There is also concern that the project will degrade the condition of the Tukituki River. The expansion of agriculture in the Canterbury region, also reliant on large irrigation schemes, has led to a significant deterioration in the water quality in the region. The risk of water quality degradation as a result of the Ruataniwha dam is particularly great because the modelling for the project assumes that
37% of the irrigated land will support dairy cows which are associated with high rates of nitrogen and phosphorus pollution...
The environmental harms from the project are certain. Dams generally reduce the flow of a river, and the occasional flushing of the river, where extra water is released from the dam to simulate floods, is unlikely to shift the gravels and scour the rocks of algae. This means that the river system will undergo ecological and morphological change...
Another sources of controversy for the Ruataniwha dam project was the proposal to deregister 22 hectares protected conservation estate and swap it for 170 hectares of nearby private farm land so that the deregistered
conservation land could be flooded.
Forest and Bird took the Minister of Conservation and the HBRIC to court arguing that the swap was not permissible under the Conservation Act 1987.