Thursday, 13 July 2006 - 2:05 PM
74-3

Experience in Using the Remote Sensing Materials to Monitor the Long-Term Dynamics of Salinization in Irrigated Soils of the Golodnaya Steppe, Uzbekistan.

Dimitry I. Rukhovich and Ekaterina V. Vilchevskaya. V.V. Dokuchaev Soil Science Institute, Pyzhevskii per. 7, Moscow, Russia

Salinization is one of the harmful soil processes known since the time of ancient civilizations. In the past, soil salinization often led to the ruin of civilizations; at present, it causes significant ecological problems and impairs the economy. Salinization control measures are costly and require adequate information support. The lack of prompt and adequate information on the salt status of soils is a serious problem. The efficient salinization control policy should be based on adequate information making the known methods of salinization control more efficient and economically feasible. The Golodnaya and Dzhizak steppes in Uzbekistan are the areas with widespread distribution of salt-affected soils. Our studies were aimed at determination of the kinds of remote sensing data suitable to assess the dynamics of soil salinization within this territory.At present, there are materials of field surveys and remote sensing data making it possible to trace the long-term dynamics of soil salinization in the Golodnaya and Dzhizak steppes. The methodology of remote sensing data interpretation for the monitoring of soil salinity was developed by Pankova and Mazikov (1985), It was tested by the example of the Usman Yusupov farm in the Golodnaya steppe. For this area, panchromatic aerial photos (PAPs) are available for a period from 1982 to 1990. However, because of economic reasons, these valuable materials were never obtained afterwards. Thus, it was necessary to find other kinds of remote sensing data, develop the methods of their interpretation for the monitoring of soil salinity, and correlate the results obtained with the materials based on PAPs. In recent years, high-resolution satellite imagery has appeared on the market. The imagery similar in its parameters to the materials of the PAPs can be relatively easily adapted to the use of the existing interpretation methodology. In particular, panchromatic IKONOS and QuickBird images obtained in August and September are suitable for the monitoring of soil salinity. However, their use for the monitoring of soil salinity is hampered by their high cost and some other reasons. At present, IRS sensors ensuring resolution of 5 m in the panchromatic regime seem to be promising. However, in this study, we used more available materials LANDSAT-7. The period of soil salinity monitoring on the basis of PAPs and LANDSAT-7 imagery comprised 20 years. It should be noted that the use of satellite imagery for this purpose involves certain problems. First of all, it is difficult to synchronize the dates of satellite imagery with the periods of soil overmoistening on the irrigated fields. As shown by Pankova and Mazikov (1985), soil overmoistening masks the features of soil salinity upon their interpretation on the basis of panchromatic images. Thus, the panchromatic channel of LANDSAT-7 proved to be not very efficient. Moreover, as the field surveys in the region are not conducted any more, it is difficult to obtain information on the real dates of irrigation. However, the use of the methodology of interpretation of multispectral imagery developed in the 1980s, made it possible to obtain synthesized images suitable (as proved by their analysis together with PAPs data) to assess the character of soil salinization. These images are synthesized from the images made in channels 7, 4, and 2. On the basis of these materials, seven maps of soil salinity dynamics during the 20-year-long period were developed. These maps were integrated in the geographic information system (including the topographic map, original remote sensing data, and maps of soil salinity), which makes it possible to estimate the distribution of salt-affected soil in the region, trace their dynamics in the past, predict future changes, and suggest optimum salinization control strategy.

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