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Water extraction in arid regions such as north Xinjiang is particularly important due to their lack of water. During the last decades, water resources in north Xinjiang have been seriously impacted by more and more coal-mining activities. Accurate extraction of rivers and broad waters in this region is becoming requisite. However, there are some limitations for existing methods to extract small rivers whose width is less than the resolution of optical imagery because most river-pixels are mixed-pixels in this region. Additionally, rivers there often share similar spectral characteristics with hill shadows, bringing more challenges to their extraction. As typical arid mountain regions, the coal-mining regions of north Xinjiang were selected as the study area in our research. In addition to a cloud removal project, the paper proposed a Blue and Near Infrared Band based Water Index (BNWI) and built the water index model using the Normalized Difference Water Index (NDWI), the Modified Normalized Difference Water Index (MNDWI) and BNWI. Based on the introduced method, the long time series of small-river and broad-water products were extracted from the Landsat MSS/TM/OLI imagery. Experiments proved the proposed method was appropriate for small rivers delineation and the MNDWI threshold method was available to broad waters extraction. The overall accuracy (OA) was above 90%. Results showed that water body was decreasing affected by human activities in coal-mining regions in the period 2002-2014.