Uncertainty of simulated groundwater recharge at different global warming levels: a global-scale multi-model ensemble study

Abstract

Abstract. Billions of people rely on groundwater as being an accessible source of drinking water and for irrigation, especially in times of drought. Its importance will likely increase with a changing climate. It is still unclear, however, how climate change will impact groundwater systems globally and, thus, the availability of this vital resource. Groundwater recharge is an important indicator for groundwater availability, but it is a water flux that is difficult to estimate as uncertainties in the water balance accumulate, leading to possibly large errors in particular in dry regions. This study investigates uncertainties in groundwater recharge projections using a multi-model ensemble of eight global hydrological models (GHMs) that are driven by the bias-adjusted output of four global circulation models (GCMs). Pre-industrial and current groundwater recharge values are compared with recharge for different global warming (GW) levels as a result of three representative concentration pathways (RCPs). Results suggest that projected changes strongly vary among the different GHM–GCM combinations, and statistically significant changes are only computed for a few regions of the world. Statistically significant GWR increases are projected for northern Europe and some parts of the Arctic, East Africa, and India. Statistically significant decreases are simulated in southern Chile, parts of Brazil, central USA, the Mediterranean, and southeastern China. In some regions, reversals of groundwater recharge trends can be observed with global warming. Because most GHMs do not simulate the impact of changing atmospheric CO2 and climate on vegetation and, thus, evapotranspiration, we investigate how estimated changes in GWR are affected by the inclusion of these processes. In some regions, inclusion leads to differences in groundwater recharge changes of up to 100 mm per year. Most GHMs with active vegetation simulate less severe decreases in groundwater recharge than GHMs without active vegetation and, in some regions, even increases instead of decreases are simulated. However, in regions where GCMs predict decreases in precipitation and where groundwater availability is the most important, model agreement among GHMs with active vegetation is the lowest. Overall, large uncertainties in the model outcomes suggest that additional research on simulating groundwater processes in GHMs is necessary.

Understanding each other's models: an introduction and a standard representation of 16 global water models to support intercomparison, improvement, and communication

“…Therefore, in this section, we present some similarities and differences among 16 GWMs in simulating the terrestrial water cycle. This information enables us to interpret the different model results found in some model comparison and ensemble studies (Zaherpour et al, 2018;Wartenburger et al, 2018;Scanlon et al, 2019), as well as those by Gudmundsson et al ( 2021), Reinecke et al (2021), and. This information also strengthens our understanding of how these models work.…”

“…However, recent evaluation studies show that there is a need to better simulate this system by including other hydrological processes, data on physical infrastructure, societal behaviour, cultural behaviour, water diversions, and virtual water, as well as by identifying its teleconnections on the global scale (Zaherpour et al, 2018;Veldkamp et al, 2018;Wada et al, 2017). Some studies also underline the need to better explain various model results and better understand how models work (Reinecke et al, 2021;.…”

Amplified Drought and Flood Risk Under Future Socioeconomic and Climatic Change

“…It implies that the use of a single combination may lead to misleading results, calling for the use of multiple GHMs and GCMs for future flood analyses. The importance of using multiple GHMs and GCMs for analyzing and projecting extreme events is evident from our uncertainty analysis and has been emphasized in earlier studies (Giuntoli et al., 2015; Gudmundsson et al., 2021; Hattermann et al., 2018; Hosseinzadehtalaei et al., 2020; Reinecke et al., 2021; Tabari et al., 2019). High dependence of projected precipitation changes on the used GCMs has also been found (Osuch et al., 2016; Xu et al., 2019), casting doubt on the credibility of the studies based on few and/or unrepresentative models (Wu et al., 2020).…”

Competency of groundwater recharge of irrigated cotton field subjacent to sowing methods, plastic mulch, water productivity, and yield under climate change

“…In general, for each 1 °C increase in average temperature and 1% increase in precipitation, there is a corresponding decrease of 1.64% and an increase of 0.05% in cotton yield (Li et al 2021). In Pakistan, the cotton yield fell from 699 to 534 kg.ha −1 under climate change, elevating cotton irrigation requirement from 960.1 to 1048.9 mm (Arshad et al 2019;Abbas 2020;Rehman 2021). In this scenario, reduction in groundwater recharge by 36.53% for irrigated cotton fields indicates that the area is vulnerable to the detrimental impact of climate change.…”