Karatoya River (also spelt Korotoa River) is a small stream in Rajshahi Division of Bangladesh, which was once a large and sacred river. A channel of it presently flows by the ancient ruins of Mahasthangarh (or Pundranagara, ancient capital of Pundravardhana) in Bogra District. The Karatoya mahatmya bears testimony to its past greatness. In the Mahabharata it is mentioned that a visit to the Karatoya after three days’ fast produces the same merit as an aswamedha (horse killing) sacrifice. Another ancient city, Sravasti, may have been located on the banks of the Karatoya, north of Mahasthangarh. However, there is a controversy about the possible location of Sravasti.
The Karatoya, known as Phuljhur rises in the Baikunthapur jungles in the extreme north-west of Jalpaiguri district (West Bengal, India) and forms for some distance the boundary between Dinajpur and Rangpur districts. It, then, meanders through Rangpur and Bogura. In the south of Bogura district, it receives the Halhalia and the united stream is then known as Phuljhur. It leaves Bogura at Chanda kona and flowing in a southerly direction past Raiganj and Shujapur is joined by the Ichhamati at Nalka. The Phuljhur then flows south past the important village of Ullapara, a few miles below which it joins the Hurasagar at Narnia after a course of about 64 kilometres (40 mi) in this district. After this junction, it takes the name of Hurasagar and passing close by Shazadpur and Hera joins the Jamuna near Bera.
The Karatoya is mentioned in the Puranas and had a high repute for sanctity. It was the eastern boundary of the old kingdom of Paundravardhana, the country of the Paundras which it separated from Kamrupa. It is shown in Van Den Brouk’s map of Bengal (C, 1660) as flowing into the Ganges and in fact. before the destructive floods of 1787 it brought down to the Atrai and to the Ganges a great volume of Teesta water. Since the main stream of the Teesta was diverted to the east in 1787, the Karatoya and the Phuljhur have gradually silted up. and they are at the present day rivers of minor importance. One channel, which joins the Baral, 48 kilometres (30 mi) east of Pabna. is still called indifferently the Buri Teesta or old Teesta and the Karto or Karatoya. Traces of an old channel, for which the name of the Karatoya is claimed, are also pointed out in the Chatmohar thana, where it appears to have been obliterated by the Baral.
The name of the river is formed of two Sanskrit words kar (hand) and toa (water), signifying, in Hindu mythology, that the river was formed by the water which was poured on the hands of Shiva, when he married Parvati.
Great changes have taken place in the course of some of the rivers in Bengal and the adjoining areas, during the period since 1500 AD. Although positive evidence is lacking, similar changes can be assumed in the remoter past. The Karatoya is one of the rivers that has changed over the years.
The map (right) shows the main rivers in North Bengal and adjoining areas. Not shown are numerous tributaries and distributaries, which connect the main rivers, and allow the main rivers to change course. Therefore, the river-system pattern undergoes continuous changes. Such changes have not been reflected in the map. Moreover, many of the rivers have local names for sections of the course, adding to the complexity of the river system.
Tectonic disturbances have broken up the Karatoya into four distinct parts. The northern part, called the Dinajpur-Karatoya, is the main source of the Atrai. It rises in a marsh in Baikanthapur in Jalpaiguri district, but also receives water from underground streams. In Khansamaupazila its name changes to Atrai. Near Birpur Upazila, Bangladesh (25°54’02.0″N 88°43’32.6″E) its divided into Dhepa River and Atrai River. In a second section, the Dinajpur-Karatoya was connected with the Rangpur-Karatoya north of Khansama, but very little water now passes down that channel. The upper part of Rangpur-Karatoya originates in the Jalpaiguri district and is known as the Deonai-Jamuneshwari up to Gobindaganj upazila. In a third section, the Jamuneshwari-Karatoya flows south-southeast to Gobindaganj upazila, where the main stream turns east through the Katakhali and falls into the Bangali River. The portion of the former river passing through Shibganj upazila is dry most of the year. It effectively separates the Rangpur-Karatoya from the Bogra-Karatoya, which flows south past Bogra town till it joins the Bangali to make Phuljhor river, which falls into the Hoorasagar. The fourth part, the Pabna-Karatoya, is a moribund river bed near Handial. Various other channels are also pointed out as parts of the Old Karatoya.