Sand mining across the Ganges-Brahmaputra-Meghna catchment; assessment of activity and implications for sediment delivery

Abstract

Abstract While issues of pollution, floods and drought in our rivers are widely studied, there is a hidden crisis with respect to the widespread global extraction of sand. Large volumes of sand are needed in the construction industry to make concrete. So far, calls for greater monitoring of sand mining activity have largely gone unmet. This is due to the fact mining is extensive, often hidden (e.g. underwater) and thus very difficult to properly assess. To meet this challenge, we use remote sensing methods to detect and monitor sand mining activities at the catchment scale, across the Ganges-Brahmaputra-Meghna river system (catchment size 1.72 million km2). Based on this analysis, here we show that mining activity is diverse and pervasive across the Ganges-Brahmaputra-Meghna catchment system for our study period of 2016-2021, with rates of extraction increasing within some of the rivers. Results show the total estimate for sand extraction is ~ 115 MTyr-1 +/- 20 MTyr-1, which is of a similar order of magnitude to the natural bedload flux of the catchment. While there are some limitations to deriving estimates based solely on imagery, this work highlights both the widespread spatial extent and large magnitude of sand mining for one of the world’s biggest catchments. Furthermore, given our estimated scale of sand extraction, it demonstrates the need to properly account for mining activities when considering delivery of sediment to deltas in terms of the management of these vulnerable systems in the face of rising sea-levels. Overall, this work stresses the urgent requirement for further similar studies of sand extraction in the world’s large rivers, which is vital to underpin sustainable management plans for the global sand commons.