LOVELAND — Government, policy and science came to a head over whether or not the Northern Integrated Supply Project is the most environmentally sustainable way to guarantee Northern Colorado’s water future.

The discussions were held at Confluence, BizWest’s first-ever conference on the future of water in Northern Colorado.

NISP, developed by the Northern Colorado Water District in Berthoud, has been a flashpoint for more than 15 years. The plan is to build the 170,000-acre-foot Glade Reservoir west of Wellington and the 45,600-acre-foot Galeton Reservoir east of Ault and store water for 15 nearby cities and water districts to meet future water demand. It also calls for expanding an existing canal to divert water from the canyon mouth of the Poudre River and moving seven miles of U.S. Highway 287.

Northern Colorado Water Conservancy District hopes to secure federal permits next year and start construction by 2023.

Brian Werner, spokesman for Northern Water, told conference attendees people are going to keep moving to the state regardless of its water situation. Unless the state wants to “figure out how to put a fence up” and prevent in-migration, urban areas will have to conserve water, build water storage systems and continue buy-and-dry deals with farmland owners.

“Any way [the authors of the Colorado Water Plan] sliced and diced it, we’re going to have a water gap,” he said. “We’re going to have more demand than there is water available, so we need to ask how we’re going to meet that demand and close that gap.”

The project’s opponents say the reservoirs would slow the Poudre River’s flow at peak times, worrying Fort Collins residents and officials who believe the river wouldn’t be able to flush contaminants as effectively, hurt wildlife environments near the river and affect the city’s whitewater rafting project set to open this summer. Fort Collins also wouldn’t directly receive water from the NISP.

Fort Collins mayor Wade Troxell said the city’s main worry is the long-term health of the river and its flow. While city officials are supportive of plans to secure enough water for the future, Troxell said everyone involved in the project has to make sure an adaptive management plan won’t cause severe environmental risk.

The Fort Collins City Council passed a resolution saying it couldn’t support NISP as presented in 2015, but have ordered city staff to hold talks with Northern Water starting in 2016.

“One of the things that as it related to the statement within the final BIS was speculation on a trajectory of inevitable decline. As a city, we don’t accept that as an inevitable outcome of the river,” he said.

LeRoy Poff, a stream and river ecologist at Colorado State University, said NISP as projected puts the Poudre at risk of a number of environmental damages if Northern Water can’t guarantee enough flow through the river.

The Poudre currently floods every two to five years into its floodplain, which Poff said resets the nearby environment by drowning encroaching plant life and moving sediment off the riverbed.

NISP is projected to slow total streamflow by 11 to 27 percent at various points in the Poudre, although it could increase flow in the winter. If that happens, Poff said if the river doesn’t get at least three days of high flow per year, the risk of environmental damages significantly increases.

Northern Water has agreed to allow free flow in the Poudre if the Glade Reservoir is at 78 percent capacity and projected to fill that year. It projects that this will occur in 90 percent of all the years the project is in effect.

But Poff said the Poudre has to flow freely for a few days per year regardless of how much water is in the reservoir, or the river’s ecology will rapidly change for the worse.

“Somebody has to pay money to let water flow down the river for three days every year instead of going into the reservoir, and in my mind, that’s the cost of doing business,” he said. “We need to pay for our environmental degradation as we go along, and we need to avoid it, frankly, so that your children and grandchildren can enjoy the river.”

Werner said it’s impossible to know exactly what will happen to the Poudre and the environments it flows through, but the demand for water and the funds already allocated to the project make this the time to move forward on the reservoirs.

“What we’re saying is that we got money on the table for this adaptive management project. Let’s look at the operations once we get moving with NISP and see what happens and what it responds,” he said.