Preprints
https://doi.org/10.5194/essd-2021-15
https://doi.org/10.5194/essd-2021-15

  02 Mar 2021

02 Mar 2021

Review status: this preprint is currently under review for the journal ESSD.

The 3D groundwater salinity distribution and fresh groundwater volumes in the Mekong Delta, Vietnam, inferred from geostatistical analyses

Jan L. Gunnink1, Hung Van Pham2,3, Gualbert H. P. Oude Essink3,4, and Marc F. P. Bierkens3,4 Jan L. Gunnink et al.
  • 1TNO Geological Survey of the Netherlands
  • 2Division of Water Resources Planning and Investigation for the South of Vietnam (DWRPIS), Ho Chi Minh city, Vietnam
  • 3Department of Physical Geography, Utrecht University, the Netherlands
  • 4Department of Subsurface and Groundwater Systems, Deltares, the Netherlands

Abstract. Over the last decades, economic developments in the Vietnamese Mekong delta have led to a sharp increase in groundwater pumping for domestic, agricultural and industrial use. This has resulted in alarming rates of land subsidence and groundwater salinization. Effective groundwater management, including strategies to work towards sustainable groundwater use, requires knowledge about the current groundwater salinity distribution, in particular the available volumes of fresh groundwater. At the moment, no comprehensive dataset of the spatial distribution of fresh groundwater is available. To create a 3D model of Total Dissolved Solids (TDS), an existing geological model of the spatial distribution and thickness of the aquifers and aquitards is updated. Next, based on the sedimentological description of the borehole data, maps of drainable porosity for each aquifer are interpolated. Measured TDS in groundwater, inferred TDS from resistivity measurements in boreholes and soft incomplete data from domestic wells are combined in an indicator kriging routine to obtain the full probability distribution of TDS for each (x,y,z) location. This statistical distribution of TDS combined with drainable porosity yields estimates of the volume of fresh groundwater (TDS < 1 g/L) in each aquifer. Uncertainty estimates of these volumes follow from a Monte Carlo analysis (sequential indicator simulation). Results yield an estimated fresh groundwater volume for the Mekong delta of 867 billion m3 with an uncertainty range of 830–900 billion m3, which is somewhat higher than previous assessments of fresh groundwater volumes. The resulting dataset can be used to support informed groundwater management decisions, e.g. to prevent further salinization of aquifers and land subsidence and are available at https://doi.org/10.5281/zenodo.4441776 (Gunnink et al, 2021).

Jan L. Gunnink et al.

Status: open (until 27 Apr 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on essd-2021-15', Anonymous Referee #1, 27 Mar 2021 reply
  • RC2: 'Comment on essd-2021-15', Anonymous Referee #2, 29 Mar 2021 reply

Jan L. Gunnink et al.

Data sets

Three-dimensional hydrogeological and salinity model of the Mekong delta, Vietnam Gunnink, Jan, Van Pham, Hung, Oude Essink, Gualbert, and Bierkens, Marc https://doi.org/10.5281/zenodo.4441776

Jan L. Gunnink et al.

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Short summary
In the Mekong Delta (Vietnam) groundwater is important for domestic, agricultural and industrial use. Increased pumping of groundwater has caused land subsidence and increased the risk of salinization, thereby endangering the livelihood of the population in the Delta. We made a model of the salinity of the groundwater by integrating different sources of information and determined fresh groundwater volumes. The resulting model can be used by researchers and policy makers.