Regional-scale assessment of multi-year soil salinity using MODIS in the Syr Darya River valley, Kazakhstan
Принципы региональной оценки многолетней засоленности пашни в Казахстанском секторе долины реки Сырдарьи по данным MODIS
Terekhov A.G. Sagatdinova G.N. Murzabaev B.A.
2022Space Research Institute of the Russian Academy of Sciences
Sovremennye Problemy Distantsionnogo Zondirovaniya Zemli iz Kosmosa
2022#19Issue 2169 - 179 pp.
In the Syr Darya River valley there is a large irrigated region — the Hungry Steppe with a total area of about 10 thousand km2. The lower part of this region, which is about 140 thousand hectares of irrigated arable land, belongs to the territory of Kazakhstan. After the collapse of the USSR, hydroelectric power plants in the upper reaches of the river basin changed their operating modes from irrigation to energy. In addition, the regional drainage system has partially lost its functionality. All this contributed to the activation of the secondary soil salinity processes. In this study, two satellite indices, normalized differential vegetation and salinity indexes (NDVI and NDSI) based on the MODIS MCD43A4 product of the period April–July 2001–2021, were tested as a basis for regional mapping of manyyear soil salinity in the Kazakhstan’s Syr Darya River valley. Official state information on the soil salinity of rural districts (district — an administrative unit with an area of irrigated arable land of 4–11 thousand hectares) of the Maktaaral and Zhetysai Regions of the Turkestan Oblast of Kazakhstan in the period 2007–2021 was used to calibrate satellite data. It was found that the best correlation with the longterm salinity of irrigated arable land has the average longterm maximum NDVI of the period June 20–July 5 (Pearson correlation coefficient R2 = 0.88), as well as the average longterm maximum NDSI of the periods April 10–25 (R2 = 0.85) and June 26–July 10 (R2 = 0.87). Also, a close correlation between the considered indices with a Pearson correlation coefficient up to 0.97 is recorded. The physical basis linking satellite data with secondary soil salinization, apparently, is the procedure of winterspring irrigation, which, in the process of removing salts, leads to spring soil waterlogging and delays in the early summer development of agricultural vegetation. Thus, the average longterm values of the NDVI and NDSI satellite indexes built on the MODIS MCD43A4, on certain calendar dates, can serve as the basis for regional mapping of the average longterm soil salinity in the test site region. One of the important purposes of the many years soil salinity mapping may be to identify areas that are systematically subjected to secondary soil salinization.
monitoring of irrigated arable land , remote sensing , secondary soil salinity , soil salinity mapping , winter irrigation
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Institute of Information and Computational Technologies, Almaty, 050010, Kazakhstan
M. Auezov South Kazakhstan State University, Shimkent, 160012, Kazakhstan
Institute of Information and Computational Technologies
M. Auezov South Kazakhstan State University
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