Amy Adams' press secretary has popped up on The Standard to give some answers. Adams has indeed declared a conflict of interest with regards to Central Plains Water, and transferred decisions relating to it to Gerry Brownlee:
Accordingly, to avoid any actual or perceived conflicts of interest, Minister Adams has transferred her responsibilities as Environment Minister to Minister Brownlee. This was done after she became Environment Minister in April 2012... Environment officials report directly to Minister Brownlee on matters concerning the Central Plains Water scheme.
I understand there has only been one Cabinet decision made regarding the Central Plains Water Scheme. On this occasion, Minister Brownlee took the paper to the relevant Cabinet committee. When this issue was discussed, Minister Adams excused herself from the Cabinet committee where it was discussed, and took no part in the discussions.
The decision in question was the one to amend the Rakaia River Water Conservation Order, allowing the river to be pillaged for irrigation.
So, while she has behaved ethically in the specific case, it doesn't answer the wider questions about the ECan dictatorship and its relaxed water management regime.