This is a much better reference. CDM Smith is the #22 on the top 500 design firms by ENR (Engineering News Record).  This is the foremost trade publication in the civil engineering world (note that water resources/managment falls under Civil Engineering)

http://enr.construction.com/toplists/designfirms/001-100.asp

Not sure if anyone else is as in-tune with the engineering world as I am but the names listed above them are very big players in the international engineering design world.  Several of the firms are publicly traded companies.