The Central Plains Water Trust says its 60,000 hectare irrigation scheme could be delayed by appeals to the Environment Court.
Six appeals against the scheme being granted consent have been filed by parties including Ngai Tahu, Fish and Game and the Christchurch City Council.
The Trust itself is also appealing against parts of the decision restricting when it can take water from rivers.
Project manager Derek Crombie says he hopes the objections of the other appellants can be resolved before going to the Environment Court.
Mr Crombie says it will take about five years to build the scheme if it's not delayed by legal challenges.