A brief summary of climate and hydrological conditions in the region.

This service is regularly 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. Outside of dry periods, less frequent updates synchronise with our latest seasonal outlooks.

Updated 23 September 2024

Next update due when there is a significant change of conditions or a new seasonal outlook.

Background

The El Niño/Southern Oscillation (ENSO) event responsible for the drought last summer gave place to a transition state with mixed signals in winter. Now, this climate driver is swinging back to a new La Niña phase. Winter brought some beneficial hydrological recovery to some dry areas of the Wairarapa, but mostly with an irregular spatial distribution with some areas partially missing out.  The weather patterns throughout the season were very irregular with alternating flows and unusual winter thunderstorms, resembling an easter flow La Niña pattern at times. 

Colour coded map showing amount of rainfall in the region over winter 2024, with higher than average rainfall in parts of Wairarapa
Winter rainfall anomalies show parts of the Wairarapa with above average rainfall. While this moderate recharge has been beneficial for drought recovery, there is no prediction of a particularly wet spring. Hence, a risk of returning dryness cannot be discarded. Credits: GWRC
View full image

Current situation

After a relatively wet winter, soil moisture levels are now back to around average for most of the region. However, as the solar radiation rapidly increases past the equinox, the Wairarapa in particular can quicky dry up under north-westerly flows. Rivers around the region are topped up after fierce late winter/early spring north-westerlies have been bringing plenty of rain, especially to the ranges. Likewise, groundwater levels are generally at their normal spring high, although reductions can occur quickly once irrigation begins, especially if combined with an early summer dry spell.

Meteorological outlook

International climate models are predicting that a reversal back to La Niña will likely take place throughout spring. In principle, we are expecting a relatively mild event. However, as the climate change signal naturally tends to amplify the La Niña circulation around New Zealand, it is likely that we will have significant warm season impacts. The expectation is to transition from a more westerly, drier regime for the Wairarapa spring initially, moving towards a more humid north-easterly flow later in the year. There is low confidence for the total seasonal accumulations at this stage, with likely irregular spatial distribution.

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 were to 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 more unreliable climate patterns with both extreme dry and extreme wet periods. We note that the warming of the land also means that evapotranspiration will greatly increase, so the soil will likely need more ongoing rain to maintain ideal moisture levels, compared to what it has needed in the past.

View the latest national drought index state

View the national drought forecasting dashboard

View the latest seasonal report:

Browse the data

Anomaly Maps

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

30 Day Rainfall Anomaly

90 Day Rainfall Anomaly

1 Day Soil Moisture Anomaly

30 Day Soil Moisture Anomaly

 

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
Updated September 20, 2024 at 11:05 AM

Get in touch

Phone:
0800496734
Email:
info@gw.govt.nz