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Drought check

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

Drought check

Updated 11 November 2021 3:58pm

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 11 November 2021
Next update due when there is a significant change of conditions, as the situation evolves 

Background

 After a significant winter recharge (400 plus mm around Long bush), the Wairarapa is still green but slowly returning to drier conditions, within the expected range for this time of the year. The New Zealand drought index from NIWA currently shows combined meteorological-hydrological conditions within the normal range for the Wellington region. As the warm season progresses, the tendency is for the dry phase of the index to start showing up, animated by clear skies and very strong solar radiation input this time of the year.  

Current situation

There has been significant early growth resulting from the mild winter temperatures, coupled with wet conditions. Soil moisture is now returning to below average, but still within the normal range for this time of the year. La Niña has re-developed, with significantly warmer than average Sea Surface Temperatures (SST) around New Zealand, and a mostly positive Southern Annular Mode (SAM). These conditions imply more traditional La Nina impacts, compared to the erratic behaviour observed this time last year.

Meteorological outlook

Most dynamical climate models are indicating a vigorous blocking anticyclone establishing east of New Zealand going into summer, with significantly warmer than average seasonal temperatures likely. Probabilistic conditions are set for extended drier periods until the end of the year, but not discarding the chance of an easterly rainfall event affecting the Wairarapa. As the season evolves, more humid weather and thunderstorms will be expected to affect the Wairarapa and other inland areas.

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