Journal articles on the topic 'Severe drought conditions'
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Ma, Shuangmei, Tianjun Zhou, Oliver Angélil, and Hideo Shiogama. "Increased Chances of Drought in Southeastern Periphery of the Tibetan Plateau Induced by Anthropogenic Warming." Journal of Climate 30, no. 16 (August 2017): 6543–60. http://dx.doi.org/10.1175/jcli-d-16-0636.1.
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The southeastern periphery of the Tibetan Plateau (SEPTP) was hit by an extraordinarily severe drought in the autumn of 2009. Overall, the SEPTP has been gripped by a sustained drought for six consecutive years. To better understand the physical causes of these types of severe and frequent droughts and thus to improve their prediction and enhance the ability to adapt, many research efforts have been devoted to the disastrous droughts in the SEPTP. Nonetheless, whether the likelihood and strength of the severe droughts in the SEPTP, such as that in the autumn of 2009, have been affected by anthropogenic climate change remains unknown. This study first identifies the atmospheric circulation regime responsible for the SEPTP droughts and then explores how human-induced climate change has affected the severe droughts in the SEPTP. It is found that the drought conditions in the SEPTP have been driven by the Indian–Pacific warm pool (IPWP) sea surface temperature (SST) through strengthening of the local Hadley circulation and anomalously cyclonic motion over the South China Sea. Ensemble simulations of climate models demonstrate a robust increase in the dry and warm meteorological conditions seen during the 2009 SEPTP autumn drought due to anthropogenic global warming. Given that warming is expected to continue into the future, these results suggest that it is likely that drought conditions will become more common in the SEPTP.
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Isaac, Susan. "How do lichens survive severe drought conditions?" Mycologist 10, no. 2 (May 1996): 89–90. http://dx.doi.org/10.1016/s0269-915x(96)80111-x.
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Zhang, Yuqing, Qinglong You, Guangxiong Mao, Changchun Chen, Xin Li, and Jinhua Yu. "Flash Drought Characteristics by Different Severities in Humid Subtropical Basins: A Case Study in the Gan River Basin, China." Journal of Climate 34, no. 18 (September 2021): 7337–57. http://dx.doi.org/10.1175/jcli-d-20-0596.1.
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AbstractIt is essential to assess flash drought risk based on a reliable flash drought intensity (severity) index incorporating comprehensive information of the rapid decline (“flash”) in soil moisture toward drought conditions and soil moisture thresholds belonging to the “drought” category. In this study, we used the Gan River basin as an example to define a flash drought intensity index that can be calculated for individual time steps (pentads) during a flash drought period over a given grid (or station). The severity of a complete flash drought event is the sum of the intensity values during the flash drought. We explored the spatial and temporal characteristics of flash droughts with different grades based on their respective severities. The results show that decreases in total cloud cover, precipitation, and relative humidity, as well as increases in 500-hPa geopotential height, convective inhibition, temperature, vapor pressure deficit, and wind speed can create favorable conditions for the occurrence of flash droughts. Although flash droughts are relatively frequent in the central and southern parts of the basin, the severity is relatively high in the northern part of the basin due to longer duration. Flash drought severity shows a slightly downward trend due to decreases in frequency, duration, and intensity from 1961 to 2018. Extreme and exceptional flash droughts decrease significantly while moderate and severe flash droughts trend slightly upward. Flash drought severity appears to be more affected by the interaction between duration and intensity as the grade increases from mild to severe. The frequency and duration of flash droughts are higher in July–October. The southern part of the basin is more prone to moderate and severe flash droughts, while the northern parts of the basin are more vulnerable to extreme and exceptional flash droughts due to longer durations and greater severities than other parts. Moderate, severe, extreme, and exceptional flash droughts occurred at approximately 3–6-, 5–15-, 10–50-, and 30–200-yr intervals, respectively, based on the copula analysis.
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Khan, Muhammad Imran, Xingye Zhu, Xiaoping Jiang, Qaisar Saddique, Muhammad Saifullah, Yasir Niaz, and Muhammad Sajid. "Projection of Future Drought Characteristics under Multiple Drought Indices." Water 13, no. 9 (April 29, 2021): 1238. http://dx.doi.org/10.3390/w13091238.
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Drought is a natural phenomenon caused by the variability of climate. This study was conducted in the Songhua River Basin of China. The drought events were estimated by using the Reconnaissance Drought Index (RDI) and Standardized Precipitation Index (SPI) which are based on precipitation (P) and potential evapotranspiration (PET) data. Furthermore, drought characteristics were identified for the assessment of drought trends in the study area. Short term (3 months) and long term (12 months) projected meteorological droughts were identified by using these drought indices. Future climate precipitation and temperature time series data (2021–2099) of various Representative Concentration Pathways (RCPs) were estimated by using outputs of the Global Circulation Model downscaled with a statistical methodology. The results showed that RCP 4.5 have a greater number of moderate drought events as compared to RCP 2.6 and RCP 8.5. Moreover, it was also noted that RCP 8.5 (40 events) and RCP 4.5 (38 events) showed a higher number of severe droughts on 12-month drought analysis in the study area. A severe drought conditions projected between 2073 and 2076 with drought severity (DS-1.66) and drought intensity (DI-0.42) while extreme drying trends were projected between 2097 and 2099 with drought severity (DS-1.85) and drought intensity (DI-0.62). It was also observed that Precipitation Decile predicted a greater number of years under deficit conditions under RCP 2.6. Overall results revealed that more severe droughts are expected to occur during the late phase (2050–2099) by using RDI and SPI. A comparative analysis of 3- and 12-month drying trends showed that RDI is prevailing during the 12-month drought analysis while almost both drought indices (RDI and SPI) indicated same behavior of drought identification at 3-month drought analysis between 2021 and 2099 in the research area. The results of study will help to evaluate the risk of future drought in the study area and be beneficial for the researcher to make an appropriate mitigation strategy.
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Alfieri, Joseph G., Peter D. Blanken, David N. Yates, and Konrad Steffen. "Variability in the Environmental Factors Driving Evapotranspiration from a Grazed Rangeland during Severe Drought Conditions." Journal of Hydrometeorology 8, no. 2 (April 1, 2007): 207–20. http://dx.doi.org/10.1175/jhm569.1.
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Abstract Nearly one-half of the earth’s terrestrial surface is susceptible to drought, which can have significant social, economic, and environmental impacts. Therefore, it is important to develop better descriptions and models of the processes linking the land surface and atmosphere during drought. Using data collected during the International H2O Project, the study presented here investigates the effects of variations in the environmental factors driving the latent heat flux (λE) during drought conditions at a rangeland site located in the panhandle of Oklahoma. Specifically, this study focuses on the relationships of λE with vapor pressure deficit, wind speed, net radiation, soil moisture content, and greenness fraction. While each of these environmental factors has an influence, soil moisture content is the key control on λE. The role of soil moisture in regulating λE is explained in terms of the surface resistance to water vapor transfer. The results show that λE transitioned between being water or energy limited during the course of the drought. The implications of this on the ability to understand and model drought conditions and transitions into or out of droughts are discussed.
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Mathbout, Shifa, Joan Albert Lopez-Bustins, Dominic Royé, and Javier Martin-Vide. "Mediterranean-Scale Drought: Regional Datasets for Exceptional Meteorological Drought Events during 1975–2019." Atmosphere 12, no. 8 (July 22, 2021): 941. http://dx.doi.org/10.3390/atmos12080941.
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Drought is one of the most complex climate-related phenomena and is expected to progressively affect our lives by causing very serious environmental and socioeconomic damage by the end of the 21st century. In this study, we have extracted a dataset of exceptional meteorological drought events between 1975 and 2019 at the country and subregional scales. Each drought event was described by its start and end date, intensity, severity, duration, areal extent, peak month and peak area. To define such drought events and their characteristics, separate analyses based on three drought indices were performed at 12-month timescale: the Standardized Precipitation Index (SPI), the Standardized Precipitation Evapotranspiration Index (SPEI), and the Reconnaissance Drought Index (RDI). A multivariate combined drought index (DXI) was developed by merging the previous three indices for more understanding of droughts’ features at the country and subregional levels. Principal component analysis (PCA) was used to identify five different drought subregions based on DXI-12 values for 312 Mediterranean stations and a new special score was defined to classify the multi-subregional exceptional drought events across the Mediterranean Basin (MED). The results indicated that extensive drought events occurred more frequently since the late 1990s, showing several drought hotspots in the last decades in the southeastern Mediterranean and northwest Africa. In addition, the results showed that the most severe events were more detected when more than single drought index was used. The highest percentage area under drought was also observed through combining the variations of three drought indices. Furthermore, the drought area in both dry and humid areas in the MED has also experienced a remarkable increase since the late 1990s. Based on a comparison of the drought events during the two periods—1975–1996 and 1997–2019—we find that the current dry conditions in the MED are more severe, intense, and frequent than the earlier period; moreover, the strongest dry conditions occurred in last two decades. The SPEI-12 and RDI-12 have a higher capacity in providing a more comprehensive description of the dry conditions because of the inclusion of temperature or atmospheric evaporative demand in their scheme. A complex range of atmospheric circulation patterns, particularly the Western Mediterranean Oscillation (WeMO) and East Atlantic/West Russia (EATL/WRUS), appear to play an important role in severe, intense and region-wide droughts, including the two most severe droughts, 1999–2001 and 2007–2012, with lesser influence of the NAO, ULMO and SCAND.
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Bonsal, Barrie, Zhuo Liu, Elaine Wheaton, and Ronald Stewart. "Historical and Projected Changes to the Stages and Other Characteristics of Severe Canadian Prairie Droughts." Water 12, no. 12 (December 1, 2020): 3370. http://dx.doi.org/10.3390/w12123370.
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Large-area, long-duration droughts are among Canada’s costliest natural disasters. A particularly vulnerable region includes the Canadian Prairies where droughts have, and are projected to continue to have, major impacts. However, individual droughts often differ in their stages such as onset, growth, persistence, retreat, and duration. Using the Standardized Precipitation Evapotranspiration Index, this study assesses historical and projected future changes to the stages and other characteristics of severe drought occurrence across the agricultural region of the Canadian Prairies. Ten severe droughts occurred during the 1900–2014 period with each having unique temporal and spatial characteristics. Projected changes from 29 global climate models (GCMs) with three representative concentration pathways reveal an increase in severe drought occurrence, particularly toward the end of this century with a high emissions scenario. For the most part, the overall duration and intensity of future severe drought conditions is projected to increase mainly due to longer persistence stages, while growth and retreat stages are generally shorter. Considerable variability exists among individual GCM projections, including their ability to simulate observed severe drought characteristics. This study has increased understanding in potential future changes to a little studied aspect of droughts, namely, their stages and associated characteristics. This knowledge can aid in developing future adaptation strategies.
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SAMBASIVARAO, A., and AR SUBRAMANIAM. "An analysis of droughts in Maharashtra by a modified Palmer's approach." MAUSAM 37, no. 3 (July 1, 1986): 377–84. http://dx.doi.org/10.54302/mausam.v37i3.2462.
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Droughts pose a serious problem in rainfed agriculture of Maharashtra. The commencement and cessation of different intensities of meteorological droughts during 1934- 77 at 23 locations of the State are identified by using the Palmer's approach. While adopting Palmer's approach, the definition of potential runoff and the weighting factors originally given by him are suitably modified for the climatic conditions of Maharashtra. The modified drought indices performed well for identification of various classes of droughts in the region. The analysis shows that the spatial distribution of drought prone areas during kharif (June-September) is similar to that of rabi season (October-February) in the region. During kharif season alone severe/extreme drought conditions prevailed for 28 out of 44 years in the State. But there are few stations like Kolhapur and Sironcha (Sub-humid) where the drought situation never touched the extreme conditions.
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Xiao, Mu, Bart Nijssen, and Dennis P. Lettenmaier. "Drought in the Pacific Northwest, 1920–2013." Journal of Hydrometeorology 17, no. 9 (September 1, 2016): 2391–404. http://dx.doi.org/10.1175/jhm-d-15-0142.1.
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Abstract The severity–area–duration (SAD) method is used in conjunction with the Variable Infiltration Capacity model (VIC) to identify the major historical total moisture (TM; soil moisture plus snow water equivalent) droughts over the Pacific Northwest region, defined as the Columbia River basin and the region’s coastal drainages, for the period 1920–2013. The motivation is to understand how droughts identified using TM (a measure similar to that used in the U.S. Drought Monitor) relate to sector-specific drought measures that are more relevant to users. It is found that most of the SAD space is dominated by an extended drought period during the 1930s, although the most severe shorter droughts are in the 1970s (1976–78) and early 2000s (2000–04). The impact of the three severe TM droughts that dominate most of the SAD space are explored in terms of sector-specific measures relevant to dryland and irrigated agriculture, hydropower generation, municipal water supply, and recreation. It is found that in many cases the most severe droughts identified using the SAD method also appear among the most severe sector-specific droughts; however, there are important exceptions. Two types of inconsistencies are examined and the nature of the conditions that give rise to them are explored.
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Boschma, S. P., and J. M. Scott. "Measuring and predicting the consequences of drought for a range of perennial grasses on the Northern Tablelands of New South Wales." Australian Journal of Experimental Agriculture 40, no. 2 (2000): 285. http://dx.doi.org/10.1071/ea98014.
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An experiment was conducted at Armidale, New South Wales to evaluate the persistence and productivity of 6 perennial grasses under 2 defoliation severities and a range of moisture/drought conditions created using a rain-out shelter. Defoliation was either moderate or severe whilst the moisture/drought conditions imposed included a non-stressed moisture treatment, and seasonal droughts simulated as 40-percentile (40-P) and 10-percentile rainfall (10-P). The treatments were applied over 2 experimental seasons; spring–summer and summer–autumn. A range of measurements was taken including plant mortality, basal area, foliage greenness, herbage mass, growth rate and digestibility. Some of these results were then used as inputs to the GrazFeed decision support system to predict liveweight gain and wool growth rate from pastures growing under such conditions. Plant mortality of over 40% was observed in Dactylis glomerata and Lolium perenne under moderate (40-P) drought conditions during spring–summer. In contrast, under severe drought conditions (10-P), less than 20% of plants died, suggesting that, when combined with defoliation stress, a more common drought can present a greater hazard to plant persistence than a severe drought during spring–summer. Plant mortality was reduced and non-significant when subjected to the summer–autumn drought treatments. Plant growth and predictions of animal productivity varied widely among the species challenged with drought and defoliation stresses. Predicted liveweight gains of weaner sheep under severe drought conditions (10-P) varied between species ranging from 20 to 110 g/day. Under the same conditions, predicted wool growth rates varied between species from 5 to 11 g/wether. day, while pasture growth rates varied from a low of 0 to more than 120 kg DM/ha. day. The animal effects were due largely to differences in herbage mass and the degree to which the grass remained green. These results highlight the importance of maintaining the most productive species in pastures through drought.
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García-Valdecasas Ojeda, Matilde, Emilio Romero-Jiménez, Juan José Rosa-Cánovas, Patricio Yeste, Yolanda Castro-Díez, María Jesús Esteban-Parra, Sergio M. Vicente-Serrano, and Sonia R. Gámiz-Fortis. "Assessing Future Drought Conditions over the Iberian Peninsula: The Impact of Using Different Periods to Compute the SPEI." Atmosphere 12, no. 8 (July 29, 2021): 980. http://dx.doi.org/10.3390/atmos12080980.
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Future drought-hazard assessments using standardized indices depend on the period used to calibrate the probability distributions. This appears to be particularly important in a changing climate with significant trends in drought-related variables. This study explores the effect of using different approaches to project droughts, with a focus on changes in drought characteristics (frequency, duration, time spent in drought, and spatial extent), estimated with a calibration period covering recent past and future conditions (self-calibrated indices), and another one that only applies recent-past records (relative indices). The analysis focused on the Iberian Peninsula (IP), a hot-spot region where climate projections indicate significant changes by the end of this century. To do this, a EURO-CORDEX multi-model ensemble under RCP8.5 was used to calculate the Standardized Precipitation-Evapotranspiration Index (SPEI) at both 3- and 12-month timescales. The results suggest that projections of drought characteristics strongly depend on the period used to calibrate the SPEI, particularly at a 12-month timescale. Overall, differences were larger for the near future when relative indices indicated more severe droughts. For the distant future, changes were more similar, although self-calibrated indices revealed more frequent and longer-lasting droughts and the relative ones a drought worsening associated with extremely prolonged drought events.
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Jiang, Yelin, Meijian Yang, Weiguang Liu, Koushan Mohammadi, and Guiling Wang. "Eco-hydrological responses to recent droughts in tropical South America." Environmental Research Letters 17, no. 2 (February 1, 2022): 024037. http://dx.doi.org/10.1088/1748-9326/ac507a.
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Abstract This study assesses the ecohydrological effects of recent meteorological droughts in tropical South America based on multiple sources of data, and investigates the possible mechanisms underlying the drought response and recovery of different ecohydrological systems. Soil drought response and recovery lag behind the meteorological drought, with delays longer in the dry region (Nordeste) than in the wet region (Amazonia), and longer in deep soil than in shallow soil. Evapotranspiration (ET) and vegetation in Nordeste are limited by water under normal conditions and decrease promptly in response to the onset of shallow soil drought. In most of the Amazon where water is normally abundant, ET and vegetation indices follow an increase-then-decrease pattern, increase at the drought onset due to increased sunshine and decrease when the drought is severe enough to cause a shift from an energy-limited regime to a water-limited regime. After the demise of meteorological droughts, ET and vegetation rapidly recover in Nordeste with the replenishment of shallow soil moisture (SM), but take longer to recover in southern Amazon due to their dependence on deep SM storage. Following severe droughts, the negative anomalies of ET and vegetation indices in southern Amazon tend to persist well beyond the end of soil drought, indicating drought-induced forest mortality that is slow to recover from. Findings from this study may have implications on the possibility of a future forest dieback as drought is projected to become more frequent and more severe in a warmer climate.
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Campos, Fernando A., Urs Kalbitzer, Amanda D. Melin, Jeremy D. Hogan, Saul E. Cheves, Evin Murillo-Chacon, Adrián Guadamuz, et al. "Differential impact of severe drought on infant mortality in two sympatric neotropical primates." Royal Society Open Science 7, no. 4 (April 2020): 200302. http://dx.doi.org/10.1098/rsos.200302.
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Extreme climate events can have important consequences for the dynamics of natural populations, and severe droughts are predicted to become more common and intense due to climate change. We analysed infant mortality in relation to drought in two primate species (white-faced capuchins, Cebus capucinus imitator, and Geoffroy's spider monkeys, Ateles geoffroyi ) in a tropical dry forest in northwestern Costa Rica. Our survival analyses combine several rare and valuable long-term datasets, including long-term primate life-history, landscape-scale fruit abundance, food-tree mortality, and climate conditions. Infant capuchins showed a threshold mortality response to drought, with exceptionally high mortality during a period of intense drought, but not during periods of moderate water shortage. By contrast, spider monkey females stopped reproducing during severe drought, and the mortality of infant spider monkeys peaked later during a period of low fruit abundance and high food-tree mortality linked to the drought. These divergent patterns implicate differing physiology, behaviour or associated factors in shaping species-specific drought responses. Our findings link predictions about the Earth's changing climate to environmental influences on primate mortality risk and thereby improve our understanding of how the increasing severity and frequency of droughts will affect the dynamics and conservation of wild primates.
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Aggile, Lakshmi Prasanna, Shweta Gautam, and B. Sudheer Kumar Reddy. "Analysis of Various Drought Indices over Mathura Region Using Geo-Spatial Technologies." IOP Conference Series: Earth and Environmental Science 982, no. 1 (March 1, 2022): 012034. http://dx.doi.org/10.1088/1755-1315/982/1/012034.
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Abstract The scarcity of water in any geophysical conditions leads to drought. The vegetation conditions and rainfall need to be assessed efficiently to develop counter measures to tackle the drought. Hence various drought indices such as Vegetation Condition Index (VCI) Standardized Precipitation Index (SPI) and Rainfall Anomaly Index (RAI) were carefully analyzed. Results of VCI showed moderate to severe droughts occurred at study region for the year 2015 in the month of September. SPI and RAI results showed that monsoon months had negative values for all the places in drought year 2015. The eastern part of the research area is found to be prone to dry condition as per the results obtained. The risk of future drought conditions can be minimized with the help of this research.
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Ma, Jianqin, Bifeng Cui, Lei Liu, Xiuping Hao, Feng Liang, Zhongfeng Jiang, and Jiangshan Yang. "Dynamic Characteristics of Drought Conditions during the Growth of Winter Wheat Based on an Improved SWAT Model." Water 14, no. 4 (February 13, 2022): 566. http://dx.doi.org/10.3390/w14040566.
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This study aimed at investigating the applicability of a SWAT (Soil and Water Assessment Tool) model in understanding the effects of drought on winter wheat. This study is based on the water requirement of the crop and addresses the absence of a SWAT model with real-time irrigation simulation. A real-time irrigation module was developed for the downstream irrigation area of the Yellow River to estimate the real-time irrigation of crops. By further simulating the dynamic evolution process of soil moisture content, a dynamic drought evaluation model of winter wheat was established, and the relative soil moisture was set as the evaluation index to assess and analyze the dynamic variation of drought evolution during the growth of winter wheat. The results showed that the improved SWAT model has strong applicability. During the growth of winter wheat, the variation trend of droughts is consistent with that of natural precipitation. For winter wheat, drought is quite normal during all growth stages, and the average frequency is 93.5%, 89.1%, 84.8%, 89.1% and 95.7%. Severe drought and extra-severe drought usually occur during the sowing–tillering stage and the tillering–greening stage, and the frequency of occurrence is 30.4% and 19.6%, respectively. This paper provides a novel approach for the study of agricultural drought in the downstream irrigation area of the Yellow River.
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Gorim, Linda Yuya, and Albert Vandenberg. "Can wild lentil genotypes help improve water use and transpiration efficiency in cultivated lentil?" Plant Genetic Resources: Characterization and Utilization 16, no. 5 (March 6, 2018): 459–68. http://dx.doi.org/10.1017/s1479262117000399.
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AbstractClimate change forecasts point to increased frequency of droughts which may affect plant growth. For protein crops such as lentil, genetic improvement of both water use and drought tolerance is necessary. Wild lentil species are known to have evolved in drought prone areas and can be introgressed into cultivated lentil, making them candidates for the evaluation of high transpiration efficiency (TE) and drought tolerance. We assessed TE, water use and drought tolerance at the plant level for five wild lentil species and in cultivated lentil. Under fully watered and moderate drought conditions, wild lentil genotypes consumed significantly less water to fix similar or more dry matter compared with their cultivated counterparts. Under severe drought conditions, the wild lentil genotype L. ervoides IG 72815 had significantly higher TE compared with L. culinaris Eston. Lens ervoides L-01-827A, had significantly higher yield compared with all other species in the presence or absence of drought and showed significantly higher (α = 5%) TE under moderate drought. Drought susceptibility index was identified as a tool to identify drought-tolerant lentil genotypes grown under severe drought. The numerous small seeds of wild lentil made it difficult to estimate drought indices that are weight based and require formulae that incorporate seed numbers.
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Chann, Kimsan, Ty Sok, Romduol Khoeun, Vuthy Men, Supattra Visessri, Chantha Oeurng, Ratha Sor, and Sarah E. Null. "Prolonged and Severe Drought in the Most Dammed Tributaries of the Lower Mekong Basin." Sustainability 14, no. 23 (December 6, 2022): 16254. http://dx.doi.org/10.3390/su142316254.
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Drought is a natural hazard that stresses ecosystems, agricultural production, food security, and local economies. Given ongoing hydropower dam development in the Sesan and Srepok Basins, the two most dammed tributaries in the Lower Mekong Basin, characterizing baseline drought events and understanding how dams modify downstream flow is needed to manage water resources and mitigate drought effects. We used the Soil & Water Assessment Tool (SWAT) to estimate streamflow data from 2001 to 2019. For both rivers, we found that runoff varied, but contributed about 75% of streamflow, followed by shallow and deep groundwater, which contributed up to 25%. We used the Standardized Runoff Index to characterize drought and detected frequent, severe, and prolonged drought events in the two basins. Severe and prolonged droughts in the 2009–2011 and 2015–2016 periods corresponded to the occurrence of Typhoon Ketsana and the El Niño-Southern Oscillation. Streamflow alteration can be caused by climatic conditions and anthropogenic activities such as hydropower dam development and operations (e.g., the timing and magnitude of water releases). Results from this study can be used as a baseline to gauge potential future droughts and design appropriate drought management plans to preserve ecosystems and food security in the Lower Mekong Basin and its tributaries.
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Naumann, Gustavo, Walter Vargas, Paulo Barbosa, Veit Blauhut, Jonathan Spinoni, and Jürgen Vogt. "Dynamics of Socioeconomic Exposure, Vulnerability and Impacts of Recent Droughts in Argentina." Geosciences 9, no. 1 (January 12, 2019): 39. http://dx.doi.org/10.3390/geosciences9010039.
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During the last 20 years, Argentina experienced several extreme and widespread droughts in many different regions, including the core cropland areas. The most devastating recent events were recorded in the years 2006, 2009 and 2011. Reported impacts of the main events induced losses of more than 4 billion U.S. dollars and more than 1 million persons were reported to be directly or indirectly affected. In this paper, we analyse the drought risk in Argentina, taking into account recent information on drought hazard, exposure and vulnerability. Accordingly, we identified the most severe droughts in Argentina during the 2000–2015 period using a combination of drought hazard indicators and exposure layers. Three main events were identified: (1) during spring 2006 droughts peaked in the northeast of Argentina, (2) in 2009 precipitation deficits indicated a drought epicenter in the central Argentinian plains, and (3) in 2011 the northern Patagonia region experienced a combination of natural disasters due to severe drought conditions and a devastating volcanic eruption. Furthermore, we analysed the dynamics of drought exposure for the population and the main economic sectors affected by municipality, i.e., agriculture and livestock production. Assets exposed to droughts have been identified with several records of drought impacts and declarations of farming emergencies. We show that by combining exposure and vulnerability with drought intensity it is feasible to detect the likelihood of regional impacts in different sectors.
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Hung, Chih-wen, and Ming-Fu Shih. "Analysis of Severe Droughts in Taiwan and its Related Atmospheric and Oceanic Environments." Atmosphere 10, no. 3 (March 25, 2019): 159. http://dx.doi.org/10.3390/atmos10030159.
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Drought is one of the important issues in climate studies. A drought index, Taiwan Meteorological Drought index (TMD index), was previously proposed and is applied here to identify historical severe droughts in Taiwan in order to clarify the corresponding large-scale backgrounds as a potential alert to the society in future. Through the TMD index, several historical severe drought cases in Taiwan are detected and characterized by significant seasonal variability in the annual cycle. Composites for large-scale atmospheric and oceanic environments over different periods within the dry season are conducted. From October to December, the colder sea surface temperature (SST) pattern of Pacific Meridional Mode (PMM) and the PMM-induced local anomalous anticyclones over the South China Sea are both in charge of the extremely dry conditions in Taiwan. From January to February, cold SST in the South China Sea and its adjacent oceans dominates local atmospheric conditions above these regions and creates an unfavorable environment for convection systems. From March to May, a massive anomalous anticyclonic circulation centering beside Alaska and extending its properties to East Asia and Taiwan generates a descending environment and in turn suppresses convection systems to develop. Therefore, the extremely dry conditions under this system are expected.
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Hellwig, Jost, Michael Stoelzle, and Kerstin Stahl. "Groundwater and baseflow drought responses to synthetic recharge stress tests." Hydrology and Earth System Sciences 25, no. 2 (February 25, 2021): 1053–68. http://dx.doi.org/10.5194/hess-25-1053-2021.
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Abstract. Groundwater is the main source of freshwater and maintains streamflow during drought. Potential future groundwater and baseflow drought hazards depend on the systems' sensitivity to altered recharge conditions. We performed groundwater model experiments using three different generic stress tests to estimate the groundwater and baseflow drought sensitivity to changes in recharge. The stress tests stem from a stakeholder co-design process that specifically followed the idea of altering known drought events from the past, i.e. asking whether altered recharge could have made a particular event worse. Across Germany, groundwater responses to the stress tests are highly heterogeneous, with groundwater heads in the north more sensitive to long-term recharge and in the Central German Uplands to short-term recharge variations. Baseflow droughts are generally more sensitive to intra-annual dynamics, and baseflow responses to the stress tests are smaller compared to the groundwater heads. The groundwater drought recovery time is mainly driven by the hydrogeological conditions, with slow (fast) recovery in the porous (fractured rock) aquifers. In general, a seasonal shift of recharge (i.e. less summer recharge and more winter recharge) will have lesser effects on groundwater and baseflow drought severity. A lengthening of dry spells might cause much stronger responses, especially in regions with slow groundwater response to precipitation. Water management may need to consider the spatially different sensitivities of the groundwater system and the potential for more severe groundwater droughts in the large porous aquifers following prolonged meteorological droughts, particularly in the context of climate change projections indicating stronger seasonality and more severe drought events.
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Chan, Wilson C. H., Theodore G. Shepherd, Katie Facer-Childs, Geoff Darch, and Nigel W. Arnell. "Storylines of UK drought based on the 2010–2012 event." Hydrology and Earth System Sciences 26, no. 7 (April 6, 2022): 1755–77. http://dx.doi.org/10.5194/hess-26-1755-2022.
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Abstract. Spatially extensive multi-year hydrological droughts cause significant environmental stress. The UK is expected to remain vulnerable to future multi-year droughts under climate change. Existing approaches to quantify hydrological impacts of climate change often rely solely on global climate model (GCM) projections following different emission scenarios. This may miss out low-probability events with significant impacts. As a means of exploring such events, physical climate storyline approaches aim to quantify physically coherent articulations of how observed events could hypothetically have unfolded in alternative ways. This study uses the 2010–2012 drought, the most recent period of severe hydrological drought in the UK, as a basis and analyses storylines based on changes to (1) precondition severity, (2) temporal drought sequence, and (3) climate change. Evidence from multiple storylines shows that the maximum intensity, mean deficit, and duration of the 2010–2012 drought were highly influenced by its meteorological preconditions prior to drought inception, particularly for northern catchments at shorter timescales. The influence of progressively drier preconditions reflects both the spatial variation in drought preconditions and the role of physical catchment characteristics, particularly hydrogeology in the propagation of multi-year droughts. There are two plausible storylines of an additional dry year with dry winter conditions repeated either before the observed drought or replacing the observed dramatic drought termination confirm the vulnerability of UK catchments to a “third dry winter” storyline. Applying the UKCP18 climate projections, we find that drought conditions worsen with global warming with a mitigation of drought conditions by wetter winters in northern catchments at high warming levels. Comparison of the storylines with a benchmark drought (1975–1976) and a protracted multi-year drought (1989–1993) shows that, for each storyline (including the climate change storylines), drought conditions could have matched and exceeded those experienced during the past droughts at catchments across the UK, particularly for southern catchments. The construction of storylines based on observed events can complement existing methods to stress test UK catchments against plausible unrealised droughts.
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Wang, Yunqian, Jing Yang, Yaning Chen, Zhicheng Su, Baofu Li, Hao Guo, and Philippe De Maeyer. "Monitoring and Predicting Drought Based on Multiple Indicators in an Arid Area, China." Remote Sensing 12, no. 14 (July 17, 2020): 2298. http://dx.doi.org/10.3390/rs12142298.
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Droughts are one of the costliest natural disasters. Reliable drought monitoring and prediction are valuable for drought relief management. This study monitors and predicts droughts in Xinjiang, an arid area in China, based on the three drought indicators, i.e., the Standardized Precipitation Index (SPI), the Standardized Soil Moisture Index (SSMI) and the Multivariate Standardized Drought Index (MSDI). Results indicate that although these three indicators could capture severe historical drought events in the study area, the spatial coverage, persistence and severity of the droughts would vary regarding different indicators. The MSDI could best describe the overall drought conditions by incorporating the characteristics of the SPI and SSMI. For the drought prediction, the predictive skill of all indicators gradually decayed with the increasing lead time. Specifically, the SPI only showed the predictive skill at a 1-month lead time, the MSDI performed best in capturing droughts at 1- to 2-month lead times and the SSMI was accurate up to a 3-month lead time owing to its high persistence. These findings might provide scientific support for the local drought management.
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Kim, Do-Woo, Hi-Ryong Byun, Ki-Seon Choi, and Su-Bin Oh. "A Spatiotemporal Analysis of Historical Droughts in Korea." Journal of Applied Meteorology and Climatology 50, no. 9 (September 2011): 1895–912. http://dx.doi.org/10.1175/2011jamc2664.1.
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AbstractThe climatological characteristics of drought in South Korea were investigated using daily precipitation data for 1777–2008. The effective drought index was used to quantify the drought intensity. As a result, five characteristics were discovered. First, South Korea can be divided into four drought subregions (the central, southern, and east coastal regions and Jeju Island) using hierarchical cluster analysis. Second, a map for long-term drought conditions in the four subregions is created that allows identification of the spatiotemporal distribution of droughts for the 231 yr at a glance. Third, droughts in South Korea have time scales that depend on the onset season. Spring (March–May) droughts tend to be short (≤200 days) because the summer (June–September) rainy season follows. Summer droughts tend to be long (>200 days) because the dry season (October–February) follows. In the dry season, droughts tend to be sustained or become severe rather than being initiated or relieved. Fourth, 5-, 14-, 34-, and 115-yr drought cycles were identified by spectral analysis. The 5-yr cycle was dominant in all of the regions, the 14-yr cycle was observed over the southern and east coastal regions, and the 34-yr cycle was observed over the central region. Fifth, the most extreme drought occurred in 1897–1903 (return period: 233 yr) and was associated with the 115-yr drought cycle. After this drought, severe droughts (return period of >10 yr) occurred in 1927–30, 1938–40, 1942–45, 1951–52, 1967–69, and 1994–96; they were caused by the consecutive shortage of summer rainfall for two or more years.
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Navarro-Cerrillo, Rafael M., Antonio Gazol, Carlos Rodríguez-Vallejo, Rubén D. Manzanedo, Guillermo Palacios-Rodríguez, and J. J. Camarero. "Linkages between Climate, Radial Growth and Defoliation in Abies pinsapo Forests from Southern Spain." Forests 11, no. 9 (September 17, 2020): 1002. http://dx.doi.org/10.3390/f11091002.
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Systematic forest networks of health monitoring have been established to follow changes in tree vigor and mortality. These networks often lack long-term growth data, but they could be complemented with tree ring data, since both defoliation and radial growth are proxies of changes in tree vigor. For instance, a severe water shortage should reduce growth and increase tree defoliation in drought-prone areas. However, the effects of climatic stress and drought on growth and defoliation could also depend on tree age. To address these issues, we compared growth and defoliation data with recent climate variability and drought severity in Abies pinsapo old and young trees sampled in Southern Spain, where a systematic health network (Andalucía Permanent Plot Network) was established. Our aims were: (i) to assess the growth sensitivity of old and young A. pinsapo trees and (ii) to test if relative changes in radial growth were related with recent defoliation, for instance, after severe droughts. We also computed the resilience indices to quantify how old and young trees recovered growth after recent droughts. Wet-cool conditions during the prior autumn and the current early summer improved the growth of old trees, whereas late-spring wet conditions enhanced the growth of young trees. Old trees were more sensitive to wet and sunny conditions in the early summer than young trees. Old and young trees were more responsive to the Standardized Precipitation-Evapotranspiration Index drought index of June–July and July–August calculated at short (one–three months) and mid (three–six months) time scales, respectively. Old trees presented a higher resistance to a severe drought in 1995 than young trees. A positive association was found between stand defoliation and relative growth. Combining monitoring and tree ring networks is useful for the detection of early warning signals of dieback in similar drought-prone forests.
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Kim, Bo Ram, Sang-Il Lee, and Su Min Yu. "Conjunctive Operation of Sand Dam and Groundwater Well for Reliable Water Supply during Drought Conditions." Water 14, no. 14 (July 17, 2022): 2249. http://dx.doi.org/10.3390/w14142249.
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Some mountainous regions without water service facilities are among the areas most vulnerable to drought. In these locations, it is particularly essential to establish practical alternatives to cope with the increase in the intensity and duration of droughts caused by climate change. This study proposes a methodology for the conjunctive use of a sand dam and groundwater well under various drought conditions. The method has been applied to a small mountainous area in South Korea. Owing to the scarcity of observational data, it is crucial to properly estimate the hydrological components necessary for judging the feasibility and reliability of conjunctive operations. The step-by-step procedures for performing the tasks are presented in this study. For the inflow of the sand dam, which is a portion of the basin runoff, two different approaches were employed and compared: the Kajiyama formula and a simple two-parameter monthly water balance model (TPM). Water budget analysis allowed for the determination of whether the current and increased water demand could be met under various drought conditions. Preliminary analysis revealed that a sand dam alone could not reliably meet the demand for 10-year or more severe drought conditions. Various water allocation scenarios between surface water (i.e., sand dam) and groundwater were tested. Conjunctive use of a sand dam and groundwater well turned out to increase the reliability of the water supply. As water demand increases and droughts become more severe, the role of groundwater increases. With appropriate resource allocation, 100% water supply reliability could be achieved, even for one year-lasting 50-year drought. We demonstrated how a system could be flexibly operated to meet the target demands monthly, given the system reliability level.
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Liang, Zheng, Xiaoling Su, and Kai Feng. "Drought propagation and construction of a comprehensive drought index based on the Soil and Water Assessment Tool (SWAT) and empirical Kendall distribution function (<i>K</i><sub>C′</sub>): a case study for the Jinta River basin in northwestern China." Natural Hazards and Earth System Sciences 21, no. 4 (April 30, 2021): 1323–35. http://dx.doi.org/10.5194/nhess-21-1323-2021.
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Abstract. Monitoring drought and mastering the laws of drought propagation are the basis for regional drought prevention and resistance. Multivariate drought indicators considering meteorological, agricultural and hydrological information may fully describe drought conditions. However, series of hydrological variables in cold and arid regions that are too short or missing make it difficult to monitor drought. This paper proposed a method combining Soil and Water Assessment Tool (SWAT) and empirical Kendall distribution function (KC′) for drought monitoring. The SWAT model, based on the principle of runoff formation, was used to simulate the hydrological variables of the drought evolution process. Three univariate drought indexes, namely meteorological drought (standardized precipitation evapotranspiration index; SPEI), agricultural drought (standardized soil moisture index; SSI) and hydrological drought (standardized streamflow drought index; SDI), were constructed using a parametric or non-parametric method to analyze the propagation time from meteorological drought to agricultural drought and hydrological drought. The KC′ was used to build a multivariable comprehensive meteorology–agriculture–hydrology drought index (MAHDI) that integrated meteorological, agricultural and hydrological drought to analyze the characteristics of a comprehensive drought evolution. The Jinta River in the inland basin of northwestern China was used as the study area. The results showed that agricultural and hydrological drought had a seasonal lag time from meteorological drought. The degree of drought in this basin was high in the northern and low in the southern regions. MAHDI proved to be acceptable in that it was consistent with historical drought records, could catch drought conditions characterized by univariate drought indexes, and capture the occurrence and end of droughts. Nevertheless, its ability to characterize mild and moderate droughts was stronger than severe droughts. In addition, the comprehensive drought conditions showed insignificant aggravating trends in spring and summer and showed insignificant alleviating trends in autumn and winter and at annual scales. The results provided theoretical support for the drought monitoring in the Jinta River basin. This method provided the possibility for drought monitoring in other watersheds lacking measured data.
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Ivanyo, Ya M., S. A. Petrova, and E. A. Kovaleva. "Ecological-Mathematical Modeling in Planning Production of Agricultural Products in Conditions of Risks." IOP Conference Series: Earth and Environmental Science 988, no. 2 (February 1, 2022): 022083. http://dx.doi.org/10.1088/1755-1315/988/2/022083.
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Abstract The article proposes an ecological-mathematical model to optimize the production of agricultural products, taking into account the risks associated with climatic events. The model describes a combination of crop and livestock production on irrigated and non-irrigated agricultural land. In this model, the target function characterizes the maximum income and damage to the environment as a result of farming in conditions of natural risks. Restrictions describe the availability of land and labor resources, production volumes, soil and water pollution, erosion of agricultural land, the combination of crop and livestock products in conditions of severe droughts or heavy rainfall. When implementing the model, a special case was considered: an ecological-mathematical model for non-irrigated lands, taking into account severe drought. The proposed model is implemented on the example of an agricultural enterprise in the Irkutsk region, which is subject to significant risks caused by extreme climatic events, primarily drought.
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van Hateren, Theresa C., Marco Chini, Patrick Matgen, and Adriaan J. Teuling. "Ambiguous Agricultural Drought: Characterising Soil Moisture and Vegetation Droughts in Europe from Earth Observation." Remote Sensing 13, no. 10 (May 19, 2021): 1990. http://dx.doi.org/10.3390/rs13101990.
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Long-lasting precipitation deficits or heat waves can induce agricultural droughts, which are generally defined as soil moisture deficits that are severe enough to negatively impact vegetation. However, during short soil moisture drought events, the vegetation is not always negatively affected and sometimes even thrives. Due to this duality in agricultural drought impacts, the term “agricultural drought” is ambiguous. Using the ESA’s remotely sensed CCI surface soil moisture estimates and MODIS NDVI vegetation greenness data, we show that, in major European droughts over the past two decades, asynchronies and discrepancies occurred between the surface soil moisture and vegetation droughts. A clear delay is visible between the onset of soil moisture drought and vegetation drought, with correlations generally peaking at the end of the growing season. At lower latitudes, correlations peaked earlier in the season, likely due to an earlier onset of water limited conditions. In certain cases, the vegetation showed a positive anomaly, even during soil moisture drought events. As a result, using the term agricultural drought instead of soil moisture or vegetation drought, could lead to the misclassification of drought events and false drought alarms. We argue that soil moisture and vegetation drought should be considered separately.
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Wasaya, Allah, Sobia Manzoor, Tauqeer Ahmad Yasir, Naeem Sarwar, Khuram Mubeen, Ismail A. Ismail, Ali Raza, Abdul Rehman, Akbar Hossain, and Ayman EL Sabagh. "Evaluation of Fourteen Bread Wheat (Triticum aestivum L.) Genotypes by Observing Gas Exchange Parameters, Relative Water and Chlorophyll Content, and Yield Attributes under Drought Stress." Sustainability 13, no. 9 (April 25, 2021): 4799. http://dx.doi.org/10.3390/su13094799.
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Water scarceness is a major threat to wheat productivity under changing climate scenarios, especially in arid and semi-arid regions. However, growing drought-tolerant wheat genotypes could be a sustainable option to enhance wheat productivity under drought stress conditions. The aim of this study was to evaluate the effect of mild to severe drought stress on gas exchange parameters, relative water content, SPAD-chlorophyll value, and yield-related parameters of 14 wheat genotypes being cultivated in arid to semi-arid areas on large scale. The genotypes were grown in earthen pots under three drought levels, namely (1) control-well watered, (2) mild water stress, i.e., 60% water holding capacity, and (3) severe water stress, i.e., 40% water holding capacity. The drought was imposed from the jointing stage to physiological maturity. Drought significantly decreased net photosynthesis, stomatal conductance, relative water contents, 100-grain weight, and grain yield in all genotypes. However, the reduction percentage was different in different genotypes under drought stress compared with well-watered conditions. The highest relative water content (65.2%) was maintained by the genotype Galaxy-2013, followed by AAS-2011 (64.6%) and Johar-2016 (62.3%) under severe drought conditions. Likewise, Galaxy-2013 showed the highest net photosynthesis and stomatal conductance under severe drought conditions. The highest grain yield per plant (6.2 g) and 100-grain weight (3.3 g) was also recorded in Galaxy-2013 under severe drought conditions, while the highest grain yield under well-watered conditions was recorded in Johar-2016, followed by Galaxy-2013. These results suggest that wheat variety Galaxy-2013 could be cultivated extensively to obtain good wheat yield under limited water conditions.
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Álvarez-Berríos, Nora L., Sandra Soto-Bayó, Eva Holupchinski, Stephen J. Fain, and William A. Gould. "Correlating drought conservation practices and drought vulnerability in a tropical agricultural system." Renewable Agriculture and Food Systems 33, no. 3 (February 27, 2018): 279–91. http://dx.doi.org/10.1017/s174217051800011x.
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AbstractRecent droughts in Puerto Rico and throughout the Caribbean have emphasized the region's agricultural vulnerability to this hazard and the increasing need for adaptation mechanisms to support sustainable production. In this study, we assessed the geographic extent of agricultural conservation practices incentivized by US Department of Agriculture Natural Resources Conservation Service (NRCS) and evaluated their large-scale contribution to drought adaptability. We identified concentrations of drought-related practices (e.g. cover crops, ponds) applied between 2000 and 2016. Using information from spatial databases and interviews with experts, we assessed the spatial correlation between these practices and areas exposed to drought as identified by the US Drought Monitor. Between 2000 and 2016, Puerto Rico experienced seven drought episodes concentrated around the south, east and southeastern regions. The most profound drought occurred between 2014 and 2016 when the island experienced 80 consecutive weeks of moderate drought, 48 of severe drought and 33 of extreme drought conditions. A total of 44 drought-related conservation practices were applied at 6984 locations throughout 860 km2 of farmlands between 2000 and 2016 through the NRCS-Environmental Quality Incentives Program (EQIP). Practices related to water availability were statistically clustered along the coasts, whereas soil and plant health practices were clustered in the mountainous region. While these concentrations strongly correlated with areas exposed to moderate drought conditions, >80% did not coincide with areas that experienced severe or extreme drought conditions, suggesting that areas highly exposed to drought conditions generally lacked drought preparedness assisted by EQIP. Climate projections indicate an increase in the frequency and intensity of drought events, particularly in the eastern region of Puerto Rico. Our analysis highlighted the need to implement more conservation practices in these areas subject to drought intensification and exposure. Government programs intended to address vulnerabilities and enhance capacity and resilience may not be reaching areas of highest exposure. Recommendations include raising producer awareness of past and future exposure and making programs more accessible to a broader audience.
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Ndayiragije, Jean Marie, Fan Li, and Athanase Nkunzimana. "Assessment of Two Drought Indices to Quantify and Characterize Drought Incidents: A Case Study of the Northern Part of Burundi." Atmosphere 13, no. 11 (November 11, 2022): 1882. http://dx.doi.org/10.3390/atmos13111882.
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Droughts are natural catastrophes that cost the health and wealth of humans due to their harmful effects on the natural environment, ecology, hydrology, and agriculture in particular. Droughts are recurring incidents that last for prolonged periods of time in the northern part of Burundi. Despite the region being prone to drought and often suffering from dry conditions, drought has not been widely investigated. For the quantification and characterization of dryness conditions, this research utilized two drought indices, the Standardized Precipitation Evapotranspiration Index (SPEI) and the Standardized Precipitation Index (SPI), at 2-, 6-, 24-, and 48-month timescales, where 2-, 6-, 24-, and 48-months correspond to agricultural and hydrological droughts, respectively. The two drought indices were compared, and the difference between SPEI and SPI was illustrated by quantifying and characterizing drought incidents. The findings revealed that different types of droughts threatened the northern part of Burundi during the periods of 1993–2000 and 2002–2009. Both indices illustrated that 2005, 2006, and 2007 were extremely dry years. The drought incidents detected by the SPEI index were classified into moderate and severe categories, characterized by long duration and greater magnitude. In contrast, the drought incidents detected by SPI were classified into the “extremely dry” category, characterized by limited duration and lower magnitude but with higher intensities. This research highlighted that SPEI differs from SPI in quantifying and characterizing droughts and highly suggests the use of both SPEI and SPI when assessing droughts. The outcome of this study will be useful in drought prevention and mitigation strategies across Burundi, specifically for agricultural purposes.
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Afrin, R., F. Hossain, and SA Mamun. "Analysis of Drought in the Northern Region of Bangladesh Using Standardized Precipitation Index (SPI)." Journal of Environmental Science and Natural Resources 11, no. 1-2 (October 1, 2019): 199–216. http://dx.doi.org/10.3329/jesnr.v11i1-2.43387.
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Drought is an extended period when a region notes a deficiency in its water supply. The Standardized Precipitation Index (SPI) method was used in this study to analyze drought. Northern region of Bangladesh was the area of study. Monthly rainfall data of northern region of Bangladesh was obtained from the Meteorological Department of Bangladesh. Obtained rainfall data was from 1991 to 2011 and values from 2012 to 2026 were generated using Markov model. Then SPI values from 1991 to 2026 were calculated by using SPI formula for analyzing drought. Analysis with SPI method showed that droughts in northern region of Bangladesh varied from moderately dry to severely dry conditions and it may vary from moderately dry to severely dry conditions normally in future but in some cases extreme drought may also take place. From the study, it is observed that the northern region of Bangladesh has already experienced severe drought in 1991, 1992, 1994, 1995, 1997, 1998, 2000, 2003, 2005, 2007, 2009 and 2010. The region may experience severe drought in 2012, 2015, 2016, 2018, 2019, 2021, 2022, 2023, 2024, 2025 and 2026 and extreme drought in 2012, 2014, 2016, 2023 and 2024.
J. Environ. Sci. & Natural Resources, 11(1-2): 199-216 2018
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Aras, Servet, and Hakan Keles. "Responses of Apple Plants to Drought Stress." Journal of Agricultural Studies 7, no. 2 (August 14, 2019): 153. http://dx.doi.org/10.5296/jas.v7i3.15271.
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In order to screen apple rootstocks for drought tolerance, two different drought levels moderate and severe stress, and a control were applied to apple cultivar Red Chief grafted onto M9 and MM106 rootstocks. Apple plants were subjected to drought stress by withholding water for 15 and 19 days in the greenhouse conditions, while the control treatment was continued watering. Data were recorded 15 (moderate drought stress) and 19 days (severe drought stress) after application of drought stress. At the end of the experiment, both rootstocks were significantly affected under drought conditions. Severe drought stress caused decrease in SPAD value in Red Chief grafted onto M9 and MM106 by 15.7 % and 11.1 %, respectively. Severe drought stress declined anthocyanin content in M9 and MM106 by 7.8 % and 28.4 %, respectively. Stomatal conductance was remarkably affected by drought stress. Effects of drought stress on plants depended on rootstocks, severity and duration of drought stress. As a result, the more invigorating rootstock MM106 was found more drought-tolerant when compared to M9 that is needed to be evaluated with more parameters.
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Dehghani, Majid, Bahram Saghafian, and Mansoor Zargar. "Probabilistic hydrological drought index forecasting based on meteorological drought index using Archimedean copulas." Hydrology Research 50, no. 5 (July 13, 2019): 1230–50. http://dx.doi.org/10.2166/nh.2019.051.
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Abstract Hydrological drought forecasting is considered a key component in water resources risk management. As sustained meteorological drought may lead to hydrological drought over time, it is conceptually feasible to capitalize on the dependency between the meteorological and hydrological droughts while trying to forecast the latter. As such, copula functions are powerful tools to study the propagation of meteorological droughts into hydrological droughts. In this research, monthly precipitation and discharge time series were used to determine Standardized Precipitation Index (SPI) and Standardized Hydrological Drought Index (SHDI) at different time scales which quantify the state of meteorological and hydrological droughts, respectively. Five Archimedean copula functions were adopted to model the dependence structure between meteorological/hydrological drought indices. The Clayton copula was identified for further investigation based on the p-value. Next, the conditional probability and the matrix of forecasted class transitions were calculated. Results indicated that the next month's SHDI class forecasting is promising with less than 10% error. Moreover, extreme and severe meteorological drought classes lead to hydrological drought condition with a more than 70% probability. Other classes of meteorological drought/wet conditions lead to normal hydrological (drought) condition with less than 50% probability and to wet hydrological condition with over 20% probability.
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Ko, Dasang, Yeongcheol Joo, and Taesam Lee. "Reliability Assessment of Agricultural Reservoirs for Water Supply under Climate Change." Journal of the Korean Society of Hazard Mitigation 20, no. 1 (February 29, 2020): 53–60. http://dx.doi.org/10.9798/kosham.2020.20.1.53.
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Recently, the frequency of drought occurrence and the resulting damage has increased due to climate change. Frequent severe droughts induce water shortages in agricultural reservoirs. The role of drought monitoring and prediction is critical for mitigating the effects of severe drought in agricultural areas. In this study, a compound standardized storage and precipitation index (CSSPI) was developed that adapted the existing drought index-the standardized precipitation index (SPI)-by adding hydrological data on storage rate. Furthermore, the future storage rate was simulated using autoregressive models (AR) to estimate the future CSSPI. A dataset containing records of reservoirs and precipitation at the three areas of Jungbu, Youngnam, and Honam was applied to estimate the current and future status of the CSSPI. The results indicate that the CSSPIs generated accurately present the past pattern of the observed data and that they can be considered as inputs for predicting future drought conditions.
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Wu, Dian, Jong-Suk Kim, Seo-Yeon Park, Guyoung Park, Woosung Nam, and Joo-Heon Lee. "Enhanced Prediction and Determination of Hydrological Drought at Ungauged River Intake Stations under Changing Climate." Applied Sciences 12, no. 22 (November 9, 2022): 11379. http://dx.doi.org/10.3390/app122211379.
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Droughts, which are expected to worsen under global climate change, have major impacts on human life and the natural environment. In this study, an analysis system was established for predicting and determining hydrological drought conditions at ungauged water stations and in watersheds connected to municipal river water intake facilities. The aim was to help prevent drought damage or minimize its effects based on an immediate response to severe drought events. A system is presented for the selection of ungauged watersheds that take in river water, and three methodologies are proposed for identifying and forecasting hydrological drought conditions. Two South Korean pilot sites among the numerous ungauged water intake plants that lack local data collection facilities were selected as study areas. In addition, a roadmap for the establishment of standards for the determination of drought conditions in ungauged river basins was proposed. The methodologies introduced in this study assume nationwide expansion and construction. Their utilization can facilitate effective drought responses, based on drought forecasting and restricted water supply criteria for each phase of water intake, at local (and other) waterworks.
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Sarker, Md, Nichol Janet, Siti Mansor, Baharin Ahmad, Shamsuddin Shahid, Eun-Sung Chung, Jeffrey Reid, and Eko Siswanto. "An Integrated Method for Identifying Present Status and Risk of Drought in Bangladesh." Remote Sensing 12, no. 17 (August 20, 2020): 2686. http://dx.doi.org/10.3390/rs12172686.
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The occurrence and severity of agricultural droughts may not be dependent upon climatic variables alone. Rather increasingly, drought is affected by human interventions such as irrigation. Anthropogenic activity has introduced uncertainty in the assessment of current drought and future drought risk in many parts of the world; neither climatic nor remote sensing data alone are able to assess drought conditions effectively. In response, we present a simple approach to assess drought by combining a remote sensing-based drought index, the Temperature Vegetation Dryness Index (TVDI), climate data (i.e., rainfall and temperature), and field observations to evaluate recent drought conditions in northwestern Bangladesh (NWB). Applying this approach, we gained five insights: (i) the TVDI successfully indicated the drought conditions of NWB and agrees with field observations, (ii) the integrated use of TVDI and climate data (such as rainfall and temperature) provides the best understanding of the difference between meteorological drought and droughts resulting from surface moisture conditions, (iii) the TVDI results agree with rainfall data (r2 = 0.40 in March and r2 = 46 in April) in a part of the study area (NWB) where irrigation is not available, (iv) the TVDI can be used along with climate data to predict the potential risk of drought, and (v) while meteorological drought exists due to low rainfall and high temperature in this NWB in pre-monsoon season, because of widespread irrigation practices, meteorological drought is unable to trigger agricultural drought over most parts of the study area. The findings imply that there is a potential risk of drought in NWB, since any disruption of irrigation water supply could trigger a severe agricultural drought over the whole region. This is similar to what is currently observed over a small part of NWB.
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Rahman, Shoumik, and Victor Mesev. "Change Vector Analysis, Tasseled Cap, and NDVI-NDMI for Measuring Land Use/Cover Changes Caused by a Sudden Short-Term Severe Drought: 2011 Texas Event." Remote Sensing 11, no. 19 (September 23, 2019): 2217. http://dx.doi.org/10.3390/rs11192217.
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Sudden short-term severe droughts have major impacts on ecosystem balance. Synoptic and replicable measurements from remotely sensed data are essential for calculating changes to land use/cover caused by severe drought conditions. In the US, Texas experienced a particularly severe drought in 2011, which adversely affected forest and grassland ecosystems in addition to $7.62 billion of agricultural loss. To assess the extent and severity of the drought we use satellite sensor data and image processing techniques to measure changes in land use/cover. Our methodology uses change vector analysis (CVA), the normalized difference vegetation index, the normalized difference moisture index, and three variables-brightness, greenness, and wetness-extracted from tasseled cap transforms (TCT). All are established techniques in remote sensing but have as yet been applied in combination to measure land use/cover changes affected by intense short-term drought conditions. Our objective is to calculate not only vegetation and bare soil indices, but also the intensity of change (magnitude) and the type of change (direction). For CVA direction, we include an improved methodology using the arctangent function based on two arguments, ATAN2 which produces results in all four possible quadrants, and complete characterization of all possible change directions. The three variables of TCT are applied to CVA magnitude and direction using vectors in three dimensions, resulting in eight change categories. Our results are based on Landsat TM sensor data for the years 2009, 2010 and 2011, which represent a short period of severe drought, above average precipitation, and severe drought respectively, for two study sites in Texas. Results indicate that land use/cover changes were affected by both an increase in precipitation in 2010 as well as a considerable decrease of precipitation in 2011 resulting in the devastating sudden drought.
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Sreekesh, S., N. Kaur, and S. R. Sreerama Naik. "AGRICULTURAL DROUGHT AND SOIL MOISTURE ANALYSIS USING SATELLITE IMAGE BASED INDICES." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-3/W6 (July 26, 2019): 507–14. http://dx.doi.org/10.5194/isprs-archives-xlii-3-w6-507-2019.
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<p><strong>Abstract.</strong> The deficiency in rainfall leads to meteorological droughts. Its manifestations are visible both in the vegetation cover and soil moisture. The present study assessed the characteristics of agricultural drought following meteorological droughts. The study also assessed the severity of meteorological droughts and their manifestation on the agriculture and soil moisture in a semi-arid area. The study has been carried out for the Malaprabha sub-basin which partly covers three districts of North Interior Karnataka, India. India Meteorological Department’s (IMD) criteria have been used to identify the drought years, and its severity has been assessed through the Standard Precipitation Index (SPI). The IMD’s monthly rainfall data were used to identify the drought years and periods for the region. Among the drought years, the mild, moderate, and severe drought along with deficit and excess rainfall years were considered to assess and characterize the soil moisture conditions and the agricultural drought. The satellite image based indices for these selected years were constructed to determine the soil moisture conditions and the agricultural drought severity. The Temperature-Vegetation Dryness Index (TVDI) was used to determine the soil moisture conditions. The indices employed to determine the agriculture drought are NDVI, Thermal Condition Index (TCI), Vegetation Condition Index (VCI), and Vegetation Health Index (VHI). These satellite-based indices were calculated using the Landsat images of the selected drought and non-drought years. The results showed that the seasonal and annual drought are frequent in the study area. There are spatial and temporal variations in the drought years and their severity. The satellite-based indices clearly indicate the spatial variation in the agriculture droughts and its intensity. It has been found that the impact of drought on agriculture has significantly reduced due to the development of well-irrigation in the sub-basin. VHI is more appropriate in determining the agricultural drought and its characteristics.</p>
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Hook, James E., and Wayne W. Hanna. "Drought Resistance in Centipedegrass Cultivars." HortScience 29, no. 12 (December 1994): 1528–31. http://dx.doi.org/10.21273/hortsci.29.12.1528.
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In our study, we sought to determine if an experimental cultivar of centipedegrass [`TC178'; Eremochloa ophiuroides (Munro) Hack.] had superior turf characteristics under extended droughts. Common centipedegrass (CC), vegetatively propagated `TC178' (VG178), and seed-propagated (F3) `TC178' (SD178) were evaluated in a 2-year controlled watering study that compared turf characteristics and drought resistance. The grasses were established under an automated rainfall shelter and were subjected to three drought regimes: watered twice per week (no stress), 2 to 3 weeks between watering (moderate), and 4 to 6 weeks between watering (severe). Turf characteristics (visual rating and clipping biomass) were measured weekly and soil water content profiles were measured daily. Visual ratings among cultivars were similar for no-stress conditions, but visual ratings of SD178 and VG178 were 18% higher than for CC for moderate stress and 28% higher for severe stress. At the end of moderate stress periods, clipping biomass of VG178 was 24% greater than for CC, but by the end of the severe stress periods, biomass from VG178 was 22% lower than for CC. Available soil water content profiles indicated that the three cultivars extracted soil water at the same rate. Visual ratings and growth decline with survival under severe stress showed that VG178 and SD178 had significantly better drought resistance than CC. `TC178' provides a superior appearance turf that will stand up to the droughts common in its adapted region.
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Warner, SM, SJ Jeffries, WA Lovis, AF Arbogast, and FW Telewski. "Tree ring-reconstructed late summer moisture conditions, 1546 to present, northern Lake Michigan, USA." Climate Research 83 (March 11, 2021): 43–56. http://dx.doi.org/10.3354/cr01637.
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Drought can affect even humid regions like northeastern North America, which experienced significant, well-documented dry spells in the 1930s, 50s, 60s, and 80s, and proxies tell us that in the years before instrumentally recorded climate, droughts could be even more severe. To get a more complete picture of pre-recorded climate, the spatial coverage of proxy-based climate reconstructions must be extended. This can better put in context past, current, and future climate, and it can lend anthropological and historical insights. With regard to tree rings as climate proxies, however, there is increasing evidence that relationships between tree growth and climate can be inconsistent over time, in some cases decreasing the utility of tree rings in the representation of climate. We developed a chronology from white cedar Thuja occidentalis tree ring widths for the period 1469-2015 C.E. with which we modeled the relationship between growth and July-September moisture conditions (Palmer Z index). The relationship was consistent across the period of instrumentally recorded climate, 1895-present, and the model explained 27% of variability. Therefore, we used the model to reconstruct July-September moisture conditions from 1546-2014. We found the most variable century to be the 20th, the least the 18th. The severest decade-scale droughts (≤0.75 SD from mean) occurred in the 1560s, 1600s/10s, 1630s, 1770s/80s, 1840s, and 1910s/20s, the severest pluvials (≥0.75 SD) in the 1610s/20s, 1660s/70s, and the 1970s/80s. The occasional occurrence of severe droughts throughout the reconstruction, increasing variability in the 20th century, and expected climate change-enhanced late summer drought, portend a future punctuated with severe droughts.
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Anderson, B., D. Manouseli, and M. Nagarajan. "Estimating scenarios for domestic water demand under drought conditions in England and Wales." Water Supply 18, no. 6 (February 13, 2018): 2100–2107. http://dx.doi.org/10.2166/ws.2018.035.
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Abstract This paper presents preliminary results from the development of the IMPETUS model, a domestic water demand microsimulation model which was developed to estimate the results of a range of scenarios of domestic demand under drought conditions. The model is intended to enable water resource management practitioners to assess the likely impact of potential interventions in particular catchment areas. It has been designed to be driven by seasonal catchment level forecasts of potential hydrological droughts based on innovative climate and groundwater models. The current version of the model is driven by reconstructed historical drought data for the Colne catchment in the east of England from 1995 to 2014. This provides a framework of five drought phases (Normal, Developing, Drought, Severe Drought and Recovering) which are mapped to policy driven interventions such as increased provision of water efficiency technologies and temporary water-use bans. The model uses UK Census 2011 data to develop a synthetic household population that matches the socio-demographics of the catchment and it microsimulates (at the household level) the consequences of water efficiency interventions retrospectively (1995–2014). Demand estimates for reconstructed drought histories demonstrate that the model is able to adequately estimate end-use water consumption. Also, the potential value of the model in supporting cost-benefit analysis of specific interventions is illustrated. We conclude by discussing future directions for the work.
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Krishnan, Lalitha, Deepak Barua, and Mahesh Sankaran. "Dry-forest tree species with large seeds and low stem specific density show greater survival under drought." Journal of Tropical Ecology 35, no. 1 (January 2019): 26–33. http://dx.doi.org/10.1017/s0266467418000421.
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AbstractTree establishment in tropical dry forests is constrained by drought-related seedling mortality during early stages of recruitment. Predicted increases in the duration of growing-season droughts in the future pose a significant threat to these ecosystems that could significantly alter their vegetation structure and composition. Here, we examined drought tolerance in seedlings of seven common dry-forest tree species from the Indian subcontinent. We conducted a dry-down experiment on 3-wk-old seedlings, and asked whether the key plant functional traits, specific leaf area (SLA), leaf dry matter content (LDMC), seed size and stem specific density (SSD) were good predictors of seedling growth under well-watered conditions, and survival during drought. Seedlings displayed substantial drought tolerance with most seedlings surviving for more than 2 wk under protracted drought. Seed size in combination with SLA predicted seedling growth under well-watered conditions and seed size predicted survival under drought. In contrast to our expectations, seedlings with lower SSD survived for longer without water. Our results suggest that dry-forest species will be differentially affected by the predicted increases in the duration of growing-season droughts, and detrimental effects will be more severe for species with smaller seeds.
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Musonda, Bathsheba, Yuanshu Jing, Vedaste Iyakaremye, and Moses Ojara. "Analysis of Long-Term Variations of Drought Characteristics Using Standardized Precipitation Index over Zambia." Atmosphere 11, no. 12 (November 24, 2020): 1268. http://dx.doi.org/10.3390/atmos11121268.
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This study examines long-term spatial and temporal trends of drought characteristics based on the Standardized Precipitation Index at three different time scales (3, 6, and 12 months) over Zambia from 1981 to 2017. Drought characteristic conditions such as duration, severity, and intensity at monthly, seasonal, and annual levels were analyzed to investigate the drought patterns over Zambia. The results show a significant increase in drought events over the southwestern regions and a decrease over the northeastern regions. It is in this regard that two stations from different locations (southwest and northeast) were analyzed. The results show increasing trends of drought over Sesheke (southwest) and decreasing trends over Kasama (northeast). More drought impacts are felt over southern compared to northern areas, which poses a serious concern to both agriculture and hydrological industries over the drought-prone areas of Southern Zambia. However, the analysis further shows that droughts were more intense, persistent, and severe over the southwest, while moderate droughts were found in some few areas of Northeast Zambia. The Mann–Kendall test trend and slope indicated that both annual and seasonal drought have increased. However, drought increment at an annual level shows a low magnitude as compared to the seasonal level. This suggested the importance of evaluating drought at an interannual and seasonal time scale over Zambia. Specifically, the drought increased determinedly before 2010 and became erratic between 2010 and 2017 with considerable regional variation. Zambia experienced moderate to severe droughts during 1991–1992, 1994–1995, 2006–2005, and 2015–2016, which resulted in serious damages to the environment and society. According to the findings of this study, it is suggested that the implications of drought can be managed by creating strategies and adaptation measures.
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Sirisena, Jeewanthi, Denie Augustijn, Aftab Nazeer, and Janaka Bamunawala. "Use of Remote-Sensing-Based Global Products for Agricultural Drought Assessment in the Narmada Basin, India." Sustainability 14, no. 20 (October 12, 2022): 13050. http://dx.doi.org/10.3390/su142013050.
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Droughts exert severe impacts on the environment, economy, and society. The south Asian region is vulnerable to droughts and the Indian sub-continent is one of the most vulnerable in the region to frequent drought disasters. This study assesses the agricultural droughts in the Narmada River Basin (NRB), India, where more than 50% of the area is utilized for agriculture, through freely available local and global remote-sensing-based data focusing on long-term rainfall trends (1989–2018) and recently weakened monsoons in 2017 and 2018. In this study, some of the widely used indices to characterize droughts (viz., Standardized Precipitation Index (SPI), simplified Rainfall Index (RIs), Normalized Difference Vegetation Index (NDVI)), soil moisture content, and reservoir surface areas were used to assess the drought conditions in the Narmada River Basin over the study period. Our analysis shows that the NRB has experienced a decreasing trend in monsoon rainfall over the past three decades. The SPI captured most of the basin’s historical droughts. The weakened monsoons during 2017–2018 show that different parts of the NRB have experienced severe or moderate drought conditions. A clear difference does not show in the NDVI and in the soil moisture contents of the basin over three hydrological years (2015/16, 2016/17, and 2017/18), except for July to September 2017/18. The estimated water area depletion using the Normalized Difference Water Index (NDWI) follows the actual water levels in three selected reservoirs in the basin, of which, two show a decline in the maximum surface area, likely due to the weakened monsoons in 2017 and 2018. This research indicates that the freely available data can be beneficial for local authorities to monitor and understand the drought conditions to support water resources management and planning for agricultural activities.
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Laddomada, Barbara, Antonio Blanco, Giovanni Mita, Leone D’Amico, Ravi P. Singh, Karim Ammar, Jose Crossa, and Carlos Guzmán. "Drought and Heat Stress Impacts on Phenolic Acids Accumulation in Durum Wheat Cultivars." Foods 10, no. 9 (September 10, 2021): 2142. http://dx.doi.org/10.3390/foods10092142.
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Droughts and high temperatures are the main abiotic constraints hampering durum wheat production. This study investigated the accumulation of phenolic acids (PAs) in the wholemeal flour of six durum wheat cultivars under drought and heat stress. Phenolic acids were extracted from wholemeals and analysed through HPLC-DAD analysis. Ferulic acid was the most represented PA, varying from 390.1 to 785.6 µg/g dry matter across all cultivars and growth conditions, followed by sinapic acids, p-coumaric, vanillic, syringic, and p-hydroxybenzoic acids. Among the cultivars, Cirno had the highest PAs content, especially under severe drought conditions. Heat stress enhanced the accumulation of minor individual PAs, whereas severe drought increased ferulic acid and total PAs. Broad-sense heritability was low (0.23) for p-coumaric acid but ≥0.69 for all other components. Positive correlations occurred between PA content and grain morphology and between test weight and grain yield. Durum wheat genotypes with good yields and high accumulation of PAs across different growing conditions could be significant for durum wheat resilience and health-promoting value.
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Mishra, Vimal, Reepal Shah, Syed Azhar, Harsh Shah, Parth Modi, and Rohini Kumar. "Reconstruction of droughts in India using multiple land-surface models (1951–2015)." Hydrology and Earth System Sciences 22, no. 4 (April 16, 2018): 2269–84. http://dx.doi.org/10.5194/hess-22-2269-2018.
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Abstract. India has witnessed some of the most severe historical droughts in the current decade, and severity, frequency, and areal extent of droughts have been increasing. As a large part of the population of India is dependent on agriculture, soil moisture drought affecting agricultural activities (crop yields) has significant impacts on socio-economic conditions. Due to limited observations, soil moisture is generally simulated using land-surface hydrological models (LSMs); however, these LSM outputs have uncertainty due to many factors, including errors in forcing data and model parameterization. Here we reconstruct agricultural drought events over India during the period of 1951–2015 based on simulated soil moisture from three LSMs, the Variable Infiltration Capacity (VIC), the Noah, and the Community Land Model (CLM). Based on simulations from the three LSMs, we find that major drought events occurred in 1987, 2002, and 2015 during the monsoon season (June through September). During the Rabi season (November through February), major soil moisture droughts occurred in 1966, 1973, 2001, and 2003. Soil moisture droughts estimated from the three LSMs are comparable in terms of their spatial coverage; however, differences are found in drought severity. Moreover, we find a higher uncertainty in simulated drought characteristics over a large part of India during the major crop-growing season (Rabi season, November to February: NDJF) compared to those of the monsoon season (June to September: JJAS). Furthermore, uncertainty in drought estimates is higher for severe and localized droughts. Higher uncertainty in the soil moisture droughts is largely due to the difference in model parameterizations (especially soil depth), resulting in different persistence of soil moisture simulated by the three LSMs. Our study highlights the importance of accounting for the LSMs' uncertainty and consideration of the multi-model ensemble system for the real-time monitoring and prediction of drought over India.
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Liu, Wenbin, Fubao Sun, Wee Ho Lim, Jie Zhang, Hong Wang, Hideo Shiogama, and Yuqing Zhang. "Global drought and severe drought-affected populations in 1.5 and 2 °C warmer worlds." Earth System Dynamics 9, no. 1 (March 19, 2018): 267–83. http://dx.doi.org/10.5194/esd-9-267-2018.
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Abstract. The 2015 Paris Agreement proposed a more ambitious climate change mitigation target on limiting global warming to 1.5 ∘C instead of 2 ∘C above preindustrial levels. Scientific investigations on environmental risks associated with these warming targets are necessary to inform climate policymaking. Based on the Coupled Model Intercomparison Project phase 5 (CMIP5) climate models, we present the first risk-based assessment of changes in global drought and the impact of severe drought on populations from additional 1.5 and 2 ∘C warming conditions. Our results highlight the risk of drought on a global scale and in several hotspot regions such as the Amazon, northeastern Brazil, southern Africa and Central Europe at both 1.5 and 2 ∘C global warming relative to the historical period, showing increases in drought durations from 2.9 to 3.2 months. Correspondingly, more total and urban populations would be exposed to severe droughts globally (+132.5 ± 216.2 million and +194.5 ± 276.5 million total population and +350.2 ± 158.8 million and +410.7 ± 213.5 million urban populations in 1.5 and 2 ∘C warmer worlds) and regionally (e.g., East Africa, West Africa and South Asia). Less rural populations (−217.7 ± 79.2 million and −216.2 ± 82.4 million rural populations in 1.5 and 2 ∘C warmer worlds) would be exposed to severe drought globally under climate warming, population growth and especially the urbanization-induced population migration. By keeping global warming at 1.5 ∘C above the preindustrial levels instead of 2 ∘C, there is a decrease in drought risks (i.e., less drought duration, less drought intensity and severity but relatively more frequent drought) and the affected total, urban and rural populations would decrease globally and in most regions. While challenging for both East Africa and South Asia, the benefits of limiting warming to below 1.5 ∘C in terms of global drought risk and impact reduction are significant.
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Bernardino, Paulo N., Martin Brandt, Wanda De Keersmaecker, Stéphanie Horion, Rasmus Fensholt, Ilié Storms, Jean-Pierre Wigneron, Jan Verbesselt, and Ben Somers. "Uncovering Dryland Woody Dynamics Using Optical, Microwave, and Field Data—Prolonged Above-Average Rainfall Paradoxically Contributes to Woody Plant Die-Off in the Western Sahel." Remote Sensing 12, no. 14 (July 21, 2020): 2332. http://dx.doi.org/10.3390/rs12142332.
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Dryland ecosystems are frequently struck by droughts. Yet, woody vegetation is often able to recover from mortality events once precipitation returns to pre-drought conditions. Climate change, however, may impact woody vegetation resilience due to more extreme and frequent droughts. Thus, better understanding how woody vegetation responds to drought events is essential. We used a phenology-based remote sensing approach coupled with field data to estimate the severity and recovery rates of a large scale die-off event that occurred in 2014–2015 in Senegal. Novel low (L-band) and high-frequency (Ku-band) passive microwave vegetation optical depth (VOD), and optical MODIS data, were used to estimate woody vegetation dynamics. The relative importance of soil, human-pressure, and before-drought vegetation dynamics influencing the woody vegetation response to the drought were assessed. The die-off in 2014–2015 represented the highest dry season VOD drop for the studied period (1989–2017), even though the 2014 drought was not as severe as the droughts in the 1980s and 1990s. The spatially explicit Die-off Severity Index derived in this study, at 500 m resolution, highlights woody plants mortality in the study area. Soil physical characteristics highly affected die-off severity and post-disturbance recovery, but pre-drought biomass accumulation (i.e., in areas that benefited from above-normal rainfall conditions before the 2014 drought) was the most important variable in explaining die-off severity. This study provides new evidence supporting a better understanding of the “greening Sahel”, suggesting that a sudden increase in woody vegetation biomass does not necessarily imply a stable ecosystem recovery from the droughts in the 1980s. Instead, prolonged above-normal rainfall conditions prior to a drought may result in the accumulation of woody biomass, creating the basis for potentially large-scale woody vegetation die-off events due to even moderate dry spells.
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Wesche, Karsten. "The importance of occasional droughts for afroalpine landscape ecology." Journal of Tropical Ecology 19, no. 2 (February 10, 2003): 197–208. http://dx.doi.org/10.1017/s0266467403003225.
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The paper presents climatic and plant ecological data for unusually severe dry-season conditions on Mt. Elgon (Uganda/Kenya) and the Bale Mountains (Ethiopia). There is clear evidence that plants are exposed to desiccation stress during high-altitude droughts, which occur on average every 7-10 y in the study sites. Although high vapour-pressure deficits and consequently high potential evapotranspiration led to conspicuous wilting of several plant species, no lethal damage was observed and plant communities maintained increased flowering activity under drought conditions. Moreover, highest outposts of ericaceous vegetation were regularly found on thin soil covering rocky outcrops, where water stress apparently is high. Probably more important than direct water stress are the extensive fires occurring under drought conditions, which cause large-scale replacement of woody vegetation by grasslands. Additional consequences of drought include adverse conditions for seedling stablishment.