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Drought check

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

Drought check

Updated 14 February 2020 2:35pm

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 we are in a dry spell of weather. It does not define an official council position on drought or drought declaration.

Current Situation

Updated 14 Feb 2020
Next update due in about two weeks or earlier, as the situation evolves

A dry spell remains over most of the country and has potential to worsen. Most of the North Island and the north-eastern part of the South Island have been very dry. The national drought monitor index shows that Northland and Auckland are classed as having a severe meteorological drought, and MPI has declared this an adverse event for Northland.

For the Wellington Region, even though the situation is not nearly as severe as for Northland, the entire region is now classed as dry. The Wairarapa is classed as between very dry and extremely dry, according to the national drought index. Currently, there is no forecast of significant rain for the region until the end of the month, and so the dryness has potential to escalate.

Meteorological Background:

The main climate influencers (i.e. “climate drivers”) such as ENSO (El Niño – Southern Oscillation) and Indian Ocean Dipole (IOD) are currently neutral, and therefore having little bearing on the evolution of the summer pattern.

The Southern Annular Mode (SAM) has been systematically on the negative side over the last few months. This climate mode helps explain the unusually strong south-westerly flow that has persisted from late spring into summer. Strong winds promote evaporation, and are a contributing factor to drying the exposed soil.

The westerly pattern is also preventing the formation of summer thunderstorms and moisture input from the subtropics, which would normally manifest during north-easterly flow this time of the year, when the sea surface temperature is sufficiently warm.

Air temperatures for the first half of the month are up to 2oC above average for most of the region, which is further contributing to increase the dryness.

Even though the region had near normal rainfall for spring, and above average rain in December in the west, the hydrological year accumulation (i.e. Jun to May) to date, and the overall dryness, are comparable to previous dry years.

River flows:

River and stream flows have been receding through January and early February with only small and short-lived interruptions from one or two fresh flows from rainfall. In the west (Kapiti Coast and Hutt Valley) rivers are reaching mean annual low flow conditions but are already well below this in the Wairarapa.

Preliminary indications are that flows in the Wairarapa have already fallen to levels that are only expected once every five years (on average) and moving towards 10 years in some cases. Restrictions for water users are now in force across all catchments in this part of the region. With no significant rainfall in the near term forecast some fairly extreme low flows can be expected.

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