Elsevier

Journal of Hydrology

Volume 526, July 2015, Pages 208-220
Journal of Hydrology

Human and climate impacts on the 21st century hydrological drought

https://doi.org/10.1016/j.jhydrol.2014.10.047Get rights and content

Highlights

  • Human water abstractions and irrigation impact future hydrological drought.

  • Projections for future hydrological drought should include human influences.

  • The impact of human water use on the future low-flow regime is significant.

Summary

Climate change will very likely impact future hydrological drought characteristics across the world. Here, we quantify the impact of human water use including reservoir regulation and climate change on future low flows and associated hydrological drought characteristics on a global scale. The global hydrological and water resources model PCR-GLOBWB is used to simulate daily discharge globally at 0.5° resolution for 1971–2099. The model was forced with the latest CMIP5 climate projections taken from five General Circulation Models (GCMs) and four emission scenarios (RCPs), under the framework of the Inter-Sectoral Impact Model Intercomparison Project.

A natural or pristine scenario has been used to calculate the impact of the changing climate on hydrological drought and has been compared to a scenario with human influences. In the latter scenario reservoir operations and human water use are included in the simulations of discharge for the 21st century. The impact of humans on the low flow regime and hydrological drought characteristics has been studied at a catchment scale.

Results show a significant impact of climate change and human water use in large parts of Asia, Middle East and the Mediterranean, where the relative contribution of humans on the changed drought severity can be close to 100%. The differences between Representative Concentration Pathways are small indicating that human water use is proportional to the changes in the climate. Reservoirs tend to reduce the impact of drought by water retention in the wet season, which in turn will lead to increased water availability in the dry season, especially for large regions in Europe and North America. The impact of climate change varies throughout the season for parts of Europe and North-America, while in other regions (e.g. North-Africa, Middle East and Mediterranean), the impact is not influenced by seasonal changes.

This study illustrates that the impact of human water use and reservoirs is nontrivial and can vary substantially per region and per season. Therefore, human influences should be included in projections of future drought characteristics, considering their large impact on the changing drought conditions.

Introduction

Climate change is expected to increase drought intensity and frequency worldwide as a result of change in precipitation patterns and rising temperature (Burke et al., 2006, Lehner et al., 2006, Feyen and Dankers, 2009, Dai, 2011, Dai, 2013, Prudhomme et al., 2014, Trenberth et al., 2014). Drought is generally related to meteorological extremes and is induced by below-normal precipitation (Wilhite and Glantz, 1985, Wilhite, 2000, Mishra and Singh, 2010). Lack of precipitation causes meteorological drought and agricultural drought over the region, but further propagates into hydrological drought via the drainage network (Tallaksen et al., 1997, Sheffield and Wood, 2007, Tallaksen et al., 2009, Sheffield et al., 2012, Van Loon et al., 2014). Various studies analysed the severity, frequency and trends of hydrological droughts using large-scale hydrological models that enable the analysis of drought over continental to global scales (Hisdal et al., 2001, Fleig et al., 2006, Feyen and Dankers, 2009, Tallaksen et al., 2009, Corzo-Perez et al., 2011, Van Huijgevoort et al., Jul. 2013, Van Huijgevoort et al., 2014, Alderlieste et al., 2014). However, the anthropogenic impact on drought is generally less well known and such impact has rarely been explored. Few exceptions are recent studies by Dai, 2011, Dai, 2013, Sheffield et al., 2012 who indicated that anthropogenic global warming is likely responsible for intensifying meteorological droughts, primarily due to enhanced evaporative demand and altered monsoon circulation over regions such as Africa and Asia. Another exception by Wada et al. (2013) showed that human water consumption substantially intensifies the magnitude of hydrological droughts regionally by 10–500%, and it alone increases global drought frequency by 30%. However, no study has yet provided a comprehensive overview of human and climate impacts on future hydrological drought at the global scale. Prudhomme et al. (2014) provided future projections of hydrological drought based on a large ensemble of five Global Climate Models (GCMs) from the latest CMIP5 (Coupled Model Intercomparison Project Phase 5), four emission scenarios or Representative Concentration Pathways (RCPs) and seven Global Hydrological Models (GHMs). Yet, they considered only the effect of climate on hydrological drought using the streamflow simulated under natural or pristine conditions such that anthropogenic influence (e.g., irrigation and reservoir regulation) on resulting drought is not explicitly incorporated.

The severe impacts of large-scale droughts have historically showed the need to improve understanding of drought mechanisms so that our society can be better prepared (Trenberth et al., 1988, Gleick, 2000, Andreadis et al., 2005, Seager, 2007, Gleick, 2010, Pederson et al., 2012). Thus, providing a comprehensive overview of future drought projections considering both human and climate impacts is a vital step, ensuring future water and food security. Here, we present for the first time a full global analysis of the impact of human activities (irrigation and reservoir regulation, Wada et al., 2013) and climate change on hydrological drought. We simulated streamflow both under natural or pristine conditions and under conditions including human influences using the global hydrological and water resources model PCR-GLOBWB (Van Beek et al., 2011, Wada et al., 2011, Wada et al., 2011, Wada et al., 2014) with five GCMs from the latest CMIP5 and four emission scenarios (here represented by RCPs 2.6, 4.5, 6.0 and 8.5). We incorporate human-induced change by including human water use for irrigation and reservoir regulation parameterized by the latest extensive global reservoir data set (GRanD, Lehner et al., May 2011). Another innovative aspect of this study is that we apply a transient spatially-distributed threshold or Q90 (30-year window) identifying drought characteristics that reflects changes in the hydrological regime over time (Wanders et al., 2014), while most studies used the threshold calculated over the control or historical period (e.g., 1971–2000). A transient threshold assumes adaptation to long-term changes in the hydrological regime as the drought is defined by a deviation from normal conditions (i.e. normal implies decadally updated 30-year averages according to the WMO guidelines) (World Meteorological Organization, 2007, Arguez and Vose, 2010). Our study stands out from earlier work by presenting for the first time the human impact on future hydrological droughts using the latest multi-model climate projections and multi-emission scenarios.

Section 2 of this paper presents a brief description of the global hydrological and water resources model PCR-GLOBWB, climate forcing data, the drought identification method and the simulation protocol. In Section 3 the simulation results are presented and the human and climate impacts on future hydrological drought are evaluated globally and per river basin. Section 4 discusses the advantages and the limitations of our approach and the associated uncertainties, and provides conclusions from this study.

Section snippets

Model simulation of streamflow

The state-of-the-art global hydrological and water resources model PCR-GLOBWB was used to simulate spatial and temporal continuous fields of discharge and storage in rivers, lakes, and wetlands at a 0.5° spatial resolution (Wada et al., 2010, Van Beek et al., 2011, Wada et al., 2014). In brief, the model simulates for each grid cell and for each time step (daily) the water storage in two vertically stacked soil layers and an underlying groundwater layer. At the top a canopy with interception

Climate impact on a global scale

On a global scale the impact of climate change on the low flow regime (dVTMclimt, Eq. 6) has been evaluated and compared for the control and the future period (Fig. 2). It is shown that climate change has a negative impact on the low flow regime (decrease of 10% or more) in South-America, Australia, Southern-Africa, Southeast Asia and the Mediterranean. Positive impacts on the low flow regime are found in Northwest Africa and large parts of Northern Europe, Russia and Canada. Differences

Discussion and conclusions

In this study the impact of climate change, and human water use and reservoirs on projected hydrological drought characteristics for the 21st century has been studied. Obtained future simulation results were compared to the control period or the pristine scenario (climate change only) and the relative contribution of humans was compared to the impact of climate change. The impact of climate change on the low flow regime and hydrological drought characteristics is projected to be severe. Large

Acknowledgments

NW was funded by a grant from the user support program Space Research of NWO (contract number NWO GO-AO/30). This work has been supported by the framework of ISI-MIP funded by the German Federal Ministry of Education and Research (BMBF) (Project funding reference number: 01LS1201A). We thank anonymous reviewers and guest Editor (Ashok Mishra) for their constructive suggestions, which helped to improve the manuscript.

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