Less Extreme Ontario Rainfall - Precipitation Intensities For Design of Buried Municipal Stormwater Systems by Yi Wang. A Thesis presented to The University of Guelph

Those with decreasing rainfall intensities
could be Singing in the Rain, with lower
stresses on their buried municipal
infrastructure systems.

Wang's Ph.D. thesis at the University of Guelph describes changes in frequent and extreme rainfall trends. The thesis is available here. Confidence limits on 2-year, 5-year, 10-year and 25-year rainfall intensities for durations of 5 minutes to 2 hours show no significant changes in most cases and decreasing rainfall intensities at many stations.

Results from page 51 show that there are more than twice as many decreases in rainfall as increases considering the 90% confidence limit, as shown below:



Table 3.2: Results of 90% Confidence Interval Comparison Test

ID     5min 10min 15min 30min 1h  2h
6034075 ---- ---- ---- ---- ---- ----   Kenora A
6037775 ---- ---- ---- ---- ---- ---   Sioux Lookout A
6057592 ---- ---- ---- ---- ---- ----   Sault Ste Marie A
6085700 ---- ---- ---- ---- ---- ----   North Bay A
6100971 ---- ---- ---- ---- ---- ----   Brockville PCC
6104175 ---- ---- ---- ---- ---- ----   Kingston Pumping Station
6105978 ---- ---- ---- ---- ---- ----   Ottawa CDA RCS
6116132 ---- ---- ---- ---- ---- ----   Owen Sound MOE
6131415 ---- ---- ---- --↓↓ --↓↓ ----   Chatham WPCP
6131983  /    /   ---- -↑↑↑ --- ----   Delhi CS
6136606 ---- ---- ---- ---- ---- ----   Port Colborne
6137362 -↓↓↓ ---- ---- ---- ---- ----   St Thomas WPCP
6139525 ↓↓↓↓  /   ↓↓↓↓ ↓↓-- --- ----   Windsor A
6142400 ---- ---- ---- ---- ---- ----   Fergus Shand Dam
6144478 ---- ---- ---- ---- ---- ----   London CS
6148105 ---- ---- ---- ---- ---- ----   Stratford MOE
6150689 ---- --- ↑↑-- ---- ↑↑-- ---   Belleville
6153301  /   ---- ---- ---- ---- ----   Hamilton RBG CS
6158355 -↓↓↓ -↓↓↓ ---- ---- ---- ----   Toronto City
6158733  /   ----  /    /    /    /     Toronto Intl A
6158875 ---- ---- ---- ---- ---- ----   Trenton A

·        The arrows and hyphens in cells represent the results of CI comparison of 2, 5, 10, and 25-year events (from left to right). An up-arrow indicates an increase of rainfall intensity occurred in the 2nd period of record, and a down-arrow  indicates a decrease of rainfall intensity. A hyphen means no significant change (α = 0.1) is shown or, in other words, the CIs are not significantly different. Cells with slashes represent records that are not stationary.

11 significant increases , 24 significant decreases
Southwestern to Central Ontario most significant decreases

Results from page 52 show that there are almost twice as many decreases as increases considering the 80% confidence limit, as shown below:

Table 3.3: Results of 80% Confidence Interval Comparison Test

ID    5min 10min 15min 30min 1h  2h
6034075 ---- ---- ---- ---- ---- ----   Kenora A
6037775 ---- ---- ---- ---- --- ↑↑--   Sioux Lookout A
6057592 --- ---- ---- ---- ---- ----   Sault Ste Marie A
6085700 ---- ---- ---- ---- ---- ----   North Bay A
6100971 ---- ---- ---- ---- ---- ----   Brockville PCC
6104175 ---- ---- ---- ---- ---- ----   Kingston Pumping Station
6105978 ---- ---- ---- --- --- ----   Ottawa CDA RCS
6116132 ---- ---- ---- ---- ---- ----   Owen Sound MOE
6131415 ---- ---- ---- -↓↓↓ --↓↓ ----   Chatham WPCP  
6131983  /   ---- --- -↑↑↑ -↑↑↑ ----   Delhi CS
6136606 ---- ---- ---- ---- ---- ----   Port Colborne 
6137362 -↓↓↓ --- ---- ---- ---- ----   St Thomas WPCP
6139525 ↓↓↓↓  /   ↓↓↓↓ ↓↓↓↓ --- ---   Windsor A
6142400 ---- ---- ---- ---- ---- ----   Fergus Shand Dam    
6144478 ---- ---- ---- --- ---- ----   London CS
6148105 ---- ---- ---- ---- ---- ----   Stratford MOE
6150689 ↑↑-- ↑↑-- ↑↑↑- --- ↑↑—  ↑↑↑↑   Belleville    
6153301  /    /   ---- --- -↓↓↓ ----   Hamilton RBG CS
6158355 ↓↓↓↓ -↓↓↓ -↓↓↓ ---- ---- ----   Toronto City
6158733  /   ----  /    /    /    /     Toronto Intl A
6158875 ---- ---- ---- ---- ---- ----   Trenton A

·        The arrows and hyphens in cells represent the results of CI comparison of 2, 5, 10, and 25-year events (from left to right). An up-arrow indicates an increase of rainfall intensity occurred in the 2nd period of record, and a down-arrow  indicates a decrease of rainfall intensity. A hyphen means no significant change (α = 0.1) is shown or, in other words, the CIs are not significantly different. Cells with slashes represent records that are not stationary.


24 significant increases , 41 significant decreases
Southwestern to Central Ontario most significant decreases

***

Ontario climate change extreme rainfallHere are Wang's tables in original graphic format:


Ontario climate change rainfall

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