wellington and the Wairarapa, with several extreme rainfall events associated with both westerly and easterly flows, and significantly mild temperatures for the season. The number of rain days was also quite high in the Wairarapa.

Current situation

There is significant early growth resulting from the mild winter temperatures coupled with wet conditions. Soil moisture is now either normal or above normal for most of the region, even though September is progressively drying compared to August.

Most climate drivers are now oscillating around neutral conditions, with a slight La Niña signature evident in the Equatorial Pacific Ocean. The Sea Surface Temperature (SST) around New Zealand remains significantly above average for the time of the year, especially to the east and north of the country.

Meteorological outlook

The ENSO (El Niño/Southern Oscillation) phenomenon in the Equatorial Pacific Ocean is expected to remain borderline between neutral and La Niña conditions over the next few months.

The SST around New Zealand is predicted to remain largely above average throughout spring. Most dynamical climate models of seasonal prediction are indicating the possibility of a blocking anticyclone establishing east of New Zealand during spring, with significantly warmer than average seasonal temperatures likely.

A vigorous westerly pattern with high variability is expected for spring, with wetter than average conditions in the west, and drier than average in the east on average. Longer dry spells are likely into spring, noting that there is also a high likelihood of extreme rainfall events in between dry periods.

The overall prognostic scenario continues to demonstrate a lack of balance in the weather systems, hitting the country from a very unstable flow over the Southern Ocean.

Climate change

The ‘normal’ longer-term water balance is becoming increasingly hard to maintain quite possibly due to climate change influences, and increased high frequency climate variability, with more unreliable weather patterns.

Droughts are expected to become more severe and frequent in the Wellington region, particularly in the Wairarapa. Even if international climate policy efforts successfully contain global warming under 1.5-2 degrees (the Paris Agreement’s ambition), it is important that we enhance our water resilience and be prepared for a “new normal” climate pattern, significantly drier than in the past.

We note that the warming temperatures also mean that evapotranspiration will greatly increase. There is some evidence that our soils are getting drier, and groundwater storage may be decreasing, in the long-term.

See the latest national drought index state.

Browse the data

Anomaly Maps

How different has recent rainfall/soil moisture been compared with the same time in previous years?

Click on the links below to see the relevant anomaly map

Site-specific graphs

Cumulative rainfall/soil moisture totals for indicator sites compared with historical averages and other recent years

Area Rainfall Soil Moisture
Kapiti Coast (lowland) Otaki at Depot  
Kapiti Coast (high altitude) Penn Creek at McIntosh  
Porirua Horokiri Stream at Battle Hill
 
Wellington City Kaiwharawhara Stream at Karori Reservoir  
Hutt Valley (upper catchment) Hutt River at Kaitoke Headworks  
Upper Hutt Upper Hutt at Savage Park Upper Hutt at Savage Park AQ
Wainuiomata Wanuiomata River at Wainui Reservoir  
Wairarapa (high altitude) Waingawa River at Angle Knob  
Wairarapa Valley (north) Kopuaranga River at Mauriceville  
Wairarapa Valley (Masterton) Ruamahanga River at Wairarapa College Wairarapa College AQ
Wairarapa Valley (south) Tauherenikau River at Racecourse Tauherenikau River at Racecourse
Wairarapa (north-eastern hills) Whareama River at Tanawa Hut Whareama River at Tanawa Hut
Wairarapa (south-eastern hills) Waikoukou at Longbush Waikoukou at Longbush