As the Warner River gets closer to protected status with a public hearing set for Thursday, here are two numbers to consider: 2,225 and 6.

Those figures are the maximum and minimum possible river flows, measured in cubic feet per second, given in a Protected Instream Flow Study that will be the subject of the hearing. The big number is the flooding level that should happen on the Warner at least once every two years for the benefit of “higher elevation flood forests,” and the little number is the absolute minimum that should be allowed to happen for at most eight days under rare, near-catastrophic drought conditions.

The fact that a relatively placid river like the Warner and its surrounding ecosystem can continue to exist when its most basic characteristic varies by a factor of 370 shows how complicated it can be to decide what is best for a waterway.

“Early on, everybody wanted to develop a single statement of what the river could have, one number that … could be used,” said Wayne Ives, the instream flow specialist for the state’s Water Management Bureau, who has been working on projects like this for two decades. “We have learned that to protect all the species that actually live in a river, there’s a natural flow paradigm. Some like high flow, some like low. You need to include variability within years and between years.”

Variability, indeed. Even within ordinary parameters, called common flow, the amount of water rushing over the bed of the Warner River can vary 13-fold, from 76 cubic feet per second in late summer and early fall to 1,062 cubic feet per second in March and April. To visualize how much water that is flowing by each second, consider a cubic foot of water is about the size of a basketball.

These flow figures will be open for discussion Thursday, Feb. 23, at 7 p.m. at Warner Town Hall. The public meeting will talk about the science of a three-year study by consultant Gomez and Sullivan Engineers of Henniker for the study, which concerns the amount of flow required at various times to support human use as well as the fish, wildlife and plant species that depend on the river. Both state and Gomez and Sullivan staff will be present at the hearing to answer questions.

The follow-up step, to determine whether any uses of the river need to be limited to protect the flow of water at certain times, is at least a year away.

The Warner is one of 19 designated rivers under the New Hampshire Rivers Management and Protection Program, which was created by the legislature in 1990. The Contoocook and Merrimack rivers are also designated rivers.

The ultimate step of the program is to create a water management plan detailing what human uses of the river can take place. Such plans take years to draw up while collecting public feedback – they exist so far only for the Lamprey River on the Seacoast and the Souhegan River in southern New Hampshire.

Even before that step, the designation of a river in the program can create change, most notably the creation of a Local Advisory Committee that reviews and gives recommendations to , state, and federal permitting agencies on proposed developments within a quarter-mile of the river.

The Warner River is designated for protection for 20.5 miles under the program, starting at the confluence of the West Branch Warner River and Andrew Brook (the outlet of Lake Todd) in Bradford, to the confluence of Hoyt Brook (where it becomes the Warner River) and continuing about 19 miles to its confluence with the Contoocook River in Hopkinton.

The Warner River Protected Instream Flow Study report can be at https://des.nh.gov/sites/g/files/ehbemt341/files/documents/r-wd-22-03.pdf

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