Preprints
https://doi.org/10.5194/esurf-2021-39
https://doi.org/10.5194/esurf-2021-39

  05 May 2021

05 May 2021

Review status: a revised version of this preprint was accepted for the journal ESurf and is expected to appear here in due course.

Sand mining far outpaces natural supply in a large alluvial river

Christopher Hackney1, Grigorios Vasilopoulos2, Sokchhay Heng3, Vasudha Darbari2, Samuel Walker2, and Daniel Parsons2 Christopher Hackney et al.
  • 1School of Geography, Politics and Sociology, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
  • 2Energy and Environment Institute, University of Hull, Hull, UK, HU6 7RX
  • 3Institute of Technology of Cambodia, Phnom Penh, Cambodia

Abstract. The world's large rivers are facing reduced sediment loads due to anthropogenic activities such as hydropower development and sediment extraction. Globally estimates of sand extraction from large river systems is lacking, in part due to the pervasive and distributed nature of extraction processes. In the Mekong River, current basin wide estimates of sand extraction are 50 Mt, and based on estimates from 2013. Here, we demonstrate the ability of high-resolution satellite imagery to map, monitor and estimate volumes of sand extraction on the Lower Mekong River in Cambodia. We use monthly composite images from PlanetScope imagery (5 m resolution) to estimate sand extraction volumes over the period 2016–2020 and show that rates of extraction have increased year on year from 24 Mt (17 Mt to 32) in 2016, to 59 Mt (41 Mt to 75 Mt) in 2020 at a rate of ~8 Mt yr−1 (6 Mt yr−1 to 10 Mt yr−1); where values in parenthesis relate to lower and upper error bounds, respectively. Our revised estimates for 2020 (59 Mt) are nearly two times greater than previous best estimates for sand extraction for Cambodia (32 Mt) and greater than current best estimates for the entire Mekong Basin (50 Mt). We show that over the five year period, only two months have seen positive (supply exceeds extraction) sand budgets under mean and upper bound scenarios (five months under the lower bound estimates). We demonstrate that this net negative sand budget to the river is driving major bed incision with a median rate of −0.26 m a−1 over the period 2013 to 2019. The use of satellite imagery to monitor sand mining activities provide a low-cost means to generate up-to-date, robust estimates of sand extraction in the worlds large rivers that are needed to underpin sustainable management plans of the global sand commons.

Christopher Hackney et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-39', Anonymous Referee #1, 27 Jun 2021
  • RC2: 'Comment on esurf-2021-39', Anonymous Referee #2, 28 Jun 2021
  • AC1: 'Comment on esurf-2021-39 - response to reviews', Christopher Hackney, 28 Jul 2021

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on esurf-2021-39', Anonymous Referee #1, 27 Jun 2021
  • RC2: 'Comment on esurf-2021-39', Anonymous Referee #2, 28 Jun 2021
  • AC1: 'Comment on esurf-2021-39 - response to reviews', Christopher Hackney, 28 Jul 2021

Christopher Hackney et al.

Christopher Hackney et al.

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Short summary
Unsustainable sand mining poses a threat to the stability of river channels. We use satellite imagery to estimate volumes of material removed from the Mekong River, Cambodia, over the period 2016–2020. We demonstrate that current rates of extraction now exceed previous estimates for the entire Mekong basin and significantly exceed the volume of sand naturally transported by the river. Our work highlights the importance of satellite imagery in monitoring sand mining activity over large areas.