Thursday, 21 January 2016 10:26

Water options for a dry future

Written by  Nick Meeten
Years of drought are having a major impact on the Californian wine industry. Years of drought are having a major impact on the Californian wine industry.

As we enjoy the warmth of spring, wine growers everywhere will be turning their thoughts towards the growing season, and water availability will surely be high on the discussion list.

Nature can be a fickle beast, and in Marlborough and Waipara the drought from last summer has not receded, so these regions are already starting this growing season on the back foot. Adding to the gloomy picture is the threat of El Ninõ conditions possibly taking hold. If this occurs, the next few years could be extremely dry, especially in our wine growing regions. However planning now so you have a Plan A' a 'Plan B' and maybe even a 'Plan C' for your water needs to deal with these variable conditions could allow you to manage your water risks with confidence and provide you with more certainty. Something that customers, insurers and bankers would also be happy to hear.

There are a variety of options available. Some people are building storage dams to grab rainfall when it occurs and store it to provide some water supply security. Others may keep their fingers crossed that nature will be kind and natural supplies will be sufficient. If not, their 'Plan B' might be to resort to thinning vines and accepting reduced yields. There is also investment into more efficient irrigation systems to make each drop of water go further.

We are however not alone in facing these challenges. In fact some others have it much worse than us. California is grappling with crippling drought, dropping ground water supplies and snow pack levels in the Rockies (which provide a big proportion of their annual water supplies) at only 25% of normal. Their 'Plan A' is gone and water shortages are forcing major and rapid changes in almost every part of the State, including the famous wine producing regions.

There is no such thing as bad water. Water can come in many different qualities and we should be judging water only on its quality, not on its history. We should be asking what quality of water is necessary for the particular usage in mind. A perfect example here is what quality of water is necessary for flushing our toilets? Most would agree that this task does not require drinking quality water. However drinking water, whilst good enough for us to consume, is not nearly high enough quality for the makers of computer silicon chips.

So what quality of water is needed by a grape vine? Where is the lowest threshold, at which point a grower, who's 'Plan A' hasn't worked and maybe 'Plan B' is also not working, would choose to reject a water source as being too low quality and instead accept stressed vines and lower yields?

One of the solutions being adopted by wineries in California's Napa and Sonoma Valleys is using recycled water. This is water which has been used before, but is then cleaned up to a high enough quality and reused for vine irrigation. The source of this used water is municipal wastewater. It's a "new normal in the wine industry," according to the Santa Rose Press Democrat[1].

Recycled water is a resource which sometimes unfortunately faces a prejudiced audience. The irony is that every drop of water on the globe is recycled water. The volume of water on our earth has more or less been the same since the beginning of time. A portion circulates around in the natural hydrological cycle. This cycle has also been going on since the beginning of time, and every drop of water has probably been through the cycle a number of times. So every drop of water on the planet has been used before, maybe in a piece of food consumed by a dinosaur, maybe in a glass of wine consumed by an ancient Greek soldier, maybe in a cell of Tutankhamun's body. It's all recycled water, and since every human being consists of about 75% water, we all mostly consist of recycled water.

In Marlborough there is around 15 million litres of used, but then cleaned again, water coming out of the Blenheim treatment station every day. Currently this is water discharged into the ocean.

This water source is reliable. It's available every day, come rain or shine. It will also be available during droughts.

What quality is this water? Remember this is water which has been through a robust treatment process to clean it and improve its quality. It's not drinkable but for other uses it could be quite appropriate. It still contains low levels of organics and nutrients etc, however according to the World Health Organisation these can be beneficial for agricultural irrigation uses [2].

Back in California, a Napa vineyard that used recycled water was studied by a group of seven university researchers [3]. They surmised that using recycled water is suitable for irrigation of vineyards over the long term. There was no indication that salinity, sodacity or specific ions would limit its use, and nutrients in the recycled water may be beneficial to vineyards, though the levels of nitrogen may be in excess of what's needed and need to be managed accordingly.

Recycled water can also contain bacteria and viruses. The risks associated with these can be managed using disinfection, drip irrigation systems, timing the application of the water to utilise the natural disinfection properties of the sun, providing intervals between the use of recycled water etc. All do-able stuff.

Would recycled water affect irrigation systems? Stephen Leitch from Southern Water Engineering advises that so long as the water is filtered with 130 micron filters (which is standard practice for irrigation systems), blocking of driplines should not be a threat.

New Zealand currently does not have standards for recycled water quality, but others do. California's recycled water regulations (Title 22) are used as the industry standard in many other US states as well as other countries in the world. In these regulations, the required quality of recycled water for use in "Vineyards with no contact between edible portion and recycled water" is "Undisinfected Secondary Recycled Water". In Blenheim the treated water should meet this level straight away, but maybe that's not good enough for some.

Winemakers routinely use their skills to blend different grape varieties together to produce a desired product. This same thinking could be applied to water to blend different qualities of water together. Blending recycled water with higher quality water from a different source (e.g ground water or dam water) would reduce the contaminants within the recycled water by dilution, but still provide more overall water to go around. A 50/50 blend equals half the contamination levels but twice as much water. Would water at this quality be above or below the acceptable threshold?

Now is the time to plan for drought, and it's nonsensical to be throwing millions of litres every day of good quality irrigation water into the ocean. We have already fielded the first enquiries in Marlborough from growers thinking about their Plan B. Ask yourself where your threshold is.

 

References:

[1] http://www.pressdemocrat.com/business/2562360-181/drought-fears-in-wine-country?page=1 

[2] http://www.who.int/water_sanitation_health/wastewater/wastewateruse2/en/ 

[3] http://californiaagriculture.ucanr.org/landingpage.cfm?articleid=ca.v068n03p59&fulltext=yes 

Nick Meeten is a consultant with Smart Alliances in Blenheim, working in the areas of Buildings, Water and Sustainability.

He returned to New Zealand in January 2015 after 5 years living in Germany and working globally leading the Green Buildings team at water technology supplier HUBER.

He is a professional member of the Institute of Professional Engineers of New Zealand. [email protected] co.nz  

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