Sediment in rivers will reduce 27%: Report

Horizons Regional Council's Sustainable Land Use Initiative aims to reduce erosion. PHOTO/ FILE

Promising findings from a Landcare Research sediment report were delivered to Horizons Regional councillors last week.

The report, which aimed to assess the impact of the Sustainable Land Use Initiative (SLUI) on sediment levels in the region's rivers, was commissioned by Horizons in 2013 and co-funded by Landcare Research.

Horizons environmental manager land Grant Cooper said SLUI had completed a huge amount of physical works over the past eight years and it was time to find out what impact these works were having.

"We think the success of SLUI isn't measured by the number of trees planted or fences built. We need to see that we're making an impact downstream.

"We also wanted to know if the rate we are currently working at is best, or if we need to increase or decrease our works programme. So Landcare Research came up with five different scenarios and predicted how each one would play out by 2043."

The first scenario modelled sediment reduction in rivers if SLUI works were to stop at the end of this year, which would result in a 9 per cent sediment reduction by 2043. The next four modelled SLUI continuing, but with different levels of farms coming on board and farmland being retired to forestry.

"What was really promising is that Scenario 3, which is the closest scenario to how we see SLUI continuing to operate over the next few years, predicts the annual sediment load in our rivers will reduce by 27 per cent as a result of SLUI works," Mr Grant said.

"Also the report breaks this information down to a catchment level. So while sediment is predicted to reduce by 27 per cent across the region, in the Middle Whangaehu catchment for example, it will be reduced by 61 per cent.

"So not only does this report tell us the work we are doing now is going to have a significant impact in 30 years' time, it also tells us which catchments are reaping the benefits and which ones we could put more preventative works into."

John Dymond, who presented to council on behalf of Landcare Research, said "This is great work, keep going.

"Horizons are leading the way from a regional council perspective with sustainable land use and other councils are starting to follow."

Chair of Horizons' catchment operations committee Murray Guy said it was really good to hear first hand from people working in the industry.

"This report will not only help us make funding applications to central Government for further support of SLUI but it'll also help us make decisions in the works programme."