Comment on “Origin of water in the Badain Jaran Desert, China: new insight from isotopes” by Wu et al. (2017)

Lucheng Zhan,Jiansheng Chen,Ling Li,David A Barry

doi:10.5194/hess-22-4449-2018

Abstract

Abstract. Precipitation isotope data were used to determine the origin of groundwater in the Badain Jaran Desert (BJD) in the study of Wu et al. (2017). Both precipitation and its isotope composition vary seasonally, so arithmetic averages of precipitation isotope values poorly represent the isotope composition of meteoric water. Their finding that the BJD groundwater is recharged by modern meteoric water from local areas including the southeastern adjacent mountains was based on arithmetic averaging. However, this conclusion is not supported by the corrected mean precipitation isotope values, which are weighted by the precipitation rate. Indeed, the available isotopic evidence shows that modern precipitation on the Qilian Mountains is more likely to be the main source of the groundwater and lake water in the BJD, as found by Chen et al. (2004).

Highlights

The Badain Jaran Desert (BJD) is characterized by a unique landscape that contains a large number of lakes and the world’s largest stationary sand dunes maintained by groundwater (Chen et al, 2004)
Both precipitation and its isotope composition vary seasonally, so arithmetic averages of precipitation isotope values poorly represent the isotope composition of meteoric water. Their finding that the BJD groundwater is recharged by modern meteoric water from local areas including the southeastern adjacent mountains was based on arithmetic averaging
Wu et al (2017) ruled out the Qilian Mountains as a recharge area for groundwater in the BJD based on the large isotopic difference between the GMWL-EL2 intersection and data from water samples mainly collected from the Shiyang River watershed (Li et al, 2016), which is located in the eastern lower area of the Qilian Mountains

Summary

Introduction

The Badain Jaran Desert (BJD) is characterized by a unique landscape that contains a large number of lakes and the world’s largest stationary sand dunes maintained by groundwater (Chen et al, 2004). Using stable and radioactive environmental isotopes, Wu et al (2017) investigated the connection between lakes and groundwater, and the origin of groundwater in the southeastern desert area They suggested that the BJD groundwater is derived primarily from modern meteoric water from local areas, including the southeastern adjacent small mountains. Wu et al (2017) reasoned that the average age of groundwater in the BJD should be much younger, since it includes modern meteoric water as indicated by tritium levels (Gates et al, 2008; Wu et al, 2017) They presented much evidence and discussion for their conclusion of groundwater recharged by modern precipitation from local areas. Water Line), which led Wu et al (2017) to conclude that groundwater and lake water in the BJD originate from modern meteoric precipitation in local areas including the adjacent small mountains. Compared with the isotope composition of the local precipitation, the source water recharging the BJD groundwater and lakes is much more depleted in D and 18O

Reanalysis on the origin of groundwater in the BJD

Findings

Concluding remarks