The Canterbury regional council has changed its plan on water takes from the Waimakariri River to allow irrigators to take water at lower flows.
The change also lowers the maximum take on the river.
Under the old plan, irrigators could only take water when the river flow exceeded 93 cumecs.
They will now be able to take water at 63 cumecs but can only take half the water available.
The change also lowers the maximum take on the river from 40 to 27 cumecs.
A commissioner for the council, Peter Skelton, says the regime caters for all current consent holders but does not provide much space for new consents to be granted.
New Zealand Fish and Game says the plan will provide less protection for the river than the old one.
But Mr Skelton says the change allows water to be taken at lower flows but preserves the higher flows which give the river its braided shape.