Guelph drinking water: Water System of the Month (August 2026)

Why this system matters

Guelph operates one of Canada's most distinctive municipal drinking-water systems. Guelph is Canada’s largest city that relies almost exclusively on groundwater; seasonal pumping from the Eramosa River into infiltration ponds recharges the Arkell Spring Grounds rather than serving as a direct drinking-water intake.

On the OpenStats water atlas, Guelph carries a direct-tier hardness reading and an OpenStats letter grade of B (Good). Among 29 direct-tier cities on the atlas, Guelph ranks #1 for hardness at 460 mg/L (very hard). The Ontario average across tracked municipalities is about 182 mg/L.

Supply and treatment

Source type on the atlas: groundwater. Named source waters include Deep limestone/dolomite bedrock aquifers; Arkell Spring Grounds / Glen Collector (shallow groundwater); Eramosa River (seasonal infiltration recharge only).

Treatment assets named in OpenStats supply research: F.M. Woods Water Treatment Plant (Primary plant receiving Arkell wells and Glen Collector water via the Arkell Aqueduct; supplies a large share of Zone 1 demand.); Distributed well treatment and point-of-entry facilities (About 19–22 operational municipal wells citywide plus the Glen Collector; treatment typically includes chlorination and, at selected sites, UV, iron sequestration, or manganese removal. Some sources are classified GUDI-WEF.).

City-owned system with a 6.5 km large-diameter aqueduct, five underground reservoirs, three water towers, and roughly 560 km of watermains across three pressure zones.

OpenStats score and ranking context

OpenStats grades drinking water A through D using Health Canada guideline limits on pH, lead, fluoride, chlorine, and turbidity, with a B grade when health parameters comply but hardness exceeds 180 mg/L or turbidity sits above the typical 1 NTU target. Guelph scores B on the current row: Good.

Hardness 460 mg/L as CaCO₃ is from a published municipal source (2015). That figure is 278 mg/L above the Ontario average (182 mg/L across 51 tracked municipalities).

Compare neighbours on the water atlas hardness sort, the hub hardness guide, and the Guelph hometown page for City Score context.

What is measured vs estimated

OpenStats labels every parameter row. Hardness on direct-tier cities comes from a cited municipal or regional report. pH is only treated as measured when the same verified source published it. Lead, fluoride, chlorine, and turbidity on this page remain atlas seed values unless the data_source field names a municipal lab report.

For Guelph, hardness is verified from Region of Waterloo / City of Guelph water softener study (2015). pH 7.2 is an atlas seed value, not quoted from the hardness study. Other health parameters in the table below are seed rows and should not be read as a current compliance certificate.

Always open the City of Guelph annual water services reports linked in the supply profile for operational compliance data.

For reporters

Share URL for this edition: https://openstats.ca/news/water-system-of-month/guelph-on-2026-08/

Water atlas city page: https://water.openstats.ca/water/guelph-on/

Hometown rankings: https://openstats.ca/cities/guelph-on/

OpenStats data desk · [email protected] · happy to walk through the parameter table on a call.