The Wikipedia article is very good and tells us that Ganges River Dolphin and its close relative the Indus River Dolphin are essentially identical in appearance, even though they have totally distinct ranges and have not interbred for thousands of years.
The Ganges subspecies can be found in the Ganges River as well as the Brahmaputra, Meghna, Karnaphuli and Sangu river systems of India, Bangladesh, Nepal and Bhutan. Relatively high population densities have been observed near the Vikramshila Gangetic Dolphin Sanctuary in India and in the Sangu River in southern Bangladesh. Very few individuals (perhaps 20) are present in Nepal in the Karnali River. The total population is unknown, but certainly numbers in the hundreds and there are perhaps as many as a few thousand.The ARKive website has a lovely (if short) video of the Susu in action. Their full Ganges River Dolphin page is here.
The IUCN Red List of Endangered Species lists the Ganges and Indus River Dolphins as "Endangered".
And finally (for now), novelist Harold Bergsma recently posted a very nice article on Desicritics.org called River Dolphins and Baoli - The Passing of an Era. Harold writes...
How many of these rare, wonderful creatures are left? I poured over the literature and sadly have to report that only four to six hundred of these blind river dolphins exist in the Indus and that their numbers are diminishing rapidly because of a number of factors. Over fishing, dam construction, navigation projects, pollution, habitat destruction and increasing food needs of a fast growing human population have all but made this animal extinct.Thanks for the article Harold, it was a very nice read. You can read more of Harold's work and find out about his award winning books at HaroldBergsma.com.
In the Ganges this creature is called the Susu. If you are interested you can go online and watch a video of a Susu leaping out of the water and hear its whistle-like call. It is wonderful to see. Only about six hundred of them still exist in an area of heavy human population which uses their fat, you guessed it, for catching catfish. In the Brahmaputra River, scientists estimate that three to four hundred of the Hihu remain. In Nepal, in isolated sections of rivers a few may still exist.