UBC Undergraduate Research

AMS sustainability project : stormwater management in the UBC Botanical Garden : phase II Shen, Lingfeng; Wong, Chung


This report discusses the practice of stormwater monitoring in the UBC Botanical Garden since August 2012, in response to the suggestions provided by the Phase I of the stormwater management project finished in May, 2012. The scope of the Phase II project is to obtain the on-site flow rates of the continuously flowing West Creek and Rock Creek, and to design a retention solution for stormwater reuse in the irrigation. A flow rate tracking system was established by setting up weirs in West Creek and Rock Creek. A set of pressure sensitive HOBO dataloggers were placed at the weirs, and the related parameters (absolute barometric pressure, atmospheric pressure, temperature, etc) were regularly collected by site visits. The data collection started from August 2012 represented the characteristics of the Botanical Garden area in both dry and rainy season. Upon the hydrograph results, the baseflow results of both creeks were studied and compared with the actual monthly accumulative irrigation demand. A supply-demand model was established, and several scenarios have been considered in terms of percentage of capture and capture locations. The baseflow at Weir #1 in West Creek is 0.8L/s. The total capture of the accumulated flow can satisfy the irrigation demand with additional potable water from July to October. On the other hand, the baseflow at Weir #2 in the merge of West Creek and Rock Creek is 2.4L/s. With a capture as low as 43 percent, it meets a total substitution of potable water irrigation for the whole year. The comparison concludes that the relatively ideal solution is to install retention device along the Old Marine Drive close to Weir #2 with a length of 220m and a volume of 150m3. This retention storage provides a safety factor of 1.21 and is recommended to be constructed by modular matrix tanks. Limitations in this project include data consistency and data availability. Incidents such as the weir foundation failure due to heavy rainfall occurred in October created discontinuity in data. Data correlation and interpolation were applied to achieve consistency, but inaccuracy can be introduced. The sediments carried from upstream also offset the actual water depth, leading to inaccurate data. The irrigation demand data were only available for less than one year, so this was not yet a good reference of the average annual irrigation demand. Disclaimer: “UBC SEEDS provides students with the opportunity to share the findings of their studies, as well as their opinions, conclusions and recommendations with the UBC community. The reader should bear in mind that this is a student project/report and is not an official document of UBC. Furthermore readers should bear in mind that these reports may not reflect the current status of activities at UBC. We urge you to contact the research persons mentioned in a report or the SEEDS Coordinator about the current status of the subject matter of a project/report.”

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