San Francisco State University
IN-16: Campus Water Balance

The campus water balance was calculated based on historical data as part of the Campus Master Plan. Existing Water Demands: The existing campus water demand is approximately 110 million gallons per year (MGY). Interior building demands are estimated to account for 83% (91 MGY) of the total demand; the remaining 17% (19 MGY) is attributed to irrigation. Supply Analysis: Campus water resources are proposed to be managed via sustainable, closed-loop systems that provide water for human and environmental needs in the Campus Master Plan. Alternative water supplies available on the SF State campus include: • Campus Wastewater: Wastewater generation is assumed to be 90% of the campus’s total interior water demand. Blackwater (wastewater from toilets, urinals, kitchen sinks and dishwashers) and greywater (wastewater including all sources except blackwater) are considered together. • Rainwater and stormwater: Rainwater is defined as precipitation collected from roofs and above-grade surfaces. Stormwater refers to runoff from the ground-plane (site hardscape and landscape areas). A rainfall-runoff model using historic rainfall data from NOAA is used to estimate runoff volumes and inter-annual variation that would occur across typical, dry and wet years. • Sewer mining: City wastewater flowing through City combined sewer mains running through campus is an additional resource that could be leveraged to augment campus wastewater resources. Seasonal and inter-annual variability Irrigation demand and rainwater and stormwater supplies are highly dependent on seasonal and inter-annual variations in temperature and rainfall. The integrated water model includes a range of projected irrigation demands for a ‘wet’ rainfall year (75th percentile, 25.6 inches), average rainfall year (50th, percentile, 17.8) and dry rainfall year (25th percentile, 14.4 inches) based on 68 years of historic rainfall data.

Current supply, including 14 million gallons of rainwater, 22 million gallons of stormwater, and 167 gallons of wastewater, is greater than the campus' current demand of 110 million gallons per year. The Campus Master Plan predicts that the future campus will require 210 million gallons per year due to a higher density of residential units. This will still be lower than the natural water supply. The campus plans to use wastewater and rainwater to reduce potable water demand.

Analysis was done by Sherwood Engineers as part of the SF State Campus Master Plan update, 2018.