Remote Sensing Inversion Of Water Transparency In Xiaolangdi Reservoir And Its Spatial Distribution Changes

The water transparency of Xiaolangdi Reservoir is a direct reflection of the comprehensive status of the water environment of the reservoir,and is closely related to various water quality parameters.The monitoring of water transparency is of great significance to protect and improve the water environment.Aiming at the problems of low efficiency and incompleteness in water transparency monitoring,the paper uses spectral feature analysis,correlation analysis and regression analysis to construct a remote sensing inversion model based on the combination of characteristic bands to monitor the water transparency of Xiaolangdi Reservoir and analyze the reasons for changes in spatial distribution.,and combined with the nutrient index method to evaluate the water quality.The research work of this paper is mainly reflected in the following aspects:(1)After analyzing the spectral characteristics,the water body spectrum has obvious characteristics near 560 nm,675nm and 705 nm.The water body spectrum is equivalent to the corresponding band of Sentinel-2 satellite.Combined with the correlation analysis,the ratio of transparency and B3 band,B4 and B5 band There is a strong correlation,which is consistent with the spectral analysis results.The single-band model,the ratio-band model and the combined-band model were respectively constructed and compared and analyzed.The binary primary inversion model based on the combination of the three characteristic bands had the highest determination coefficient and the smallest error,and this model was used as the water transparency remote sensing inversion model.(2)During the water and sediment regulation cycle of Xiaolangdi Reservoir,the spatial distribution of transparency changes from low in the west to high in the east,until the new water and sediment regulation is completed,and returns to the distribution of low in the west and high in the east.The average transparency is highest in winter and lowest in summer.,mainly affected by factors such as water storage,water temperature,accumulation of impurities,plant growth in water,and human activities;from 2017 to 2021,the overall spatial distribution of transparency is low in the west and high in the east,and the annual average water transparency first decreases and then increases,mainly affected by the adjustment It is affected by factors such as water and sediment adjustment time,upstream water quality,rainfall,and water storage.The correlation analysis with other water quality parameters shows that the transparency level of the water body is affected by a variety of factors,which is a comprehensive reflection of the water environment of the reservoir.From the analysis of the relationship with meteorological factors,it is concluded that both rainfall and temperature will have an impact on the transparency of water bodies,and the temperature has a greater impact.Using the results of water transparency inversion,combined with the nutrient index method,the water quality of the reservoir area was evaluated.The experiment showed that the overall water quality of the reservoir was maintained at a medium or above level during the water and sediment regulation cycle and the five years from 2017 to 2021.