2019 CSCE Annual Conference - Laval (Greater Montreal)

2019 CSCE Annual Conference - Laval (Greater Montreal) Conference


Title
A Hydrologic Model to Estimate Delta Water Availability in Alberta

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Author(s)
Dr. Zahidul Islam, Alberta Environment and Parks (Presenter)
Mr. Michael Seneka, Alberta Environment and Parks
Ms. Joey Hurley, Government of Alberta, Department of Environment and Parks
Ms. Shoma Tanzeeba, Government of Alberta, Department of Environment and Parks
Abstract

‘Delta Water’ is defined as the excess stormwater runoff generated from the increase in impervious surfaces associated with urban development.  When allocated sustainably, stormwater use can offset potable water use and augment traditional water supplies.  Albertans recognize the value in previously undervalued resources such as wastewater and stormwater. As a result, the Government of Alberta is exploring ways enable access to these alternative sources in a way that is protective of public and environmental health.  For stormwater allocation purposes, this includes understanding the volumes of runoff generated as a result of urban development. A consistent and scientifically defensible approach is required to support decision making under Alberta’s regulatory framework for water management. In support of this policy initiative, we developed a hydrologic model to estimate delta water availability in Alberta. The spatial and temporal scale of the model has been chosen in such a way that the model can be applicable province-wide in a township scale (100 km2) as well as in a project scale (1-10 km2), and can provide delta water assessments based on long term historical climate data. Moreover, the model structure has been designed in such a way that balances the model implementation complexity with the scientific integrity. We have used the daily gridded climate dataset (1955-2016) from Alberta Climate Information Service, wall- to-wall landcover dataset (2010) from Alberta Biodiversity Monitoring Institute, and the soil texture data from Harmonized World Soil Database to prepare the model baseline scenario (pre-development). The hydrologic model includes Degree-Day snowmelt model, Morton’s evapotranspiration model, and SCS Runoff Curve Number model to simulate the pre-development surface runoff in a daily scale. The simulated daily runoff is then converted into long term mean annual runoff and calibrated against historical mean annual runoff at a township scale. The model has the ability to input the post-development landcover (for example, converting agricultural land or grassland into urban developments), re-generate the long term mean annual runoff due to landcover changes, and simulate the long term mean delta water in a township or project scale. We have tested the model at township scales province-wide, and also applied it for project case studies. Once the policy approved, applicants and regulators alike will have access to the final model, creating a transparent regulatory decision making process.