Mr Coulton, who has only been in Parliament a little over 12 months, will replace Nationals colleague, Fiona Nash, who resigned after crossing the floor on tax concessions for carbon-sink forestry plantations late last year.

Mr Coulton will work with Opposition spokesman for the environment, Greg Hunt, who embarked on a 3500 kilometre trip through the Murray Darling Basin in November.

"Mark will bring to the position a passion and expertise in land management and vital grassroots issues," Mr Hunt said.

"Prior to being elected to Parliament, Mark was mayor of the Gwydir Shire Council and a farmer and grazier with over 30 years land management experience in the Northern region of NSW.

"Mark has demonstrated a genuine interest in the need for urgent water infrastructure works to help save water in the Murray-Darling system."

The Opposition have pledged to continue pushing for the roll-out of on-farm infrastructure savings ahead of further water buybacks this year.

Mr Hunt said on his trip through the Murray Darling Basin he estimated 600 gigalitres could be saved by "replumbing" rural Australia.

In its pre-budget submission, the National Farmers Federation said the investment in new irrigation infrastructure was "overdue".

"Despite accelerating water buy-back, the corresponding infrastructure component to achieve water-use efficiency is yet to materialise," the NFF submission said.

"While governments have entered the water market to hasten water buy-back plans to restore environmental flows and secure water for critical human needs, the fundamental premise of being able to achieve water-savings…is via water efficiency gains through investment in infrastructure.

"Accelerating just one-half of the equation has distorted the price of water in relation to its lack of availability."