An internal report by Natural Resources Tasmania and released under RTI, showed half of the state's rivers had experienced ecological decline, prompting concerns from academics and water ecologists about the pressure the resource is under.

Tasmanian Irrigation accounts for less than half of irrigation in the state and TI chief executive Andrew Kneebone said while they were expanding into new areas, all new schemes were subject to strict environmental controls and licences.

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However, he said, TI was not the regulator when it came to water quality. The regulator is Natural Resources and Environment Tasmania, a government department, which controls water licensing.

It was revealed in budget estimates last week that water quality control rests with NRE, formerly DPIPWE, and not the Environmental Protection Authority.

Mr Kneebone said Tasmanian Irrigation accounted for less than 10 per cent of the irrigation extraction licences in Tasmania but their schemes were subject to strict environment licences.

It was also revealed NRE does not require regular metering as part of its practices, however some "high-risk catchments" are metered. The data is kept by the licence-holder and provided "on request".

However, a review of those policies has been announced.

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"There are a lot of historic arrangements in place, where farmers have their own extraction agreements," he said.

Tasmanian Irrigation has developed 15 irrigation schemes in Tasmania and has planned at least five more, one including the Tamar Irrigation Scheme, which recently failed to secure its water sales threshold despite strong expressions of interest. Mr Kneebone said there were "a signficant amount of people who extract water" for irrigation, but irrigators who sign up with TI are subject to random audits as a way of quality control.

"Our schemes are designed so there is no agriculture run off and we audit between 10-15 per cent of our schemes each year and produce a report that goes to the Minister.

Information released under Right to Information to the Tasmanian Greens show audits by TI had increased from 29 to 56 from 2016. However, the number of schemes found to be non-compliant rose from zero in 2016 to 13 in 2020-21.

Mr Kneebone said the majority of new schemes "take water from Hydro catchments and not the rivers" and are backed by Hydro schemes to maintain the balance of the impact of climate change and environmental damage.

However, he said legacy agreements did allow people to extract directly from the river, and some TI did on occasion extract directly from the freshwater river systems.

He said TI did not enforce fencing of livestock from irrigators on its schemes, but workswith landowners to set their dams up in an informal way to minimise the impact on the environment.

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