With Land satellite data of fifteen years combining aero data

this paper analyzed and studied 15 years’ dynamic change of water resources using types and water quality by remote sensing technique and field investigation in Taohu and Gehu Lake of Taihu drainage area. The used water resources types were divided into purse net area for breeding fish

fish pool surrounded

bottomland used

inning farm and natural lake by remote sensing approach. The actual area of different using types and density of purse net in some period were calculated with GIS approach. For the purse net of breeding fish in lake bringing a lot of economical benefits in recent years

purse net area and natural lake area have been changed rapidly for about 15 years. There was no purse net area in 1980s. In 1994

the ratio of purse net area to total lake area is 15% in Gehu Lake

and 27% in Taohu Lake. However

the ratio rapidly increased up to 78.8% in Gehu Lake

and up to 83.8% in Taohu Lake in 1998. This ratio greatly exceeds that of logical purse net area to total lake area

which should be less than 20%. Multi-spectral remote sensor can inspect and survey the dynamic change of purse net density at any time

so that the results may avoid false area data that are caused for the personal sake. Excessive density of purse net for breeding may cause aquatic plants decreasing greatly. This paper analyzed 15 year’s occupied proportion change of the aquatic plants by remote sensing approach in Taohu and Gehu lakes. 1980s

the proportion of aquatic plants occupid area to total lake area is more than 50% in Gehu Lake

and is more than 75% in Taohu Lake. In the mid-1990s

a lot of aquatic plants were cut down. There are a few aquatic plants in Gehu natural lake area protected. In 1998

only about 5% proportion of aquatic plants occupid area existed in the middle of Taohu Lake. Most space of the lakes could be used as purse net for breeding fish. This case brought on that the utilized value of the lakes by way of drinking

tour and aquatic animals and plants resources declined greatly. Furthermore

the content of nitrogen and phosphorus in the lakes was increased due to the effect of purse net of breeding fish. Pollution and eutrophication in the local lakes tend to be serious. It is effective that water environment indicators such as the concentrations of suspended substance and chlorophyll-a can be obtained by the use of multi-spectral remote sensing technology being applied to Taihu Lake and Dianchi Lake. However

the ability to inverse water environment under complex water quality or ecological conditions is limited with multi-spectral remote sensor owing to the wide wave band width. It could be a trend that hyper-spectral or super-spectral remote sensing technology is applied to complex water environment.