Press Release

Environmental Group Green Power has published the latest findings of its "Tung Chung River Ecological and Water Quality Survey", which revealed a downward trend in the number of native fish species downstream and in the estuary of Tung Chung River. Furthermore, the assessment found that ongoing pollution from brownfields and rural development in the lower Tung Chung River region is continuing to degrade water quality. If pollution sources are not effectively intercepted, they will impact the future conservation efforts of Tung Chung River by the authorities. Green Power has also urged the authorities to follow the practices of mainland China and foreign countries in establishing water quality indicators based on the conservation of local aquatic species as soon as possible, so that the impact of water quality on river organisms can be effectively monitored.

Signs of Decline in Fish Diversity

Tung Chung River is one of Hong Kong's few remaining large natural rivers, and its natural landscape from its source to its estuary and bay has been largely preserved. With its rich biodiversity and having the second richest fish biodiversity in Hong Kong, the two stretches of Tung Chung River have even been designated as Ecologically Important Streams. The Rice Fish (Oryzias curvinotus) and Glass Goby (Gobiopterus macrolepis) are among the variety of native and rare fish species that these stretches harbour.

Tung Chung River's main stem, which originates from Lantau Peak, is known as the "West Stream"; while the other that originates from Sunset Peak is known as the "East Stream". Since 2018, Green Power has been conducting ecological and water quality assessments along the West Stream and East Stream of Tung Chung River to continuously monitor for relevant changes.

Mr Henry Lui, Senior Conservation Manager of Green Power, pointed out that the government had already announced the Tung Chung New Town Extension in 2012, and commenced related construction works in Tung Chung West during the dry season of 2021-22, including the levelling of two large public housing land plots. Green Power conducted four wet-season fish assessments prior to the commencement of the construction in 2018-2021 and three wet-season fish assessments during the construction period from 2022 to 2023. In the estuarine area, the number of native fish species recorded before construction ranged from 19 to 33, with an average of 26 species. During the construction period, the number of species recorded ranged from 13 to 16, with an average of 15 species, representing a decrease of approximately 40%. In the area adjacent to the estuary and downstream of the West Stream, the number of species recorded before construction ranged from 10 to 12, with an average of 11 species. During the construction period, the number of species recorded ranged from 6 to 9, with an average of 8 species, representing a decrease of nearly 30%.

Mr Lui pointed out that the decline in native fish species reflected an overall reduction in riverine biodiversity and also indicated changes in both the river and basin environments. He highlighted that the fish assessment areas did not directly overlap with the ongoing construction works but still seemed to be affected by the project. This impact was likely due to vegetation removal during land levelling, making the topsoil more susceptible to erosion by rainwater and surface run-off into the river, depositing sediment downstream and altering the riverine micro-habitats, leading to a decrease in fish populations. Lui stated, "The assessment shows that the impact of the project on the river environment extends far beyond the construction site. We hope that the authorities will implement strict conservation measures during construction and complete the work as soon as possible to allow the natural river ecosystem to recover."

Mr Lui added that illegal pollution activities within the river basin could also be contributing to the fish decline. He had discovered and reported several water pollution incidents in the lower reaches of the river to the authorities over the past two years. He hoped for the authorities to proactively patrol the vicinity of the Tung Chung River to identify and crack down on illegal pollutant discharge activities.

Multiple Readings Indicate Deteriorating Water Quality

Regarding water quality survey, the latest results demonstrated continuous deterioration in water quality downstream of the East Stream. The conductivity of the river water ranged from 50 to 118 μS/cm, with an average of 73.2 μS/cm. Ammonia-N value ranges from 0.065 to 0.167 mg/L, with an average of 0.101 mg/L. Phosphate-P value ranges from 0.004 to 0.089 mg/L, with an average of 0.040 mg/L. Mr Lui explained that the relative conductivity reflected the content of conductive substances in the river’s water, including conductive pollutants. Ammonia and Phosphate, which are measured by Ammonia-N value and Phosphate-P value, are common pollutants found in domestic and industrial wastewater, and their higher concentrations indicate that the river has been polluted by rural and industrial wastewater.

Mr Lui further explained the contamination of water quality downstream of the East Stream, comparing it with the West Stream. Due to nearby rural residential developments and brownfield operations being less severe near the West Stream, its water quality was comparatively better. The specific conductivity of the river’s water ranged from 30.8 to 53.7 μS/cm, averaging 38.7 μS/cm. Ammonia-N value ranged from 0.006 to 0.038 mg/L, averaging 0.019 mg/L, while Phosphate-P value ranged from 0.000 to 0.024 mg/L, averaging 0.008 mg/L. "Overall, the concentrations of the three pollutants in the East Stream are much higher than those in the West Stream, with the relative conductivity averaging nearly 50% higher; Ammonia-N value is 3 to 18 times higher; and Phosphate-P value is 1.6 to 89 times higher. This indicates severe pollution from nearby villages and brownfields wastewater in the downstream of the East Stream, which negatively impacts the ecology of the Tung Chung River", Lui said.

Mr Lui pointed out that following the increasing level of development of the Tung Chung River basin, the river would face greater pollution threats in the future. Even though the Tung Chung New Town Extension will introduce Hong Kong’s first "Sustainable Urban Drainage System" to Tung Chung Valley, run-off within the area will only flow into the Tung Chung River after being collected and treated during rainfall. However, if pollution cannot be intercepted at the source, the system may not be able to cope with the heavily contaminated water sources. “The authorities must strengthen enforcement to eliminate illegal discharge; otherwise, no matter how much hardware is installed, it will not help conserve Tung Chung River,” he said.

National Guidelines Were Launched Since 2017

Mr Lui also urged the authorities to promptly establish water quality indicators based on the conservation of local aquatic organisms. He mentioned that many regions globally, including the United States, Canada, the European Union, Australia, and New Zealand, have been using water quality indicators based on the health of aquatic organisms for many years. The Chinese Ministry of Ecology and Environment has also introduced a similar "Guidelines for Deriving Numerical National Water Quality Criteria" in 2017. Due to differences in regional environments and the tolerance of aquatic organisms to pollutants, such water quality indicators are highly regionalised. Therefore, Hong Kong also needs to base its indicators on local species to effectively monitor and prevent the impact of pollution on freshwater ecosystems and better conserve precious rivers, including Tung Chung River.

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