The study of lake environment by using remote sensing technique to take the Jianghan lakes as an example
Zou Shang Hui
Department of Geography, Central China Normal university, Wuhan, Hubei, China
Abstract
The study results by using remote sensing have shown: that the area and the number of the Jianghan lakes have greatly decreased since 1950's the lake environment such as water quality is deteriorating. The speed of lake swamping is discussed, and it indicates that the halophyte will completely cover the Honghu lake in the next thirty years. With a land use program formulated by DTM, the lake environment will be well rebuilt.
Introduction
The Jainghan lake groups all over the Jianghan plain like stars in the sky. Since 1950's of the century, large-scale and unchecked activities of reclamation have resulted in a sharp decrease in the number and area of the Jianghan lake groups. The laudatory to the "Province of a thousand lakes" has been faced irrevocably lost. Even though lakes exist there, they all have been faced with a serious swamping crisis.
The action of reclamation and natural siltation of lakes which have resulted in the vicissitudes of lakes from water to land and the tendency of swamping are clearly reflected in the satellite remote sensing image. Thus we can make the historical lakes (palaeolakes), which sometimes could not be discovered in the field investigation reappear and forecast its future evolution tendency by using remote sensing.
Interpreting the Landsat MSS image and making The historical Jianghan lake groups reappear
- The Synthetic Spectra of Lake Facise Sediments
ad a Shallow Layer of water in Palaelakes have specific image
properties.
In the places of palaeolakes, the sticky and blue-grey lake facise sediments (gley horizon) are deposited. Consequently the places of palaelakes are mostly single-cropping paddy field. During the imaging of the first tem days in June. There is only a shallow layer of water in the fields, without any seedings or sometimes or sometimes with seedings just planted in. the integral spectral of "water" and the lake facise sediments underneath obtained by the sensor differ sharply from the spectra of other water or crops (Fig.1). Therefore, there are specific image properties of these palaelakes.
- The Swamping Vanguard Plants Wild Rice and Reed
are the important Signs indicating that the Lakes Are becoming
Marshes.
The vanguard plants which show signs of the swamping tendency and even of the transformation from lakes into land are usually wild rice and reed. So the communities of wild rice and reed is an important mark to locate the palaelakes d the bank belt of shallow lakes, in which the image features present dense grain, villose structure, and red or rose color, differing from farm crops.
- Reappearing the Palaelakes with Image Feature
of Embankments Encircling Low Paddy Fields.
For natural and human reasons, the Jainghan lakes
have been spitted and dismembered showing a broken appearance. If we can
delimit the extent of the initial embankments we will be able to
retrieve the location of the palalakes. Although most embankments have
already been destroyed today, the minor relief feature of embankments in
different land use are still shown distinctly on the image, revealing three color belt structure.
