"In contrast, changes taking place in the Saraswati Valley in the early second millennium were probably a major contributor to the Indus decline. In Harappan times, the Saraswati was a major river system flowing from the Siwaliks at least to Bahawalpur, where it probably ended in a substantial inland delta. The ancient Saraswati River was fed by a series of small rivers that rose in the Siwaliks, but it drew the greater part of its waters from two much larger rivers rising high in the Himalayas: the Sutlej and the Yamuna. In its heyday the Saraswati appears to have supported the densest settlement and provided the greatest arable yields of any part of the Indus realms. The Yamuna, which supplied most of the water flowing in the Drishadvati, a major tributary of the Saraswati, changed its course, probably early in the second millennium, to flow into the Ganges drainage. The remaining flow in the Drishadvati became small and seasonal: Late Harappan sites in Bahawalpur are concentrated in the portion of the Sarawati east of Yazman, which was fed by the Sutlej. At a later date the Sutlej also changed its course and was captured by the Indus. These changes brought about massive depopulation of the Saraswati Valley, which by the end of the millennium was described as a place of potsherds and ruin mounds whose inhabitants had gone away. At the same time new settlements appeared in the regions to the south and east, in the upper Ganges-Yamuna doab. Some were located on the palaeochannels that mark the eastward shift of the Yamuna. Presumably many of the Late Harappan settlers had originated in the Saraswati Valley."