Study On The Optical Characteristics Of Dongping Lake Based On Remote Sensing Inversion

Dongping Lake as the second largest freshwater lakes in Shandong Province,occupy an important position in the"South to North Water Diversion Project"and"West to EastWater Diversion Project in Shandong",the safety monitoring of water quality problems won't be ignored.The traditional water quality monitoring methods are often subject to some restrictions on time and space,only understand the point profile of research area,in order to understand the overall water quality and research the distribution characteristics of eutrophication important characteristic parameters,through the introduction of remotesensing monitoring,statistical analysis method and UV absorption spectroscopy on the distribution characteristics of chlorophyll a,transparency and dissolved organic matter analysis in Dongping Lake,provided the basis for rapid monitoring of water quality and precision control of Dongping Lake.Based on this,the main conclusions are as follows:?1?Landsat 8 OLI remote sensing image is analyzed in the relativity of chlorophyll-a in Dongping Lake with 74 measured sample data in this paper,analysis the correlation of the band of Landsat8 OLI images with chlorophyll-a concentration,respectively established inversion models.According to this,drawn the distribution pattern of chlorophyll-aconcentration in Dongping Lake.Accordingly,it is found that chlorophyll-a is moresensitively to the images of Landsat8 visible B3 and B4 band,showing the overall higher than the shore distribution trend.?2?In this study,remote sensing inversion in Dongping Lake was carried out by using three Landsat8 OLI image data and quasi synchronous ground measured data.The resultsillustrate the band ratio model of Band3+Band4 of OLI could be used to estimate Secchi depth in this region,with RE of 19.77%and RMSE of19.35cm,respectively.In addition,SDD was deeper in north waters than in south waters.Based on these,the distribution of water transparency in Dongping lake during the rainy,flat and dry seasons was plotted,and its distribution trend and cause were analyzed.?3?Through the analysis of a_?280?,a_?350?and a_?440?and the base band OLI images on the correlation in Dongping Lake was found between each band in winter the CDOM and OLI images showed significant correlation.Study on inversion of the winter water qualityparameters could be influenced by the concentration of CDOM in Dongping Lake.Insummer it was significantly correlated and it is the lowest in autumn,no significant;The chlorophyll a seasonal differences lead to the seasonal changes of the CDOM;Due to the reasons for the smaller CDOM absorption coefficient and it's larger variation in winter CDOM concentration,the model fitting overall relative error,is 129%.The effect is not very ideal.?4?To investigate the CDOM absorption characteristics,sources and spatial distribution of seasonal changes in Dongping Lake,respectively collected 35 surface water samples inAugust,December,2013 and March,2014.The water quality parameters,spatialdistribution of CDOM absorption coefficient at 440nm[a_?440?],carbon-specific CDOMabsorption coefficient[a^*_?440?],the value of M,as well as the relationships between CDOM and water quality parameters were studied.The results showed that the a_?440?adhered to the law of dry water period>wet period>normal water period,and the distribution pattern of a_?440?was similar to the distribution of a^*_?440?but negatively correlated with M value.Through correlation analysis found that the a_?440?and COD,DOC were significantlycorrelated?P<0.05?in wet and normal water period,simultaneously the Chla and other water quality parameters were significantly correlated?P<0.05?.It is indicated that the main source of CDOM in the wet and normal water period were exogenous injection,but also affected by different degrees of endogenous injection.And it is also confirmed this result in the Geostatistical Analysis?the coefficient of nugget was respectively 0.30,0.38?.The a_?440?only has a significant correlation with DOC?P<0.05?in the dry season,withremoved the abnormal value,the nugget coefficient is 0.10,it is mainly related to theconcentration of suspended matter in water presumably.In the three season,the a_?440?were significantly correlated with DOC?P<0.05?,it is considered that the tracing and estimation of DOC can be effectively realized by using CDOM concentration in Dongping Lake.