In this July 18, 2019, photo, retired Indian civil servant R. Devarajan with his wife Padmini sit at the terrace of their house equipped with rain water harvesting system in Chennai, India. For Devarajan and Padmini, Chennai's acute water shortage has reinforced the wisdom of their decision years ago to install a rainwater harvesting system in their three-story home. (AP Photo/Manish Swarup)