A feasibility analysis of site-level stormwater reuse for commercial developments in Canada

Municipalities are experiencing a growing water management challenge as a result of population growth in water-dependent communities. The rising cost of potable water, in addition to limits placed on stormwater discharges, provide opportunities for the wide-scale implementation of stormwater reuse. This thesis presents a feasibility analysis of a novel site-level stormwater reuse concept for commercial developments in Canada. Historical rainfall data and SWMM 5.0 were used to evaluate the hydrologic potential of the reuse system to replace potable water for end-use demands of toilet flushing and garden irrigation on single- and multi-tenant commercial sites. Performance criteria were used to evaluate: (i) the volume and percent potable water replaced with reclaimed stormwater, (ii) the volume and frequency of potable water 'top-ups' to the reclaimed stormwater storage facility, and (iii) the volume and frequency of overflows in the reclaimed stormwater storage facility. A discounted payback method was used to determine the length of time (in years) required for annual water savings to equal the initial capital investment of the stormwater reuse system. The analysis was performed from the perspective of the private landowner in six Canadian locations, including Vancouver, Edmonton, Regina, Saskatoon, Toronto, and Quebec City. The methodology and results presented is intended to provide insight to landowners and municipal bodies on the potential of site-level stormwater reuse to aid large-scale adaption and implementation. The results suggest that regions with high average annual rainfall depths produce high potable water replacement rates ranging from 64% to 99% while cities that experience seasonal arid conditions and lower average annual rainfall depths achieve llower potable water replacement rates in the range of 30% and 83%. The test locations of Vancouver and Quebec achieved longer payback periods of 10 years to 26 years due to the relative low cost of potable water. The Saskatoon and Regina locations produced shorter payback periods ranging from 3 to 6 years due to the higher potable water prices. Toronto was found to have relatively short payback periods ranging from 4 to 5 years on account of its high potable water replacement rates and high potable water prices.