Impact of middle route S-N water transfer project on “algae bloom” in middle & lower reach of Hanjiang river

The ultimate reason for the appearance of “algae bloom” in middle lower reach of Hanjiang river is serious water pollution and excessive high concentration of nitrogen and phosphorus pollutants. In spring, when the low water flow is under a certain value, the river in lower reach, flowing slowly, turns into a “long narrow lake”. When air temperature rises, algae propagate rapidly and the phenomenon of “algae bloom” appears. Numerical simulation result obtained by WQRPSQ model indicates that after the completion of middle route project of S N Water transfer, under the scheme of transferring 8.2 billion m\+3 of water and without water supplement for Hanjiang river from the Yangtze, as the reservoir regulation causes the increment of spring discharge, the years meeting the hydrological condition of “algae bloom” appearance will not increase. Water transfer imposes little influence on the duration of “algae bloom” appearing in lower reach of Hanjiang river. Under other water transfer schemes, due to the implementation of “diverting water from the Yangtze to Hanjiang river” project, the present “algae bloom” phenomenon will be controlled basically.