You're mentioning heavy industry, so in addition to already mentioned climate control a very strong and useful function of waterfalls would be

Reducing pollution

Tiny water droplets that are included in a mist are capable of capturing and holding dust and pollution fine particles. Then being heavy they fall down on earth and are eventually washed to sewer system. As the droplets small enough are not that easy to distribute over the city, as the city grows the mist generators (namely waterfalls) are added.

In modern times China uses this technique, however instead of waterfalls they have special mist cannons.

The mist cannon, which is not well-known but gaining popularity, is a large machine mounted on a truck that sprays water mist. (...)

 

"The truck works by nebulizing water into tiny particles, with diameters in microns, the same as PM2.5 and PM10, and spraying them into the air, and then they could combine with the dust and fine particles to fall to the ground," Xu said. (...)

 

According to tests conducted by researchers with the China National Environmental Monitoring Center, the mist cannon and the chemicals¹ can together "cut the PM10 by 20 percent, PM2.5 by 5 percent and nitrogen oxides by 10 percent", according to Xu.

 

There are two trucks covering 35 streets

¹The chemicals are used to capture pollution fallen to streets, mostly from cars.

You're mentioning heavy industry, so in addition to already mentioned climate control a very strong and useful function of waterfalls would be

Reducing pollution

Tiny water droplets that are included in a mist are capable of capturing and holding dust and pollution fine particles. Then being heavy they fall down on earth and are eventually washed to sewer system. As the droplets small enough are not that easy to distribute over the city, as the city grows the mist generators (namely waterfalls) are added.

In modern times China uses this technique, however instead of waterfalls they have special mist cannons.

The mist cannon, which is not well-known but gaining popularity, is a large machine mounted on a truck that sprays water mist. (...)

"The truck works by nebulizing water into tiny particles, with diameters in microns, the same as PM2.5 and PM10, and spraying them into the air, and then they could combine with the dust and fine particles to fall to the ground," Xu said. (...)

According to tests conducted by researchers with the China National Environmental Monitoring Center, the mist cannon and the chemicals¹ can together "cut the PM10 by 20 percent, PM2.5 by 5 percent and nitrogen oxides by 10 percent", according to Xu.

There are two trucks covering 35 streets

¹The chemicals are used to capture pollution fallen to streets, mostly from cars.