Water budget investigation for FortWhyte Alive
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Date
2020-10
Authors
Ayumu, Bernard
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Abstract
FortWhyte Alive; a protected urban green space located in southwestern Winnipeg has in recent years been experiencing water quality deterioration (eutrophication) in its five (4 interconnected, 1 isolated) endorheic lakes. With the pathways of nutrients to these lakes not fully understood, a water budget (2018 – 2019) investigation was conducted using innovative approaches to identify the contribution of all possible water sources particularly groundwater inflow to the lakes. The interconnected lakes (Devonian, Lake 3, Lake 2, and Muir) formed part of a single sub-basin while Lake Cargill formed part of another sub-basin. Surface inflows to all the lakes were estimated from HOBO water loggers while potential evaporation from the lakes was estimated from stable water isotopes analyses of 100 lake water samples ranging from 0 - 7 m. Surface inflows via Devonian contributed about 31% of the total surface inflow received by the interconnected lakes while contributions via Lake 3 and Muir were 43% and 26% respectively. Surface inflow depth in the interconnected lakes was about 53% of the system’s total inflow while groundwater inflow depth was about 8% of the system’s total inflow. The surface inflow depth in Lake Cargill was about 35% of its total lake inflow with no groundwater inflow. Lakewater loss was about 2.3% of the total outflow. The E: I ratios for the interconnected lakes and Lake Cargill were 0.75 and 1.03 respectively. The high evaporation rates in the lakes and large water residence times (> 3years) contributed to lake eutrophication.
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Keywords
Endorheic lakes, Stable water isotopes, Water budget, Eutrophication