Andrew Curtis: Let ideas flow on managing water

A major blaze was fought near Christchurch during bone-dry conditions last year. Photo / Alan Gibson
A major blaze was fought near Christchurch during bone-dry conditions last year. Photo / Alan Gibson

• Andrew Curtis is chief executive of IrrigationNZ, a national not-for-profit membership organisation for farmers and growers who use irrigation. It carries out training on efficient water use.

As year's went, 2017 was a fairly dramatic one. In February, one of the biggest fires in New Zealand history ignited on the Port Hills amid tinder-dry conditions, causing thousands of residents to be evacuated. In March, the Upper North Island was soaked, Auckland experienced its wettest March day in nearly 60 years, and more than 300 homes were flooded.

July brought flooding to Otago and Canterbury, with snow and strong winds in other areas. The end of the year saw a marked change, with many regions experiencing record low levels of rain in November.

Too much or too little water plagued the country for much of 2017. What's worrying is that forecasts indicate last year was not an exception but a taste of things to come.

According to the Ministry for the Environment many regions, including Auckland, are forecast to experience more frequent droughts, but also more intense rainfall.

Rainfall patterns will also change, for example in much of the Upper North Island spring rainfall will decrease but rainfall at other times of the year may increase.

New Zealand is not short of water. According to Niwa, we receive an average of 550 billion cubic metres of rain each year, or which 80 per cent flows out to sea, supporting river ecosystems along the way.

Another 18 per cent of rainfall evaporates and around 2 per cent is used for irrigation, urban and industrial use.

By 2050 our population is expected to reach 6 million. We'll need to feed more people from the same land area, and supply water and power to new homes and businesses. Reduced rainfall in spring for some areas will affect our ability to produce food during our most critical growing period.

With challenges on the horizon and changes to where, when and how much rain we receive, we need to think today about how we will manage our water resources in times of drought or deluge.

California, with a booming population and scarce water, is at the forefront of innovative water management. Near Bakersfield, 30 square miles (78sq km) of wetland stores underground water and provides a wildlife habitat for native birds.

The site is called the Kern Water Bank. Rainfall, water from rivers carried via aqueducts and flood overflows from the Kern River recharge groundwater supplies through a series of "leaky" ponds.

The recharged groundwater is piped through canals to Bakersfield (population 380,000) and to neighbouring farms to grow crops. The wetland is home to more than 20,000 birds, and endangered species like burrowing owls.

In Europe, where extensive paved areas in cities prevent natural groundwater recharge and create more stormwater runoff, smaller wetlands are also common. The wetlands both recharge underground water and filter pollutants.

The solutions we may need to use could have their origins in the past. During the 1930s drought turned much of Canada's western prairies into a dust bowl. Poor harvests and low grain prices drove farmers off the land or to suicide. Water storage was seen as the way forward.

It took until the 1960s for the Gardiner Dam to be completed. It provides water to 40 per cent of Saskatchewan's population, for irrigation and for hydro electricity generation which powers 100,000 homes.

The dam also provides flood control in times of high flow through the South Saskatchewan River.

The main reservoir and a half dozen satellite lakes fed by canals are home to vacation villages, 12 parks, and three marinas. The fertile surrounding countryside grows peas, grasses and potatoes. The dam is one of 15,000 in Canada. Like New Zealand, much of its power is from hydro generation.

Here in New Zealand we are starting to develop new ways of managing water. A project to recharge groundwater using the same "leaky pond" technology used at the Kern Water Bank has been successfully trialled by farmers near Ashburton, with groundwater levels rising up to 7km away from the pond. Small-scale wetlands are used to absorb stormwater. They have yet to be used on a large scale as part of strategy to recharge groundwater levels.

We use water for drinking, watering gardens, in businesses and industry. This summer, irrigation has helped ensure that you can continue to buy local fruit and vegetables during record-breaking dry weather. Water also provides much of our electricity, and supports river and lake ecosystems.

The first week of 2018 saw campers flooded out, wrecking the plans of many holidaymakers. Meanwhile, a number of areas were still officially in drought.

Water is critical to our nation's wellbeing, yet much of our planning assumes we will get the right amount of water when its required. Maybe it's time we accepted that's not realistic.

We are facing changing times, but we also have a vital opportunity to get it right by developing innovative approaches to manage water which meet our needs for domestic water use, business, food and energy production.

- NZ Herald

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