Kim Taylor thinks the Southern Forest Irrigation Scheme threatens the Donnelly River.

The former Director General of the Department of Water in WA has condemned the proposed $70 million Southern Forest Irrigation Scheme as “a massive gamble on future streamflow, a gamble of $60 million of taxpayers’ money, and a gamble on the river environment which is already highly stressed due to a drying climate.”

Kim Taylor has spent 40 years of his working life in government, including 20 in water resources assessment and management, and two years as Director General of the Department of Water. He also served as General Manager of the Office of the Environmental Protection Authority (EPA).

He claims water modelling for the scheme is flawed and that it’s incapable of supplying the proposed 9 gigalitres for horticulture in the face of a drying climate and the Donnelly River’s declining streamflows.

Mr Taylor said that no detailed catchment modelling had been done when an economic analysis of the scheme was done in 2016 or when the scheme’s cooperative was formed in May 2017.

He believes that stream flow gauging of the Donnelly River over the last 10 years showed the scheme could only meet the required 9 gigalitres of water in 40 per cent of those years. By 2030 that would drop to just 20 per cent or less.

“High uncertainty”

Even the Water Department’s initial consultants on the project reported that there was “high uncertainty” in their model’s predicted streamflows, according to Mr Taylor.

He said the modelling doesn’t consider long-term declining groundwater, which is a major cause of reduced streamflow.

“It is astonishing that the Water Department would consider that a model which does not take into account declining groundwater levels could reliably predict future streamflow in a drying climate,” he said in a report on the scheme.

The scheme plans to dam Record Brook, a tributary of the Donnelly River, but the Department has not done any streamflow gauging there for 20 years, Mr Taylor claims. Streamflow monitoring by farmers shows just half a gigalitre into the brook in a year of average or slightly above average rainfall.

“If the Government wants to take a gamble, it should at least have the best reliable catchment modelling it can to make its decision. The current modelling does not meet this,” he said in the report.

“Best practice”

However, the Department of Water and Environmental Regulation (DWER) said that its modelling was done independently by Hydrology and Risk Consulting (HARC). The model was developed in line with the eWater “CRC Guidelines for rainfall-runoff modelling: Towards best practice model application (2011)” and reviewed by an independent third party, Eco Logical Australia, and was found to be fit-for-purpose.

The department said it recognises that models have limitations in replicating the complexity of environmental systems. The modelling report, which is publicly available, explains these limitations, all of which have been provided to the Department of Primary Industries and Regional Development, stakeholders in the Warren-Donnelly and the Southern Forests Irrigation Cooperative.

It says water supply reliability was assessed on projected rainfall, and that its modelling assumes a dry future climate and accordingly a realistic assessment has been made of when water would be available.

Any water supply risks will be managed through rules which protect and prioritise environmental flows, and by varying supply from year to year depending on available water. Water will only be taken once there’s enough flow to meet all environmental requirements.

 All water availability risks will be borne by the scheme and not the environment.

Ecosystem stress

Mr Taylor’s criticism of the scheme isn’t limited to its failure to meet the horticultural industry’s needs. He also condemns its impact on forest ecosystems that are undergoing acute water stress in a drying climate when streamflows in the Donnelly River have declined by 70 per cent since 1975.

He thinks that while water infrastructure in the Manjimup area is needed for the horticultural area to cope with the drying climate, the government should “go back to the drawing board” and work with the industry to develop a more sustainable way to optimise the region’s water use.

Mr Taylor’s claims have been strongly refuted by Jeremy Bower, CEO of the Southern Forests Irrigation Co-operative, who says his comments and figures are unsubstantiated.

“We rely on DWER for scientific advice. They’ve undertaken detailed assessment of the scheme, investigating environmental and reliability risks, used the standard approach to future climate scenarios, including the use of dry climate projections out to 2030/2050,” Mr Bower said.

“That approach has been reviewed and endorsed by the Bureau of Meteorology and the CSIRO, so we’re comfortable with those scientific organisations providing advice to us,” he said.

He said DWER uses a longer-term period in its analysis which is an approach endorsed by the World Meteorological Organisation.

“According to DWER, Taylor has used rainfall reduction factors 10-15 per cent drier than any predictions that DWER have seen out to 2030 and 2050.”

He also claims Mr Taylor hasn’t factored in the critical role of dam storage to capture additional water in wet years to carry over into dry years.

Mr Bower claims the ability of the scheme to move water around the region in a drying climate makes a very strong case for the project.

The scheme has now been referred to the Environmental Protection Authority for assessment.

 

Photo: David Steele/Shutterstock