''In the future, wars will be fought over water, not oil,'' Mr Wills said.
He was invited to attend the prestigious World Water Week conference in Stockholm, Sweden, last month, which was organised by the Stockholm International Water Institute with the theme, ''Water Co-operation - Building Partnerships''. He attended as a member of the World Farmers' Organisation (WFO) - the first time the WFO had been at the event - and took part in a panel discussion.
He said about 2700 people attended and the printed programme ran to 140 pages.
Many government-funded and United Nations organisations were represented as well as major companies such as Shell, Coca-Cola and Pepsi Cola.
The conference made him appreciate even more New Zealand's privileged position with water resources.
He said despite agriculture using 70% of the world's water, he was the only farmer to be invited to take part in the programme in the 23 years the conference has been held.
''When I made mention that I was a farmer it generated some excitement,'' Mr Wills said.
He said the conference looked at water issues on a global scale rather than by country.
''The United Nations' figures surrounding water usage say that 70% of [the world's] water used is for agriculture, 20% for industry and 10% for households and that is quite extraordinary.
''The UN said 90% of the world's power production is water-intensive.''
He said by 2035 the UN estimates there would be a 50% increase in power production and water withdrawals were expected to increase by 50% by 2025 by developing countries and by 18% in developed countries.
He said in addition there would be a 70% increase in food demand by 2025, and meeting that need was a huge challenge.
''Where was the water going to come from?''Without question the farmers using 70% of the world's water have to be part of the solution.''
He said many countries struggled with the lack of water and it was only going to get worse unless measures were put in place.
''I got a real appreciation of so many issues that we [New Zealand] don't generally think about.
''We need to recognise that we are in a very privileged position with water.''
He was interested in trans-boundary issues, in which a river, such as the Nile, flowed through several countries, and what happened at the beginning of the river such as dams or pollution, could hugely impact on the countries further downstream.
''Those countries relied on international negotiation, which we don't think about in New Zealand.
''It does put things in perspective for us. What I took away from the week was what a lucky country we are when it comes to water.
''We are not confronted by many of those issues.
''But that did not mean being wasteful or dropping our standards.
''We farmers still have got to do our best with water management.
''We still need to use our water more efficiently.''
The conference produced the 2013 Stockholm Statement, which outlined sustainable development goals for water.
''We need to look at what we can do to assist [to meet those goals].
''Some of those issues are not going to be solved in a hurry.
''We are a virtual exporter of water and while our dairy and meat production is water-intensive many countries can't even think about producing those because they don't have the water.''
He said New Zealand had the potential to produce more energy as well.
''About 90% of our water is let run away unused so we need to build more dams and more irrigation.''
He said with the global food security issues there was a lot of interest in New Zealand.
''The rest of the world is looking at New Zealand and saying those guys are in a good spot
''In future, wars will be fought over water, not oil.
''In comparison with the rest of the world, we are in such a privileged position, but that is no excuse not to do better.'
2013 STOCKHOLM STATEMENT
The World Water Week conference attendees put together the week's annual Stockholm Statement.
By 2030 the following should have been achieved:
1. A doubling of global water productivity. Bruce Wills gave, as an example, New Zealand's move from border dyke irrigation to spray irrigation, which means increased production.
2. A realisation of the human right to safe drinking water and sanitation.
3. Increased resilience to water-related disasters, such as flood and drought.