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Rainfall trends

We all know it’s been wet in the last few months…but how wet? To answer that, we need data over a long period. Long-time Kuaotunu resident Alastair Brickell and his wife Harriette have been recording daily rainfall records at their Kuaotunu property for over 41 years (15,000 days) and this can give us some information, although that is still only a relatively short record of recent events.

The results are shown here as a graph displaying the total rainfall each year with the average being 1677mm/year.

The Informer asked Alastair to enlarge on the findings from his rain gauge and recordings.

Kuaotunu Weather Records

By Alastair Brickell

There had been a rough trend of steady decrease in the amount of rainfall each year (forty years) and also in its variability over the last four decades until last year, which was the record breaker, with 2381mm in the rain gauge. This might even prove to be the start of another cycle of high rainfall as was experienced during the 1980’s since weather often follows 40-60 year cycles. That was a very wet period with several major events such as February 1985 which saw severe flooding in Thames, including in the hospital, and deaths in Te Aroha. July 1987 saw flooding over the Whitianga Esplanade only to be followed by the extreme year of 1988 with Cyclone Bola in March, with the subsequent deluge of our wettest month in 41 years occurring later that year in July with 598mm. That was even wetter than September 2019 (545mm) which saw the Kuaotunu SH25 bridge damaged and closed for weeks and the School of Mines Lane bridge demolished in what was actually a lower than average rainfall year.

The last four complete months (November 2022-February 2023) have been the wettest four consecutive months in the record with 1710mm, about 33% higher than the next wettest four consecutive months in Cyclone Bola year (1988). That’s even more than our yearly average! In fact, the first three months of this year have already produced more than occurred during the whole of 1982, our lowest year with only 1148mm. So no wonder we’re all feeling rather damp!

The bigger picture however, puts this all into a bit of perspective. The period around the 1870’s to 1930’s was much more wet and extreme with more serious rain events than we’ve experienced this summer occurring about every 10-15 years or so. Nobody living today remembers these events, so we’ve become very complacent and dangerously used to our relatively calm century. However, maybe it could be prudent for us all to consider long term planning for a possible return to the former extreme conditions. We should never forget that nature is fractal and works in natural cycles on every scale.

Footnote for The Informer’s readers:

Alastair and Harriette are happy to provide the raw data in digital format to anyone interested and Alastair is interested to compare this data with that recorded elsewhere by others in the district. Huge daily variations in rainfall can occur over very small distances.


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