From Fortune Brainstorm Green to SXSW Eco and beyond, Will Sarni is one of world’s most sought-after speakers on global water and sustainability issues — and with good reason. Author of Corporate Water Strategies and Water Tech: A Guide to Investment, Innovation and Business Opportunities in the Water Sector and director and practice leader for enterprise water strategy with Deloitte Consulting LLP, he advises some of the world’s leading companies on water-related risks looming over business and industry. Ensia caught up with Sarni at his home base in Denver.