By Erica Bonhomme, Matt Follett and Arlen Foster
The City of Iqaluit is the capital of Nunavut and a thriving and growing Arctic community of approximately 8,000 residents, government offices and small to medium-sized businesses. Iqaluit obtains and distributes potable water to its residents and businesses from Lake Geraldine, an engineered reservoir located approximately one kilometre north of the city centre. The reservoir is currently designed to provide water to a population of up to approximately 8,300 people.
Lake Geraldine is refilled annually during the open water season (spring to fall) by natural inflows from snowmelt and precipitation. Summer capacity of the reservoir is about 1.8 million m3. However, approximately 700,000 m3 of this is converted to ice during the winter months. Over winter, Iqaluit draws down from the approximately 1.1 million m3 of available liquid water in the reservoir.
As the population of Iqaluit grows and as a result of aging infrastructure losses, water demand has been increasing. Each year, the city is at risk of an over-winter water shortage. As such, it has begun to study the feasibility of additional sources and storage of water, with the aim of implementing a permanent additional supply to Lake Geraldine by 2026.
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The problem
Over the past several years, more than 80% of the available water stored within Lake Geraldine has been used over the winter. This leaves little for unanticipated uses of water, such as major leaks or firefighting. The reservoir must be at full capacity at the onset of winter, to reduce the risk of potential water shortages during the cold months.
In the summer of 2018, after a dry winter and meagre spring runoff (freshet), it was predicted that the reservoir would not fill to full capacity naturally prior to the next winter. The Chief Medical Officer of Health identified the potential shortage of potable water as a public health emergency.
A short 2019 freshet and sealift delay began indicating that Iqaluit would be dealing with another emergency situation. By early summer 2019, after again predicting a potable water shortage for the coming winter, the Minister of Community and Government Services declared the situation an emergency for the second consecutive year. Compounding the 2019 water shortage, flows in regional watersheds were at historic lows throughout summer, limiting what may have been a re-implementation of the 2018 solution.
The solution
Over a period of just several weeks in both 2018 and 2019, Nunami Stantec designed systems to supplement water from the Apex River watershed to Lake Geraldine. Despite the urgency of the situations, the design of water supplementation was carefully planned to protect the Arctic char of the Apex River and their habitat.
The designs directly used the geomorphology and hydrology of the local watersheds to optimize the use of equipment and water conveyance. In September 2018, just under 200,000 m3 of water was transferred from the Apex River to Lake Geraldine. This filled the reservoir to spillway elevation.
In 2019, approximately 460,000 m3 of water was transferred from Unnamed Lake to the Apex River, and 570,000 m3 were transferred from Apex River to Lake Geraldine in just over one month. This filled the reservoir to within 15 cm of spillway elevation.
The dual sources used in the 2019 program required careful planning, consideration of complex logistics, specialized design, and close monitoring over the duration of the project.
Community impact and environmental considerations
Upon recognizing potential water shortages in 2018 and 2019, Iqaluit initiated public communications to encourage conservation and implemented various loss and demand reduction initiatives.
Despite the emergency circumstances, the city wanted to avoid permanently impacting aquatic ecosystems and cultural resources. The Apex River is known to have a resident population of Arctic char, identified during previous studies. Nunami Stantec designed and implemented the 2018 and 2019 supplementation projects in a way that would not significantly impact fish and fish habitat. This meant maintaining withdrawals at less than 10% of the flow of the river, and by adding water to the river system when flows were below 30% mean annual discharge.
Through close communications with Fisheries and Oceans Canada (DFO) biologists, Nunami Stantec biologists and geoscientists designed and implemented a fish and fish habitat monitoring program in 2018 that was used to confirm these predictions. The design of the 2019 program, combined with the monitoring completed in 2018 was sufficient that DFO did not require fish and fish habitat monitoring in 2019.
The potential for Unnamed Lake to be used as a water source was identified by Nunami Stantec during a feasibility study in 2017 and furthered through consultations with the Amaruq Hunters and Trappers Association. They also provided advice on the cultural use of the area.
Due to the overlap of some of the project infrastructure with a traditional trail, Nunami Stantec completed an archaeological survey of the project area, during which a new site was documented. All project components related to design and execution were considerate of ecological, environmental and cultural factors.
2018 emergency resupply
In 2018, while the environmental aspects of the challenge were being managed, the municipal engineering team of Nunami Stantec was active designing a pumping and piping system that would transfer the nominated volume of water to Lake Geraldine in the short remaining season.
The exercise required Nunami Stantec to complete the following tasks:
- Evaluate route options from Apex River to Lake Geraldine and from Apex to an adjacent lake in the Geraldine watershed;
- Prepare profiles of each route;
- Evaluate the hydraulics of the most favourable routes to Lake Geraldine with a multiple set of 100 mm diameter hoses, which were available in Iqaluit (Government of Nunavut owned), with two possible submersible pumps;
- Complete design for the pumping and piping schematic including Fisheries and Oceans Canada intake screen requirements, metering requirements, distribution manifold design, and options for arrangement of the available hoses to optimize transfer volumes.
The system design needed to ensure the transfer of up to 400,000 m3 of water in 60 days, pumping 20 hours per day. The project team completed a pumping analysis and determined that it was possible to meet these requirements utilizing the available 100 mm firehose. They also determined that transfer of the required volume of water could be completed with two Flygt BS-2201 submersible pumps.
2019 emergency resupply
The 2019 water supply project was based on sourcing from the Apex River, but there were some significant differences to the 2018 design. This water supply emergency was more complicated to resolve than in 2018 in several ways.
Firstly, water levels in Lake Geraldine were lower than in 2018. In fact, they were at historic lows due to the previously noted low runoff in the spring of 2019. This required doubling of the desired pump rate from 95 litres per second (2018) to 200 litres per second.
Secondly, as noted previously, the historic low flow levels in the Apex River prevented pumping at the required rate as it exceeded the DFO required minimum river flows and maximum withdrawal rates. Otherwise the pumping rate would have taken all the water from the river.
Therefore, maintaining these minimum river flows to prevent harmful effects to fish, required transferring water from another source to increase the flow in the Apex River. This was the Unnamed Lake.
In the early spring of 2019, before the status of the emergency was fully clear, Nunami Stantec had completed the design of the 300 mm HDPE piping and pumps system from Apex River to Lake Geraldine as a semi-permanent installation. The new Sulzer J604 pumps were optimized for the final route and piping type.
Piping and pumps were sourced and shipped on the first sea lift to Iqaluit and were installed in the selected route from Apex to Geraldine in August 2019. By the time the 2019 water emergency was present, this new piping configuration was available for use. Due to the higher flow capacity of the 300 mm piping, the higher pump rate from Apex to Lake Geraldine was able to be accommodated.
To address the water transfer from Unnamed Lake, Nunami Stantec evaluated aerial photography and available digital terrain mapping, and selected a functional route from Unnamed Lake to the Apex River. This routing was longer than the Apex to Lake Geraldine route which would normally require additional pumping energy, but with a much lower head requirement due to differing elevations.
Numami Stantec repurposed the flexible hoses and manifolds used in 2018 and determined that it would be possible to pump water from Unnamed Lake directly into the Apex River. This would require different pumps and a secondary generator site. Both the Apex River and Unnamed Lake pumping systems were put into operation at the same time. Both functioned as designed, continuously pumping at rates of between 150 and 200 litres per second, for up to 24 hour per day, until Lake Geraldine was filled.
The final outcome of pumping from Unnamed Lake into the Apex River, and from the Apex River to Lake Geraldine, allowed Lake Geraldine to be brought up to the maximum full level prior to freeze up in September. Apex River maximum withdrawal and minimum thresholds were also met.
Project legacy
The design of the 2018 emergency supply project has been used as the basis to install a semi-permanent pipeline from the Apex River to Lake Geraldine. Supplementing from Apex River is intended to begin in spring of each year until a permanent supply is implemented demonstrating the efficacy of this solution for the medium term.
Supplementation from Unnamed Lake allowed valuable hydrological data to be collected for the Apex River watershed as a whole. This will inform the City of Iqaluit’s ongoing studies of long-term water supply. An access road constructed to Unnamed Lake will facilitate future supplementation efforts and provide access to recreational areas.
Erica Bonhomme, Matt Follett and Arlen Foster are with Stantec. This article appears in ES&E Magazine’s February 2020 issue.
