Are rainwater tanks useful in Townsville?

Townsville’s ongoing drought has encouraged many of us, especially the keen gardeners, to think seriously about bores, grey water systems and rainwater tanks. This post attempts to arrive at a credible answer to the first question we must ask about tanks: are they even useful?

We have been hearing from two schools of thought on the question for as long as we have been in Townsville, more than 25 years: “Yes, of course!” and “No! The dry season is so long and so dry that no tank will last through it.” One group must be wrong, and the only way to find out is to crunch a few numbers. Continue reading “Are rainwater tanks useful in Townsville?”

Dry season, 2016

Just over a year ago I wrote:

The Dry arrived this week, with an almost-audible thump: humidity halved between Tuesday and Wednesday. After hanging around the high fifties (RH at 9 am, figures from this chart) for the first three weeks of [April], it was 22, 32 and 52% on Wednesday – Friday this week …

The same change of weather hit us yesterday and last night, three weeks later than last year. For me, at least, it’s the confirmation that our Wet has truly ended – not that we really needed one, since the only rain we had in April was about 20mm in the middle of the month, as per the BoM data, and we’ve only had a bit of drizzle this month. The garden has been telling us, too: the frangipanis are shedding their leaves and the Cape York lilies have died back, amongst other indications.

In the six months November-April we’ve had rainfall totals of 26, 111, 76, 95, 558 (March was a good month!) and 21 mm respectively, for a not-so-grand total of 887 mm. March alone put us well above our record-low 2015 rainfall total but we would still have liked more. Ross Dam is at 26%, an alarmingly low level for the start of the Dry. I may say more about that in a follow-up post but, meanwhile, the TCC chart here will show you what’s going on.

Extreme weather – Townsville

Weather is not climate (climate is what you expect, while weather is what you get) but bizarre weather can be a sign of a changing climate. In fact, Hansen showed a while ago (see my discussion here) that if the climate is warming, which no reasonable person seriously doubts any more, then we will get more extreme weather events – and you can read ‘more extreme weather events’ two ways, because they will individually be more extreme and there will also be more of them.

This is being borne out very close to home for me. I noted recently that Townsville had had the coldest May day in 22 years. Early this week we had the wettest July day in more than 70 years. The Townsville Bulletin reported that …

More than six times the total average July rainfall was dumped across Townsville in just 24 hours with an average of 89mm clocked from 9am Monday [July 9] to 9am [Tuesday]. More than 40 regions from Bowen to Cairns were drenched with over 100mm of rain …

Daily rainfall records were set along the northern coastline … With 145mm, Innisfail recorded their wettest July day in 125 years while Lucinda totalled 141mm, making it their heaviest rain in 118 years. Burdekin residents also saw record-breaking falls with Home Hill’s wettest July day in 87 years and Ayr’s heaviest falls in 59 years.

Just a little less locally, cane farmers fear another wet winter will reduce their yield and delay their harvest. But wet winters are part of the longer-term climate change on which our extreme weather is superimposed.

The BoM publishes interactive Climate Trend Maps and playing with them is simultaneously kind of fun, instructive and perturbing. Here are some maps to to think about, if you haven’t time to play:

  • Queensland annual rainfall, diminishing rapidly along the coast except up around Cooktown – but the *winter* rainfall is actually increasing, although not as much as the annual total is decreasing. Spring rain is not changing much, so the decreased annual rainfall is actually a large decrease in Summer-Autumn (our Wet), partially compensated by a small increase in Spring (on the North coast) and Winter.
  • At the same time our maximum temperatures are trending higher in all seasons (click here and toggle through the seasons).
  • So are sea surface temperatures, which is one reason coral reef scientists despair about the future of the Great Barrier Reef – see the press release and Statement from the 12th International Coral Reef Symposium in Cairns, 9-13 July 2012.