By, J. Richard Wakefield
June 9, 2016.
The Township of Middlesex Centre, just west of London, Ontario, has introduced a new tax. It’s $15 per month for storm sewer run off. Hmm, isnt that infrastructure component supposed to be paid for by property taxes?
Their rationale is explained here. Every property in the township will begin to get this new tax, including those who are not on the water/sewer system. Again, isnt this supposed to be covered by our property taxes?
In that link it lays out who is going to pay what:
Customers will be charged $14.88 per month. Industrial, commercial and institutional customers with properties larger than 0.4 hectares(1.0 acre) will pay an additional $42.18 per month/per 0.4 hectore(1.0 acre).
There’s going to be a lot of pissed off people once they see this new tax hit their mail.
The reason for the new tax was sent out in a letter. The interesting part of that letter says:
New development and unpredictable weather has resulted in more stormwater than ever before.
How do they know that? What data are they using to come to that conclusion? What does “ever before” mean?
This site is mostly about temperature data, which all comes from Environment Canada from Canadian stations. So I already had that data on hand in an Access Database for a number of locations around the country. So I looked at the precipitation data for as many stations around London I could get that had a long dataset (EC doesn’t have data on line for London per se after 1935).
The closest station that has at least 100 years of complete data is Woodstock. (Note that subsequent stations chosen here after are those with complete datasets with no gaps or missing data, which is common for other locations, such as Toronto.)
Here is the total precipitation per year for Woodstock:
The black line is the ten-year moving average. Total precipitation since 1989 has been dropping. Welland also has seen a drop in total precipitation since the mid 1980’s.
This is not what is seen at other locations, for example Belleville:
Clearly there is no over all trend since the 1940s.
Yes, there is the odd high precipitation rates, which appear to have a 30 and so year frequency. But they are clearly above the upper standard deviation (top 15%) of the time. There is no evidence at all there is any change in that rate.
Yet the township is relying on assumptions that not only there will be an increase (note the words WILL BE as opposed to MIGHT BE) in the near future (see Part Two), but that there already has already been an increase in the frequency and the intensity of rain now than “ever before”.
As a side note, what does “ever before” mean? To me it means 4.5 billion years, the age of the earth. It could also mean 14 billion years for the age of the Universe. But clearly that is not what the township means. “Ever before” can only mean one thing: since records began. It would be much clearer if they had said that instead of “ever before”.
So how many years have records been kept? For Environment Canada that has been since around 1870, but only for a very very few number of stations. At one time, in the mid 1980s, EC had some 1300 stations Canada wide. That grew from less than a dozen stations prior to 1900. The number of stations has dropped considerably since then. Rough count is less than 500 today. That means EC extrapolates measurement data for the closed locations from data at existing stations.
Is there an increase in the daily downpour? If there was, to keep the total trend flat, there must be more drought days to compensate for the higher daily rainfall. Let’s look at the highest rain fail in a single day per year and see if there is a trend to more today:
There are three spikes of heavy one day downpour since 1980. Is this a trend for more in the future? Not when you look at the probability of how much rain falls in a single day. This graph tells a very interesting story.
The data from Environment Canada for the Woodstock location shows that when it does rain, the least amount of it we will get (1mm or less) happens 17% of the time. The rest of the amount we get drops off in a decay curve such that really heavy downpours occupy a very very small percent of probability of happening. For example, out of 11,231 days it has rained since 1871 there has been just one single day that dropped 125mm, and that was in 2010. The percent of probability of rain above 50mm in a single day is just 0.5%.
This means that very heavy rain is a very very rare event in the Woodstock area. This means that the likelihood of another day of near that amount of rain won’t happen for another 120 years at least! Of 50mm or more rain in one day, over the next 120 years (12,000+ days) should happen in just 60 of those days.
To conclude, there is no evidence that rain, total rain per year, or daily rain fall, is increasing anywhere in the Province of Ontario. If anything, with Welland and Woodstock, the trend is for less rain over the past 40 years.
What will the future rainfall be then? That is examined in Part Two.