Social perception and response to the drought process: a case study of the drought during 2009–2010 in the Qianxi’nan Prefecture of Guizhou Province

Studies carried out on the drought process, which can be classed as a gradual disaster, can help us to understand the disaster mechanism and offer strategies for disaster prevention. This paper uses the example of the drought in the Qianxi??nan Prefecture of Guizhou Province from July 2009 to May 2010. Data have been collected from government gazetteers, meteorological monitoring data, and field surveys to build up a sequence of meteorological drought indices. The categorization of the victims?? perception of drought impact, and the stages of drought responses of different subjects (government, social organizations, and the public), has also been examined by the same way. By contrasting the differences between the metrological drought indices, and victims?? perception of drought impact, researchers explored the drought cognition features of victims, social response features, and dynamic relationships between drought development and social responses. The results were as follows: The drought evolution process could be divided into 6 phases, and victims?? perception of drought impact could be divided into 7 phases. They were consistent in time period, and the victims?? perception of drought was subjective and based on their direct experiences. Their response has the characteristics of long term and concentration on a time. The responses of government and social organizations obviously fell behind those of victims, but they were effective and intensive in both timescale and effort. As the drought developed, responses shifted from individual to social responses and from practical to economic, political, and technological responses. On the basis of the results, the author has suggested methods of preparing stakeholders against possible drought risks.     

Metallogeny during continental outgrowth in the Columbia supercontinent: Isotopic characterization of the Zhaiwa Mo–Cu system in the North China Craton

The Eastern Qinling Molybdenum Belt (EQMB) in central China represents the largest Mo province in the world. Located at the southern margin of the North China Craton, this Mo province is largely associated with Mesozoic granitoids. Here we report Re–Os isochron age of 1761 ± 33 Ma (2σ, MSWD = 2.9) from molybdenite in the recently discovered Zhaiwa porphyry Mo–Cu system within the EQMB. This age coincides with the peak eruption period (1.78−1.75 Ga) of the Xiong'er Group volcanic rocks which unconformably overlie the Taihua Supergroup and are interpreted to have developed on a continental arc. The Re concentrations (1 to 43 ppm) of the Zhaiwa molybdenites are similar to those of typical porphyry Cu–Mo–Au systems developed on continental arcs. The δ³⁴S values of the Zhaiwa ores (2.7–7.3‰, average 5.2‰) suggest that the sulfur was mainly sourced from a magmatic system. The sulfides from the ores yield Sr_i average of 0.70533, similar to that of the Xiong'er Group (0.70547), albeit higher than that of the Kuanping Group (0.70334) and lower than the Taihua Supergroup (0.70763), suggesting a mixed source. The average ε_Nd(1.76 Ga) of the sulfides from the ores (0.9) falls between the averages of the Taihua Supergroup (ca. − 6.8) and the Kuanping Group (ca. 7.4). The Pb isotope ratios of the ores are similar to, but slightly higher than those of the Taihua Supergroup, reflecting preferential leaching of radiogenic Pb from the Taihua Supergroup by magmatic fluids. Integrated data and interpretations constrain the Zhaiwa Mo–Cu deposit to be a porphyry mineral system developed within a ca. 1.76 Ga continental arc related to oceanic plate subduction beneath the southern margin of the North China Craton. A correlation between tectonic settings and metallogenic types clearly indicate that the Xiong'er Group was formed in a volcanic arc, confirming Paleo-Mesoproterozoic continental outgrowth along the margins of the Columbia supercontinent. The isotopic characterization of the Zhaiwa deposit provides new insights into the enigma of the widespread distribution of large and super-large Mo deposits of EQMB along the southern margin of the North China Craton.     

Impacts of acid mine drainage on a stream in subtropical China during a major flood event

Field and laboratory work was carded out to investigate the chemistry and ecotoxicity of stream water affected by acid mine drainage in a tributary catchment of the Pearl River in subtropical China during a major flood event that corresponded to a return period of 100 years occurred in the study area. The results indicate that stream water was affected by acid mine drainage from the Dabaoshan Mine at least to a distance of 25 km downstream of the mine water discharge point. It appears that sulfide-H^＋ from the waste rock dumps was readily available for discharging and the amount of H^＋ being transported outwards depended on the volume of out-flowing waters. However, there was a lag time for the discharge of the metals. This may be attributed to the slower release of metals, relative to H^＋, because it might take more time for the dissolution of heavy metal-bearing compounds. Fe, Zn and Al were the major metals of potential toxicity contained in the AMD-affected stream water, followed by Mn, Cu, Pb, As, Cd and Ni. Acute toxicity tests show that the AMD-affected stream water at 3.5 km downstream of the discharge point was highly toxic to the test organisms.     

Constraints on the paleogeographic evolution of the North China Craton during the Late Triassic–Jurassic

This paper reports U–Pb–Hf isotopes of detrital zircons from Late Triassic–Jurassic sediments in the Ordos, Ningwu, and Jiyuan basins in the western-central North China Craton (NCC), with the aim of constraining the paleogeographic evolution of the NCC during the Late Triassic–Jurassic. The early Late Triassic samples have three groups of detrital zircons (238–363 Ma, 1.5–2.1 Ga, and 2.2–2.6 Ga), while the latest Late Triassic and Jurassic samples contain four groups of detrital zircons (154–397 Ma, 414–511 Ma, 1.6–2.0 Ga, and 2.2–2.6 Ga). The Precambrian zircons in the Late Triassic–Jurassic samples were sourced from the basement rocks and pre-Late Triassic sediments in the NCC. But the initial source for the 238–363 Ma zircons in the early Late Triassic samples is the Yinshan–Yanshan Orogenic Belt (YYOB), consistent with their negative zircon ε_Hf(t) values (−24 to −2). For the latest Late Triassic and Jurassic samples, the initial source for the 414–511 Ma zircons with ε_Hf(t) values of −18 to +9 is the Northern Qinling Orogen (NQO), and that for the 154–397 Ma zircons with ε_Hf(t) values of −25 to +12 is the YYOB and the southeastern Central Asian Orogenic Belt (CAOB). In combination with previous data of late Paleozoic–Early Triassic sediments in the western-central NCC and Permian–Jurassic sediments in the eastern NCC, this study reveals two shifts in detrital source from the late Paleozoic to Jurassic. In the Late Permian–Early Triassic, the western-central NCC received detritus from the YYOB, southeastern CAOB and NQO. However, in the early Late Triassic, detritus from the CAOB and NQO were sparse in basins located in the western-central NCC, especially in the Yan’an area of the Ordos Basin. We interpret such a shift of detrital source as result of the uplift of the eastern NCC in the Late Triassic. In the latest Late Triassic–Jurassic, the southeastern CAOB and the NQO restarted to be source regions for basins in the western-central NCC, as well as for basins in the eastern NCC. The second shift in detrital source suggests elevation of the orogens surrounding the NCC and subsidence of the eastern NCC in the Jurassic, arguing against the presence of a paleo-plateau in the eastern NCC at that time. It would be subsidence rather than elevation of the eastern NCC in the Jurassic, due to roll-back of the subducted paleo-Pacific plate and consequent upwelling of asthenospheric mantle.     

Permian–Triassic amalgamation of Asia: Insights from Northeast China sutures and their place in the final collision of North China and Siberia

The Central Asia Orogenic Belt (CAOB) corresponds to the domain where Siberia and Mongolia were welded to North China. The eastern extension of the CAOB in Northeast China is disputed, since both suture location and timing are poorly documented. This paper reports for the first time the recognition of two suture zones in the southern part of Northeast China (Manchuria), between the Fushun Mishan and Yilan-Yitong faults. In the Jilin Province, west-directed thrust sheets involving successively, from west to east, passive continental margin rocks, metamorphic rocks and ophiolites, block-in-matrix formations and arc plutons indicate a Permian–Early Triassic collision. In the Liaoning Province, arc plutonism and top-to-the-north ductile shearing, coeval with the emplacement of an ophiolitic nappe, suggest a Palaeozoic collision. These two sutures are correlated with the Ondor Sum and Solonker sutures, described in Inner Mongolia. A new geodynamic model involving rifting and collision of the southern part of the Xilinhot Block with North China is proposed.     

Paleoproterozoic gabbronoritic and granitic magmatism in the northern margin of the North China craton: Evidence of crust–mantle interaction

Paleoproterozoic Xuwujia gabbronorites in the northern margin of the North China craton occur as dykes, sills and small plutons intruded into khondalite (aluminous paragneisses, sedimentary protoliths deposited at ca. 2.0–1.95 Ga), and as numerous entrained bodies and fragments of variable scales in the Liangcheng granitoids (ca. 1.93–1.89 Ga). These gabbronoritic dykes are present at all locations where ca. 1.93–1.92 Ga ultra-high-temperature metamorphism is recorded in the khondalite. A gabbronorite sample from the Hongmiaozi dyke gives zircon ²⁰⁷Pb/²⁰⁶Pb mean ages of 1954 ± 6 Ma (core domains) and 1925 ± 8 Ma (rim domains). These ages, as well as previously reported ages, constrain the age of mafic magmatism to be at ca. 1.96–1.92 Ga (∼1.93 Ga). One sample from the Xigou gabbro intruded by the Liangcheng granitoids gives a zircon ²⁰⁷Pb/²⁰⁶Pb mean age of 1857 ± 4 Ma, which is interpreted as the age of a metamorphic overprint. The Xuwujia gabbronorites comprise mainly gabbronorite compositions, as well as some norite, olivine gabbronorite, monzonorite, quartz gabbronorite, and quartz monzonorite. Chemically, they are tholeiitic and can be divided into two groups: a high-Mg group (6.2–22.9 wt.% MgO) and a relatively low-Mg group (2.2–5.7 wt.% MgO). The high-Mg group shows negative Eu-anomalies (Eu/Eu* = 0.53–0.72), slight light rare earth element enrichment (La/Yb_N = 0.56–1.53), and small negative anomalies in high field-strength elements. The ?Nd (t = 1.93 Ga) values vary from +0.3 to +2.4. The low-Mg group shows varied Eu-anomalies (Eu/Eu* = 0.48–1.05), and is enriched in light rare earth elements (La/Yb_N = 1.51–11.98). The majority shows negative anomalies in high field-strength elements (e.g., Th, Nb, Zr, and Ti). Initial ?Nd (at 1.93 Ga) values for low-Mg gabbronorites vary from −5.0 to 0. The Xuwujia gabbronorites possibly experienced assimilation of crust, and fractional crystallization of initially olivine and hypersthene (the high-Mg group), and then olivine, clinopyroxene, and plagioclase (the low-Mg group). The slightly younger Liangcheng granitoids consist of garnet-bearing granite, granodiorite and quartz-rich granitic compositions. They are intermediate to felsic calc-alkaline rocks, thought to be derived from surrounding metasedimentary crust. Xigou gabbro could represent early cumulates. The granitoids have relatively high-Mg numbers (up to 54), and show some chemical affinities with the gabbronorites, which could have resulted from incorporation of gabbronoritic melts. The occurrence and chemical variations of the Xuwujia gabbronorites and Liangcheng granitoids can be interpreted to have resulted from crust–mantle interaction, with mingling and partial mixing of mantle (gabbronoritic) and crustal (granitic) melts. The Xuwujia gabbronorites originated from a mantle region with high potential temperatures (∼1550 °C), possibly associated with a plume or more likely a ridge-subduction-related mantle upwelling event. They could have had extremely high primary intrusion temperatures (up to 1400 °C). Emplacement of these magmas was likely responsible for the extensive crustal anatexis (Liangcheng granitoids) and the local ultra-high-temperature metamorphism. These sequences may have followed ca. 1.95 Ga continent–continent (arc?) juxtaposition and were themselves followed by significant regional uplift and exhumation in the northern margin of the North China craton.     

An assessment of the carrying capacity of groundwater resources in North China Plain region–Analysis of potential for development

Over-exploitation of groundwater in North China Plain (NCP) has resulted in a series of eco-environment problems. Sustainable use of groundwater resources in NCP, in particular management of groundwater resource carrying capacity (GRCC), faces an unprecedented challenge. Here we define GRCC, and a new assessment method is tentatively proposed and applied to evaluate GRCC based on the whole NCP, city administrative units and county administrative units. Our study divided the NCP into three zones, i.e. non-overexploited non-overloaded zone (NNZ), overexploited but non-overloaded zone (ONZ), and overexploited overloaded zone (OOZ). Results confirmed 27.6% of counties belonged to NNZ. However, 58.9% of counties and NCP as a whole belonged to ONZ, and 13.5% of counties belonged to OOZ. Spatially, NNZs were mainly distributed in Beijing, parts of eastern coastal cities and Henan Province. OOZs were mostly distributed in middle-eastern part of Cangzhou, parts of Dezhou, Tianjin and Binzhou, and the remaining areas belonged to ONZs. We suggest two approaches for enhancing GRCC, i) increasing the amount of available groundwater and ii) improving the water use efficiency. An increase of 11.0 billion cubic meters to the available groundwater levels combined with water use efficiency improvements up to 479 CNY per cubic meter of the world mean, the gross domestic product (GDP) sustained by groundwater in the NCP could reach 11.1 trillion CNY and maintain a 20 years of GDP development assuming the current rate of growth.     

Chemical and strontium isotopic characteristics of shallow groundwater in the Ordos Desert Plateau,North China: Implications for the dissolved Sr source and water–rock interactions

In this study, the chemical and Sr isotopic compositions of shallow groundwater and rainwater in the Ordos Desert Plateau, North China, and river water from the nearby Yellow River, are investigated to determine the dissolved Sr source and water–rock interactions, and quantify the relative Sr contribution from each end-member. Three groundwater systems have been identified, namely, GWS-1, GWS-2 and GWS-3 according to the watershed distribution in the Ordos Desert Plateau. Ca²⁺ and Mg²⁺ are the most dominant cations in GWS-1, while Na⁺ is dominant in GWS-3. In addition, there is more SO₄²⁻ and less Cl⁻ in GWS-1 than in GWS-3. The shallow groundwater in GWS-2 seems to be geochemically between that in GWS-1 and GWS-3. The ⁸⁷Sr/⁸⁶Sr ratios of the shallow groundwater are high in GWS-1 and GWS-2 and are low in GWS-3. By geochemically comparing the nearby Yellow River, local precipitation and deep groundwater, the shallow groundwater is recharged only by local precipitation. The ionic and isotopic ratios indicate that carbonate dissolution is an important process controlling the chemistry of the shallow groundwater. The intensity of the water–rock interactions varies among the three groundwater systems and even within each groundwater system. Three end-members controlling the groundwater chemistry are isotopically identified: (1) precipitation infiltration, (2) carbonate dissolution and (3) silicate weathering. The relative Sr contributions of the three end-members show that precipitation infiltration and carbonate dissolution are the primary sources of the shallow groundwater Sr in GWS-3 whereas only carbonate dissolution is responsible for the shallow groundwater Sr in GWS-1 and GWS-2. Silicate weathering seems insignificant towards the shallow groundwater's chemistry in the Ordos Desert Plateau. This study is helpful for understanding groundwater chemistry and managing water resources.     

Sediment salt-load in the St Lucia Estuary during the severe drought of 2002–2006

The purpose of this study was to determine whether there was a sufficiently high residual salt load in the dry sediments of the St Lucia Estuary to cause salinity problems should it later fill up with either freshwater or seawater. The estuary lakes have suffered the effects of a severe drought since 2002 with the result that many areas were dry, and the salinity of the residual water varied between 4 psu and up to five times that of seawater. Measurements of the salts content in the sediments to a depth of 20 cm showed that more than 2 million tonnes of salt was held in this layer of the sediment in 2006. Recent management of the estuary (since 1970) has ensured that the mouth was not artificially opened. This was to prevent the inflow of seawater, with its salts, that would otherwise enter while the drought was in place. The results of the sediment salinity data showed that if the drought had been broken and the lake area filled with rain and river water, the resulting salinity would be about 6 psu. In March 2007, Cyclone Gamede in the Indian Ocean off the east coast of South Africa produced a wave climate at sea that resulted in the mouth breaching; thus introducing an estimated 12 million tonnes of salts. The high salinity in the system resulting from this breach is expected to have an adverse effect on the ecology of the system, whereas the residual salinity in the sediments would not have caused an environmental problem. If the estuary and lake system were to fill completely with seawater, the residual salts together with seawater will raise the salinity to an initial value higher than 40 psu, which will have the effect of suppressing much of the important submerged vegetation that is vital for sustaining juvenile fish in the system. Many of the large fauna will also suffer from a shortage of freshwater.     

Assessment of agricultural drought during crop-growing season in the Sudano–Sahelian region of Cameroon

Natural Hazards - Drought is a recurrent phenomenon in the Sudano–Sahelian region of Cameroon. However, it has received very little attention, especially, on its impacts on the growing season...     

Hydrogeochemical characteristics of groundwater and pore-water and the paleoenvironmental evolution in the past 3.10 Ma in the Xiong’an New Area,North China

The groundwater level has been continuously decreasing due to climate change and long-time overexploitation in the Xiong’an New Area, North China, which caused the enhanced mixing of groundwater in different aquifers and significant changes in regional groundwater chemistry characteristics. In this study, groundwater and sediment pore-water in drilling cores obtained from a 600 m borehole were investigated to evaluate hydrogeochemical processes in shallow and deep aquifers and paleo-environmental evolution in the past ca. 3.10 Ma. Results showed that there was no obvious change overall in chemical composition along the direction of groundwater runoff, but different hydrochemical processes occurred in shallow and deep groundwater in the vertical direction. Shallow groundwater (< 150 m) in the Xiong’an New Area was characterized by high salinity (TDS > 1000 mg/L) and high concentrations of Mn and Fe, while deep groundwater had better water quality with lower salinity. The high TDS values mostly occurred in aquifers with depth < 70 m and >500 m below land surface. Water isotopes showed that aquifer pore-water mostly originated from meteoric water under the influence of evaporation, and aquitard pore-water belonged to Paleo meteoric water. In addition, the evolution of the paleoclimate since 3.10 Ma BP was reconstructed, and four climate periods were determined by the δ¹⁸O profiles of pore-water and sporopollen records from sediments at different depths. It can be inferred that the Quaternary Pleistocene (0.78–2.58 Ma BP) was dominated by the cold and dry climate of the glacial period, with three interglacial intervals of warm and humid climate. What’s more, this study demonstrates the possibilities of the applications of pore-water on the hydrogeochemical study and further supports the finding that pore-water could retain the feature of paleo-sedimentary water.© 2021 China Geology Editorial Office.     

Spatial and decadal variations in satellite-based terrestrial evapotranspiration and drought over Inner Mongolia Autonomous Region of China during 1982–2009

Evapotranspiration (ET) plays an important role in exchange of water budget and carbon cycles over the Inner Mongolia autonomous region of China (IMARC). However, the spatial and decadal variations in terrestrial ET and drought over the IMARC in the past was calculated by only using sparse meteorological point-based data which remain quite uncertain. In this study, by combining satellite and meteorology datasets, a satellite-based semi-empirical Penman ET (SEMI-PM) algorithm is used to estimate regional ET and evaporative wet index (EWI) calculated by the ratio of ET and potential ET (PET) over the IMARC. Validation result shows that the square of the correlation coefficients \((R^{2})\) for the four sites varies from 0.45 to 0.84 and the root-mean-square error (RMSE) is  \(0.78\) mm. We found that the ET has decreased on an average of 4.8 mm per decade (\(p=0.10\)) over the entire IMARC during 1982–2009 and the EWI has decreased on an average of 1.1% per decade (\(p=0.08\)) during the study period. Importantly, the patterns of monthly EWI anomalies have a good spatial and temporal correlation with the Palmer Drought Severity Index (PDSI) anomalies from 1982 to 2009, indicating EWI can be used to monitor regional surface drought with high spatial resolution. In high-latitude ecosystems of northeast region of the IMARC, both air temperature \((T_{a})\) and incident solar radiation \((R_{s})\) are the most important parameters in determining ET. However, in semiarid and arid areas of the central and southwest regions of the IMARC, both relative humidity (RH) and normalized difference vegetation index (NDVI) are the most important factors controlling annual variation of ET.     

Effects of landscape patterns on soil erosion processes in a mountain–basin system in the North China

This study was taken up to investigate the effects of landscape patterns on the soil erosion processes in a mountain–basin watershed. The revised universal soil loss equation and sediment delivery distribution models were used to estimate the soil erosion processes. The landscape patterns include the landscape metrics at the landscape level, landscape composition and configuration indicators on the basis of source–sink landscape theory. In the study area, the grassland, bare land, farmland and construction land were the sediment-source landscape; the forest and shrub were the sediment-sink landscape. The correlation analysis results showed that the soil erosion processes were significantly associated with the landscape patterns of the study area. At the landscape level, fragmentation metric was positively correlated with soil erosion; diversity metric was negatively related to soil erosion and sediment yield at the sub-basin scale. Among the source–sink landscape composition and configuration indicators, the composition indicator was positively correlated with soil erosion rate and sediment yield. In the configuration landscape indices, the shape index was negatively correlated with soil erosion rate and sediment yield; the fragmentation index was positively correlated with soil erosion rate and negatively correlated with sediment delivery rate. These results indicated that the optimization measures, such as increase in the area, connectivity and regularity of sediment-sink landscape, or decrease in the proportion, connectivity and regularity of sediment-source landscape, were favorable for soil conservation. Furthermore, the landscape indicators based on the source–sink theory could provide more information for landscape pattern optimization to reduce soil erosion.     

Analysis of the susceptibility of interdependent infrastructures using fuzzy input–output inoperability model: the case of flood hazards in Tehran

Natural Hazards - Advancement in technology has contributed to increment in complexity of systems and infrastructures. Furthermore, it has complicated the management of systems to deal with natural...     

Review: Water–rock interactions and related eco-environmental effects in typical land subsidence zones of China

Land subsidence is common in some regions of China. Various eco-environmental problems have arisen due to changes in water–rock interactions in these subsided areas, for which a comprehensive understanding of the hydrogeological setting is needed. This paper presents the general status of land subsidence in three typical subsided areas of China through the compilation of relevant data, and reviews some typical changes in the water–rock interactions in subsided areas along with related eco-environmental issues. It is found that the subsidence development and distribution are controlled by the groundwater-withdrawal intensity externally, and by the thickness and compressibility of unconsolidated sediments internally. The physical changes and related effects of water–rock interactions in subsided areas include: (1) the decreased ground elevation that caused floods, waterlogged farmland, etc.; (2) the differential subsidence that caused ground fissures; and (3) the change of seepage field that caused substantial reduction of the water resource. Chemically, the changes and related effects of water–rock interactions include: (1) the change to the chemical environment or processes due to the hydrogeologic structure alteration, which caused groundwater pollution; and (2) hydrologic mixing (seawater intrusion, artificial recharge; exchange with adjacent aquifers or aquitards), which degraded the groundwater quality. Further research on the subsided areas in China is suggested to reveal the mechanisms regarding biological and gaseous (meteorological) changes from the perspective of interacting systems among water, rocks, biological agents and gases.