(IMAGE) Science China Press Caption Low concentrations were found in the Qinghai-Tibetan Plateau, and then nutrients increase in the river at 3500 km-3000 km upstream the river mouth and further downwards to the river mouth. Vertical arrows show the confluence of major tributaries, and horizontal arrow indicates the location of the Three Gorges Reservoir. Credit ©Science China Press Usage Restrictions Use with credit. License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.