Image Of The Miyajimanuma Lake
Lake Miyajimanuma is located in Bibai City in the central part of Hokkaido Island, Japan (43°20'N, 141°43'E), it is a permanent freshwater lake of 30ha in the middle basin of a river Ishikari-gawa. It is an important stop-over for greater white-fronted geese and tundra swans, and it is a northernmost site of White-fronted Goose Anser albifrons with largest number in the country. Every spring and autumn, up to 40,000 White-fronted Geese stay the lake.
A number of swans and ducks also stay the lake, in total about 60,000 individuals. Yet the lakes face serious pollution - the sediment, manure, fertilizer and other pollutants influenced by both natural and human process. It is as a remainder of the Ishikairi Peatland which used to be the largest mire in Japan.
Natural processes include mineral weathering while human processes include landuse change and agricultural production activities.Fig. 1 SPOT 5 remote sensing image of the Miyajimanuma lake area (R: green G: red B: near IR ).Miyajinanuma marsh and the surrounding are composed of a complicate ecosystem. Miyajimanuma receive effects in physics, chemistry which mainly come from the agricultural activities and have multi-functionality with them. Firstly, water resource is worth to notice.
Spring water used to come from the bottom of the lake, but now melting snow and rainwater form the marsh. In addition, the water usage association, formed by local farmers, uses water drawn from the Ishikari and warmed in the marsh via a water channel in the east edge for irrigation, but only when they are planting rice. Surrounding areas of Miyajimanuma are agricultural lands, mainly for rice crop, and lowland swamp vegetation such as Alnus japonica, Salix and Phragmites australis are found around lakes and marshes.
1.1.2 Miyajimanuma at risk
Human activities, mainly agricultural production activities, in the surrounding area have resulted in water quality deterioration and eutrophication was getting worse. Agricultural land use information within the catchment area has become important for determining the relationships between agricultural activities and water quality change thereby protecting the wetland.Disappearance and Deterioration of Lake EcosystemThough each lake has various features which depend on its origin and climate, each one locates on the end of the catchment and stores the water which receives complicated physical, chemical and biological effects in the catchment. In addition, each lake generally forms a complicated material cycle which is influenced by the climate factor like temperature, light and wind and by the biological factor like phytoplankton, zooplankton and fish.
Lakes have various functions as ecosystem like water purification, climate regulation and the habitat for many animals including waterfowls. Each lake plays an important role as a water resource like "water jar" for our life and farming and as a place for our recreation. But almost of all lakes have had disappeared because of reclamation works on agricultural and residential land reform. Even in remained lake, the water environment and ecosystem has markedly deteriorated because of water quality deterioration, eutrophication, habitat deterioration, range of alien species and extinct species which have been depended on various human activities in the catchment.Represented by Kushiro Marsh, which is larger than any other marsh in Japan, Hokkaido has many marshes left in which we have some groups of lakes.
Some of them are registered in the Ramsar marsh. As the world has lake problems, lakes in Hokkaido have disappeared and deteriorated while we converted marsh to fields in agricultural policy in 1960s. In the lake in the peat land, we have low diversity of species because the lake has low productivity and only specific species group can adapt to acid and oligotrophication lake. Though these lakes also have the feature that its water has high concentrated dissolvable organic matter, the case that people investigate its quality of hydrochemistry is rare in the world.
Therefore, we have some unclear points left about the role of lakes in the marsh, the soundness of hydrochemistry, and the response and tolerance of ecosystem to artificial disturbance like N-P input and control of water level for agriculture. Naturally we haven't made clear policy about conservation and regeneration and not make clear measure about agriculture which harmonizes the environment based on science yet.Over the past decade, the agricultural production activities around Miyajimanuma greatly increasing the threat of manure spills. The consequences are clear.
Too often, we've found our lakes covered with algae or choked with weeds, or heard about sewage overflows and fish kills. The culprit is most often runoff pollution.
1.1.3 Monitor the Mijajimanuma and its surroundings is needed
Therefore, an understanding of the trends of pollutions accumulation in the environment is necessary to assess the current state and potential future problems of surface water quality. Efficient Conservation of Ecosystem and EnvironmentEffective extraction of agricultural land use information could provide a method for sustainable management of land resources and policy development. Remote sensing imagery-based land use classification is an effective means for extraction of agriculture land use information, and it would help to underpin the principles of sustainable development of agriculture.People viewed the remarkable deterioration as problem and the necessity of conservation of environment and the wise use has been profoundly reputed in the Ramsar Convention.
Though lately restoration projects in addition to conservation of lake system have been implemented not only in Japan but in the world, people have adaptively examined it as a measure in each area.
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