Spatial–Seasonal Isotopic Variations in a Surface–Groundwater System in an Extremely Arid Basin and the Associated Hydrogeological Indications
Abstract. Climate warming accelerates the global water cycle. However, the relationships between climate warming and hydrological processes in the alpine arid regions remain unclear. Herein, high spatiotemporal resolution sampling of surface water and groundwater was performed at the Qaidam Basin, an extremely arid area in the northeastern Tibetan Plateau. Stable H-O isotopes and radioactive 3H isotopes were combined with atmospheric simulations to examine climate change and hydrogeological characteristics. The surface water heavy isotopes enrich during the wet season and deplete during the dry season. The contribution of precipitation to river discharge was considerably higher in the eastern region of the basin (approximately 45 %) than in the central and western regions (10 %–15 %). The H-O isotopic compositions showed a gradually negative spatial pattern from the west to the east in the Eastern Kunlun Mountains water system; a reverse pattern occurred in the Qilian Mountains water system. This distribution pattern was jointly regulated by the westerly water vapor transport intensity and local hydrothermal conditions. Increased precipitation and cryosphere shrinkage caused by climate warming mainly accelerated basin groundwater cycle. In the eastern and southwestern Qaidam Basin, precipitation and ice/snow meltwater infiltrate structural channels that favor water flow, such as fractures and fissures, facilitating rapid seasonal groundwater recharge and increased terrestrial water storage. However, under future increases in precipitation in the southwestern Qaidam Basin, compensating for water loss from long-term melting of ice and snow will be challenging, and the total water resources may show an initially increasing and then decreasing trend.
Yu Zhang et al.
Status: open (until 12 Jul 2023)
- RC1: 'Comment on hess-2023-67', Michael Stewart, 08 Jun 2023 reply
Yu Zhang et al.
Yu Zhang et al.
Viewed (geographical distribution)
This paper aims to use isotopic measurements in an extremely arid basin in the northeastern Tibetan Plateau to study the water resources of the area and their responses to climate change. The objective is a worthy one, but not very clearly enunciated. The aim of the research is within the scope of HESS and the paper contributes significant new data and analysis of the results. The conclusions reached are substantial and important, particularly as they are for such a climatically difficult area to research.
The extensive data and scientific methods employed allow the authors to reach well-founded interpretations and conclusions. The conclusions reached are substantial. The methods and assumptions are valid and clearly described. The authors give adequate credit to related work and cite appropriate references.
However, the paper is difficult to read and understand. I think this is partly because: 1) it lacks a clear focus and therefore the paper seems to ramble on without direction (as noted above the objective does not seem clearly enunciated), 2) the language is frequently difficult with often very general terms used (such as “Associated Hydrological Indications” in the title”) instead of more specific terms that would give a clearer picture, or 3) to a less extent the use of combined words (such as “spatiotemporal”, “spatial-seasonal”) makes for difficult reading. Simple words are generally clearer. However, I realise combined words are being increasingly used in scientific papers, and can have specific meanings in some contexts.
A better title might be “Isotopic variations in surface waters and groundwaters of an arid basin and their responses to climate change”.
1) The captions to all of the figures need to be more informative. Eg What data does the inset in Fig. 3a show? Also the light lines in Figs. 4 and 5 show distribution patterns in the δ18O data, but there is no mention of these in the captions. Fig. 11 caption does not identify what is in Figs. 11a and 11b.
2) I don’t think Fig. 2 is necessary for the paper, although it is interesting.
3) How is skew defined? The formula used should be explained in Sampling and methods (Sect. 3.) if skew is in fact an important part of the paper. I’m not sure that it is. For example:
L258 The paper states “The basin surface water mean δ18O and δD values were positively skewed by −0.08‰ to 1.08‰ and 0.63‰ to 10.58‰, respectively, in the wet seasons.” How is this different from “The basin surface water mean δ18O and δD values were more positive by −0.08‰ to 1.08‰ and 0.63‰ to 10.58‰, respectively, in the wet seasons.”? The latter sentence is much easier to understand (assuming it correctly expresses the intended meaning. If it doesn’t, I don’t know what the original sentence means.)
Again, L614-615 states “The mean values of surface water δ18O and δD … are negatively skewed from west to east …”. Does this mean that “The mean values of surface water δ18O and δD … decrease from west to east …”?
L19 Use of the word “hydrothermal” is not helpful to the reader. Hydrothermal usually refers to water heated by the Earth's internal heat underground, which is not what the writer means.
L137 “Altun fault” not “Alun fault”
L162 “phreatic” not “phrenic”
L178 Should be “the precision was improved to less than ± 0.8 TU” not “more than ± 0.8 TU”.
L499 Should be “fell” not “fall”