He made the remarks in a meeting with Vice-President and head of the Department of Environment Masoumeh Ebtekar on Wednesday evening.
Kawai referred to the Japan prime minister's upcoming visit to Tehran and said that Japan is ready to help Iran to protect its water resources and improve quality of drinking water and implement the national plans Iran adopted to thwart climate change.
He said that Japan is prepared to transfer its experience to Iran to deal with air pollution, climate change and fighting the greenhouse effects.
Katsuyuki visited Tehran at the head of a delegation to prepare the ground for Japan's Prime Minister Shinzo Abe visit to Tehran.
Following the removal of nuclear-related sanctions against Iran in January, Tehran and Tokyo are willing to speed up cooperation, particularly in the oil sector.
On January 22, the Japanese cabinet approved lifting sanctions on Iran, joining the ranks of the world's major economies to normalize trade ties with the Islamic Republic.