Let’s face it, 2020 and 2021 have been really strange years. With the COVID-19 crisis dumped in our laps suddenly last March, it seems like life came to a standstill. We were stuck inside, limited, and prevented from going just about anywhere and facing an uncertain road ahead.
As summer arrived, at least we were all able to get out and enjoy a bit of fresh air. The question then became where to go and what to do in the days of “social distancing”. It has also been a very hot and humid summer with very little rain. One place that I had never visited before was the Waterbury State Park reservoir and dam.
It’s a bit off the beaten path, a quarter-mile off VT Route 100, but perhaps that is what’s so great about it. The day I visited, there were only a few people there and plenty of solitude, summer breezes, and the sound of the water cascading over the dam.
Waterbury Reservoir is also a great place to fish and sometimes there can be quite a few people taking advantage of that along with swimming and wading in the water. There is also a picnic area and places to have a small bonfire near the parking area.
The Waterbury Reservoir is the ninth-largest body of water in the state of Vermont. It was created in the 1930s by the Vermont Civilian Conservation Corps as a flood control project to protect towns and villages along the Winooski River Valley.
The term “reservoir” can refer to a man-made or natural lake, as well as cisterns and subterranean reservoirs. In this section we focus only on man-made reservoirs.
Man-made reservoirs are made when dams are constructed across rivers, or by enclosing an area that is filled with water. There are two main types of man-made reservoirs: impoundment and off-stream (also called off-river).
Reservoirs can vary in size and be as small as a pond and as big as a large lake. There is so much variability when it comes to reservoirs – they can differ in size, shape and location. For this reason, it can be misleading to make blanket statements about reservoirs without “significant qualification as to their type”.
Depending on the purpose of a reservoir, operators will fill a completed reservoir with water, let water flow on through the dam and downstream, or leave the reservoir site empty until it is needed (e.g. a dry dam site for flood mitigation).
Click image to enlarge.
An impoundment reservoir is formed when a dam is constructed across a river. Impoundment reservoirs are usually larger than off-river reservoirs and are the most common form of large reservoirs.
Off-stream reservoirs are reservoirs that are not on a river course. Rather, off-stream reservoirs are formed by partially or completely enclosed waterproof banks .
The embankments around an off-stream reservoir are usually made from concrete or clay. The size of an off-river reservoir will depend on how large of an area is excavated and how high the embankment is built.
Off-stream reservoirs are generally simple in shape and “virtually uniform in depth”  compared to impoundment reservoirs, which tend to have shallower shores and varying volumes and shapes.
Environmental Impact Assessment and Stakeholder Engagement
An environmental impact assessment (EIA) must be completed prior to construction beginning on a large or impactful reservoir and dam site. The EIA process is regulated at the federal government level by the Canadian Environmental Assessment Agency.
The Alberta government also has its own process for completing an EIA. Alberta Environment and Sustainable Resource Development is responsible for the laws that are related to EIAs in Alberta (the Environmental Protection and Enhancement Act and the Water Act). At an inter-governmental level, the Canada-Alberta Agreement on Environmental Assessment Cooperation is an agreement between the federal government and the government of Alberta that streamlines the EIA process and ensures that the EIA meets the requirements set out by both levels of government .
An EIA may include, but is not necessarily limited to, an analysis of the following:
Whether the safety of navigation is impacted by the proposed structure;
The impact of the structure on migratory fish; and
The impact of the structure on endangered riparian species or fragile ecosystems.
Depending on the location of the dam and reservoir, stakeholders may need to be consulted before construction can begin.
The construction of a reservoir and dam involves many steps that are taken carefully to ensure the dam is operational and meets all safety standards and environmental regulations.
Diverting the River
Before construction can begin, the river must be diverted in order to make the building process easier. Water can be diverted through constructed channels on the surface alongside the river or through underground tunnels through the rock alongside the river. Both of these methods allow the water to travel downstream of the reservoir site and minimize the amount of water travelling to the construction zone.
A temporary dam called a cofferdam is built above the main site of the permanent dam. The cofferdam is intended to protect the construction site in the event of a flood.
On wide rivers, a cofferdam may be built on one side of the river to allow water to flow through half of the riverbed. The area behind the cofferdam will be drained and the first half of the main dam will be constructed. This side of the main dam will not be constructed to completion. There will still be some holes in this section of the dam. The cofferdam will then be removed and the water will flow through the holes in the incomplete main dam.
Another set of cofferdams is built on the other side of the river and the rest of the main dam is fully constructed. In the final step, the original cofferdam will be reconstructed and the portion of the main dam behind the cofferdam is completed. Once the cofferdam is removed for the last time, the dam is complete and water is stored in the reservoir.
In some cases, rather than constructing an on-stream dam, a dam is built off-stream in a topographical depression suitable for holding water (off-stream reservoir). Once the dam is completed, the river will be diverted to the off-stream storage site .
Preparing the Foundation of the Dam
A crucial step in the lifecycle of building a dam is preparing its foundation. This is the first step in construction for an off-stream dam. For an on-stream structure, the dam foundation is prepared after the river has been diverted.
Once the construction site is drained of water, the dam foundation is excavated. All loose soils and sediment are removed, roots and vegetation are grubbed and all water is removed from the site until bedrock is exposed.
If a dam is being built utilizing a valleywall on one or both sides, any blocks of the valley wall that are unstable are removed. Hundreds to thousands of cubic metres of unsuitable rock may have to be removed to reach bedrock with the appropriate strength, stiffness and permeability characteristics required for construction.
The bedrock geology will be surveyed for faults and cavities. Any cavities are filled with grout to increase the stability of the bedrock and to prevent water from leaking underneath the dam. Concrete may be used to fill larger openings such as surface cracks, fissures or irregular surfaces. The foundation surface of the dam will be moistened with some water and with the use of a roller it will be compacted to increase strength, stiffness and stability, while reducing permeability.
Finally, if applicable, a mass concrete footing area for an intake tower (a tower used to control water supply for a hydroelectric plant) is constructed and spot rock bolts are installed below the intake tower .
Dam construction depends on the type of dam being built (see Table 1). Arch, gravity and buttress dams are built with concrete and are supported by steel. These dams are used for on-stream storage. These dams used the weight of their structure, abutments, anchors and a solid geological foundation to support them.
Embankment dams (either earthfill or rockfill) are made primarily of soil or rock found in or near the construction area to minimize transportation costs. Erosion is a major concern for embankment dams and continuous maintenance such as vegetation control is required. The requirements for the foundation are not as extensive for embankment dams as they are for concrete dams.
Filling the Reservoir
Once the dam structure is in place, the reservoir is almost ready to be filled. The land that will be underwater is first surveyed for anything that could potentially contaminate the water. Trash and debris are removed. Then, information signs will be placed around the reservoir and roads leading to the construction area will be barricaded. The reservoir can then be filled.
For on-stream storage, water will have already begun collecting behind the dam. However, for off-stream storage, water must be diverted to the reservoir.
During the filling process the reservoir site is carefully monitored. Operators will watch for seepage of water through the dam and stay alert for mudslides or landslides, which can occur when the soil and new embankment areas around the filling reservoir are inundated and become wetter than normal.
Water quality is monitored at the inflow and outflow of the reservoir and the reservoir water itself. Water quality can be affected by the reservoir since the water that was formerly flowing is now still. Over time, nutrients in the water can build-up and result in the growth of algae blooms (in Alberta, where most reservoirs are located closer to the mountains and inflows often have lower nutrient loads, algae bloom growth is less of a problem than it is in other jurisdictions). Chemicals can also become concentrated in the reservoir, making the water unsuitable for drinking. In Alberta, there are regulations for water quality in a reservoir. The Canadian Fisheries Act regulates the harmful alteration of fish habitat and any required compensation .
Testing Valves and Floodgates
Valves are placed in the dam so that water can pass through the dam and go downstream. Valves are tested to ensure that minimum required flows are met and that they can withstand the passage of higher flows if needed . Spillways are common and are often required for safety purposes. A spillway is a part of a dam that allows water to automatically flow over the dam during a flood event.
In exceptional cases, when a dam needs to pass flows that are larger than what a valve can pass (e.g. during a flood event), a floodgate is used. These floodgates are tested periodically to ensure that safety standards are met.
Monitoring the Dam
The dam will “settle” over time. Since a dam is such a large structure, its height will eventually decrease because its weight will compact it down. The structural integrity of the dam is monitored during this process to ensure that the dam is still functional and safe.
Seepage is also monitored. This is particularly important because as the dam ages, tiny micro-fractures can form and the water can begin to pass through the dam wall. Once water begins to pass through, the hole will only get bigger and the problem will become greater.
The location of the dam is also monitored. The dam may shift slightly upstream or slightly downstream, which would indicate that the structure is unstable. It can also tilt to one side, which is another sign that the dam is unstable .
Summer lasted well into October this year, and it extended the busy season at the 850-acre Waterbury Reservoir.
Waterbury State Park often reported its parking lot was full on sunny days.
Little River State Park had more than 41,700 visitors — a 10 percent increase in overall use from 2016, boosted by new bike trails and upgraded campsites.
Waterbury State Park had just over 37,800 visitors to its day-use area, down 18 percent from 2016’s record 46,000. In total, nearly 80,000 visitors were logged in at the reservoir’s parks during the summer, not counting people who used access points that aren’t staffed.
The parks have five access points, several unstaffed, so those people and boats aren’t counted toward the total, but “anecdotally yes, we have seen an increase in usage, always dependent on weather,” said Chad Ummel, the reservoir’s “floating ranger.”
Summer was cold and rainy to start, and in June the reservoir had to close briefly when rainfall pushed the water level too high, but unexpected warmth in October boosted the overall numbers, Ummel said. The state parks actually extended their closing date to Oct. 10.
There was also an overflow effect: “When Lake Champlain has algae blooms, for instance, we do note that we receive more usage,” as when North Beach in Burlington had to be closed this summer, Ummel said.
Three years ago, the state government took over management of the remote campsites along the reservoir, and have been tracking the numbers of campers who visit. The sites are available only on a first-come, first-served basis.
“There was an initial transition because people have been camping on the reservoir for 80 years with virtually no regulation, no oversight, and there was a little bit pushback initially,” Ummel said. “But we found that most people have been quite appreciative for the state’s efforts, the composting toilets, just the presence on the water and overseeing has made for a more tranquil and enjoyable experience for most.”
Most campers seem to be Vermonters, Ummel said, but other New Englanders who have heard about the remote campsites often stay overnight.
“Once it became summer, it became nice,” said Chuck Hughson, co-owner of Waterbury Sports.
The store opened two years ago in Waterbury, and Hughson says added bike paths in Little River State Park and Perry Hill have definitely attracted more people to mountain biking, he said; the numbers show in his bike-rental business.
“More people are going out with their friends and realizing they can do it too,” Hughson said.
There was no break between fishing and hunting season at the Fly Rod Shop in Stowe, manager Parker Wright noted. “Lots of people come in looking for gear saying ‘Hi, I’m going down to the reservoir,’” he said.
The shop was much busier in October than in years prior, probably due to the weather, Wright said.
There were also lots of people getting out on the water in boats, canoes, kayaks, or on stand-up paddleboards.
“Waterbury Reservoir continues to be a tremendous resource for people to go paddling on,” said Steve Brownlee, owner of Umiak Outdoor Outfitters.
“One of the benefits that we have seen is more people renting boats late in the season. We had terrific warm temperatures in the months of September and October. But the other big difference is the new regulations for keeping the water level high is something new in the last two summers,” Brownlee said.
At the end of 2015, the state decided the Waterbury Reservoir should be maintained at its summertime levels year-round, at about 590 feet above sea level.
In the past, the reservoir was drained every fall to between 540 and 560 feet above sea level, making room for spring runoff, then restored before summer. Now, water flow through the dam is managed to more closely match the natural flow of the Little River.
Exhausted after playing all day, visitors headed into town, and businesses in Waterbury continue to see growth.
“The bars and restaurants love the increased traffic from people enjoying the trails and reservoir,” said Alyssa Johnson, Waterbury’s economic development director. “The activities feed off each other well. There’s nothing better than good food and a cold beer after a day outside.”
“The Waterbury Reservoir is unique. It is a true multi-use body of water where nearly everything is allowed from innertubes to seaplanes,” Ummel said. “So it’s a fascinating scope of use where you get to see people on stand-up paddleboards, and jet ski circles around them. It’s an exciting body of water.”