Renewable water – The next ‘big thing’

By CHRIS MILLS | 8 October 2018

When cattle and sheep are dying in vast numbers across Eastern Australia, how sane is it for the driest inhabited continent in the world not to capture and redirect wastewater and stormwater from our cities and towns into food and beverage production? Energy is a major component of the cost of treating and moving water. Renewable energy sources can become an essential component of responding to the effects of climate change and climbing temperatures

Fortunately, there are some very bright and committed minds working on this issue, especially in our state and territory water supply agencies.

In Western Australia, it seems that necessity has become the mother of invention. Perth relies in part on drawing groundwater from aquifers beneath the city, but as the water level dropped precipitously, the decision was taken to replenish ground water by using the outflow from an advanced water recycling plant. There are substantial rewards from water harvesting and recycling; this project will eventually return 28 billion litres of water a year to the aquifer. Here is some information on how Perth’s groundwater replenishment works.

Other States are doing some fine work on recycling waste and storm water and using it to enhance the environment and replenish reserves. Sydney Water  is an example. There are many large cities and towns in the areas currently ravaged by drought where harvested and recycled water could be diverted for agricultural use.

Australia is sometimes called ‘The Lucky Country’. In many areas across the nation, the way to create a paradise of production is “just add water”. An aerial view of Griffith in the centre of the Murrumbidgee Irrigation Area reveals that it is an inland sea of highly productive crops. However, as the climate dries, Australia must find new ways of delivering water for this irrigation.

Converting a liability into an asset is one way of producing new resources at low cost. Australians are reluctant to let their water treatment authorities recycle waste water back into the mains supply – this psychological resistance is often called the ‘yuk’ factor. Treated waste water is sometimes dumped, even though it is perfectly safe to drink. This water has consequently been preserved for other uses and if it is safe for humans to drink, then it is safe to provide this water for animals and irrigation.

Moving large volumes over long distances can be expensive as energy is required to overcome the friction of flow. Renewable energy can be applied to solve this problem. Wind and solar generators are ideally located near power transmission lines to reduce the cost of installation. This restriction need not be the case where wind and solar generators provide the energy for pumping water – the power stations are purpose-built to provide the energy for pumps in remote locations. When the wind is blowing, and/or the sun is shining, the water flows. When it is not, well placed reservoirs provide water from the cost-free force of gravity.

Does stock-feed irrigation work in times of drought? I have some personal experience here, albeit from about sixty years ago, so some of the finer details are sketchy. A large water-main ran though my father’s farm, built in 1949 by World War II refugees. He obtained permission to tap the pipeline to irrigate a hectare of lucerne, and as the water-main flowed up some 200 metres to a reservoir, the water pressure was about 25 atmospheres. No need for pumps – just turn on the tap.

After an irrigation pipeline was laid, my job was to move the sprinklers every second day. While the water was running, I would mow the fully-grown lucerne, rake it up and take it to the eagerly waiting sheep. Strip watering provided continuous food production. In a hot summer, my experience suggests that it takes about 100 square metres of irrigated lucerne pasture to keep a sheep in top condition.

In the future, renewable energy generation will expand, and there will be many days when the wind blows and the sun shines, creating surplus energy. Rather than slowing wind-farm generation, this surplus can be productively used to move water across a smart water management network. Energy sinks can include pumped-hydro and irrigation reservoir storage. A super-smart power and water network could include dual-use pumped-hydro and irrigation reservoirs. Sprinklers and drip-lines could be instructed by the Internet-of-Things to turn on and draw surplus renewable energy for agriculture production.

Renewable water systems can convert ‘White Elephants’ into ‘Gold Elephants’. Some states, such as Victoria, have installed large seawater desalination plants. While the Wonthaggi plant is effective at producing large quantities of potable water – about a third of Melbourne’s requirement – the 90 Megawatts of power consumption is expensive and polluting if sourced from coal-fired generators. Dedicated renewable energy generators or surplus renewable energy could reduce this cost, with desalination occurring when environmental conditions are favourable. There are several other Australian desalination plants. Wastewater and stormwater recycling also uses reverse-osmosis to purify water but requires less energy and is an ideal water source for agricultural irrigation.

As the climate warms, some agricultural production such as vineyards can move south to Tasmania. However, there is no possibility of moving substantial areas of livestock and orchard production south – there is not enough land.

The solution is to move water to existing agriculture land by installing smart renewable energy powered irrigation systems, harvesting waste and storm water from our cities and towns and delivering this water to make farms and orchards productive and reliable suppliers.

Investment in a renewable water supply is a strategic decision. As China imports more Australian safe food and beverages in ever greater quantities, we must ensure that we are a reliable supplier. There will still be good years and dry years, but as our food production plains become warmer, the inexorable shift will be to less reliable production if we don’t drought-proof the land. In a continent that is ‘girt by sea’ and with boundless insolation, we will become increasingly reliant on the sea to water our cities and agriculture.

POSTSCRIPT: Availability of water is one of the prerequisites for a much-needed decentralisation plan.

(Chris Mills is a MSc in Systems Management and is a systems designer and builder. This article first appeared in Pearls and Irritations.)