Kusaha, where the breach in the Kosi River embankment took place on 18 August 2008, is said to be a diminutive form of Kaushik Ashram, the home of the Rishi Vishvamitra, believed to be the author of the Rig Veda, one of holiest books of the Hindus. There are a few other villages in the area named Kusaha as well, and in all likelihood the sage could have lived in any of those, too. According to Hindu mythology, Kaushiki, or the River Kosi as it is called today, is Vishvamitra's elder sister. Let us look more closely at some of the stories and legends from this part of Southasia.
One story is about an eminent ascetic named Richeek, of Rishi Bhrigu's lineage, who was given to deep meditation. One day, he went to the palace of King Gaadhi, son of King Kaushika, and asked for the hand of his daughter, Satyavati. Gaadhi was a royal and Richeek an indigent Brahmin, and hence the king turned down the proposal. But as Richeek was leaving, the king, making what he believed to be an impossible demand, told Richeek that if he could present him with a thousand horses, as fair as the moon, as swift as the wind and each with one dark ear, then he would accept the proposal. Richeek proceeded to beseech the god Varun for the horses, which the latter made available through the River Ganga. Legend has it that it was at Asvatirtha, near Kannauj in Uttar Paradesh, on the banks of the Ganga, where the river delivered the horses. Richeek went to the king with the thousand horses, and the king dutifully allowed his daughter Satyavati to marry the poor, aged ascetic.
Male progeny of Kaushik are known as Kaushik, while females are known as Kaushiki. As such, Satyavati was called Kaushiki and Visvamitra was called Kaushik, and thus Kaushiki was the elder sister of Visvamitra. When she died, Satyavati is said to have taken on the form of the River Kaushiki. Years later, when Vishvamitra was moving from Ayodhya towards Sonebhadra (the Sone River) with Ram and Lakshman, he acquainted the two princes with his elder sister. The verses relating to this episode appear in Valmiki's Ramayana. In the Bal Kaand section (Verse 34), the episode is narrated as follows:
O Raghava, I had an elder sister who was eminently virtuous. She was called Satyavati. She had been married to the sage Richeek.
Entirely devoted to her spouse, Satyavati's body departed to the heavens. But on Earth, she began to flow in the form of the munificent River Kaushiki.
It is for the good of the world that this sister of mine flowed in the form of a river from her refuge in the Himalaya. It is indeed a charming river of divinely holy waters.
O Raghunandan, I have great affection for my sister Kaushiki, and hence I dwell regularly and ever so happily on her bank itself, close to the Himalaya.
The virtuous Satyavati is renowned as the dutiful. That extremely fortunate and pious lady is present here in the form of the glorious River Kaushiki.
O Ram, I had come away from my sister to Siddh Ashram in order to perfect the true mode of sacrificial worship. Now I have attained that perfection by the virtue of your splendour.