Policy Comments & Advocacy

Green Power has recently completed the latest "Ecological and Water Quality Survey of Tung Chung River". The results indicate that the diversity of odonates (which includes dragonflies and damselflies) and native fishes in Tung Chung River basin and Tung Chung Bay continues to decline during the implementation of Tung Chung New Town Extension project, with signs of water pollution also observed. We are writing to bring these findings to your attention and to offer several recommendations for your consideration helping halt the deterioration of biodiversity and water quality of Tung Chung River which is ecologically important and unique.

Tung Chung River is a rare large natural river in Hong Kong, largely retaining its natural state from its source to its estuary, and supports rich biodiversity. Certain sections are even designated as "Ecologically Important Streams". However, since the commencement of the Tung Chung West development works in late 2021, our long-term monitoring data show that the average number of odonate species per year has declined from over 30 species before the works to just over 20 species in recent years. Some species, such as Common Bluetail (Ischnura senegalensis), Lesser Emperor (Anax julius), Asian Pintail (Acisoma panorpoides) and Blue Chaser (Potamarcha congener), have even disappeared from the survey area. Furthermore, some common odonate species which remain present in the survey area, including Orange-tailed Sprite (Ceriagrion auranticum ryukyuanum), Yellow Featherlegs (Copera marginipes), Forest Chaser (Lyriothemis elegantissima), Russet Percher (Neurothemis fulvia) and Green Skimmer (Orthetrum sabina sabina), have demonstrated significant population declines in recent years. Similarly, fish diversity has been impacted, with significant declines recorded at the estuary from 26 species before the works to the lowest record of 13 species in 2023. Although a slight recovery was observed this year (22 species), species numbers have not returned to pre-construction levels.

During implementation of the Tung Chung West New Town Extension project, habitats that originally supported odonates—including marshes, lowland farmland (with irrigation ditches), ponds, and stream courses—have been progressively lost to various developments and other change in land use, leading to a substantial reduction in odonate diversity.

Regarding water quality, consistently elevated levels of ammonia nitrogen and phosphate phosphorus have been recorded in the lower reaches of the “East Stream”, suggesting potential contamination from untreated wastewater, possibly from brownfield activities, runoff/discharge from nearby villages and construction activities.

We acknowledge that your office has consistently valued the conservation of Tung Chung River and has implemented various measures to mitigate the impacts of the works and other polluting activities. However, as ecological pressures intensify, we recommend that your office consider the following actions:

1. Enhance Pollutant Interception: Install sedimentation ponds, interceptors and/or purification facilities at the discharge outlets of village storm drains and along the boundaries of construction sites to prevent sediments and pollutants from entering the river directly.

2. Reconstruct Key Habitats: Recreate ecological ponds and streams outside the construction zone to compensate for the loss of critical odonate habitats due to the project.

3. Establish Local Ecological Water Quality Standards: Develop water pollution indicators based on the tolerance of Hong Kong's aquatic organisms, with reference to China's "Technical guideline forderiving water quality criteria for freshwater organisms"¹. This would allow for the scientific formulation and review of conservation measures.

We believe that through further preventive and compensatory measures, the valuable ecological integrity of Tung Chung River can be maintained, achieving a balance between development and conservation.

Thank you for taking the time to consider this letter. We are pleased to provide further information and assistance and look forward to your response and follow-up actions.