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Geographical setting
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The landscape of Hong Kong is dominated by hills and ravines and flat land is restricted to the low floodplains and coastal regions. In this hilly domain, hundreds of small rocky streams flow through steep ravines. These hill streams are typically fast flowing at their upland sources, and gradually reduce speed as they wind along hill cuttings to reach the lowlands. There are only a few long and meandering rivers in Hong Kong and are found only in the floodplains of the northern and northwestern New Territories.
There are over 2 500 km of natural streams and rivers in Hong Kong, mostly located in hillsides remote from developed areas. Many of these natural streams and rivers are good habitats supporting a variety of wildlife. They have important ecological functions and carry high aesthetic and landscape value.
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| A hill stream in Luk Keng |
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A natural stream or river refers to a natural channel with natural water fed from upper terrains, which covers both perennial stream and river with water flowing throughout the year as well as intermittent ones with water-flow only during the wet season. The streambed is natural and not manmade, which could consist of mixtures of bedrocks, boulders, cobbles, gravels, sand, silt or clay. The banks are also largely natural and defined, covered with bank-side and riparian vegetation.
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| A river at Lok Ma Chau |
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Riparian vegetation
| Riparian vegetation provides food for many aquatic organisms in the stream as well as sheltering effect that is important for regulating the water temperature. Riparian vegetation also serves important functions including purifying water by removing sediments and contaminants; reducing the risk of flooding; and reducing erosion on stream bank. |
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| Riparian Vegetation along Tai Shing Stream |
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Major stream fauna
| Freshwater fish can be found in all types of streams and rivers, from swift flowing hill streams to trickling lowland rivers and estuaries. Each type of streams and rivers has its own ecological characteristic and supports specific communities of aquatic organisms, and each freshwater fish species has its own niche and special adaptations to survive in its habitats. For instance, loaches and gobies are common in hill streams while cyprinds, catfish and snakeheads are common in lowland streams and rivers. |
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| Chinese Rasbora (Rasbora steineri) |
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Macroinvertebrates such as shrimp, dragonflies, mayflies, stoneflies and caddisflies spend their whole larval stages in natural streams and rivers. They form an important part of the stream ecosystem and are commonly used as indicator of stream/river water quality.
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| Rose Bitterling (Rhodeus ocellatus) |
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| A dragonfly larva |
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| A freshwater shrimp |
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