"It's about time and the latest events where many people have become sick are a clear signal that this is nothing we can wait on, rather we must do something quickly," says Thomas Pettersson, a researcher at Chalmers University in Gothenburg.
More than 20,000 people in Östersund and Skellefteå got parasites from drinking water in 2010. Thousands went to the hospital.
Climate change is expected to bring more precipitation to Sweden, which means there can be more damaging runoff in the water supply.
The National Food Agency and the Swedish Water & Wastewater Association says measures should include clearer rules, better water and treatment plants, expanded water protection areas, and increased knowledge about the risks in the towns and cities.