Interactive comment on “Formation and dynamics of sandy dunes in the inland areas of the Hexi Corridor”

The paper of Bing-Qi Zhu focusses on formation and dynamic of changes of aeolian landforms (only sanddunes) and desertiﬁcation in the Hexi Corridor in China. The methods used are satellite image interpretations, ﬁeld investigations and observations, comprehensive evidences from geomorphological, aeolianâ ˘A ˇRphysical, granulometri-cal and geochemical analysis to discuss the formation of dune landforms, the mecha-nism of desertiﬁcation and their environmental implications in the Hexi Corridor. The author concludes, that the Gobi area in the west Hexi Corridor is not the main source area of sandstorms in the middle and east of the corridor except north proba-bly. In the past half century, the warming and humidiﬁcation of local climate is the main cause of the reduction of sandstorms in the study area, and the Hexi Corridor has a potential trend of antiâ ˘A ˇRdesertiﬁcation, which is mainly controlled by climate change but not by human activities. For the oases areas of the corridor, however, the effective measures to restrict desertiﬁcation depend on human activities. Restriction of the de-cline of groundwater is the key to preventing desertiﬁcation in oases. The abstract is a bit too long and should be shortened. paper current

The author concludes, that the Gobi area in the west Hexi Corridor is not the main source area of sandstorms in the middle and east of the corridor except north probably. In the past half century, the warming and humidification of local climate is the main cause of the reduction of sandstorms in the study area, and the Hexi Corridor has a C1 potential trend of antiâȂŘdesertification, which is mainly controlled by climate change but not by human activities. For the oases areas of the corridor, however, the effective measures to restrict desertification depend on human activities. Restriction of the decline of groundwater is the key to preventing desertification in oases. The abstract is a bit too long and should be shortened.
The focus on dune formation in the Hexi corridor in China is an interesting approach and could be of international interest -but this paper should be rejected in its current version for the following six main reasons: (1) The paper discusses also desertification processes -which should appear in the title and in my opinion this is not the scope of this journal.
(2) The structure and data used for this paper is a bit confusing. The author used different topics, e.g. geomorphological parameters such as transport processes and dune movement, grain-size and geochemical data, meteorological data sometimes without clear connection between these different processes, data and the methods used. The manuscript shows in some parts a lot of details and methods, but at a closer look, quite a lot of things are missing (e.g. to the methods or the quality / origin of the data) or they are not appropriate. In part, this may result from the different data and sometimes confusing structure of the text, which is often not concise enough to see the main research question(s) and follow a line of arguments.
(3) The movements of sand including desertification processes were already mentioned and discussed decades ago, e.g. by Zhu et al. (1988). There is a long reference list including 32 papers in Chinese -but important international papers on desertification and sand movement are missing. There are more international papers focusing on desertification and dune movement worldwide and in China, which must be considered, e.g. the review on desertification in China from Wang et al. (2008). In addition, papers focusing on the aeolian sediments in the Hexi corridor (e.g. Nottebaum et al.) are not considered.

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(4) The substantial conclusions by the author are: the Hexi Corridor has a potential trend of antiâȂŘdesertification, which is mainly controlled by climate change but not human activities. For the oasis of the corridor, however, the effective measures to restrict desertification depend on human activities. The first statement is based on the metrological data and not (enough) testified with other data, the second is not very new.
(5) What is not discussed and also important: The lowering of groundwater table in this region is due to the enlargement of the irrigation around the oasis especially after Second World War. This leads to reduction in river discharge and lowering of groundwater table and resulting in the drying of Gaxun Nur and adjacent lakes at the lower reaches of the Heihe River. This fact is already known and published since decades (e.g. Zhu Zhenda about 30 years ago). In addition, the lowering of discharge of groundwater table increased the salt content in the ground water and reduced areas with populous trees already in the 1980th of the last century One other main point: It should be considered, why a reduction in groundwater caused dune movements. There is no relation between these two factors -except and maybe with flat sand sheets in the floodplains of larger rivers or close to lakes vegetated with trees. Quite a lot of trees in these areas were mainly destroyed in former times (before 1980) for firewood (see Zhu et al. 1988) and enhanced the desertification processes in sandy regions. However, the main and important factor for dune movement and desertification is grazing and overgrazing. This is not mentioned at all. Several of these aspects were described and discussed in numerous international papers. In addition, some of the other figures should be improved..