Christine Scott: On farm water storage not right

Christine Scott.

Twelve years ago, I along with my fellow regional councillors of the time undertook a strategic study on water issues. Right back then we identified the need for water storage - what form it would take was to be investigated.

The obvious answer, it seemed to me, was on farm storage. Easy isn't it? And this is the answer that four of our councillors are offering.

But over the years as I got more and more involved with water issues and the tension between meeting the different aspirations of the Resource Management Act, the answer became increasingly more difficult to find.

The purpose of the RMA is to provide for cultural, social and economic wellbeing while protecting the life supporting capacity of natural resources. That is provide for our economic, and consequently social wellbeing but make sure there is sufficient water to maintain our aquatic ecosystems.

We do have plenty of water in the Tukituki and Ngaruroro but not in the right place at the right time. In summer droughts there just isn't enough water in either the Tukituki or the Ngaruroro for ecosystems and for irrigation.

Yet our primary production is absolutely essential for our Hawke's Bay economy, and all the jobs involved in the production sector, processing and support services are critical for our social wellbeing. So storage must be the answer, but how?

Our first order investigations identified 20 sites along the hills backing the Ruataniwha Plains, but none were found suitable on geotechnical grounds for small community schemes. So the "on farm" bit is not looking too good in that area. You could dig up vast areas of the plains, and line it for extremely inefficient water storage with very high evaporation.

The down side of this is significant loss of productive land, high cost, and poor environmental outcomes because of the lack of control over cumulative effects and high water loss.

Then there is the problem of filling these reservoirs. The water is fully allocated across the plains so where is all the extra water to come from? It takes far more water in a reservoir than is actually needed for the crop because of evaporation. With large surface area to volume this is increased significantly.

And with the predicted changes to our climate being longer, hotter, dryer summers it will be even worse.

Finally on a cost basis the sum of all these endeavours, especially when you take the cost of loss of productive land to create your storage area, is higher than one efficient community storage - so in most cases is just too prohibitive for the farmer.

On farm storage rarely delivers high security needed to commit to crops but essentially serves as a short buffer. For the sake of transparency, there are around 16 consented dams for irrigation with none under formal consideration. Contrary to the statements made by this group of councillors HBRC does not put up obstacles to construction of on farm dams for irrigation. The council is required to consent dams under the Building Act for safety reasons.

The need for this is as obvious as the need for a warrant of fitness for a car. Only with dams the extent of the information required matches the impact or risk.

It is risk management as directed by government that drives the cost. Council faces these same costs for its flood protection dams. The inconvenient truth is that the on farm storage - while it may work in the right terrain, is very limited.

The cumulative effects on the environment cannot be as well controlled, it has a greater environment footprint, will require a far greater water take which is counter productive, and is far more costly.

What responsible council would want to go down that path?

- Christine Scott is deputy chair of the Hawke's Bay Regional Council.

- Views expressed here are the writer's opinion and not the newspaper's. Email: editor@hbtoday.co.nz