Predicting annual rainfall for hydro lakes

Predicting rainfall

Imagine if we could forecast how much rain was going to fall in New Zealand year by year.

That would enable us to prepare for dry years, control hydro lake levels more effectively and assist farmers with planning.

With assistance from Meridian Energy, Associate Professor Earl Bardsley and PhD student Varvara Vetrova are studying winds and water temperatures in the Pacific Ocean and how they influence rainfall in the South Island's southern lakes.

"If we can work out how different wind patterns and ocean circulation influence rainfall we will be able to develop statistical models to predict river inflows to the main hydrostorage lakes in the Waitaki hydro-scheme," says Dr Bardsley.

The researchers are testing different environmental variables such as sea surface temperatures and pressures and studying historical data to run a series of analytical tests over different seasons and measuring them against existing data in the Waitaki region. Preliminary results of this work were presented in December 2013 to an International Congress on Modelling and Simulation, in Adelaide, Australia. 

To protect our southern lakes from seasonal erosion, Dr Bardsley proposes that instead of using lakes for hydro storage, we should pump water up into a high storage basin when it's plentiful – namely the natural rock basin of Lake Onslow in Central Otago. This would also provide grid buffer as we move toward renewable energy with fluctuating power output. 

"The Onslow Basin is a gift of nature and has the capacity to be the largest energy store in the world," says Dr Bardsley.

He is simulating energy systems incorporating the Onslow scheme with PhD student Mohamed Majeed, who presented a paper on the economic value of the scheme to the 2014 New Zealand Electricity Engineers Association conference.