Increased Drought Risk Research Articles

Spatial and temporal analysis of drought risk during the crop-growing season over northeast China

Northeast China as an important agricultural zone for commercial and economic crop in China suffered from increased drought risk that seriously threatened agricultural production and food security in recent decades. Based on precipitation datasets from 71 stations from 1960 to 2009 and on the reliable statistical methods of the Mann–Kendall test, Sen’s slope and the Standardized Precipitation Index, we analyzed the temporal and spatial variation of drought occurrence during the crop-growing season (from May to September) and summer (from June to August). The results showed that regional mean precipitation during the crop-growing season and summer over the last 40 years has decreased at the rate of −1.72 and −1.12 mm/year, respectively. According to timescale analysis of abrupt changes, there were two distinct time series (1965–1983 and 1996–2009) with decreasing precipitation trends at a 95 % confidence level. A comparison between the two time series of these two periods demonstrated that more frequent and more severe drought occurred during 1996–2009. Furthermore, drought risk in recent decades has become even more serious both in severity and in extent. Especially in the crop-growing season of 2001 and summer of 2007, over 25 % (2.0 × 105 km2) of study area experienced severe drought (serious and extreme droughts). Our results highlight the urgent need for the development of effective drought adaptations for cropland over northeast China.

Spatial sensitivity of grassland yields to weather variations in Austria and its implications for the future

Agricultural production fulfills economic, ecological and structural functions. Despite technological advances, agricultural production remains sensitive to climate variations. In central Europe, climate change is predicted to bring more rainfall in winter, less rainfall in summer, and increased drought risk among other effects. Grassland agriculture, which is the dominant land use in Alpine regions, may be significantly affected by these climatic changes in the future. Motivated by this issue, the susceptibility of grassland yields to weather variations in Austria is empirical evaluated as a case study. The major objective of this study is to derive spatially distributed indications for climate change exposure by assessing the impacts of weather variations on past yield. It is assumed that reduced water supply during summer constitutes a threat to grassland productivity in regions that are warmer and drier already today. On the contrary, increased spring temperatures may improve grassland productivity in cooler regions like Alpine valleys, since the earlier snow melt leads to an extension of the growth period. Regression analyses are used for evaluating the relation between yearly yields and spring temperatures or water supply in summer, respectively. Water supply is thereby expressed by aggregated precipitation sums and the Climatic Water Balance (CWB). Input data are a meteorological time series as well as yearly yields available for 25 years between 1970 and 2010 and 99 districts in Austria. Yearly yields show a significant (P < 0.05) and positive dependency on water supply in summer for the eastern Austrian lowlands. The combination of temperature in spring and CWB in summer is only significant for six districts in the east of Austria. The positive impact of higher spring temperatures could not be verified. Generally, the regression coefficients are not very high, which indicates that temperature and water supply do not fully describe grassland productivity. Projected climate change may increasingly constitute a risk to yield reliability in the east of the country. That in turn, requires consideration in agricultural development plans and a quantification of these impacts from a social-economic perspective.

A CMIP5 multimodel projection of future temperature, precipitation, and climatological drought in China

ABSTRACTIn this study, fine‐resolution multimodel climate projections over China are developed based on 35 climate models and two emissions scenarios (RCP4.5 and RCP8.5) from phase five of the Coupled Model Intercomparison Project (CMIP5) by means of Bias Correction and Spatial Disaggregation. The yearly‐averaged temperature is projected to increase by 0.8 to 1.6 °C (0.8 to 1.7 °C), 1.5 to 2.7 °C (2 to 3.7 °C), and 1.9 to 3.3 °C (3.4 to 6 °C) under RCP4.5 (RCP8.5) in three time slices (2010–2039, 2040–2069, and 2070–2099), respectively. The most warming occurs in winter and the least in summer, and the inland areas in the northwest will warm much faster than the southeast. Under the background of surface warming, the probability of extreme low temperatures in winter defined as the monthly temperature being lower than the 9th percentile of the climatological distribution will sharply reduce to 0.1–1.7% under RCP4.5 for the period 2010–2039 and even lower for the following decades. For precipitation change, a remarkable increase is found over most areas of China except the Southwest, ranging from approximately 2 to 20%. The projected precipitation changes are highly robust in northern China, but inconsistent in southern China. In spite of widespread precipitation increases, most areas of China quantified by the Palmer Drought Severity Index are projected to become drier as a consequence of increasing evaporation driven by temperature increases. Detailed examination shows that drought that is moderate or severe according to current climate standards will become the norm in the future. Not only will incidences of severe and extreme drought increase dramatically in the future, but extreme wet events will also become more probable. Furthermore, the increasing drought risk in Southwest China and the Qinghai‐Tibetan Plateau is nearly twice that for other parts of China.

MENINGKATKAN KAPASITAS MASYARAKAT DALAM MENGATASI RISIKO BENCANA KEKERINGAN

Drought risk in Indonesia , particularly in Java Island will continuously increase. Global warming, environmental degradation, increased population, and poverty will more and more increase drought risk faced by the community. It is estimated that approximately 77% of the districts and cities in Java Island have experienced one to eight months of water deficit in one year. In 2025 the number of districts and cities experience water deficit will become 78.4% with a deficit from one month to twelve months or one full year. To reduce the risk posed by drought, community’spreparedness will need to be enhanced through the provision of water to deal with drought. Several rain harvesting techniques such as construction of water reservoirs, water tanks and absorption wells, as well as conservation of ground water, may be applied in high risks areas. Such rain harvesting techniques have indeed been implemented in many areas by traditional communities. Community’s capacity may be enhanced through continuous drought risk reduction programs that are based in the grassroots level and involve all relevant stakeholders. The role ofthe community becomes very crucial because in reality the people and local organizations constitute the keys in disaster risk reduction initiatives. The present initiatives involve community’s participation that is based on the following principles: based on the problems faced and the opportunities available in the community; using feasible solutions; encouraging partnerships with external parties; employing local knowledge and skills; focusing on the original conditions; and with clearly visible outputs.

Site-specific impacts of climate change on wheat production across regions of Germany using different CO2 response functions

Impact of climate change on crop growth, groundwater recharge and nitrogen leaching in winter wheat production in Germany was assessed using the agro-ecosystem model HERMES with a downscaled (WETTREG) climate change scenario A1B from the ECHAM5 global circulation model. Three alternative algorithms describing the impact of atmospheric CO2 concentration on crop growth (a simple Farquhar-type algorithm, a combined light-use efficiency – maximum assimilation approach and a simple scaling of the maximum assimilation rate) in combination with a Penman–Monteith approach which includes a simple stomata conduction model for evapotranspiration under changing CO2 concentrations were compared within the framework of the HERMES model. The effect of differences in regional climate change, site conditions and different CO2 algorithms on winter wheat yield, groundwater recharge and nitrogen leaching was assessed in 22 regional simulation case studies across Germany. Results indicate that the effects of climate change on wheat production will vary across Germany due to different regional expressions of climate change projection. Predicted yield changes between the reference period (1961–1990) and a future period (2021–2050) range from −0.4tha−1, −0.8tha−1 and −0.6tha−1 at sites in southern Germany to +0.8tha−1, +0.6tha−1 and +0.8tha−1 at coastal regions for the three CO2 algorithms, respectively. On average across all regions, a relative yield change of +0.9%, +3.0%, and +6.0%, respectively, was predicted for Germany. In contrast, a decrease of −11.6% was predicted without the consideration of a CO2 effect. However, simulated yield changes differed even within regions as site conditions had a strong influence on crop growth. Particularly, groundwater-affected sites showed a lower vulnerability to increasing drought risk. Groundwater recharge was estimated to change correspondingly to changes in precipitation. The consideration of the CO2 effect on transpiration in the model led to a prediction of higher rates of annual deep percolation (+16mm on average across all sites), which was due to higher water-use efficiency of the crops. In contrast to groundwater recharge, simulated nitrogen leaching varied with the choice of the photosynthesis algorithm, predicting a slight reduction in most of the areas. The results underline the necessity of high-resolution data for model-based regional climate change impact assessment and development of adaptation measures.

Evaluation of risk of hydrological droughts by the trivariate Plackett copula in the East River basin (China)

East River, one of the major tributaries of Pearl River, is the major source of water supply for mega-cites within and in the vicinity of the Pearl River Delta, China. The availability and variability of water resources of the East River basin are therefore of practical importance. This study aims to investigate the probabilistic behavior of hydrological droughts in the East River basin using the trivariate Plackett copula. Daily streamflow data for the period of 1975–2009 from 3 hydrological stations in the East River basin are analyzed. Defining hydrological droughts by drought severity, duration, and minimum flow, secondary return periods are computed. Results show that the Plackett copula satisfactorily models bivariate and trivariate probability distributions of correlated drought variables. Results of risk evaluation show an increasing drought risk from the upper to the lower East River basin. This result is important for basin-scale water resources management in the East River basin.

Analysis of the periods of maximum consecutive wet days in China

[1] Using daily precipitation data from China during the period 1960–2005, the maximum number of consecutive rainy (or wet) days is investigated. Linear regression and the modified Mann-Kendall test are used to evaluate trends in the wet days. Results indicate (1) that four consecutive wet days occur more frequently; however, their (fractional) contribution to the total amount of precipitation is small. On the other hand, one wet day is prevalent in winter and its (factional) contribution is the largest. (2) In the northwest China, the number and the total precipitation of the maximum consecutive wet days are increasing annually as well as in winter, implying wetting tendency in northwest China and in winter. (3) Decreasing total precipitation is observed in the basins of the Yellow, Liaohe, and Haihe rivers. The number and the fractional precipitation contribution of the maximum consecutive wet days are also decreasing, pointing to a higher risk of droughts in these regions, and these regions are heavily populated with highly developed socioeconomy and are also the major agricultural areas. In this sense, negative impacts are evident because of increasing drought risk as a result of decreasing total precipitation. Besides, a higher risk of droughts can also be expected in southeast China in winter, but a lengthening of maximum consecutive wet days is not evident in China. Higher drought risk in southeast China may threat the water supply, for example, the water supply for Hong Kong and Macau. However, increasing fractional contribution of shorter consecutive wet days may imply intensifying precipitation in China.

Impact of an extreme dry and hot summer on water supply security in an alpine region

Climate change will induce an increasing drought risk in western and southern Europe and a resulting increase in water stress. This paper investigates the impact of both the extreme hot and dry summer of 2003 and the PRUDENCE CHRM climate change scenario summer for 2071-2100 on the monthly water balance (available water resources versus water demand) within the Kitzbueheler Region in the Austrian Alps. As a baseline period the climate normal period from 1961 to 1990 was chosen. In both summer scenarios total flow and ground water recharge decrease substantially, due to the decrease in precipitation and increase in evapotranspiration However, regional water availability is still sufficient to serve all water demand stakeholders. As a result of decreased snow cover duration, flow seasonality changes within the CHRM scenario. Especially springs are very vulnerable to these climatological conditions; average local groundwater recharge is reduced by 20% up to 70% within both scenarios. Due to the hydrogeological characteristics of the case study area and the typical small structured alpine water supply infrastructure, local deficits can occur. But also groundwater aquifers in the valleys show a decrease in water availability. These results are supported by observations made in 2003 throughout Austria and Switzerland.

“If only it would rain”: Farmers’ perceptions of rainfall and drought in semi-arid central Tanzania

Farmers in semi-arid East Africa prioritize drought as their major productivity-reducing problem, while scientists identify soil degradation as a major threat. The question that needs to be addressed is how farmers perceive drought. Insight into farmers’ perceptions of drought could be the missing link towards increased and sustainable production. During the period from 2004 to 2006, a study was conducted in Goima Ward, Tanzania. The study included questionnaires with mainly open-ended questions ( N=120), in-depth interviews, group discussions, field visits, picture assignment and 1-day seminar with farmers, extension workers, government officials, and scientists. Farmers saw drought in a broader perspective than that of deficient rainfall. Drought indicators were area-specific. Farmers recognized differences in drought vulnerability between soil types, location and state of land, land management practices and farmer types. Farmers perceived an increased drought risk. Farmers’ perceptions can be related to the scientific concept of agricultural drought. Since the amount of rainfall cannot be influenced, the efficiency of the rains can be a focal point for addressing farmers’ concerns about drought. Any viable strategy to reduce farmers’ vulnerability to drought and to improve productivity should be integrated into farmers’ existing strategies to adapt to and cope with ecological insecurity.

Application of relative drought indices in assessing climate-change impacts on drought conditions in Czechia

The common versions (referred to as self-calibrated here) of the Standardized Precipitation Index (SPI) and the Palmer Drought Severity Index (PDSI) are calibrated and then applied to the same weather series. Therefore, the distribution of the index values is about the same for any weather series. We introduce here the relative SPI and PDSI, abbreviated as rSPI and rPDSI. These are calibrated using a reference weather series as a first step, which is then applied to the tested series. The reference series may result from either a different station to allow for the inter-station comparison or from a different period to allow for climate-change impact assessments. The PDSI and 1–24 month aggregations of the SPI are used here. In the first part, the relationships between the self-calibrated and relative indices are studied. The relative drought indices are then used to assess drought conditions for 45 Czech stations under present (1961–2000) and future (2060–2099) climates. In the present climate experiment, the drought indices are calibrated by using the reference station weather series. Of all drought indices, the PDSI exhibits the widest spectrum of drought conditions across Czechia, in part because it depends not only on precipitation (as does the SPI) but also on temperature. In our climate-change impact experiments, the future climate is represented by modifying the observed series according to scenarios based on five Global Climate Models (GCMs). Changes in the SPI-based drought risk closely follow the modeled changes in precipitation, which is predicted to decrease in summer and increase in both winter and spring. Changes in the PDSI indicate an increased drought risk at all stations under all climate-change scenarios, which relates to temperature increases predicted by all of the GCMs throughout the whole year. As drought depends on both precipitation and temperature, we conclude that the PDSI is more appropriate (when compared to the SPI) for use in assessing the potential impact of climate change on future droughts.

Ancient Austrocedrus Tree-Ring Chronologies Used to Reconstruct Central Chile Precipitation Variability from a.d. 1200 to 2000

Abstract An expanded network of moisture-sensitive tree-ring chronologies has been developed for central Chile from long-lived cypress trees in the Andean Cordillera. A regional ring width chronology of cypress sites has been used to develop well-calibrated and verified estimates of June–December precipitation totals for central Chile extending from a.d. 1200 to 2000. These reconstructions are confirmed in part by historical references to drought in the seventeenth and eighteenth centuries and by nineteenth-century observations on the position of the Río Cipreses glacier. Analyses of the return intervals between droughts in the instrumental and reconstructed precipitation series indicate that the probability of drought has increased dramatically during the late nineteenth and twentieth centuries, consistent with selected long instrumental precipitation records and with the general recession of glaciers in the Andean Cordillera. This increased drought risk has occurred along with the growing demand on surface water resources and may heighten socioeconomic sensitivity to climate variability in central Chile.

Land evaluation modelling to assess the effects of climate change on winter wheat potential in England and Wales

SUMMARYThe effects of climate change on crop suitability in England and Wales were estimatedby systematically adjusting agroclimatic data inputs to a land evaluation model. Mean temperature risesof 1 and 2°C increased drought risk and reduced the length of time whe soil was at field capacity over-winter by raising potential evapotranspiration. In eastern England, this change had a detrimental effect on the potential for cultivating winter wheat because of drought stress. In northern and western England and Wales, drier conditions promoted greater opportunities for soil tillage, especially when temperature rises wereassociated with decreased precipitation. The effect of increased temperature was offset by increased precipitation. The magnitude of the drought stress and length of field capacity periods are similar to current mean conditions when a + 1 °C temperature change is coupled with a 10% increase in precipitation. This demonstrates that winter wheat suitability in England and Wales is affected more by changes in precipitation than by changes in temperature. The local limitations of soils and relief notwithstanding, it appears that the northern and western areas of England and Wales are most likely to gain from a warmer, drier climate.

The impact of climate change on the soil/moisture regime of Scottish mineral soils

The likely impact of climate change on the moisture regime of Scottish soils and consequently on agriculture and land use has been addressed using a novel Geographic Information Systems (GIS) approach. Current estimates of changes in summer precipitation by the year 2030 are 0% with an associated uncertainty of ±11%. This study considers the worst case scenario of a decrease in rainfall by 11% which will lead to some low rainfall areas experiencing an increased drought risk, particularly on lighter soils. Wet areas with heavy soils could benefit from an increase in the accessibility period for machinery. As the major agricultural land in Scotland is located on the relatively dry east coast where localised problems due to drought are not uncommon even under the present climate, the detrimental effects of a decrease in rainfall for the whole of Scotland are therefore likely to outweigh the benefits. Approximately 8% of Scotland has been identified in this study as soil/climate combinations which will be susceptible to drought should summer rainfall decrease by 11% and summer temperature increase by 1·4° C.