scholarly journals A review of drought indices: predominance of drivers over impacts and the importance of local context

2021 ◽  
Author(s):  
Sarra Kchouk ◽  
Lieke A. Melsen ◽  
David W. Walker ◽  
Pieter R. van Oel
Keyword(s):  
Scientific Literature ◽  
Geographic Area ◽  
Early Warning Systems ◽  
Sub Saharan Africa ◽  
Local Context ◽  
Drought Indices ◽  
Drought Event ◽  
Human Welfare ◽  
Drought Impact ◽  
Drought Impacts

Abstract. Drought monitoring and Early Warning Systems (DEWS) are seen as helpful tools to tackle drought at an early stage and reduce the possibility of harm or loss. They usually include indices attributed to meteorological, agricultural and/or hydrological drought: physically based drought drivers. These indices are used to determine the onset, end and severity of a drought event. Drought impacts are less monitored or even not included in DEWS. Therefore, the likelihood of experiencing drought impacts is often simply linearly linked to drivers of drought. The aim of this study is to evaluate the validity of the assumed direct linkage between drivers of drought and drought impact. We reviewed scientific literature on both drivers and impacts of drought. We conducted a bibliometric analysis based on 5000+ scientific studies in which selected drought indices (drivers) and drought impacts were mentioned in relation to a geographic area. Our review shows that there is a tendency in scientific literature to focus on drivers of drought, with the preferred use of meteorological and remotely sensed drought indices. Studies reporting drought impacts are more localised, with relatively many studies focusing on Sub-Saharan Africa and Australasia for impacts with regard to food security and water security, respectively. Our review further suggests that drought-impacts studies are dependent on both the physical and human processes occurring in the geographic area, i.e. the local context. With the aim of increasing the relevance and utility of the information provided by DEWS, we argue in favour of additional consideration of drought impact indices oriented towards sustainable development and human welfare.

Selecting indicators of drought impacts: the importance of context

2021 ◽  
Author(s):  
Sarra Kchouk ◽  
Pieter van Oel ◽  
Lieke Melsen
Keyword(s):  
Early Stage ◽  
Contextual Information ◽  
Geographic Area ◽  
Early Warning Systems ◽  
Sub Saharan Africa ◽  
Drought Impacts ◽  
Direct Linkage ◽  
Drought Indicators ◽  
Sub Saharan ◽  
Drought Early Warning

<p>Drought Early Warning Systems (DEWS) and Drought Monitoring Systems (DMS) are the principal tools used to tackle drought at an early stage and reduce the possibility of harm or loss. They are based on the use of drought indicators attributed to either : meteorological, agricultural and hydrological drought. This means that it is mostly hydro-climatic variables that are used to determine the onset, end and severity of a drought.  Drought impacts are rarely continuously monitored or even not included in DEWS and DMS. In this configuration, the likelihood of experiencing impacts is linearly linked to the severity of climatic features only. The aim of our study is to question the direct linkage between the delivery of hydro-climatic information and the detection of drought impacts and their severity. We reviewed scientific literature on drought drivers and impacts and analyzed how these two compare. We conducted a bibliometric analysis based on 4000+ scientific studies sorted by geographic area in which selected (i) drought indicators and (ii) impacts of drought were mentioned. Our review points toward an attachment to a conceptual view of drought by the main and broader use of meteorological (computed and remotely sensed) drought indicators. Studies reporting impacts related to food and water securities are more localized, respectively in Sub-Saharan Africa and Australasia. This mismatch suggests a tendency to translate hydroclimatic indicators of drought directly into impacts while neglecting relevant local contextual information. With the aim of sharpening the information provided by DEWS and DMS, we argue in favor of an additional consideration of drought indicators oriented towards the SDGs.</p>

scholarly journals Exploring the link between drought indicators and impacts

2015 ◽  
Vol 15 (6) ◽  
pp. 1381-1397 ◽  
Author(s):  
S. Bachmair ◽  
I. Kohn ◽  
K. Stahl
Keyword(s):  
Standardized Precipitation Index ◽  
Early Warning Systems ◽  
Drought Indices ◽  
Indicator Values ◽  
Drought Impact ◽  
Federal States ◽  
Drought Impacts ◽  
Drought Conditions ◽  
Drought Indicators ◽  
Impact Data

Abstract. Current drought monitoring and early warning systems use different indicators for monitoring drought conditions and apply different indicator thresholds and rules for assigning drought intensity classes or issue warnings or alerts. Nevertheless, there is little knowledge on the meaning of different hydro-meteorologic indicators for impact occurrence on the ground. To date, there have been very few attempts to systematically characterize the indicator–impact relationship owing to sparse and patchy data on drought impacts. The newly established European Drought Impact report Inventory (EDII) offers the possibility to investigate this linkage. The aim of this study was to explore the link between hydro-meteorologic indicators and drought impacts for the case study area Germany and thus to test the potential of qualitative impact data for evaluating the performance of drought indicators. As drought indicators two climatological drought indices – the Standardized Precipitation Index (SPI) and the Standardized Precipitation Evapotranspiration Index (SPEI) – as well as streamflow and groundwater level percentiles were selected. Linkage was assessed though data visualization, extraction of indicator values concurrent with impact onset, and correlation analysis between monthly time series of indicator and impact data at the federal state level, and between spatial patterns for selected drought events. The analysis clearly revealed a significant moderate to strong correlation for some states and drought events allowing for an intercomparison of the performance of different drought indicators. Important findings were strongest correlation for intermediate accumulation periods of SPI and SPEI, a slightly better performance of SPEI versus SPI, and a similar performance of streamflow percentiles to SPI in many cases. Apart from these commonalities, the analysis also exposed differences among federal states and drought events, suggesting that the linkage is time variant and region specific to some degree. Concerning "thresholds" for drought impact onset, i.e. indicator values concurrent with past impact onsets, we found that no single "best" threshold value can be identified but impacts occur within a range of indicator values. Nevertheless, the median of the threshold distributions showed differences between northern/northeastern versus southern/southwestern federal states, and among drought events. While the findings strongly depend on data and may change with a growing number of EDII entries in the future, this study clearly demonstrates the feasibility of evaluating hydro-meteorologic variables with text-based impact reports and highlights the value of impact reporting as a tool for monitoring drought conditions.

scholarly journals Moving from drought hazard to impact forecasts

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Samuel J. Sutanto ◽  
Melati van der Weert ◽  
Niko Wanders ◽  
Veit Blauhut ◽  
Henny A. J. Van Lanen
Keyword(s):  
River Flow ◽  
Meteorological Drought ◽  
Early Warning Systems ◽  
Drought Indices ◽  
Warning Systems ◽  
Drought Management ◽  
Drought Impact ◽  
Drought Impacts ◽  
Drought Hazard ◽  
Drought Early Warning

Abstract Present-day drought early warning systems provide the end-users information on the ongoing and forecasted drought hazard (e.g. river flow deficit). However, information on the forecasted drought impacts, which is a prerequisite for drought management, is still missing. Here we present the first study assessing the feasibility of forecasting drought impacts, using machine-learning to relate forecasted hydro-meteorological drought indices to reported drought impacts. Results show that models, which were built with more than 50 months of reported drought impacts, are able to forecast drought impacts a few months ahead. This study highlights the importance of drought impact databases for developing drought impact functions. Our findings recommend that institutions that provide operational drought early warnings should not only forecast drought hazard, but also impacts after developing an impact database.

scholarly journals Exploring the link between drought indicators and impacts

2014 ◽  
Vol 2 (12) ◽  
pp. 7583-7620 ◽  
Author(s):  
S. Bachmair ◽  
I. Kohn ◽  
K. Stahl
Keyword(s):  
State Level ◽  
Early Warning Systems ◽  
Drought Indices ◽  
Federal State ◽  
Drought Impact ◽  
Federal States ◽  
Drought Conditions ◽  
Drought Indicators ◽  
Ground Truthing ◽  
Impact Data

Abstract. Current drought monitoring and early warning systems use different indicators for monitoring drought conditions and apply different indicator thresholds and rules for assigning drought intensity classes or issue warnings or alerts. Nevertheless, there is little knowledge on the meaning of different hydro-meteorologic indicators for impact occurrence on the ground. To date, there have been very few attempts to systematically characterize the indicator–impact-relationship owing to the sparse and patchy data for ground truthing hydro-meteorologic variables. The newly established European Drought Impact report Inventory (EDII) offers the possibility to investigate this linkage. The aim of this study was to explore the link between hydro-meteorologic indicators and drought impacts for the case study area Germany and thus to test the potential of qualitative impact data for evaluating the performance of drought indicators. As drought indicators two climatological drought indices as well as streamflow and groundwater level percentiles were selected. Linkage was assessed though data visualization and correlation analysis between monthly timeseries of indicator–impact data at the federal state level, and between spatial patterns for selected drought events. The analysis clearly revealed a significant moderate to strong correlation for some states and drought events allowing for an intercomparison of the performance of different drought indicators. While several commonalities could be identified regarding "best" indicator, indicator metric, and time-scale of climatic anomaly, the analysis also exposed differences among federal states and drought events, suggesting that the linkage is time-variant and region specific to some degree. Concerning thresholds associated with drought impact onset, we found that no single "best" threshold value can be identified but impacts occur within a range of indicator values. While the findings strongly depend on data and may change with a growing number of EDII entries in the future, this study clearly demonstrates the feasibility of ground truthing hydro-meteorologic variables with text-based impact reports and highlights the value of impact reporting as a tool for monitoring drought conditions.

scholarly journals Impacts of European drought events: insights from an international database of text-based reports

2015 ◽  
Vol 3 (9) ◽  
pp. 5453-5492 ◽  
Author(s):  
K. Stahl ◽  
I. Kohn ◽  
V. Blauhut ◽  
J. Urquijo ◽  
L. De Stefano ◽  
...  
Keyword(s):  
Water Supply ◽  
Drought Indices ◽  
Public Water Supply ◽  
Research Database ◽  
Impact Categories ◽  
Drought Impact ◽  
Drought Impacts ◽  
Wide Range ◽  
Promising Source ◽  
Over Time

Abstract. Drought is a natural hazard that can cause a wide range of impacts affecting the environment, society, and the economy. Assessing and reducing vulnerability to these impacts for regions beyond the local scale, spanning political and sectoral boundaries, requires systematic and detailed data regarding impacts. This study presents an assessment of the diversity of drought impacts across Europe based on the European Drought Impact report Inventory (EDII), a unique research database that has collected close to 5000 impact reports from 33 European countries. The reported drought impacts were classified into major impact categories, each of which had a number of subtypes. The distribution of these categories and types was then analyzed over time, by country, across Europe and for particular drought events. The results show that impacts on agriculture and public water supply dominate the collection of drought impact reports for most countries and for all major drought events since the 1970s, while the number and relative fractions of reported impacts in other sectors can vary regionally and from event to event. The data also shows that reported impacts have increased over time as more media and website information has become available and environmental awareness has increased. Even though the distribution of impact categories is relatively consistent across Europe, the details of the reports show some differences. They confirm severe impacts in southern regions (particularly on agriculture and public water supply) and sector-specific impacts in central and northern regions (e.g. on forestry or energy production). As a text-based database, the EDII presents a new challenge for quantitative analysis; however, the EDII provides a new and more comprehensive view on drought impacts. Related studies have already developed statistical techniques to evaluate the link between drought indices and impacts using the EDII. The EDII is a living database and is a promising source for further research on drought impacts, vulnerabilities, and risks across Europe. A key result is the extensive variety of impacts found across Europe and its documentation. This data coverage may help drought policy planning at national to international levels.

scholarly journals Skill of large-scale seasonal drought impact forecasts

2020 ◽  
Vol 20 (6) ◽  
pp. 1595-1608
Author(s):  
Samuel J. Sutanto ◽  
Melati van der Weert ◽  
Veit Blauhut ◽  
Henny A. J. Van Lanen
Keyword(s):  
Machine Learning ◽  
Logistic Regression ◽  
Large Scale ◽  
Standardized Precipitation Index ◽  
Early Warning Systems ◽  
Learning Approaches ◽  
Discriminative Ability ◽  
Drought Impact ◽  
Drought Impacts ◽  
Impact Data

Abstract. Forecasting of drought impacts is still lacking in drought early-warning systems (DEWSs), which presently do not go beyond hazard forecasting. Therefore, we developed drought impact functions using machine learning approaches (logistic regression and random forest) to predict drought impacts with lead times up to 7 months ahead. The observed and forecasted hydrometeorological drought hazards – such as the standardized precipitation index (SPI), standardized precipitation evaporation index (SPEI), and standardized runoff index (SRI) – were obtained from the The EU-funded Enhancing Emergency Management and Response to Extreme Weather and Climate Events (ANYWHERE) DEWS. Reported drought impact data, taken from the European Drought Impact Report Inventory (EDII), were used to develop and validate drought impact functions. The skill of the drought impact functions in forecasting drought impacts was evaluated using the Brier skill score and relative operating characteristic metrics for five cases representing different spatial aggregation and lumping of impacted sectors. Results show that hydrological drought hazard represented by SRI has higher skill than meteorological drought represented by SPI and SPEI. For German regions, impact functions developed using random forests indicate a higher discriminative ability to forecast drought impacts than logistic regression. Moreover, skill is higher for cases with higher spatial resolution and less lumped impacted sectors (cases 4 and 5), with considerable skill up to 3–4 months ahead. The forecasting skill of drought impacts using machine learning greatly depends on the availability of impact data. This study demonstrates that the drought impact functions could not be developed for certain regions and impacted sectors, owing to the lack of reported impacts.

scholarly journals Linking drought indices to impacts to support drought risk assessment in Liaoning province, China

2019 ◽  
Author(s):  
Yaxu Wang ◽  
Juan Lv ◽  
Jamie Hannaford ◽  
Yicheng Wang ◽  
Hongquan Sun ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Random Forest ◽  
Liaoning Province ◽  
Drought Monitoring ◽  
Drought Indices ◽  
Drought Risk ◽  
Drought Vulnerability ◽  
Random Forest Analysis ◽  
Drought Impact ◽  
Drought Impacts

Abstract. Drought is a ubiquitous and reoccurring hazard that has wide ranging impacts on society, agriculture and the environment. Drought indices are vital for characterizing the nature and severity of drought hazards, and there have been extensive efforts to identify the most suitable drought indices for drought monitoring and risk assessments. However, to date, little effort has been made to explore which index(s) best represents drought impacts for various sectors in China. This is a critical knowledge gap, as impacts provide important ‘ground truth’ information. They can be used to demonstrate whether drought indices (used for monitoring or risk assessment) are relevant for identifying impacts, thus highlighting if an area is vulnerable to drought of a given severity. The aim of this study is to explore the link between drought indices and drought impacts, using Liaoning province (northeast China) as a case study due to its history of drought occurrence. To achieve this we use independent, but complementary, methods (correlation and random forest analysis). Using multiple drought indices – Standardized Precipitation Index (SPI), Standardized Precipitation Evapotranspiration Index (SPEI), Soil Moisture (SoilM) and the Normalized Difference Vegetation Index (NDVI) – and drought impact data (on crop yield, livestock, rural people and the economy) correlation and random forest analysis were used to identify which indices link best to the recorded drought impacts for cities in Liaoning. The results show that the relationship varies between different categories of drought impacts and between cities. SPEI with a 6-month accumulation (SPEI6) had a strong correlation with all categories of drought impacts, while SPI12 had a weak correlation with drought impacts. Of the impact datasets, drought suffering area and drought impact area had a slightly strong relationship with all drought indices in Liaoning province, while population and number of livestock with difficulty in accessing drinking water had weak correlations with the indices. Based on the linkage, drought vulnerability was analyzed using various vulnerability factors. Crop cultivated area was positively correlated to the drought vulnerability for five out of the eight categories of drought impacts, while the total population had a strong negative relationship with drought vulnerability for half the drought impact categories. This study can support drought planning efforts in the region, and provides a methodology for application for other regions of China (and other countries) in the future, as well as providing context for the indices used in drought monitoring applications, so enabling improved preparedness for drought impacts.

scholarly journals Linking drought indices to impacts to support drought risk assessment in Liaoning province, China

2020 ◽  
Vol 20 (3) ◽  
pp. 889-906
Author(s):  
Yaxu Wang ◽  
Juan Lv ◽  
Jamie Hannaford ◽  
Yicheng Wang ◽  
Hongquan Sun ◽  
...  
Keyword(s):  
Risk Assessment ◽  
Strong Relationship ◽  
Liaoning Province ◽  
Drought Monitoring ◽  
Drought Indices ◽  
Drought Risk ◽  
Drought Impact ◽  
Drought Impacts ◽  
Standardised Precipitation Index ◽  
The Impact

Abstract. Drought is a ubiquitous and recurring hazard that has wide-ranging impacts on society, agriculture and the environment. Drought indices are vital for characterising the nature and severity of drought hazards, and there have been extensive efforts to identify the most suitable drought indices for drought monitoring and risk assessment. However, to date, little effort has been made to explore which index (or indices) best represents drought impacts for various sectors in China. This is a critical knowledge gap, as impacts provide important ground truth information for indices used in monitoring activities. The aim of this study is to explore the link between drought indices and drought impacts, using Liaoning province (northeast China) as a case study due to its history of drought occurrence. To achieve this we use independent, but complementary, methods (correlation and random forest analysis) to identify which indices link best to drought impacts for prefectural-level cities in Liaoning province, using a comprehensive database of reported drought impacts in which impacts are classified into a range of categories. The results show that the standardised precipitation evapotranspiration index with a 6-month accumulation (SPEI6) had a strong correlation with all categories of drought impacts, while the standardised precipitation index with a 12-month accumulation (SPI12) had a weak correlation with drought impacts. Of the impact datasets, “drought-suffering area” and “drought impact area” had a strong relationship with all drought indices in Liaoning province, while “population and number of livestock with difficulty in accessing drinking water” had weak correlations with the indices. The results of this study can support drought planning efforts in the region and provide context for the indices used in drought-monitoring applications, so enabling improved preparedness for drought impacts. The study also demonstrates the potential benefits of routine collection of drought impact information on a local scale.

scholarly journals Contributions to uncertainty in projections of future drought under climate change scenarios

2012 ◽  
Vol 9 (11) ◽  
pp. 12613-12653 ◽  
Author(s):  
I. H. Taylor ◽  
E. Burke ◽  
L. McColl ◽  
P. Falloon ◽  
G. R. Harris ◽  
...  
Keyword(s):  
Drought Index ◽  
Drought Indices ◽  
Climate Projections ◽  
Drought Event ◽  
Climate Change Scenarios ◽  
Future Projections ◽  
Sources Of Uncertainty ◽  
Drought Impacts ◽  
Standardised Precipitation Index ◽  
Future Emissions

Abstract. Drought is a cumulative event, often difficult to define and involving wide reaching consequences for agriculture, ecosystems, water availability, and society. Understanding how the occurrence of drought may change in the future and which sources of uncertainty are dominant can inform appropriate decisions to guide drought impacts assessments. Uncertainties in future projections of drought arise from several sources and our aim is to understand how these sources of uncertainty contribute to future projections of drought. We consider four sources of uncertainty; climate model uncertainty associated with future climate projections, future emissions of greenhouse gases (future scenario uncertainty), type of drought (drought index uncertainty) and drought event definition (threshold uncertainty). Three drought indices (the Standardised Precipitation Index (SPI), Soil Moisture Anomaly (SMA) and Palmer Drought Severity Index (PDSI)) are calculated for the A1B and RCP2.6 future emissions scenarios using monthly model output from a 57 member perturbed parameter ensemble of climate simulations of the HadCM3C Earth system model, for the baseline period, 1961–1990, and the period 2070–2099 (representing the 2080s). We consider where there are significant increases or decreases in the proportion of time spent in drought in the 2080s compared to the baseline and compare the effects from the four sources of uncertainty. Our results suggest that, of the included uncertainty sources, choice of drought index is the most important factor influencing uncertainty in future projections of drought (60%–85% of total included uncertainty). There is a greater range of uncertainty between drought indices than that between the mitigation scenario RCP2.6 and the A1B emissions scenario (5%–6% in the 2050s to 17%–18% in the 2080s) and across the different model variants in the ensemble (9%–17%). Choice of drought threshold has the least influence on uncertainty in future drought projections (0.4%–7%). Despite the large range of uncertainty in drought projections for many regions, projections for some regions have a clear signal, with uncertainty associated with the magnitude of change rather than direction. For instance, a significant increase in time spent in drought is consistently projected for the Amazon, Central America and South Africa whilst projections for Northern India consistently show significant decreases in time spent in drought. We conclude that choice of which drought index (or drought indices) to use when undertaking drought impacts assessments is of considerable importance relative to choices relating to the other three included sources of uncertainty in this study. This information will help ensure that future drought impacts assessments are designed appropriately to account for uncertainty.

scholarly journals Impacts of European drought events: insights from an international database of text-based reports

2016 ◽  
Vol 16 (3) ◽  
pp. 801-819 ◽  
Author(s):  
Kerstin Stahl ◽  
Irene Kohn ◽  
Veit Blauhut ◽  
Julia Urquijo ◽  
Lucia De Stefano ◽  
...  
Keyword(s):  
Water Supply ◽  
Drought Indices ◽  
Public Water Supply ◽  
Research Database ◽  
Impact Categories ◽  
Drought Impact ◽  
Drought Impacts ◽  
Wide Range ◽  
Promising Source ◽  
Over Time

Abstract. Drought is a natural hazard that can cause a wide range of impacts affecting the environment, society, and the economy. Providing an impact assessment and reducing vulnerability to these impacts for regions beyond the local scale, spanning political and sectoral boundaries, requires systematic and detailed data regarding impacts. This study presents an assessment of the diversity of drought impacts across Europe based on the European Drought Impact report Inventory (EDII), a unique research database that has collected close to 5000 impact reports from 33 European countries. The reported drought impacts were classified into major impact categories, each of which had a number of subtypes. The distribution of these categories and types was then analyzed over time, by country, across Europe and for particular drought events. The results show that impacts on agriculture and public water supply dominate the collection of drought impact reports for most countries and for all major drought events since the 1970s, while the number and relative fractions of reported impacts in other sectors can vary regionally and from event to event. The analysis also shows that reported impacts have increased over time as more media and website information has become available and environmental awareness has increased. Even though the distribution of impact categories is relatively consistent across Europe, the details of the reports show some differences. They confirm severe impacts in southern regions (particularly on agriculture and public water supply) and sector-specific impacts in central and northern regions (e.g., on forestry or energy production). The protocol developed thus enabled a new and more comprehensive view on drought impacts across Europe. Related studies have already developed statistical techniques to evaluate the link between drought indices and the categorized impacts using EDII data. The EDII is a living database and is a promising source for further research on drought impacts, vulnerabilities, and risks across Europe. A key result is the extensive variety of impacts found across Europe and its documentation. This insight can therefore inform drought policy planning at national to international levels.

Sign in / Sign up

Export Citation Format

Share Document