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Boulder Reservoir Maintenance

Boulder Reservoir dam

Beginning Sept. 1, 2020, until March 2021, access to Boulder Reservoir will be limited while the reservoir is drained to allow Northern Water, in coordination with the City of Boulder, to perform necessary maintenance on Boulder Reservoir and its dams to ensure visitor safety and effective water delivery to municipal and agricultural water users. This is routine, required maintenance work that will take place every 5-10 years. 

The Boulder Reservoir shoreline and basin are closed until Spring of 2021.

Northern Water Reservoir Maintenance Project Information

Boulder Reservoir Project Map

Click to enlarge the map below of project impacts:

map of reservoir maintenance impacts

Recreation Impacts

Draining of the reservoir will prevent boating, swimming, watercraft and other on-water activities beginning in September 2020 until the reservoir is refilled. During this time the reservoir will be closed to boating and other on-water recreation once the reservoir drawdown begins Sept. 1 (due to strong currents and shallow water). 

As Boulder Reservoir has had a shortened recreational season due to the coronavirus pandemic, city staff recognize that these additional limitations on Boulder Reservoir use may be disappointing to impacted recreationists. However, performing the maintenance work when some recreation activities, such as swimming, are already restricted due to COVID-19 will ensure that additional impacts will be avoided and recreation can return to full service once the pandemic subsides.

Boating and watercraft activity will be limited or restricted. Trail access on the North Shore will continue, except for the designated trail accessing the water line. Trail access in the vicinity of the north and south dams may be impacted during periods of construction in those areas.


The shoreline and basin are closed to all public access. Dangerous conditions exist, including whirlpools, strong currents and deep mud. City staff are enforcing the closure and trespass violators will be prosecuted and subject to a fine of up to $1,000 and incarceration for up to 90 days.

Project Description

The Northern Colorado Water Conservancy District (“Northern Water”), in coordination with the City of Boulder, will be performing necessary Boulder Reservoir dam and reservoir maintenance. This work includes sediment removal and erosion control maintenance. The reservoir will be drained to remove sediment from the area around the reservoir outlet, which naturally builds up over time. Maintenance will also occur on dam outlet works structures, as well as the on the land between the north and south dams known as Fisherman's Point. 

Reservoir levels will be significantly lower than normal between September 2020 and March 2021 while the work takes place. Reservoir levels will likely be back to normal by April 2021. Work will include heavy machine access, sediment hauling and deposition in the vicinity of the north dam and erosion control on Fisherman's Point. Construction equipment access and activity will be in the vicinity of the north dam and Fisherman's Point. 

The water that's being drained from the reservoir will be put to use within Northern Water District boundaries. The City of Boulder owns Boulder Reservoir, but operations and maintenance related to water storage and dam safety are primarily managed by Northern Water. Boulder Reservoir recreation in the form of boating, other water sports and trails are managed by Boulder Parks and Recreation.

Project Benefits

Boulder Reservoir is a key part of our community's water supply. Draining and removing sediment from reservoirs as well as dam outlet inspection are routine maintenance practices that typically occur once every five to 10 years to ensure dam safety and effective water delivery to municipal and agricultural water users. Erosion control work will reduce sedimentation in the reservoir and enhance visitor safety. 

Environmental and Wildlife Considerations

Northern Water is coordinating with Colorado Parks and Wildlife and with city staff to mitigate environmental impacts.   

Species of conservation concern that use Boulder Reservoir and surrounding wetlands for nesting include the Northern Harrier, Osprey and American Bittern. Boulder Reservoir will be drained outside of nesting season, which will limit impacts on nesting and migrating species during the most critical point in their life cycle. The reservoir will be refilled as quickly as possible after maintenance work is completed this winter and prior to spring migration and nesting seasons. Therefore the reservoir will still  function as a stopover point for migrating species in spring 2021. 

Draining Boulder Reservoir may impact over-wintering species of birds that utilize the Reservoir for forage, including Bald Eagles and Northern Harrier. Refilling the reservoir as quickly as possible after maintenance will minimize impacts to these species. 


For general project questions please contact Water Resources Manager Kim Hutton at [email protected] For questions regarding recreation impacts, contact Stacy Cole with Parks and Recreation at [email protected]