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Remote Sens. 2016, 8(8), 630; doi:10.3390/rs8080630

Cropping Intensity in the Aral Sea Basin and Its Dependency from the Runoff Formation 2000–2012

1
Department of Remote Sensing, Institute of Geography and Geology, University of Würzburg, Oswald-Külpe-Weg 86, 97074 Würzburg, Germany
2
NGO MapTailor, 83022 Rosenheim, Germany
3
Scientific Information Center of the Interstate Commission on Water Coordination in Central Asia (SIC ICWC), Karasu 4, 100187 Tashkent, Uzbekistan
4
Department of Physical Geography, Institute of Geography and Geology, University of Würzburg, Am Hubland, 97074 Würzburg, Germany
*
Author to whom correspondence should be addressed.
Academic Editors: Soe Myint and Prasad S. Thenkabail
Received: 23 June 2016 / Revised: 21 July 2016 / Accepted: 26 July 2016 / Published: 29 July 2016
(This article belongs to the Special Issue Monitoring Agricultural Land-Use Change and Land-Use Intensity)
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Abstract

This study is aimed at a better understanding of how upstream runoff formation affected the cropping intensity (CI: number of harvests) in the Aral Sea Basin (ASB) between 2000 and 2012. MODIS 250 m NDVI time series and knowledge-based pixel masking that included settlement layers and topography features enabled to map the irrigated cropland extent (iCE). Random forest models supported the classification of cropland vegetation phenology (CVP: winter/summer crops, double cropping, etc.). CI and the percentage of fallow cropland (PF) were derived from CVP. Spearman’s rho was selected for assessing the statistical relation of CI and PF to runoff formation in the Amu Darya and Syr Darya catchments per hydrological year. Validation in 12 reference sites using multi-annual Landsat-7 ETM+ images revealed an average overall accuracy of 0.85 for the iCE maps. MODIS maps overestimated that based on Landsat by an average factor of ~1.15 (MODIS iCE/Landsat iCE). Exceptional overestimations occurred in case of inaccurate settlement layers. The CVP and CI maps achieved overall accuracies of 0.91 and 0.96, respectively. The Amu Darya catchment disclosed significant positive (negative) relations between upstream runoff with CI (PF) and a high pressure on the river water resources in 2000–2012. Along the Syr Darya, reduced dependencies could be observed, which is potentially linked to the high number of water constructions in that catchment. Intensified double cropping after drought years occurred in Uzbekistan. However, a 10 km × 10 km grid of Spearman’s rho (CI and PF vs. upstream runoff) emphasized locations at different CI levels that are directly affected by runoff fluctuations in both river systems. The resulting maps may thus be supportive on the way to achieve long-term sustainability of crop production and to simultaneously protect the severely threatened environment in the ASB. The gained knowledge can be further used for investigating climatic impacts of irrigation in the region. View Full-Text
Keywords: irrigated cropland extent; cropland vegetation phenology; land and water management; MODIS; Landsat; Central Asia irrigated cropland extent; cropland vegetation phenology; land and water management; MODIS; Landsat; Central Asia
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Conrad, C.; Schönbrodt-Stitt, S.; Löw, F.; Sorokin, D.; Paeth, H. Cropping Intensity in the Aral Sea Basin and Its Dependency from the Runoff Formation 2000–2012. Remote Sens. 2016, 8, 630.

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