Is water security necessary? An empirical analysis of the effects of climate hazards on national-level economic growth

Incorporating learning into direct policy search for flood risk management

Direct policy search (DPS) is a method for identifying optimal policies (i.e., rules) for managing a system in response to changing conditions. In this article, we introduce a new adaptive way to incorporate learning into DPS. The standard DPS approach identifies "robust" policies by optimizing their average performance over a large ensemble of future states of the world (SOW). Our approach exploits information gained over time, updating prior beliefs about the kind of SOW being experienced. We first run the standard DPS approach multiple times, but with varying sets of weights applied to the SOWs when calculating average performance. Adaptive "metapolicies" then further improve performance by specifying how control of the system should switch between policies identified using different weight sets, depending on our updated beliefs about the relative likelihood of being in certain SOWs. We outline the general method and illustrate it using a case study of efficient dike heightening that simultaneously minimizes protection system costs and flood damage resulting from rising sea levels and storm surge. The solutions identified by our adaptive algorithm dominate the standard DPS on these two objectives, with an average marginal damage reduction of 35.1% for policies with similar costs; improvements are largest in SOWs with relatively lower sea level rise. We also evaluate how performance varies under different ways of implementing the algorithm, such as changing the frequency with which beliefs are updated.

Flood Mitigation in the Transboundary Chenab River Basin: A Basin-Wise Approach from Flood Forecasting to Management

Rapid and reliable flood information is crucial for minimizing post-event catastrophes in the complex river basins of the world. The Chenab River basin is one of the complex river basins of the world, facing adverse hydrometeorological conditions with unpredictable hydrologic response. Resultantly, many vicinities along the river undergo destructive inundation, resulting in huge life and economic losses. In this study, Hydrologic Engineering Centre–Hydrologic Modeling System (HEC-HMS) and HEC–River Analysis System (HEC-RAS) models were used for flood forecasting and inundation modeling of the Chenab River basin. The HEC-HMS model was used for peak flow simulation of 2014 flood event using Global Precipitation Mission (GMP) Integrated Multisatellite Retrievals-Final (IMERG-F), Tropical Rainfall Measuring Mission_Real Time (TRMM_3B42RT), and Global Satellite Mapping of Precipitation_Near Real Time (GSMaP_NRT) precipitation products. The calibration and validation of the HEC-RAS model were carried out for flood events of 1992 and 2014, respectively. The comparison of observed and simulated flow at the outlet indicated that IMERG-F has good peak flow simulation results. The simulated inundation extent revealed an overall accuracy of more than 90% when compared with satellite imagery. The HEC-RAS model performed well at Manning’s n of 0.06 for the river and the floodplain. From the results, it can be concluded that remote sensing integrated with HEC-HMS and HEC-RAS models could be one of the workable solutions for flood forecasting, inundation modeling, and early warning. The concept of integrated flood management (IFM) has also been translated into practical implementation for joint Indo-Pak management for flood mitigation in the transboundary Chenab River basin.

Climate Change Projections of Dry and Wet Events in Iberia Based on the WASP-Index

The Weighted Anomaly of Standardized Precipitation Index (WASP-Index) was computed over Iberia for three monthly timescales (3-month, 6-month and 12-month) in 1961–2020, based on an observational gridded precipitation dataset (E-OBS), and between 2021 and 2070, based on bias-corrected precipitation generated by a six-member climate model ensemble from EURO-CORDEX, under two Representative Concentration Pathways (RCPs), RCP4.5 and RCP8.5. The area-mean values revealed an upward trend in the frequency of occurrence of intermediate-to-severe dry events over Iberia, which will be strengthened in the future, particularly for the 12-month WASP (12m-WASP) intermediate dry events under RCP8.5. Besides, the number of 3-month WASP (3m-WASP) intermediate-to-severe wet events is projected to increase (mostly the severest events under RCP4.5) but no evidence was found for an increase in the number of more persistent 12m-WASP wet events under both RCPs. Despite important spatial heterogeneities, an increase/decrease of the intensity, duration and frequency of occurrence of the 12m-WASP intermediate-to-severe dry/wet events was found under both scenarios, mainly in the southernmost regions of Iberia (mainly Comunidad Valenciana, Región de Murcia, Andalucía in Spain, Alentejo, and Algarve in Portugal), thus becoming more exposed to prolonged and severe droughts in the future. This finding corroborates the results of previous studies.

Worldwide Research on Socio-Hydrology: A Bibliometric Analysis

The technical and scientific analysis regarding studies of the water surface or groundwater has increasingly taken on a great social impact, which has led to the creation of the term socio-hydrology. Since decision making has a greater weight, considering the social perspective, its study has become more important in the past 20 years. This article aims to carry out a bibliometric analysis related to socio-hydrology using the Scopus database and the application of VOSviewer software for the evaluation of the intellectual structure of socio-hydrology, its conceptual evolution, and its tendencies. The methodology considers (i) search criteria of the research field, (ii) search and document selection, (iii) software and data extraction, and (iv) analysis of results and trends. The results show us the term socio-hydrology as a new scientific discipline that has traces in the Scopus database in the past two decades. However, its application stems from recognising ancestral knowledge alongside other forms of knowledge. Socio-hydrology practice requires participatory models, where the community has a great influence, and for the most part, it guarantees results for the common good. The trend of this topic is growing and open to the criteria of sustainability.

How Do Floods and Drought Impact Economic Growth and Human Development at the Sub-National Level in India?

This paper tries to shift the focus of research on the impact of natural disasters on economic growth from global and national levels to sub-national levels. Inadequate sub-national level information is a significant lacuna for planning spatially targeted climate change adaptation investments. A fixed-effect panel regression analyses of 19 states from 2001 to 2015 assess the impacts of exposure to floods and droughts on the growth of gross state domestic product (GSDP) and human development index (HDI) in India. The flood and drought exposure are estimated using satellite data. The 19 states comprise 95% of the population and contribute 93% to the national GDP. The results show that floods indeed expose a large area, but droughts have the most significant impacts at the sub-national level. The most affected GSDPs are in the non-agriculture sectors, positively by the floods and negatively by droughts. No significant influence on human development may be due to substantial investment on mitigation of flood and drought impacts and their influence on better income, health, and education conditions. Because some Indian states still have a large geographical area, profiling disasters impacts at even smaller sub-national units such as districts can lead to effective targeted mitigation and adaptation activities, reduce shocks, and accelerate income growth and human development.

The Effect of Rainfall on Economic Growth in Thailand: A Blessing for Poor Provinces

Rainfall is related to economic growth and generally has beneficial impacts on dry and poor areas that are mostly dependent on rainfed agriculture. Thailand is a service-based, upper middle-income country with a tropical climate although rainfall varies regionally. The volume of precipitation in the northern and northeastern regions is rather low while the southern region has the highest rainfall due to its narrow topography running north-south bordering the Andaman Sea to the west and the Gulf of Thailand to the east. The present study explored the effect of rainfall on the growth of the gross provincial product (GPP) by economic sector and subsector using provincial-level panel data from 1995 to 2015. The feasible generalised least squares (FGLS) estimator with fixed effect was used in the regression models. We found that the main impacts of the weather occurred through rainfall and reduced GPP growth at the national level. For the sector level, the results showed that rainfall had a significant negative impact on the agricultural and service sectors while it had a positive but not significant impact on the industrial sector. However, rainfall remains vital in poor regions although it could be detrimental to certain subsectors in those regions. The results confirmed that the positive effects of rainfall mostly affected the economies of poor provinces and suggested that average rainfall could be the key climate effect on economic growth in Thailand.

Drought evaluation using the GRACE terrestrial water storage deficit over the Yangtze River Basin, China

Droughts are some of the worst natural disasters that bring significant water shortages, economic losses, and adverse social consequences. Gravity Recovery and Climate Experiment (GRACE) satellite data are widely used to characterize and evaluate droughts. In this work, we evaluate drought situations in the Yangtze River Basin (YRB) using the GRACE Texas Center for Space Research (CSR) mascon (mass concentration) data from 2003 to 2015. Drought events are identified by water storage deficits (WSDs) derived from GRACE data, while the drought severity evaluation is based on the water storage deficit index (WSDI), standardized WSD time series, and total water storage deficit (TWSD). The WSDI is subsequently compared with the Palmer drought severity index (PDSI), standardized precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI), and standardized runoff index (SRI). The results indicate the YRB experienced increased wetness during the study period, with WSD values increasing at a rate of 5.20mm/year. Eight drought events are identified, and three major droughts occurred in 2004, 2006, and 2011, with WSDIs of -2.05, -2.38, and -1.30 and TWSDs of -620.96mm, -616.81mm, and -192.44mm, respectively. Our findings suggest that GRACE CSR mascon data can be used effectively to assess drought features in the YRB and that the WSDI facilitates robust and reliable characterization of droughts over large-scale areas.

Declining vulnerability to river floods and the global benefits of adaptation

The global impacts of river floods are substantial and rising. Effective adaptation to the increasing risks requires an in-depth understanding of the physical and socioeconomic drivers of risk. Whereas the modeling of flood hazard and exposure has improved greatly, compelling evidence on spatiotemporal patterns in vulnerability of societies around the world is still lacking. Due to this knowledge gap, the effects of vulnerability on global flood risk are not fully understood, and future projections of fatalities and losses available today are based on simplistic assumptions or do not include vulnerability. We show for the first time (to our knowledge) that trends and fluctuations in vulnerability to river floods around the world can be estimated by dynamic high-resolution modeling of flood hazard and exposure. We find that rising per-capita income coincided with a global decline in vulnerability between 1980 and 2010, which is reflected in decreasing mortality and losses as a share of the people and gross domestic product exposed to inundation. The results also demonstrate that vulnerability levels in low- and high-income countries have been converging, due to a relatively strong trend of vulnerability reduction in developing countries. Finally, we present projections of flood losses and fatalities under 100 individual scenario and model combinations, and three possible global vulnerability scenarios. The projections emphasize that materialized flood risk largely results from human behavior and that future risk increases can be largely contained using effective disaster risk reduction strategies.

Water security in one blue planet: twenty-first century policy challenges for science

Water-related risks threaten society at the local, national and global scales in our inter-connected and rapidly changing world. Most of the world's poor are deeply water insecure and face intolerable water-related risks associated with complex hydrology. Most of the world's wealthy face lower water-related risks and less complex hydrology. This inverse relationship between hydrological complexity and wealth contributes to a divided world. This must be addressed if global water security is to be achieved. Using a risk-based framework provides the potential to link the current policy-oriented discourse on water security to a new and rigorous science-based approach to the description, measurement, analysis and management of water security. To provide the basis for this science-based approach, we propose an encompassing definition rooted in risk science: water security is a tolerable level of water-related risk to society. Water security policy questions need to be framed so that science can marshal interdisciplinary data and evidence to identify solutions. We join a growing group of scientists in asserting a bold vision for science leadership, calling for a new and comprehensive understanding of the planet's water system and society's water needs.