Impact of climate change on rainfed rice and options for adaptation in the lower Mekong Basin

We assessed the potential impact of climate change on the yield of rainfed rice in the lower Mekong Basin and evaluated some adaptation options, using a crop growth simulation model. Future climate projections are based on IPCC SRES A2 and B2 scenarios as simulated by ECHAM4 global climate model downscaled for the Mekong Basin using the PRECIS system. We divided the basin into 14 agro-climatic zones and selected a sub-catchment within each zone for the model and assessed the impact for the period of 2010–2030 and 2030–2050. In general, the results suggest that yield of rainfed rice may increase significantly in the upper part of the basin in Laos and Thailand and may decrease in the lower part of the basin in Cambodia and Vietnam. The increase is higher during 2030–2050 compared to the period of 2010–2030 for A2 scenario. For B2 scenario, yield increase is higher during 2010–2030. The impact is mainly due to the change in rainfall and CO₂ concentration in the atmosphere. We have tested widely used adaptation options such as changing planting date, supplementary irrigation, and reduction in fertility stress and found that negative impact on yield can be offset and net increase in yield can be achieved.     

Exposure,vulnerability, and adaptation of major maize-growing areas to extreme temperature

Driven by increasing demand for food and industrial consumption, world’s maize supply is under stress. Besides, the extreme temperature events are now exposing more threat to maize yield with ongoing climate change. Thus, a comprehensive analysis on maize exposure (exposure is defined as the cultivated area which is exposed to extreme temperature stress), vulnerability (here it means how much yield losses with each temperature increase/decrease at a national scale), and adaptation to extreme temperature is essential to better understand the effects on global maize production, especially in major production countries. It was found that warming trends during the growing season have extensively dominated the main maize-growing areas across the globe. And along with this mean temperature trend was the increasing heat stress and decreasing cold stress among most regions. Moreover, from 1981 to 2011, maize yield losses caused by heat stress in China, India, and the USA were 1.13, 0.64 and 1.12% per decade, respectively, while Mexico has been experiencing a reduction of yield loss due to decreased cold stress of 0.53% per decade. Furthermore, during the period of 2021–2051, the extreme heat stress would increase substantially, while the low temperature was estimated to drop slightly during the growing seasons. Such pattern had also been found over the key reproductive stage of maize. Accordingly, through the sensitivity test of two adaption measures, improved high-temperature-tolerant varieties and changing maize calendar earlier could both mitigate extreme meteorological stress on maize, while the former method would be the most effective way to do so. Our study could provide a paradigm for other crops and other countries in the world to analyze their exposure and vulnerability to the temperature stress and make corresponding adaptation measures.

     

中国旱灾农业承灾体脆弱性诊断与评价

旱灾是世界上影响面最广、造成农业损失最大的自然灾害类型，世界近一半的国家干旱严重。中国旱灾频繁，每年旱灾损失占各种自然灾害损失的15%以上，随着人口和农业的快速发展，农业承灾体脆弱性对灾情的放大也在增加。基于灾害系统理论，从致灾因子和耕地承灾体的区域组合角度，在旱灾频发高值区，选择雨养农业、灌溉农业和水田农业为主要承灾体类型，构建了农业旱灾脆弱性生产压力和生活压力，灾前—灾中易损性和灾中—灾后适应性等农业旱灾承灾体脆弱性诊断指标体系。提出脆弱性评价的区域模型，即：雨养农业的易损—适应模型（兴和）、灌溉农业的生产—生活压力模型（邢台）和水田农业的需水—灌水模型（鼎城）。基于农业承灾体脆弱性评价，提出制定适应降水变化的波动土地利用结构调整区域政策、建立农业生态—生产范式、建立“水银行”管理机制、建立用水效益和开源节流的评估体系以及加强“截水—抽水—控水”为一体的灌溉系统工程建设，提高灌溉应急能力等对策，以期为农业旱灾的防御和区域粮食安全决策提供科学依据。     

Application of the self-calibrated palmer drought severity index and standardized precipitation index for estimation of drought impact on maize grain yield in Pannonian part of Croatia

Recent global warming and more frequent droughts are causing significant damage to maize production. A reliable estimate of drought intensity and duration is essential for testing maize hybrids to drought tolerance. For this purpose, the self-calibrating 10-day palmer drought severity index (scPDSI) and standardized precipitation index (SPI) for 1, 2, 3, 6, 9, 18, 27, and 36 10-day scales were used to estimate the effects of drought on grain yield of 32 maize hybrids evaluated in 2017 and 2018 at eight experimental locations in the Pannonian part of Croatia. Time series of observed 10-day mean air temperature, relative humidity, and precipitation totals for a set of “reference” weather stations of the croatian meteorological and hydrological service (DHMZ) for the period 1981–2018 were used to calculate the scPDSI and SPI indices. According to the 10-day scPDSI and SPI for different time scales, 2018 proved to be a “normal year,” while 2017 experienced a “mild to moderate drought,” which resulted in a 13% reduction in maize grain yield at eight experimental locations compared to 2018. The correlation between grain yield and drought indices for summer months was the highest for the 10-day scPDSI. To some extent, correlations between summer months’ SPI for the 3 10-day time scale and maize grain yield were comparable to the corresponding correlations for the 10-day scPDSI. However, for other SPI time scales considered, the corresponding correlations were weaker and less informative. The dependence of grain yield on scPDSI values was not the same for all hybrids, indicating their different tolerance to drought. The reduction in grain yield due to drought was primarily caused by insufficient grain filling (lower 1000-grain weight) and, to some extent, by a reduction in the number of grains. In this study, application of 10-day scPDSI data proved to be more relevant in detecting effects of drought on agronomic traits than application of SPI data for the most time scales.

     

Assessment of precipitation and drought variability in the Weihe River Basin,China

The amount and distribution of precipitation play crucial roles in the occurrence of drought in the Weihe River Basin (WRB), China. Using the precipitation data (1960–2010) of 21 meteorological stations, the spatial and temporal characteristics of short-, medium-, and long-term droughts on 3-, 6-, and 12-month time scales, respectively, were examined using the theory of runs and the Standardized Precipitation Index (SPI). The trends of the drought characteristics were analyzed by a modified Mann-Kendall (MMK) test method. Furthermore, comparative analysis of the SPI at different time scales was conducted. The results showed that (1) the main drought type was moderate drought, which occurred frequently in July and October; (2) the drought intensity and frequency were highest in the 1990s, and the drought severity and drought duration in the northwest was more serious than that in the east; (3) an increasing trend of short droughts appeared mainly in the spring and fall; an increasing trend of medium droughts mainly occurred in the 1990s and that of long-term droughts were mainly presented in the northwest region of the WRB; (4) SPI-3 can better reflect precipitation in the current month, SPI-6 has an advantage in characterizing drought persistence, and SPI-12 performs well in capturing extraordinary droughts; and (5) it was also observed that there is a strong relation between the precipitation distribution and drought zones in the basin, and the drought conditions changed continuously with the seasons depending upon the amount and spatial distribution of precipitation .     

Spatio-temporal distributions of climate disasters and the response of wheat yields in China from 1983 to 2008

Climate disasters are now on the rise and more likely to increase in frequency and/or severity under climate change in the future. To clearly illustrate spatial–temporal distributions of climate disasters and the response of wheat yields to disasters over the past three decades, several disaster indices including the impact of climate disasters, the sensitivity to climate disasters and the response index of wheat yield losses to climate disasters were defined and calculated. The impact and sensitivity indices were examined by the agricultural production losses due to climate disasters, and the response of wheat yields to climate disasters was assessed by wheat yield loss compared with the 5-year moving average. The results showed that the indices of climate disaster impacts and sensitivities as well as response index of wheat yields to climate disasters could represent the spatial–temporal distributions of climate disasters well in the whole China. Droughts in northern China had higher impacts and sensitivities than those in southern China during the period 1983–2008, but the impacts of floods were opposite. In northern China, although impacted area by drought was larger than that by flood, the flood sensitivities were larger than drought sensitivities when flood happened. Although drought significantly affected wheat yields in most of the regions with drier conditions during 1983–2008 in major wheat-producing regions, better management practices like irrigation and drought-tolerant cultivars applied in the Huang-Huai-Hai Plain can adapt to climate disasters especially droughts. To ensure the stability of agricultural production, future food security will need to be achieved through quantifying the relative effects of climate disasters and effective adaptation to increasingly frequent extreme climate events.     

Assessing Vulnerability to Agricultural Drought: A Nebraska Case Study

Recent drought events in the United States and the magnitude of drought losses indicate the continuing vulnerability of the country to drought. Until recently, drought management in many states, including Nebraska, has been largely response oriented with little or no attention to mitigation and preparedness. In 1998, Nebraska began to revise its drought plan in order to place more emphasis on mitigation. One of the main aspects of drought mitigation and planning is the assessment of who and what is vulnerable and why. This paper presents a method for spatial, Geographic Information Systems-based assessment of agricultural drought vulnerability in Nebraska. It was hypothesized that the key biophysical and social factors that define agricultural drought vulnerability were climate, soils, land use, and access to irrigation. The framework for derivation of an agricultural drought vulnerability map was created through development of a numerical weighting scheme to evaluate the drought potential of the classes within each factor. The results indicate that the most vulnerable areas to agricultural drought were non-irrigatedcropland and rangeland on sandy soils, located in areas with a very high probability of seasonal crop moisture deficiency. The identification of drought vulnerability is an essential step in addressing the issue of drought vulnerability in the state and can lead to mitigation-oriented drought management.     

Spatial and temporal changes of agro-meteorological disasters affecting maize production in China since 1990

Agro-meteorological (AM) disasters have been reported to be more frequent with climate change. In this study, the spatial and temporal changes in the frequency of major AM disasters affecting maize production are investigated by analyzing observed records at 224 national AM stations in China from 1991 to 2009. To investigate the temporal changes of the disasters with climate warming, the whole study period was separated into a cool period (1991–2000) and a warmer one (2000–2009). We found drought was the most common disaster with a frequency of 49 %, followed by chilling injures (19.46 %). The frequency of disasters affecting maize increased significantly during the reproductive growth period than the vegetative growth period. Spatial patterns of major disaster frequency were characterized by region-specific, with more cold stress in northeastern China, drought in northern and western China, and rainstorms in southwestern China. Our study highlighted that the frequency and scope both increased significantly, implying a potential increasing risk for maize production. It is critical and important for local farmers and governors to take reasonable and timely adaptation measures based on the latest disasters’ features to mitigate the potential yield loss from AM disasters in order to ensure food security in China.     

Climate change and soil moisture: A case study

An important aspect of regional climate change is alteration in soil moisture availability. The EPIC (Erosion Productivity Impact Calculator — Sharpley and Williams, 1990) model is applied to estimate soil hydrology consequences in a representative subcatchment (24 km²) of Lake Balaton, Hungary. The study is based on the soil hydrology parameters of the EPIC model, which exhibit a relatively fast response to the climate variations. To specify the regional climate scenario for Hungary in semi-annual time resolution, a statistical approach computing regression between regional and hemispherical mean climate characteristics is employed. The semi-annual scenarios are further refined by applying the principle of geographical analogy. This difference corresponds to a 0.5 °K increase of the hemispherical mean temperature, i.e. the climate after 20–40 years of monotonous warming (IPCC, 1996a). Diurnal statistical parameters which correspond to present (base-line) and future climates of the investigated site are finally introduced into the built-in weather generator of the EPIC model. A supplementary factor of variation in soil hydrology is crop-rotation, responsible for half of the standard deviations, as compared to the hypothetical maize monoculture experiment. Climate generated differences in transpiration, soil moisture content, and crop-available water during water stress days. In connection with the assumed warming, there is a general trend towards drought during the vegetation growing period.     

Identifying climate risk causing maize (Zea mays L.) yield fluctuation by time-series data

A long time series in crop yield is usually expressed as a long-term trend and a short-term fluctuation due to agricultural technological advance and climatic anomaly. The real climate risk is related to the short-term fluctuation in crop yield. In the paper, the climate risk of maize yield response to long-term climate variables is tested with the long time series (1961–2015) by a trend base line method. The long time series of maize yield is divided into short-term fluctuating meteorological yield and long-term trend yield. The long time series of climate variables are also divided into fluctuating variables and trend variables. After that, Pearson correlation analysis between fluctuating maize yield and fluctuating climate variables is used to identify risk factor causing maize yield fluctuation. Our results reveal that the main risk factors are night-time precipitation and extreme high temperature in growing season. Comparing climate risks in maize-producing provinces, much more climate risks are identified in some regions such as Liaoning province. The results provide useful information for reducing maize yield loss under climatic change.

     

Damage Evaluation of Agro-meteorological Hazards in the Maize-Growing Region of Songliao Plain,China: Case Study of Lishu County of Jilin Province

Agro-meteorological hazards such as drought, waterlogging and cool summer occur with very high frequency and affect maize production and social-economic development in the maize-growing region of Songliao Plain, China. Moreover, both the frequency of these hazards and loss from them are considered to be increasing with global warming. The purpose of this paper is to quantitatively analyze the relationships between the fluctuation of maize yield and drought, waterlogging and cool summer, and to evaluate the consequences of these hazards in the maize-growing area of Songliao Plain, taking Lishu county as a case study area based on GIS (Geographic Information System). Crop yield-climate analysis and regression analysis were employed to analyze and quantify relationships between the fluctuation of maize yield and drought, waterlogging and cool summer, and to evaluate the consequences of these hazards. The parameters and model of damage evaluation were presented using weighted comprehensive analysis, and the degree of damage of drought, waterlogging and cool summer to maize production was comprehensively evaluated and regionalized. It is shown that from 1949 to 1990, the negative value years of the fluctuation of maize yield due to meteorological hazards accounted for 55% of seasons, of which 14% was caused by drought, 30% by waterlogging, 4% by cool summer and drought, 9% by cool summer and waterlogging, 13% by drought and waterlogging, 30% by drought, waterlogging and cool summer. Studies on the instability and spatial variation of the fluctuations in maize yield in Lishu county showed that the middle plains are stable areas to climatic influence, while southeastern hills and low mountains, the low lands of the plains along the East Liao River and the western plain are unstable areas in terms of areas in maize yield. The synthetic index of the degree of damage to maize of drought, waterlogging and cool summer showed a strong positive correlation with the ratio of the amount damaged to the normal yield of maize. This suggests that this index can be used to evaluate such damage. The degree of damage of drought, waterlogging and cool summer to maize in Lishu county shows the regional characteristics, which increase gradually from the center to the west and east, this being almost identical with the spatial distribution of the fluctuation of maize yield due to these hazards. This study can be expected to provide the basis for developing strategies to mitigate agro-meteorological hazards and reducing the losses from them, and adjust the medium and long-term distribution of agricultural activities so as to adapt to environmental changes.     

Evaluation of effective management plan for an agricultural watershed using AVSWAT model,remote sensing and GIS

In the present investigation, an effort has been made to identify the critical sub-watersheds for the development of best management plan for a small watershed of Eastern India using a hydrological model, namely, AVSWAT2000. A total of 180 combinations of various management treatments including crops (rice, maize ground nut and soybean), tillage (zero, conservation, field cultivator, mould board plough and conventional practices) and fertilizer levels (existing half of recommended and recommended) have been evaluated. The investigation reveled that rice cannot be replaced by other crops such as groundnut, maize, mungbean, sorghum and soybean since comparatively these crops resulted in higher sediment yield. The tillage practices with disk plough have been found to have more impact on sediment yield and nutrient losses than conventional tillage practices for the existing level of fertilizer. Sediment yield decreased in the case of zero tillage, conservation tillage, field cultivator, moldboard plough, and conservation tillage as compare to conventional tillage. Lowest NO₃–N loss was observed in zero tillage in all the fertilizer treatments, whereas field cultivator, moldboard plough and disk plough resulted in increase of NO³–N loss. As compared to conventional tillage, the losses of soluble phosphorus were increased in moldboard plough. The losses of organic nitrogen were also increased as fertilizer dose increased. After zero tillage the conservation tillage preformed better in all the fertilizer treatments as per loss of organic nitrogen and organic phosphorus is concerned. It can be concluded that the sediment yield was found to be the highest in the case of disk plough followed by moldboard plough, field cultivator, conventional tillage, field cultivator and least in zero tillage practices. The nutrient losses were found to be in different order with tillage practices, resulted highest in disk plough tillage practices. In view of sediment yield and nutrient losses, the conservation tillage practice was found to be the best as the sediment yield is less than the average soil loss whereas nutrient loss is within the permissible limit.     

Drought in Bulgaria and atmospheric synoptic conditions over Europe

Drought in Bulgaria is analyzed from the multiple viewpoints of statistical occurrence, spatial patterns, and synoptic conditions. A new index of drought, the SD (spatial-dryness) index, characterizes drought by both intensity and spatial extent. The occurrence of the SD index is analyzed using global gridded data sets. Examination of transitional probabilities of multiple months and years with drought occurrence suggests persistence is sufficiently frequent to be important for climate-related environmental planning. Finally, it is shown that specific seasonal synoptic patterns are associated with wet and dry conditions in Bulgaria. This revised version was published online in July 2006 with corrections to the Cover Date.     

Global challenges and adaptations in management practices to preserve soil carbon pool with changing climate

Increasing CO₂ levels and its consequent effects have been prominent with climate change. Three out of ten transgressed planetary boundaries reflect our planet’s status at tipping point. Soil Organic Carbon (SOC) which helps soil supply water and nutrients to plants through roots is inherently related to various ecological systems and needs urgent attention. Although the total SOC globally is more than the total carbon in biosphere and atmosphere, the vulnerability of SOC due to anthropogenic activities is unavoidable. The environmental factors affecting sequestration of SOC, soil fertility, crop production, accelerated SOC removal with rising temperatures, green-house gases emissions and climate change are interrelated. Thus, it is impossible to understand and estimate the various scenarios of impacts on SOC pool with ever-changing ecosystems and related processes in soil environment completely. Based on currently predicted climate change scenarios, if deforestation is controlled and reestablishment is achieved, tropical forests can trap atmospheric CO₂ in the cheapest way and function as the largest sink on earth. The agricultural management practices (AMPs), which have been practiced in the last two decades and found helpful are suitable. However, some innovative adaptations such as crop modelling, selecting types of residue to change microbial communities, practices of grassland-grazing and low-C-emission AMPs are also necessary. To achieve the millennium development goals, we must accomplish food security, which relates all 17 sustainable development goals (SDGs) also relays agricultural systems, soil systems, ecosystem services, soil fertility and how best we nurture SOC pool with supportive AMPs.     

Assessment on agricultural drought vulnerability in the Yellow River basin based on a fuzzy clustering iterative model

Drought is one of the major natural disasters occurring in China and causes severe impacts on agricultural production and food security. Therefore, agricultural drought vulnerability assessment has an important significance for reducing regional agricultural drought losses and drought disaster risks. In view of agricultural drought vulnerability assessment with the characteristics of multiple factors and uncertainty, we applied the fuzzy comprehensive evaluation framework to agricultural drought vulnerability model. The agricultural drought vulnerability assessment model was constructed based on the multi-layer and multi-index fuzzy clustering iterative method, which can better reveal the drought vulnerability (including sensitivity and adaptation capacity). Furthermore, the cycle iterative algorithm was used to obtain the optimal index weight vector of a given accuracy by setting the objective function. It provides a new approach to weight determination of agricultural drought vulnerability assessment. In this study, agricultural drought vulnerability of 65 cities (as well as leagues and states) in the Yellow River basin was investigated using a fuzzy clustering iterative model and visualized by using GIS technique. The results showed clear differences and regularities among the spatial distribution of agricultural drought vulnerability of different regions. A large number of the regions in the basin consisted of those exhibiting high to very high vulnerability and were mainly distributed throughout Qinghai, Gansu, northern Shaanxi, and southern Shanxi, accounting for 46 % of the total assessment units. However, the regions exhibiting very high vulnerability were not significantly affected by droughts. Most of the regions exhibiting moderate vulnerability (21.5 % of the assessment units) were mainly concentrated among agricultural irrigation areas, where agriculture is highly sensitive to droughts, and drought occurrence in these regions will likely cause heavy losses in the future. The regions exhibiting slight to low vulnerability were relatively concentrated, accounting for 32.3 % of the assessment units, and were mainly distributed in the plains of the lower reaches of the Yellow River, where the economy was rather well developed and the agricultural production conditions were relatively stronger.     

Severity–duration–frequency curves in the mitigation of drought impact: an agricultural case study

Severity–duration–frequency (SDF) curves are very useful in the analysis of drought phenomena. Station-level information obtained from SDF curves can be interpolated to obtain severity maps for fixed return period, in order to jointly analyse the spatial variability of drought characteristics (e.g. severity, duration and frequency). This approach is limited because the severity is usually quantified through indices that use hydrological and meteorological data, depending on the type of requirements. Therefore, drought indices can only reflect hydrological conditions, but are unable to quantify economic losses associated with droughts. In other words, SDF curves do not allow effective quantification of the impact expected with a certain return period. This paper proposes the methodology drought economic risk assessment (DERA) as an approach that emphasizes the importance of the relationship between a generic drought index (which quantifies water deficit) and the economic impact of the failure to meet water demand. Using integrated SDF curves, this relationship enables drought severity and corresponding impacts to be mapped. This procedure was applied to agricultural droughts (sunflower crop) in Umbria Region (central Italy). The agricultural drought impact variable was identified by sunflower yield (Y); the economic impact variable by net benefit depletion (EL); and the drought index by Relative Severity Index (RSI), which is quantifiable by a soil–water balance model. The relationships Y = g(RSI) and EL = f(Y) were specifically determined. Using DERA, it was possible to derive curves for SDF, impact–duration–frequency, and economic losses–duration–frequency (ELDF), which were then used to map severity, impact and economic losses for the assigned return period and duration. From the ELDF curves, further information was obtained by mapping critical drought durations for the assigned return period and economic loss threshold. The case study supports the potential of the proposed approach, both in the planning and real-time management of drought effects.     

Assessment of tectonic-controlled rock fall processes threatening the ancient Appia route at the Aurunci Mountain pass (central Italy)

The Ningxia Hui Autonomous Region of China (Ningxia), one of main agriculture areas in northwest China, has been severely affected by drought. Based on observed meteorological data, outputs of 20 global climate models and drought disaster data, future climate change and relevant drought hazard in the twenty-first century were projected in Ningxia, with the scenarios of RCP2.6 and RCP4.5; the risks of people, crop, and agriculture economy to drought disasters are quantitatively assessed, with the application of physical vulnerability curve models, probability distribution functions and Monte Carlo simulation method. It is found that the climate in Ningxia is likely to have a warming and wetting tendency in the twenty-first century. The extent of drought hazard is likely to increase. The increase rate is greater under RCP4.5 than that under RCP2.6. In general, the risks of population, crop, and agriculture to drought disasters are likely to increase in Ningxia in the twenty-first century. The magnitude of increase is likely to reach the greatest in the immediate term (2016–2035), followed by the increase in the medium term (2046–2065), and the long term (2081–2100). In comparison with RCP2.6, the drought disaster risks under the scenario of RCP4.5 are likely to increase further in three periods of the twenty-first century. The findings of this work have potential to provide data support for drought disaster risk management and support risk-based decision-making.

     

Water resource impacts of climate change in southwestern Bulgaria

This study assesses the regional impact of climate change on runoff in a mountainous region of southwestern Bulgaria. A GIS-based distributed hydrologic model and two climate change scenarios – HadCM2 and CCC – were employed for years around 2025 and 2085. Results from both scenarios demonstrate the basin's sensitivity of runoff to climate change, which produce significant spatial and temporal changes in the basin's water yield with maximum runoff shift into early spring and further decreases in summer runoff. There could be no reduction in mean annual runoff, except under the Hadley scenario by 2085. Changes in the magnitude of mean monthly and peak flow are associated with early snowmelt and a reduction in snow cover in spring. Increases in spatial variability of runoff reflect the basin's complex physiographic characteristics. The increase of spatial and temporal variability in runoff points to different strategies for future water resource management. This revised version was published online in July 2006 with corrections to the Cover Date.     

Drought risk assessment using remote sensing and GIS techniques

Beginning with a discussion of drought definitions, this review paper attempts to provide a review of fundamental concepts of drought, classification of droughts, drought indices, and the role of remote sensing and geographic information systems for drought evaluation. Owing to the rise in water demand and looming climate change, recent years have witnessed much focus on global drought scenarios. As a natural hazard, drought is best characterized by multiple climatological and hydrological parameters. An understanding of the relationships between these two sets of parameters is necessary to develop measures for mitigating the impacts of droughts. Droughts are recognized as an environmental disaster and have attracted the attention of environmentalists, ecologists, hydrologists, meteorologists, geologists, and agricultural scientists. Temperatures; high winds; low relative humidity; and timing and characteristics of rains, including distribution of rainy days during crop growing seasons, intensity, and duration of rain, and onset and termination, play a significant role in the occurrence of droughts. In contrast to aridity, which is a permanent feature of climate and is restricted to low rainfall areas, a drought is a temporary aberration. Often, there is confusion between a heat wave and a drought, and the distinction is emphasized between heat wave and drought, noting that a typical time scale associated with a heat wave is on the order of a week, while a drought may persist for months or even years. The combination of a heat wave and a drought has dire socio-economic consequences. Drought risk is a product of a region’s exposure to the natural hazard and its vulnerability to extended periods of water shortage. If nations and regions are to make progress in reducing the serious consequences of drought, they must improve their understanding of the hazard and the factors that influence vulnerability. It is critical for drought-prone regions to better understand their drought climatology (i.e., the probability of drought at different levels of intensity and duration) and establish comprehensive and integrated drought information system that incorporates climate, soil, and water supply factors such as precipitation, temperature, soil moisture, snow pack, reservoir and lake levels, ground water levels, and stream flow. All drought-prone nations should develop national drought policies and preparedness plans that place emphasis on risk management rather than following the traditional approach of crisis management, where the emphasis is on reactive, emergency response measures. Crisis management decreases self-reliance and increases dependence on government and donors.     

青海省玉树旱涝态势变化规律分析

选取青海省玉树1953~2013年月降水数据,基于标准化降水指数SPI,利用频率分析、小波周期分析等方法对玉树县近61年来旱涝强度、频率分布、周期性变化等旱涝态势演变特征进行了研究。研究结果表明:(1)SPI-3、SPI-6和SPI-12三种尺度标准化降水指数对旱涝指示程度存在差别,相比大时间尺度,小时间尺度的标准化降水指数值更为分散,波动幅度更大,对干旱和洪涝的识别更为敏感。近年来,随着玉树县水土流失和沙化,当地土壤持水力程下降趋势,对干旱和洪涝较为敏感,因此玉树县可采用三种尺度标准化降水指数。(2)近61年,玉树县重旱平均发生概率为2.1%,重涝平均发生概率为1.3%。(3)未来几年,预计玉树县仍呈现偏涝趋势。(4)玉树县SPI-12以18a为主周期进行变化。