Has Government Water Protection Policy Taken Effect on Preventing Harmful Algal Blooms in Erhai Lake?

As the second largest freshwater lake in Yunnan Province of China, Erhai Lake has suffered harmful algal blooms (HABs) since 1996. In January 2017, Dali government issued a series of ecological protection measures to prevent the outbreak of HABs. In order to evaluate the effectiveness of those protection measures, we studied the spatiotemporal distribution of HABs in Erhai Lake by using multi-source remote sensing data during 2016-2018. The results demonstrate that coverage area and frequency of HABs occurrence were decreasing after January 2017, which indicates a good respond to water protection regulations. However, in 2018, HABs still occurred around residential and tourist area. Furthermore, drastic measures also impeded local economic development due to shuttering businesses and banning farming around lake. Therefore, there is still a long way to go for local government to achieve long-term goals of sustainable economy and water environment stability of Erhai region.

1. INTRODUCTION

Freshwater lakes play an important role for human use and provide wildlife habitats for aquatic fauna and flora [1]. As the second largest freshwater lake in Yunnan province of China, Erhai Lake is the indispensable water resource in Dali city [2]. Nevertheless, with the rapid development of economy, the problem of water eutrophication in Erhai Lake has become increasingly serious in recent decades [3]. In 1996, 2003 and 2013, large-scale HABs occurred in Erhai Lake [4]. HABs is the most intuitive and prominent problems caused by water eutrophication, which will aggravate the deterioration of water quality, damage the normal life [5]. Therefore, it is imperative to control the water environment and eventually influence the people’s outbreaks of HABs in Erhai Lake. Fortunately, since January 2017, a series of drastic water protection measures have been adopted by local government to prevent, suppress and mitigate HABs of the Erhai Lake, such as abating nonpoint source pollution, accelerating sewage interception and treatment project, enhancing supervision of drainage basin pollution and so on.