20 slides, may be of interest for classes you're teaching:
http://www.waquarium.org/_library/documents/water-disaster.pdfAlso available online as a Powerpoint slide show at http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=5&ved=0CEEQFjAE&url=http%3A%2F%2Fwww.surferswithoutborders.org%2FWater_Bottle_files%2Fwater-disaster.pps&ei=UHGBUuXOIsvOkQfRooCYDQ&usg=AFQjCNEx1aXFGcXDxU6tgGYMmlnF1_NvOw&bvm=bv.56146854,d.eW0
