An Evaluation of the Average Annual Global Water Balance

David R. Legates; John R. Mather

doi:10.2307/215350

Temporal and spatial variability of the global water balance

Climatic Change ◽

10.1007/s10584-013-0798-0 ◽

2013 ◽

Vol 120 (1-2) ◽

pp. 375-387 ◽

Cited By ~ 14

Author(s):

Gregory J. McCabe ◽

David M. Wolock

Keyword(s):

Water Balance ◽

Spatial Variability ◽

Temporal And Spatial Variability ◽

Temporal And Spatial ◽

Global Water

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GlobWat – a global water balance model to assess water use in irrigated agriculture

Hydrology and Earth System Sciences ◽

10.5194/hess-19-3829-2015 ◽

2015 ◽

Vol 19 (9) ◽

pp. 3829-3844 ◽

Cited By ~ 19

Author(s):

J. Hoogeveen ◽

J.-M. Faurès ◽

L. Peiser ◽

J. Burke ◽

N. van de Giesen

Keyword(s):

Water Balance ◽

Water Use ◽

Open Water ◽

Water Balance Model ◽

Green Water ◽

Balance Model ◽

Irrigated Agriculture ◽

High Resolution Data ◽

Food And Agriculture ◽

Global Water

Abstract. GlobWat is a freely distributed, global soil water balance model that is used by the Food and Agriculture Organization (FAO) to assess water use in irrigated agriculture, the main factor behind scarcity of freshwater in an increasing number of regions. The model is based on spatially distributed high-resolution data sets that are consistent at global level and calibrated against values for internal renewable water resources, as published in AQUASTAT, the FAO's global information system on water and agriculture. Validation of the model is done against mean annual river basin outflows. The water balance is calculated in two steps: first a "vertical" water balance is calculated that includes evaporation from in situ rainfall ("green" water) and incremental evaporation from irrigated crops. In a second stage, a "horizontal" water balance is calculated to determine discharges from river (sub-)basins, taking into account incremental evaporation from irrigation, open water and wetlands ("blue" water). The paper describes the methodology, input and output data, calibration and validation of the model. The model results are finally compared with other global water balance models to assess levels of accuracy and validity.

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Variations of global and continental water balance components as impacted by climate forcing uncertainty and human water use

Hydrology and Earth System Sciences ◽

10.5194/hess-20-2877-2016 ◽

2016 ◽

Vol 20 (7) ◽

pp. 2877-2898 ◽

Cited By ~ 73

Author(s):

Hannes Müller Schmied ◽

Linda Adam ◽

Stephanie Eisner ◽

Gabriel Fink ◽

Martina Flörke ◽

...

Keyword(s):

Water Resources ◽

Water Balance ◽

Water Use ◽

Climate Forcing ◽

Land Area ◽

Water Balance Components ◽

Climate Forcings ◽

The Impact ◽

Global Water

Abstract. When assessing global water resources with hydrological models, it is essential to know about methodological uncertainties. The values of simulated water balance components may vary due to different spatial and temporal aggregations, reference periods, and applied climate forcings, as well as due to the consideration of human water use, or the lack thereof. We analyzed these variations over the period 1901–2010 by forcing the global hydrological model WaterGAP 2.2 (ISIMIP2a) with five state-of-the-art climate data sets, including a homogenized version of the concatenated WFD/WFDEI data set. Absolute values and temporal variations of global water balance components are strongly affected by the uncertainty in the climate forcing, and no temporal trends of the global water balance components are detected for the four homogeneous climate forcings considered (except for human water abstractions). The calibration of WaterGAP against observed long-term average river discharge Q significantly reduces the impact of climate forcing uncertainty on estimated Q and renewable water resources. For the homogeneous forcings, Q of the calibrated and non-calibrated regions of the globe varies by 1.6 and 18.5 %, respectively, for 1971–2000. On the continental scale, most differences for long-term average precipitation P and Q estimates occur in Africa and, due to snow undercatch of rain gauges, also in the data-rich continents Europe and North America. Variations of Q at the grid-cell scale are large, except in a few grid cells upstream and downstream of calibration stations, with an average variation of 37 and 74 % among the four homogeneous forcings in calibrated and non-calibrated regions, respectively. Considering only the forcings GSWP3 and WFDEI_hom, i.e., excluding the forcing without undercatch correction (PGFv2.1) and the one with a much lower shortwave downward radiation SWD than the others (WFD), Q variations are reduced to 16 and 31 % in calibrated and non-calibrated regions, respectively. These simulation results support the need for extended Q measurements and data sharing for better constraining global water balance assessments. Over the 20th century, the human footprint on natural water resources has become larger. For 11–18% of the global land area, the change of Q between 1941–1970 and 1971–2000 was driven more strongly by change of human water use including dam construction than by change in precipitation, while this was true for only 9–13 % of the land area from 1911–1940 to 1941–1970.

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GlobWat – a global water balance model to assess water use in irrigated agriculture

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-12-801-2015 ◽

2015 ◽

Vol 12 (1) ◽

pp. 801-838 ◽

Cited By ~ 7

Author(s):

J. Hoogeveen ◽

J.-M. Faurès ◽

L. Peiser ◽

J. Burke ◽

N. van de Giesen

Keyword(s):

Water Balance ◽

Water Use ◽

Open Water ◽

Water Balance Model ◽

Green Water ◽

Balance Model ◽

Irrigated Agriculture ◽

Global Soil ◽

Spatially Distributed ◽

Global Water

Abstract. GlobWat is a freely distributed, global soil water balance model that is used by FAO to assess water use in irrigated agriculture; the main factor behind scarcity of freshwater in an increasing number of regions. The model is based on spatially distributed high resolution datasets that are consistent at global level and calibrated against values for Internal Renewable Water Resources, as published in AQUASTAT, FAO's global information system on water and agriculture. Validation of the model is done against mean annual river basin outflows. The water balance is calculated in two steps: first a "vertical" water balance is calculated that includes evaporation from in situ rainfall ("green" water) and incremental evaporation from irrigated crops. In a second stage, a "horizontal" water balance is calculated to determine discharges from river (sub-)basins, taking into account incremental evaporation from irrigation, open water and wetlands ("blue" water). The paper describes methodology, input and output data, calibration and validation of the model. The model results are finally compared with other global water balance models.

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Bringing it all together

Hydrology and Earth System Sciences ◽

10.5194/hess-9-3-2005 ◽

2005 ◽

Vol 9 (1/2) ◽

pp. 3-14 ◽

Cited By ~ 20

Author(s):

J. C. I. Dooge

Keyword(s):

Water Balance ◽

Water Molecule ◽

Conceptual Models ◽

Hydrological Cycle ◽

Point Of View ◽

Deterministic Analysis ◽

Hydrologic Processes ◽

Complex Processes ◽

Non Linear ◽

Global Water

Abstract. The various elements of the hydrological cycle are discussed in outline from the point of view of making progress in analysis through appropriate simplification of these complex processes. Parallels between stochastic and deterministic analysis and between linear and non-linear conceptual models are referred to. The emphasis is on similarities and contrasts between the analysis of hydrologic processes over the range of scales from the water molecule to the global water balance.

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