As per legend, once there lived a holy person who was the grandson of Lord Brahma, and his name was Gadhi, and he had a beautiful daughter Satyavathi.
On hearing the beauty of the pious woman Satyavathi, sage Richika approached Gadhi to arrange marriage for him with his daughter Satyavathi. Richika also donated lot of horses to Gadhi, and married Satyavathi.
Through his spiritual powers, Richika blessed his wife and his mother in law, to give birth to a noble child, and gave a bowl of milk to both of them, after chanting the divine mantras. After some time, Satyavathi gave birth to Jamadagni, and his son was Lord Parashurama, and her mother gave birth to Vishwamitra, a great sage, who was the king of Kusha, and hence he was called as Kaushika and his sister was called as Kaushiki.
After the death of her husband Richika, Satyavathi turned into a holy river called as Kaushiki, and the holy river can be found at Nepal. As per legend, Sage Viswamitra was very much attached with his sister Kaushiki, and he had performed meditation on the banks of River Kaushiki.
Most of the ancient holy women are becoming either holy rivers or as divine stars, and blesses the human beings and gives them prosperity through their divine powers.
Yamuna and Tapti are the daughters of Lord Surya, and they have become worshipful River goddesses and they came to the earth in order to remove the sins of the human beings. All the river goddesses are controlled by Lord Varuna, the ocean god. The river goddesses are worshipful deities and they contain the features of Ma Parvati. But most of the rivers are getting polluted day by day, due to the garbage thrown by the people in the holy rivers. Let us pray to Lord Shiva, and let us take efforts to maintain cleanliness in the Holy Rivers, and be blessed.