Keith said the lack of "drip feed of snow melt'' over the summer irrigation season would mean a lack of reliable water for pivot irrigators and heighten the "vulnerability'' of the river.
While not "here to do away with farming'', she told the hearing farmers should consider land uses that were "appropriate to the amount of water available''.
Keith was called as a witness by lawyer Maree Baker-Galloway, acting for the Otago Fish and Game Council which is seeking to uphold the Otago Regional Council's plan change 5A decision requiring a minimum flow of 900 litres per second in the river.
The council is appealing its 5A decision, alongside irrigators represented by the LCG.
In answer to LCG lawyer Phil Page, Lindis Valley farmer Tim Davis told the hearing he was not aware there were major snow packs in the Lindis catchment that "stayed around''.
And, as snow melt occurred in spring, rather than during the summer irrigation season, he did not see the relevance of Keith's argument.
It was his understanding climate change was likely to bring warmer, wetter weather with more rain in summer.
The hearing is expected to conclude this week.