Vol. 3 No. 2 (2025): July–December
2025-12-10
Open Access

Spatial Assessment of Changes in the Normalized Difference Water Index Between 2015 and 2025

Asadbek Chaqanov
Kholniso Doniyorova
https://doi.org/10.35938/jhee-2025-2-00007

Received: 2026-10-13

Published: 2025-12-10

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Abstract

This study assessed spatial changes in the Normalized Difference Water Index (NDWI) between 2015 and 2025 in Angor District, Uzbekistan. Landsat 8 Collection 2 Level-2 imagery was processed in Google Earth Engine using cloud, shadow, snow and radiometric saturation masks. NDWI was calculated from green and near-infrared surface reflectance for individual images, followed by annual median compositing. Spatially aligned rasters were compared using pixel-wise subtraction, descriptive statistics and five change intervals. The analysis covered 603,231 valid comparison pixels. Mean NDWI decreased from −0.300216 in 2015 to −0.310154 in 2025, yielding a mean difference of −0.009937. The standard deviation declined from 0.184392 to 0.153999. Negative differences occurred in 57.28% of pixels, while positive differences occurred in 42.72%. Most pixels (97.69%) fell within −0.2 < ΔNDWI ≤ 0.2, indicating predominantly small index differences. Values exceeding 1 occurred in 0.64% of valid pixels in 2015 and were retained in the reported statistics. The findings indicate a modest overall shift towards more negative NDWI values but do not independently demonstrate a reduction in surface-water extent. Additional quality screening, seasonal analysis and validated water classification are required to establish the hydrological significance of the observed differences.

Keywords

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About the Authors

Asadbek Chaqanov
chaqqonovasadbek62@gmail.com
Kholniso Doniyorova
xolisxon19930426@gmail.com

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How to Cite

Spatial Assessment of Changes in the Normalized Difference Water Index Between 2015 and 2025. (2025). Journal of Hydraulic and Environmental Engineering, 3(2). https://doi.org/10.35938/jhee-2025-2-00007 (Original work published 2026)

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