the monsoons that fed the rivers further diminished the Hakra dried-up some 4,000 years ago, becoming an intermittent river, and the urban Harappan civilisation declined, becoming localized in smaller agricultural communities. Identification of a mighty physical Rigvedic Sarasvati with the Ghaggar-Hakra system is therefore problematic, since the Gagghar-Hakra had dried-up well before the time of the composition of the Rigveda. In the words of Wilke and Moebus, the Sarasvati had been reduced to a "small, sorry trickle in the desert", by the time that the Vedic people migrated into north-west India. Rigvedic references to a physical river also indicate that the Sarasvati "had already lost its main source of water supply and must have ended in a terminal lake (samudra) approximately 3000 years ago," "depicting the present-day situation, with the Sarasvatī having lost most of its water." Rigvedic descriptions of the Sarasvati also do not fit the actual course of the Gagghar-Hakra. "Sarasvati" has also been identified with the Helmand or Haraxvati river in southern Afghanistan, the name of which may have been reused in its Sanskrit form as the name of the Ghaggar-Hakra river, after the Vedic tribes moved to the Punjab. Sarasvati of the Rigveda may also refer to two distinct rivers, with the family books referring to the Helmand River, and the more recent 10th mandala referring to the Ghaggar-Hakra. The identification with the Ghaggar-Hakra system took on new significance in the early 21st century, with some suggesting an earlier dating of the Rigveda; renaming the Indus Valley Civilisation as the "Sarasvati culture", the "Sarasvati Civilization", the "Indus-Sarasvati Civilization" or the "Sindhu-Sarasvati Civilization," suggesting that the Indus Valley and Vedic cultures can be equated; and rejecting the Indo-Aryan migrations theory, which postulates an extended period of migrations of Indo-European speaking people into South Asia between ca. 1900 and 1400 BCE. Etymology is the feminine nominative singular form of the adjective (which occurs in the Rigveda as the name of the keeper of the celestial waters), derived from ‘sáras’ + ‘vat’, meaning ‘having sáras-’. Sanskrit means ‘lake, pond’ (cf. the derivative ‘lake bird = Sarus crane’). Mayrhofer considers unlikely a connection with the root * ‘run, flow’ but does agree that it could have been a river that connected many lakes due to its abundant volumes of water-flow. may be a cognate of Avestan Haraxvatī, perhaps originally referring to Arədvī Sūrā Anāhitā (modern Ardwisur Anahid), the Zoroastrian mythological