The New Situation of Diatom Bloom in the Middle and Lower Reaches of Hanjiang River under River Chief System

Abstract. In the middle and lower reaches of the Hanjiang River in February 2018, another serious diatom bloom occurred. The Changjiang Water Resources Commission promptly initiated an emergency plan to use the cascade reservoirs at the middle and lower reaches of the Hanjiang River to carry out water scheduling. At the same time, six monitoring sections were set up to daily monitor in the middle and lower reaches of the Hanjiang River. From 9 February to 18 March, this bloom had lasted more than 30 d. It is the longest since the record was recorded. The emergency dispatch measures adopted during the outbreak of the diatom bloom have stopped the further development of diatom bloom and played a good role. Analysing the causes of diatom bloom can provide a more comprehensive basis for further optimizing emergency dispatch. This paper analyzes the key hydrological factors that occur in this diatom bloom and proposes a water dispatching optimization plan and specific countermeasures. However, to permanently solve the diatom bloom problem, it is necessary for local environmental protection departments to work actively under the current requirements of the river chief system. Comprehensive protection of the Hanjiang River water ecological environment, completely solve the watershed problem of non-point source pollution.