WATCH: Current Knowledge of the Terrestrial Global Water Cycle

Abstract

Water-related impacts are among the most important consequences of increasing greenhouse gas concentrations. Changes in the global water cycle will also impact the carbon and nutrient cycles and vegetation patterns. There is already some evidence of increasing severity of floods and droughts and increasing water scarcity linked to increasing greenhouse gases. So far, however, the most important impacts on water resources are the direct interventions by humans, such as dams, water extractions, and river channel modifications. The Water and Global Change (WATCH) project is a major international initiative to bring together climate and water scientists to better understand the current and future water cycle. This paper summarizes the underlying motivation for the WATCH project and the major results from a series of papers published or soon to be published in the Journal of Hydrometeorology WATCH special collection. At its core is the Water Model Intercomparison Project (WaterMIP), which brings together a wide range of global hydrological and land surface models run with consistent driving data. It is clear that we still have considerable uncertainties in the future climate drivers and in how the river systems will respond to these changes. There is a grand challenge to the hydrological and climate communities to both reduce these uncertainties and communicate them to a wider society.

Future discharge drought across climate regions around the world modelled with a synthetic hydrological modelling approach forced by three general circulation models

“…The WFD were successfully used in multiple hydrological studies (e.g. Corzo Perez et al, 2011a;Haddeland et al, 2011;Harding et al, 2011;Prudhomme et al, 2011;Gudmundsson et al, 2012;Stahl et al, 2012;Van Vliet et al, 2012;Van Huijgevoort et al, 2013;Van Loon et al, 2014). In this study the WFD were used to identify the reference hydrological situation for every selected location, with the synthetic hydrological modelling approach.…”

Water security, global change and land–atmosphere feedbacks

“…Land surface and global hydrology models provide an alternative approach to the global estimation of components of the terrestrial water cycle [27]. The WATCH Forcing Data provide a single global dataset of the climate variables required to drive hydrological models, which covers the period 1901-2001.…”

Projecting water yield and ecosystem productivity across the United States by linking an ecohydrological model to WRF dynamically downscaled climate data

“…However, one way or another, most catchments in the US have experienced some level of human influence (National Research Council, 2002). Hydrology and ecosystems can be influenced significantly by human activities on various temporal and spatial scales (Foley et al, 2005;Harding et al, 2011). Hydraulic projects such as dam constructions, reservoir management (Hu et al, 2008), groundwater withdrawals for irrigation and domestic use, and land use/cover change all affect watershed balances (Foley et al, 2005;Piao et al, 2007;Wang and Hejazi, 2011;Schilling et al, 2008) and ecosystem productivity (Zhang, Y. et al, 2014).…”

“…In response, the hydrological cycle and ecosystems have been markedly changed through various physical, chemical, and biological processes during the past century (Labat et al, 2004;Milly et al, 2005;Dai et al, 2009;Harding et al, 2011;Sedláček and Knutti, 2014). Mounting evidence has suggested that climate and its change has played an important role in controlling the water cycle by changes in evaporation, transpiration, and runoff (McCabe, 2002;Hamlet et al, 2007;Syed et al, 2010;Wang and Hejazi, 2011;Chien et al, 2013;Hegerl et al, 2014;Huntington and Billmire, 2014;McCabe and Wolock, 2014;Sun et al, 2014).…”

“…Mounting evidence has suggested that climate and its change has played an important role in controlling the water cycle by changes in evaporation, transpiration, and runoff (McCabe, 2002;Hamlet et al, 2007;Syed et al, 2010;Wang and Hejazi, 2011;Chien et al, 2013;Hegerl et al, 2014;Huntington and Billmire, 2014;McCabe and Wolock, 2014;Sun et al, 2014). Also, climate can exert a dominant control on vegetation structural and phenological characteristics through variations in air temperature, precipitation, solar radiation, wind, and CO 2 concentration (Nemani et al, 2003;Harding et al, 2011;Wang et al, 2014;Zhang, F. et al, 2014;. Climate change affects vegetation dormancy onset date, timing of bud burst, net primary production (NPP), gross primary production (GPP), and ecosystem respiration (Nemani et al, 2003;Scholze et al, 2006;Pennington and Collins, 2007;Anderson-Teixeira et al, 2011;Gang et al, 2013;Peng et al, 2013;Zhang et al, 2013;Williams et al, 2014;Piao et al, 2015;Wang et al, 2015).…”