Method to Evaluate Index of Water Bodies Density in Northeast China

Meteorological assessment of ecological qualities is proposed by China Meteorological Administration. The assessment is applied to evaluate ecological quality and its effect with appropriate indexes and proper methods. The trial evaluation scheme of ecological quality meteorology selects humidity, vegetation cover-age, water environment, land degeneration, and disaster occurrence indexes for evaluation, among which water environment is the most important one. However, there isn't a satisfactory way to evaluate index of water environment so far.Apractical method is proposed to evaluate the contribution of water body to ecological quality using MODIS data and ground observational data. Moderate resolution imaging spectroradiometer data is obtained from DVBS (Digital Video Broadcast by Satellite) by China Meteorological Administration. And the ground observational data is obtained from Water Affairs Bureau.First, several huge water bodies are chosen, as small area water bodies cannot be well monitored by MODIS. The area of these indicative water bodies has a preferable relationship with that of total water bodies. By analyzing water and other objects' spectral characteristics on EOS/MODIS images, the distinguished water compound bands are decided to get the method to recognize water area from remote sensing images. Then the threshold values of the channel reflectance and bright temperature of MODIS data are determined to distinguish water body from other objects. MODIS data of clear days in different seasons are adopted as much as possible to make statistical comparisons with ground observational data, thus a regression model can be set up between areas of indicator water bodies and total water area.Second, river length, lake and reservoir areas and length of coastline are chosen as indicators of water environment index. Each indicator has a weight to decide its contribution to water environment index, and the weight is calculated by normalization methods. So the water environment index is calculated by the summation of river length, lake and reservoir areas and length of coastline multiplied their weights respectively.Finally, the method is applied to evaluate water body indexes in Northeast China, and is proven feasible and practicable.