"Water is an increasingly valuable and scarce resource and is becoming as important an issue as carbon," he told delegates at last week's LEAF President's Event. "We will find it harder and harder to defend irrigation systems that spray water up in the air."
He described LEAF as "a great example of how the industry can take responsibility for its own future - and water is central to that".
Former MP Michael Jack, food and agriculture adviser to HSBC and a member of water regulator OfWat's advisory panel, echoed the importance of careful water management.
"However you get your water, whether from abstraction or down a pipe, we can say for sure that it's going to cost more," he said.
Agricultural consultant Louise Manning, who helped develop the tool with 36 farmers and growers, said: "Individual businesses need to focus on their water footprint.
It's about both using water wisely and minimising the impact on your surroundings. We now want 'water champions'
- although some will want to do it quietly on their own," she added.
The online application is free to LEAF members, otherwise it costs £70 +VAT.