ie: “If the population continues to grow at ___ rate per year in ______country, then purified water needs will increase to a level of _____. ”

or maybe

“If purified water needs increase to a level of_____, then ______ country (or state, city, town) will need to add____ purification plants.”

Just an idea to get you thinking.

If we continue to produce as much excess packaging for consumer products as we do today without an increased recycling effort, the Earth will be covered in a thin layer of milk cartons, plastic wrap and small cardboard boxes in a few years.

If we continue to use potable water as a society at the present rate, those sources will be diminished if not extinguised for our grandchildren.

etc…