Tony Abbott has moved to calm nerves in the Coalition by telling the party it cannot expect to ride high in the polls for the entirety of the Parliament.

Mr Abbott also sought to quell a brawl between South Australian and East Coast MPs over water, by appointing his two respective shadow ministers, Barnaby Joyce, from Queensland, and Simon Birmingham from Adelaide, to nut out a compromise position on the Murray-Darling Basin.

The government is expected to introduce a bill tomorrow allocating extra water to be sent down the river and the Coalition is split.

With MPs worried about the narrowing polls and Mr Abbott’s strategy, sources said the Opposition Leader told the party room this morning the Coalition was going through ‘‘slightly more difficult times’’ but it would be unrealistic to expect it to ride high in the polls for an entire three years.