Mid to late holocene climate evolution of the lake telmen basin, north central mongolia, based on palynological data   总被引：2，自引：0，他引：2  

Sarah J. Fowell  Barbara C. S. Hansen  John A. Peck  P. Khosbayar  Enebish Ganbold 《Quaternary Research》2003,59(3):353-363

Palynological and sedimentological data from Lake Telmen, in north-central Mongolia, permit qualitative reconstruction of relative changes in moisture balance throughout the mid to late Holocene. The climate of the Atlantic period (7500–4500 yr ago) was relatively arid, indicating that Lake Telmen lay beyond the region of enhanced precipitation delivered by the expanded Asian monsoon. Maximum humidity is recorded between 4500 and 1600 cal yr B.P., during the Subboreal (4500–2500 yr ago) and early Subatlantic (2500 yr–present) periods. Additional humid intervals during the Medieval Warm Epoch (1000–1300 A.D. or 950–650 ago) and the Little Ice Age (1500– 1900 A.D. or 450–50 yr B.P.) demonstrate the lack of long-term correlation between temperature and moisture availability in this region. A brief aridification centered around 1410 cal yr B.P. encompasses a decade of cold temperatures and summer frost between A.D. 536 and 545 (1414–1405 yr B.P.) inferred from records of Mongolian tree-ring widths. These data suggest that steppe vegetation of the Lake Telmen region is sensitive to centennial- and decadal-scale climatic perturbations.  相似文献   

干旱区引水渠道渗漏补给能力实验研究     

王琴 《地下水》2015,(3)

针对干旱区山前倾斜平原地层透水能力强、地下水埋深大、补给水源水质普遍较好、泥沙含量高等特点,对渠道渗漏补给能力进行实验研究,寻求适合干旱区特点的快速高效、经济可行并且能够长期运行的地下水人工补给方案。研究结果表明:引水渠道采用下部混凝土板防渗、上部干砌石防渗以增加渠道渗漏量的人工补给地下水方式是可行的。  相似文献   

Effects of groundwater level on vegetation in the arid area of western China   总被引：1，自引：0，他引：1  

《China Geology》2021,4(3):527-535

At present, investigation about the relationship between the change of groundwater level and vegetation mostly focuses on specific watersheds, i.e. limited in river catchment scale. Understanding the change of groundwater level on vegetation in the basin or large scale, be urgently needed. To fill this gap, two typical arid areas in the west of China (Tarim Basin and Qaidam Basin) were chosen the a typical research area. The vegetation status was evaluated via normalization difference vegetation index (NDVI) from 2000 to 2016, sourced from MODN1F dataset. The data used to reflect climate change were download from CMDSC (http://data.cma.cn). Groundwater level data was collected from monitor wells. Then, the relationship of vegetation and climate change was established with univariate linear regression and correlation analysis approach. Results show that: Generally, NDVI value in the study area decreased before 2004 then increased in the research period. Severe degradation was observed in the center of the basin. The area with an NDVI value > 0.5 decreased from 12% to 6% between 2000 and 2004. From 2004 to 2014, the vegetation in the study area was gradually restored. The whole coverage of Qaidam Basin was low. And the NDVI around East Taigener salt-lake degraded significantly, from 0.596 to 0.005, 2014 and 2016, respectively. The fluctuation of groundwater level is the main reason for the change of surface vegetation coverage during the vegetation degradation in the basin. However, the average annual precipitation in the study area is low, which is not enough to have a significant impact on vegetation growth. The annual average precipitation showed an increase trend during the vegetation restoration in the basin, which alleviates the water shortage of vegetation growth in the region. Meanwhile, the dependence of surface vegetation on groundwater is obviously weakened with the correlation index is –0.248. The research results are of some significance to eco-environment protection in the arid area of western China.© 2021 China Geology Editorial Office.  相似文献   

Quantifying groundwater recharge and discharge for the middle reach of Heihe River of China using isotope mass balance method          下载免费PDF全文

Zhang Han  Chen Zong-yu  Tang Chang-yuan 《地下水科学与工程》2021,9(3):225-232

Quantifying the inflow and outflow of groundwater is essential to understand the interaction between surface water and groundwater. It is difficult to determine these elements in relation to groundwater recharge and discharge to the river, because they cannot be directly measured through site specific study. The methods of isotope mass balance combining with water budget were used to quantify the groundwater recharge from and discharge to the Heihe River, northwest China. The mean isotope ratios of monthly monitoring data for one hydrological year were selected to be the isotope rations of end members in isotope mass balance. The results from the isotope mass balance analysis, incorporating with the 35-year hydrological data, suggest that about 0.464×10~9 m~3/a of runoff flowing out Qilian Mountains is contributed to groundwater recharge(about 28% inflow of the Heihe River), while about 1.163×10~9 m~3/a of runoff is discharged from groundwater in the middle reach of the river, which accounts for about 46% of river runoff in the basin. The analysis offers a unique, broad scale studies and provides valuable insight into surface water-groundwater interaction in arid area.  相似文献   

An Overview of Distribution Characteristics and Formation Mechanisms in Global Arid Areas     

Xinyang Yan  Qiang Zhang  Xiaomin Yan  Sheng Wang  Xueyuan Ren  Funian Zhao 《地球科学进展》2019,34(8):826-841

The ecological environment in arid areas is extremely fragile and especially sensitive to climate response. Continuous research on the climate and its impact mechanism in the arid zones is of great scientific significance for deeper understanding of the cause of climatic formation and better prediction of climate in arid regions. Some research progresses in recent decades both at home and abroad have been overviewed, including the distribution of arid areas, the causes of arid area climatic formation and arid area climate change. Studies have shown that AI index is an effective criterion for dividing arid areas. There are 8 major arid areas in the world; climatic formation in arid areas is the result of multiple factors; there are 6 kinds of influencing factors, such as Hadley Cell, land-air interaction and so on; the unlikely trend between dry and wet is obvious in arid areas, and some regions are facing more severe drought trends such as North Africa and China-Mongolia, while others show a trend of wetting such as the Midwest of the United States. At present, there are still some scientific problems to be solved urgently:The response of various arid regions to global warming is quite different, and climate prediction in these zones is both important and difficult; the uplift of the Qinghai-Tibet Plateau has a tremendous impact on the arid area of China-Mongolia, but the models of this field are not perfect enough; there are no accepted conclusions about the causes of climatic formation in different arid regions and the causes of their different wet and dry trends. At present, it is still impossible to quantitatively distinguish the relative contributions of various influencing factors in the climate evolution of drylands and their response processes.  相似文献   

Pleistocene Loess-Paleosol Sequences in Arid Central Asia State of Art   总被引：1，自引：1，他引：0  

Xin Wang  Jinhui Zhang  Jia Jia  Mi Wang  Qiang Wang  Jianhui Chen  Fei Wang  Zaijun Li  Fahu Chen 《地球科学进展》2019,34(1):34-47

Loess of central Asia is located in a linkage zone between the European and Chinese loess depositional belts. Paleoclimate signatures from loess-paleosol sequences here is a key for completely understanding the spatial-tempo paleoclimate changes of Euro-Asia and for understanding the interactions between westerlies and Asia monsoon system during geological time. However, paleoclimate investigations of loess-paleosol sequences in arid central Asia is relatively weak than those from Europe and Chinese Loess Plateau. Specific, correlations of paleoclimate records with Chinese loess is required for better understanding “westerly regimes” in central Asia and its phase relationship with monsoon Asia on various time scale. In this work, we reviewed new advantages of loess study in central Asia during the last decades. Based on the stratigraphic and paleoclimatic correlations of loess-paleosol sequences between central Asia and the Chinese Loess Plateau, we discussed aridification history of Asia on tectonic time scale, the hydroclimate changes in arid central Asia and its phase relationship with Monsoonal Asia on orbital and millennial time scale during the Pleistocene.  相似文献   

Quartz OSL and K-feldspar pIRIR dating of a loess/paleosol sequence from arid central Asia,Tianshan Mountains,NW China     

《Quaternary Geochronology》2015

Loess deposits surrounding the high mountainous regions of arid central Asia (ACA) play an important role in understanding environmental changes in Eurasia on orbital and sub-orbital time scales. However, problems with dating loess in ACA have limited the interpretation of climatic and environmental data, especially Holocene data. We selected a typical loess/paleosol sequence (LJW10) on the northern slope of the Tianshan Mountains in ACA consisting of 280 cm of loess with multiple paleosols formed in the upper 170 cm of the section. We applied quartz OSL dating to coarse-grained (63–90 μm) fractions, and newly developed K-feldspar pIRIR dating protocols to both coarse-grained and medium-grained (38–63 μm) fractions of the samples from LJW10 section. Internal checks of the quartz OSL dating indicate that the single-aliquot regenerative-dose protocol on large aliquots (5 mm) is appropriate for equivalent dose (D_e) determinations and that the quartz ages of the loess samples are likely to be reliable. Luminescence characteristics and internal checks of the pIRIR dating indicate the pIRIR signal at a 170 °C stimulation temperature with a 200 °C preheat can be used for both coarse-grained and medium-grained D_e determinations. Anomalous fading tests for the pIRIR 170 °C signal indicate the pIRIR signals are stable and the anomalous fading of the pIRIR 170 °C signal can be ignored. Sunlight bleaching tests of the loess indicate the residual dose for the pIRIR 170 °C signal can also be ignored as it corresponds to only ∼9 years for the medium-grained K-feldspar and ∼85 years for the coarse-grained K-feldspar. The pIRIR ages of five medium-grained and coarse-grained K-feldspar samples are consistent with coarse-grained quartz OSL ages, and both the medium-grained and coarse-grained ages increase uniformly with depth, indicating these pIRIR ages are reliable. Based on the coarse-grained quartz OSL ages, and on coarse-grained and medium-grained K-feldspar pIRIR ages, an age-depth model for the paleosol-loess sequence was established by using a Bacon age-depth model. This model suggests eolian loess deposition began by at least ∼16 ka ago and that paleosol development on these eolian loess deposits began ∼5.5 ka, continuing to the present, with periods of high effective moisture at 5.5–4.9, 4.6–4.1, and 3.4–3.1 ka. This sequence suggests overall relative aridity during the early Holocene and an increase in effective moisture beginning ∼5.5 ka during the mid-late Holocene in ACA.  相似文献   

Chronology of relict lake deposits in the Spiti River, NW Trans Himalaya: Implications to Late Pleistocene–Holocene climate-tectonic perturbations     

Binita Phartiyal  Anupam Sharma  Pradeep Srivastava  Yogesh Ray 《Geomorphology》2009,108(3-4):264-272

The Spiti River that drains through the arid Trans-Himalayan region is studied here. The relict deposits exposed along the river provide an opportunity to understand the interaction between the phases of intense monsoon and surface processes occurring in the cold and semi arid to-arid Trans-Himalayan region. Based on geomorphological observation the valley is broadly divided into the upper and lower Spiti Valley. The braided channel and the relict fluvio-lacustrine deposits rising from the present riverbed characterize the upper valley. The deposits in the lower valley occur on the uplifted bedrock strath and where the channel characteristics are mainly of meandering nature. Conspicuous is the occurrence of significantly thick lacustrine units within the relict sedimentary sequences of Spiti throughout the valley. The broad sedimentary architecture suggests the formation of these palaeolakes due landslide-driven river damming. The Optically Stimulated Luminescence (OSL) dating of quartz derived from the bounding units of the lacustrine deposits suggests that the upper valley preserves the phase of deposition around 14–6 ka and in the lower valley around 50–30 ka. The review of published palaeoclimatic palaeolake chronology of Spiti Valley indicates that the lakes were probably formed during the wetter conditions related to Marine Isotope Stage III and II. The increased precipitation during these phases induced excessive landsliding and formation of dammed lakes along the Spiti River. The older lacustrine phase being preserved on the uplifted bedrock strath in the lower valley indicates late Pleistocene tectonic activity along the Kaurick Chango normal fault.  相似文献   

The characteristics of water resources and the changes of the hydrological process and environment in the arid zone of northwest China   总被引：10，自引：0，他引：10  

G. Wang  G. Cheng 《Environmental Geology》2000,39(7):783-790

 Water resources in the arid zones of northwest China mainly come from mountain areas and then flow to and disappear in the piedmont plains. These water resources, with inland river basins as the geographic unit, form relatively independent ecosystems and the surface runoff flowing out of the mountain mouth becomes the only water source available for the middle and lower reaches of these basins. Both the ecosystem stability and sustainable development depend on the surface water and groundwater resources of these inland river basins. Over the last 50 years, exploitation of water and land resources in the arid northwest regions of China has been expanding, forming 390.07×10⁴ ha of irrigation oases, with construction of 622 reservoirs of different sizes with a total storage capacity of 65.5×10⁸ m³ ensuring the sustainable development of industrial and agricultural production. In the meantime it has also caused a series of environmental changes. Discharge of the majority of rivers has been drastically reduced (even dried up), river courses have been shortened, and terminal lakes contracted or dried up. Land desertification and soil salinization has developed rapidly. Vegetation is degrading and biodiversity is decreasing, as compared with the early 1950s; the natural grassland area is decreasing by 16–75.4%. Economical and high-effective use of water resources and harmonization of eco-environment benefits with economic benefits are the fundamental ways to achieve sustainable development of arid northwest China. Received: 20 January 1999 · Accepted: 4 May 1999  相似文献   

芒崖凹陷干旱气候背景下网状河流沉积体系及演化   总被引：4，自引：0，他引：4  

王随继  任明达 《地球学报》2000,21(1):92-97

通过对柴达木盆地芒崖凹陷上新统露头的结构单元分析和对钻井剖面上砂岩、泥岩的空间分布关系及岩相转换的Ｍａｒｋｏｖ链模式等方面的研究,得出研究区中－上新统是网状河流沉积体系并在上上新统转化为瓣状河流沉积体系这一新认识。孢粉化石资料、深干裂以及钙质结核等指示网状河流发育姑干旱气候背景下。网状河流向瓣状河流的演化受到盆地基底的沉降速率及与气候密切相关的植被覆盖程度等因素的控制。  相似文献