Correlation analysis between drought indices and terrestrial water storage from 2002 to 2015 in China

Drought monitoring is a key topic in environmental monitoring and assessment although there is still a need to determine the correlation between drought monitoring indices and remote sensing products. We analyzed the correlation between the self-calibrating Palmer Drought Severity Index (sc_PDSI), the Standardized Precipitation Index and the Standardized Precipitation Evapotranspiration Index (SPEI) and terrestrial water storage monitored through the Gravity Recovery and Climate Experiment (GRACE) on a monthly timescale from 2002 to 2015 in China. As a consequence of anomalies in the soil water budget, the highly significant correlation between the sc_PDSI and the GRACE satellite-observed terrestrial water storage suggested that these two datasets are the most suitable for use in monitoring droughts. In comparing the three drought indices, the sc_PDSI was introduced as a means of drought monitoring in the Yangtze, Pearl, Huaihe, Southeast and Songhua River Basins, whereas the SPEI was found to be more applicable to other major river basins, such as the Inland River Basin. These diverse spatial behaviors are caused by the differences between the hydrological droughts characterized by these three drought indices.     

Evaluation of drought and wetness episodes in a cold region (Northeast China) since 1898 with different drought indices

Drought identification and drought severity characterization are crucial to understand water scarcity processes. Evolution of drought and wetness episodes in the upper Nen River (UNR) basin have been analyzed for the period of 1951–2012 using meteorological drought indices and for the period of 1898–2010 using hydrological drought indices. There were three meteorological indices: one based on precipitation [the Standardized Precipitation Index (SPI)] and the other two based on water balance with different formulations of potential evapotranspiration (PET) in the Standardized Precipitation Evapotranspiration Index (SPEI). Moreover, two hydrological indices, the Standardized Runoff Index and Standardized Streamflow Index, were also applied in the UNR basin. Based on the meteorological indices, the results showed that the main dry period of 1965–1980 and wet periods of 1951–1964 and 1981–2002 affected this cold region. It was also found that most areas of the UNR basin experienced near normal condition during the period of 1951–2012. As a whole, the UNR basin mainly had the drought episodes in the decades of 1910, 1920, 1970 and 2000 based on hydrological indices. Also, the severity of droughts decreased from the periods of 1898–1950 to 1951–2010, while the severity of floods increased oppositely during the same periods. A correlation analysis showed that hydrological system needs a time lag of one or more months to respond to meteorological conditions in this cold region. It was also found that although precipitation had a major role in explaining temporal variability of drought, the influence of PET was not negligible. However, the sole temperature driver of PET had an opposite effect in the UNR basin (i.e., misestimating the drought detection) and was inferior to the SPI, which suggests that the PET in the SPEI should be determined by using underlying physical principles. This finding is an important implication for the drought research in future.     

Evaluation of time scale of meteorological,hydrological and agricultural drought indices

Natural Hazards - The present study was carried out to characterize drought in the Marathwada region of Maharashtra, which experiences recurring droughts, through meteorological, hydrological and...     

The relationship between the Normalized Difference Vegetation Index and drought indices in the South Central United States

Natural Hazards - Drought indices are useful for quantifying drought severity and have shown mixed success as an indicator of drought damage and biophysical dryness. While spatial downscaling of...     

Durations of soil formation and soil development indices in a Holocene Mediterranean floodplain

Holocene and late Pleistocene alluvial sequences of the mid-Medjerda floodplain (Northern Tunisia) reveal three types of soils with gradual transitions: Fluvisols (Calcaric), Cambisols (Calcaric) and Calcic Luvisols (Chromic). Stratigraphic cross-correlations, palaeomagnetic secular variation, and ¹⁴C and IRSL dating enable detailed information about ages and durations of soil formation in the floodplain.Weakly developed Fluvisols (Calcaric) commonly reveal late Holocene ages with soil formation durations lasting between 100 and 300 years. Hence, Holocene soil formation is detectable in the exposures from durations of around 100 years onwards. Cambisols show predominantly mid-Holocene ages. The durations of soil formation are between 800 and 5000 years. Calcic Luvisols (Chromic) feature late Pleistocene ages, with durations of soil formation between 10,000 and 40,000 years.Profile Development Indices were computed from simple field parameters like soil structure, soil colour, horizon thickness and leaching features. The derived development indices show good correlation (R² = 0.804) with the calculated durations of soil formation. Field parameters are well suited for a quantitative development index of Holocene soil formation, even if very weak developed soils are predominant. The study shows that maturity stages of Holocene alluvial soils in a homogeneous Mediterranean environment are predominantly driven by soil formation duration.     

A comparative frequency analysis of three standardized drought indices in the Poyang Lake basin,China

Regional drought frequency analysis was carried out in the Poyang Lake basin (PLB) from 1960–2014 based on three standardized drought indices: the standardized precipitation index (SPI), the standardized precipitation evapotranspiration index (SPEI) and the standardized Palmer drought index (SPDI). Drought events and characteristics were extracted. A Gumbel–Hougaard (GH) copula was selected to construct the bivariate probability distribution of drought duration and severity, and the joint return periods (T _a ) were calculated. Results showed that there were 50 (50 and 40) drought events in the past 55 years based on the SPI (SPEI and SPDI), and 9 (8 and 10) of them were severe with T _a more than 10 years, occurred in the 1960s, the 1970s and the 2000s. Overall, the three drought indices could detect the onset of droughts and performed similarly with regard to drought identification. However, for the SPDI, moisture scarcity was less frequent, but it showed more severe droughts with substantially higher severity and longer duration droughts. The conditional return period (Ts|d) was calculated for the spring drought in 2011, and it was 66a and 54a, respectively, based on the SPI and SPDI, which was consistent with the record. Overall, the SPI, only considering the precipitation, can as effectively as the SPEI and SPDI identify the drought process over the PLB under the present changing climate. However, drought is affected by climate and land-cover changes; thus, it is necessary to integrate the results of drought frequency analysis based on different drought indices to improve the drought risk management.     

Correlation between joint orientation and geophysical stresses in a test area on the Canadian Shield

SummaryCorrelation Between Joint Orientation and Geophysical Stresses in a Test Area on the Canadian Shield It is contended that the orientation of the geophysical stress field in an area can be deduced from an analysis of the orientation of the joints which it has produced. As a test area, a reasonably homogeneous region of the Canadian Shield in the vicinity of Three-Mile-Lake in Ontario (roughly lat. 45° 10N and longitude 79° 25W) was chosen for analysis. It was found that the stresses were indeed homogeneous over an area of about 10 × 4 km with the exception of a small area which also shows petrographic and geomorphic peculiarities. Thus, local tectonic anomalies can immediately be recognized in the joint patterns.

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ZusammenfassungKorrelation zwischen der Lage von Klüften und dem geophysikalischen Spannungsfeld in einem Testgebiet im kanadischen Schild Es wird die Hypothese aufgestellt, daß die Hauptachsenrichtungen des geophysikalischen Spannungsfeldes aus der Lage der von ihm verursachten Klüfte abgeleitet werden kann. Um die Hypothese zu prüfen, wurde ein verhältnismäßig homogenes Gebiet des kanadischen Schildes in der Nähe vom Three-Mile-See in Ontario (ungefähr 45° 10N Breite und 79° 25W Länge) ausgewählt. Es wurde festgestellt, daß das abgeleitete Spannungsfeld über ein Gebiet von 40 km² tatsächlich homogen ist, mit Ausnahme einer kleinen Fläche, welche auch petrographische und geomorphologische Anomalien aufweist. Es können daher tektonische Anomalien sofort in den Klüftediagrammen erkannt werden.

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RésuméCorrelation entre l'orientation des clivages et les contraintes tectoniques dans une région d'épreuve du bouclier Canadien L'hypothèse est maintenue que l'orientation du champ des contraintes tectoniques peut être déduite par une analyse de l'orientation des clivages qu'il a produite. Comme région d'épreuve, une région à peu près homogène du bouclier Canadien dans le voisinage du Lac-des-Trois-Miles (45° 10N, 79° 25W) a été choisie. Il est démontré que les contraintes sont actuellement homogènes dans une région de 40 km², y exceptée une petite région où l'on observe aussi des péculiarités pétrographiques et géomorphologiques. Ainsi, les anomalies tectoniques locales peuvent être reconnues immédiatement dans les dessins du clivage.

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With 14 Figures     

Empirical relationships between aftershock area dimensions and magnitude for earthquakes in the Mediterranean Sea region

Fault dimension estimates derived from the aftershock area extent of 36 shallow depth (≤ 31 km) earthquakes that occurred in the Mediterranean Sea region have been used in order to establish empirical relationships between length, width, area and surface-wave/moment magnitude. This dataset consists of events whose aftershock sequence was recorded by a dense local or regional network and the reported location errors did not exceed on average 3–5 km. Surface-wave magnitudes for these events were obtained from the NEIC database and/or published reports, while moment magnitudes as well as focal mechanisms were available from the Harvard/USGS catalogues. Contrary to the results of some previously published studies we found no evidence in our dataset that faulting type may have an effect on the fault dimension estimates and therefore we derived relationships for the whole of the dataset. Comparisons, by means of statistical F-tests, of our relationships with other previously published regional and global relationships were performed in order to check possible similarities or differences. Most such comparisons showed relatively low significance levels (< 95%), since the differences in source dimension estimates were large mainly for magnitudes lower than 6.5, becoming smaller with increasing magnitude. Some degree of similarity, however, could be observed between our fault length relationship and the one derived from aftershock area lengths of events in Greece, while a difference was found between our regional and global fault length relationships. A calculation of the ratio defined as the fault length, derived from our relationships, to the length estimated from regional empirical relationships involving surface ruptures showed that it can take a maximum value of about 7 for small magnitudes while it approaches unity at Ms 7.2. When calculating the same ratio using instead global empirical relationships we see the maximum value not exceeding 1.8, while unity is reached at Mw 7.8, indicating the existence of a strong regional variation in the fault lengths of earthquakes occurring in the Mediterranean Sea region. Also, a relationship between the logarithms of the rupture area and seismic moment is established and it is inferred that there is some variation of stress drop as a function of seismic moment. In particular, it is observed that for magnitudes lower than 6.6 the stress drop fluctuates around 10 bar, while for larger magnitudes the stress drop reaches a value as high as 60 bar.     

西南某岩溶区地下水系统示踪试验与解析

以西南某典型岩溶区为例,解析示踪试验在岩溶管道连通性以及获取水文地质参数中的应用。选择落水洞为投放点,分别从落水洞西侧和东侧寻找地下水出露点作为接收点,判别落水洞地下径流的实际去向以及落水洞与接收点之间的水力联系。结合Qtracer2软件对示踪试验成果进行定量解析,确定示踪剂回收率、地下水平均流速、最快流速,估算出岩溶管道结构特征和水文地质参数。结果表明：落水洞与接收点JS01、JS03之间不存在直接水力联系;落水洞与接收点JS02存在水力联系且岩溶管道极为发育,含水介质不均匀,地下水运移路径较为通畅,为典型的紊流流态;落水洞地下径流的主要方向是由西向东,但在丰水期雨量较大期间,接收点JS04能够接收到荧光素钠,说明丰水期水位上涨后两者间会有水力联系,导致部分水量向落水洞西侧排泄。     

Magnetic screening of a pollution hotspot in the Lausitz area, Eastern Germany: correlation analysis between magnetic proxies and heavy metal contamination in soils

This investigation was carried out within the scope of EU-FP5 project MAGPROX. In parallel with the work of Kalinski et al. (2004, submitted), in which the magnetic signatures of the same soil profiles were analysed in more detail. The ‘hot spot’ under investigation was situated in the Lausitz area, Eastern Germany, between two major power plants, Schwarze Pumpe and Boxberg. This heavily industrialized region is known as the Black Triangle, named after the large lignite deposits and the old-technology power plants, among other petrochemical plants, refineries, textile manufacturing and glasswork industries. The relationship between magnetic parameters and heavy metal concentrations (Fe, Mn, Zn, Pb, Cu, Cr, Cd, Co and Ni) in soil profiles was determined statistically using linear regression analysis. Strong positive correlation was observed between heavy metal concentrations as viewed preliminarily from the heavy metal and magnetic susceptibility distributions with depth (soil profiles), and from the correlation coefficients obtained.MAGPROX team–FP5 RTD Project No. EVK2-CT-1999-00019     

Alleviating drought and water scarcity in the Mediterranean region through managed aquifer recharge

Drought and water scarcity can significantly impair the sustainable development of groundwater resources, a scenario commonly found in aquifers in the Mediterranean region. Water management measures to address these drivers of groundwater depletion are highly relevant, especially considering the increasing severity of droughts under climate change. This study evaluates the potential of managed aquifer recharge (MAR) to offset the adverse effects of drought and water scarcity on groundwater storage. Los Arenales aquifer (central Spain), which was unsustainably exploited for irrigation in the second half of the twentieth century, is employed as a case study. Two neighbouring zones within this aquifer are contrasted, namely, Los Arenales (LA) and Medina del Campo (MC). The primary difference between them in terms of water resources management is the wide-scale implementation of MAR systems in LA since the early 2000s. Several groundwater statistical methods are used. Groundwater-level trend analysis and average piezometric levels show in LA a faster recovery of aquifer storage and less susceptibility to drought compared to MC. On the other hand, standardised precipitation indexes and standardised groundwater level indexes of detrended groundwater-level time series, which do not include the effects of MAR, show that LA can be more negatively affected by drought and groundwater abstraction. The sharper recovery of piezometric levels in LA when considering MAR, and bigger drought impacts observed when the effects of this measure are removed, demonstrate that MAR can effectively alleviate the impacts of water scarcity and drought, providing an adaptation solution to climate change worldwide.

     

Characterizing agricultural drought in the Karamoja subregion of Uganda with meteorological and satellite-based indices

Karamoja is notoriously food insecure and has been in need of food aid for most years during the last two decades. One of the main factors causing food insecurity is drought. Reliable, area-wide, long-term data for detecting and monitoring drought conditions are critical for timely, life-saving interventions and the long-term development of the region, yet such data are sparse or unavailable. Due to advances in satellite remote sensing, characterizing drought in data-sparse regions like Karamoja has become possible. This study characterizes agricultural drought in Karamoja to enable a comprehensive understanding of drought, concomitantly evaluating the suitability of NDVI-based drought monitoring. We found that in comparison with the existing data, NDVI data currently provide the best, consistent, and spatially explicit information for operational drought monitoring in Karamoja. Results indicate that the most extreme agricultural drought in recent years occurred in 2009 followed by 2004 and 2002 and suggest that in Karamoja, moderate to severe droughts (e.g., 2008) often have the same impact on crops and human needs (e.g., food aid) as extreme droughts (e.g., 2009). We present in a proof-of-concept frame, a method to estimate the number of people needing food assistance and the population likely to fall under the integrated food security phase classification (IPC) Phase 3 (crisis) due to drought severity. Our model indicates that 90.7% of the variation in the number of people needing aid can be explained by NDVI data and NDVI data can augment these estimates. We conclude that the biggest drivers of food insecurity are the cultivation of crops on marginal land with insignificant inputs, the lack of irrigation and previous systematic incapacitation of livestock (pastoral) alternatives through government programming. Further research is needed to bridge empirical results with social–economic studies on drought impacts on communities in the region to better understand additional factors that will need to be addressed to ensure livelihood resilience.     

多元逐步回归分析应用于固化土强度与微结构参数相关性评价

用石灰固化不同含盐量的滨海盐渍土,固化后土微结构参数发生了变化,力学强度大幅度提高。多元逐步回归分析计算结果表明二者之间存在着良好的相关关系,颗粒粒度分维、颗粒定向分维、等效直径、扁圆度和面积比是对固化土力学强度影响较为显著的5个微结构参数。借助土微结构参数与强度间的相关性计算分析,从另外一个角度验证石灰对滨海盐渍土的固土作用。     

An analysis of the drought in Yunnan, China, from a perspective of society drought severity

Drought disaster management entails not only understanding meteorological drought as a natural hazard but also evaluating the adverse societal impacts related to the economy and human lives. For the purpose of quantifying the drought severity from the perspective of society drought, a drought index, namely “Society Drought Severity Index” (SDSI), was put forward to analyze the drought in Yunnan Province of China. In SDSI for Yunnan, the drought severity was represented by the weighted discrepancy between the “appropriate” water needs and the total available water resources, inspired by the established Palmer Drought Severity Index (PDSI). Technically, the trend in historical water consumption records in agricultural, industrial, and domestic sectors was applied to represent the appropriate water needs; an apparent “runoff” was used to represent the available water resource in Yunnan. The SDSI of Yunnan revealed a trend toward increasing drought severity, which resulted from a combination of meteorological changes and water needs escalation. Moreover, the spatial center of the 2010 drought in Yunnan based on SDSI was different from that identified by PDSI, which exactly reflected the influence of water needs on drought severity. The SDSI was deemed to be a beneficial tool for drought disaster management and drought risk governance.     

Analyzing spatiotemporal changes in wildfire regime and exposure across a Mediterranean fire-prone area

We evaluated the spatiotemporal changes in wildfire regime and exposure in a fire-prone Mediterranean area (Sardinia, Italy) in relation to changes in ignition patterns, weather, suppression activities, and land uses. We also used wildfire simulations to identify fine-scale changes in wildfire exposure of important features on the island. Sardinia experienced a sharp reduction in fire number and area burned between the periods 1980–1994 and 1995–2009. Despite this decrease, losses and fatalities from wildfires continue. This suggests that localized areas and seasons of high wildfire risk persist on the island. Our analysis showed (1) a reduction in area burned (60,000–20,000 ha/year) and ignitions (3,700–2,600 fires/year), (2) an advance of 15 days for the fire season peak, (3) an increase in spring temperatures, and (4) an increase in fire exposure for WUI areas. Little change was noted for land use types and associated fuels. Most likely the reduction in fire activity may be due to a combination of social factors and suppression capabilities. On the other hand, simulation modeling suggested pockets of high wildfire exposure in specific places. The combined empirical analyses and simulation modeling provided a robust approach to understanding the spatiotemporal dynamics of wildfire risk on the island.     

全风化花岗岩物理化学特征数值统计及指标相关性分析

广布于华南(尤其是香港)地区全风化花岗岩与地质灾害关系密切。其物化指标统计结果以及相互关系研究似很欠缺。通过对香港九龙两处边坡上部3个探坑中48个全风化花岗岩样品物理化学实验结果分析，本文给出了物理化学性质统计值，并对比表面积和阳离子交换容量等主要指标进行了相关分析。这就将物理化学指标问相关关系具体量化，揭示了它们同矿物成分间的关系，并可对化学、物理化学和矿物学实验分析结果进行校验。本文结果对分析其风化特征及其工程地质性质，有一定实际意义。