Albuquerque, New Mexico is hot and dry. Consequently, water conservation is a hot topic down there. I did this for Alibi magazine for an article about how their underperforming surface water treatment plant (see the Colorado River and the actual treatment plant in the background) means they are pumping their aquifer for more water than planned.
So I naturally went with dippy birds. Conceptually it has to do with how dippy birds consume water at a regular pace and the water treatment plant can't keep up with that pace, much like how the water treatment plant in the news article can't produce enough water to provide for Albuquerque's rate of consumption. I also used dippy birds because they are adorable.
My other idea was using an hourglass image, where the water treatment plant is at the top and the water is very slowly dripping down into the bottom bulb. I liked it because hourglasses are usually filled with sand and the water treatment plant is filtering out that sand, but I didn't think it made an interesting visual and it didn't work well for the square dimensions for the job. The water drop that's falling has the water treatment plant logo in it! But the sketch just didn't do it for me :P.