Land cover changes around lake basin have caused aquatic environmental degradation such as eutrophication or water pollution. In particular, increase of nitrogen and phosphorus components to the lake due to land cover changes of surrounding areas has been serious. Estimating influent loads from lake basin to the lake through rivers is very important in the management of lake environment. In this paper, the relation between total amount of nitrogen to the lake and land cover distribution was investigated with remote sensing. Lake Kasumigaura was selected as a test site for the case study. LANDSAT MSS data from 1979, 1984 and 1990 were analyzed to produce land cover distribution map of the area. Land cover categories include urban area, paddy field, forest area and field. Lake basin areas were delineated with DEM for individual rivers to the lake. And the relation between total nitrogen of rivers and land cover distribution at the lake basin was analyzed. As a result, it was found that urban area and field in the land cover categories gave influence to the eutrophication of Lake Kasumigaura. Furthermore, in order to evaluate total annual pollution load (total nitrogen) to Lake Kasumigaura, (1) basic unit of total nitrogen load for each land cover categoris (2) influent annual total nitrogen to the lake were estimated from land cover change patterns from MSS data and from the total nitorgen concentration measured at each rivers to the lake.
Importance of in-flight radiometric calibration of satellite sensors has been increased. A snow field is a candidate as a ground target for vicarious calibration and cross calibration in the visible to near-infrared region because of its high reflectance and spatial uniformity. This study focuses on the advantages and disadvantages of a snow field for in-flight calibration in order to show the validity of a snow field as a ground target. The reflectance data was obtained at the Sarobetsu and the Konsen Plateau areas in Hokkaido, Japan.The snow reflectance was changeable in terms of temporal stability due to a variety of snow grain size, water content and impurities. However, the reflectance of the snow field was nearly flat spectrally in the 400-900 nm region and very uniform spatially. For the some properties of the snow field, the percent uncertainties and the sources of uncertainty or errors for the calibration are estimated. As a result, the snow fields can be selected as a good ground target for vicarious calibration using simultaneous in-situ measurements with data acquisition by satellite sensors and for cross calibration between sensors on the same platform.
In the present study, we propose a new index called a Vegetation-Soil-Water (VSW) index to monitor land cover conditions. The VSW index is defined as a natural extension of PVI for monitoring not only vegetationconditions but also soil and water conditions as well. VSW index is defined using a triangle on a NIR-Red scatter plot. The PVI measures only vegetation parameters, whereas the VSW index monitors vegetation, soil and water parameters simultaneously by measuring the distances in the scatter plot. Landsat Thematic Mapper (TM) scenes were used for the analyses. Wetland plants in Kushiro Mire were in the beginning of their growing season in June, and in their maximum growth stage in August. All the vegetation was dead in October. These scenes show how the vegetation changes seasonally and year by year for 5 years. We determined the end member spectral points for vegetation, soil and water (VSW) with an algorithm to fit a triangle to the spectral distribution. This automatic end member determination also standardizes the spectral responses of scenes. Scatter plots of the TM scenes on NIR-red axes were overlaid with the determined VSW end member points. The VSW index was used to monitor land cover change in the Kushiro wetland with Landsat TM images to evaluate the effectiveness of our approach for wetland monitoring. Changes in the vegetative components of the Kushiro wetland, both seasonally and over the full 5 year period we examined, could be easily resolved from these color composite images.