B. Vasiljevic, E. McBean, and R. Rudra University of Guelph Guelph, Ontario, Canada Designs for sewers, culverts, and stormwater management ponds rely upon the intensity- duration-frequency (IDF) curves Stormwater facilities intended to last for decades Implications also for water supplies Wells become submerged Implication of rainfall intensity is clear and profound Duration (min) I(mm/hr) Partial Duration Series Annual Maxima Duration mm I(mm/hr) 2 YR YR YR Interpretation of Trends in Precipitation Increases in precipitation intensity are occurring throughout Ontario The changes of rainfall intensities in southern Ontario are more profound, but substantial regardless For example, there is evidence of the five-year storm increasing at 2% per year in Waterloo so in thirty years, this translates to a sixty percent increase in precipitation intensity in thirty years in Waterloo if these trends continue Design features for water infrastructure must be modified, to reflect the changes in intensity that are being observed. StreetFromTo Pipe Size ( mm) 23 (South) MH1MH2300 MH2CBMH3300 CBMH3MH4375 MH4CBMH CBMH5 #1 750 #1 WETLAND (North) FUTMH11300 MH11CBMH12375 CBMH12DCBMH DCBMH13MH MH8 #2 600 #2FOREBAY600675 Conclusions There is evidence that rainfall intensities are changing, since the five year storm of four decades ago is now the two year recurrence interval storm, and hence translates to implications for design of urban infrastructure. Implications to water supply systems are highly relevant Questions?