scholarly journals An integrated model for the assessment of global water resources – Part 2: Applications and assessments

2008 ◽  
Vol 12 (4) ◽  
pp. 1027-1037 ◽  
Author(s):  
N. Hanasaki ◽  
S. Kanae ◽  
T. Oki ◽  
K. Masuda ◽  
K. Motoya ◽  
...  
Keyword(s):  
Water Resources ◽  
Water Use ◽  
Water Availability ◽  
Asian Monsoon ◽  
Environmental Flow ◽  
Water Withdrawal ◽  
Monsoon Region ◽  
Asian Monsoon Region ◽  
Meteorological Forcing ◽  
Global Water

Abstract. To assess global water resources from the perspective of subannual variation in water availability and water use, an integrated water resources model was developed. In a companion report, we presented the global meteorological forcing input used to drive the model and six modules, namely, the land surface hydrology module, the river routing module, the crop growth module, the reservoir operation module, the environmental flow requirement module, and the anthropogenic withdrawal module. Here, we present the results of the model application and global water resources assessments. First, the timing and volume of simulated agriculture water use were examined because agricultural use composes approximately 85% of total consumptive water withdrawal in the world. The estimated crop calendar showed good agreement with earlier reports for wheat, maize, and rice in major countries of production. In major countries, the error in the planting date was ±1 mo, but there were some exceptional cases. The estimated irrigation water withdrawal also showed fair agreement with country statistics, but tended to be underestimated in countries in the Asian monsoon region. The results indicate the validity of the model and the input meteorological forcing because site-specific parameter tuning was not used in the series of simulations. Finally, global water resources were assessed on a subannual basis using a newly devised index. This index located water-stressed regions that were undetected in earlier studies. These regions, which are indicated by a gap in the subannual distribution of water availability and water use, include the Sahel, the Asian monsoon region, and southern Africa. The simulation results show that the reservoir operations of major reservoirs (>1 km3) and the allocation of environmental flow requirements can alter the population under high water stress by approximately −11% to +5% globally. The integrated model is applicable to assessments of various global environmental projections such as climate change.

scholarly journals An integrated model for the assessment of global water resources – Part 2: Anthropogenic activities modules and assessments

2007 ◽  
Vol 4 (5) ◽  
pp. 3583-3626 ◽  
Author(s):  
N. Hanasaki ◽  
S. Kanae ◽  
T. Oki ◽  
N. Shirakawa
Keyword(s):  
Water Resources ◽  
Asian Monsoon ◽  
Storage Capacity ◽  
Anthropogenic Activities ◽  
Integrated Model ◽  
Crop Growth ◽  
Water Withdrawal ◽  
Monsoon Region ◽  
Asian Monsoon Region ◽  
Global Water

Abstract. To assess global water resources from the perspective of subannual variation in water resources and water use, an integrated water resources model was developed. In a companion report, we presented the global meteorological forcing input used to drive the model and two natural hydrological cycle modules, namely, the land surface hydrology module and the river routing module. Here, we present the remaining four modules, which represent anthropogenic activities: a crop growth module, a reservoir operation module, an environmental flow requirement module, and an anthropogenic withdrawal module. In addition, we discuss the results of a global water resources assessment using the integrated model. The crop growth module is a relatively simple model based on heat unit theory and potential biomass and harvest index concepts. The performance of the crop growth module was examined extensively because agricultural water comprises approximately 70% of total water withdrawal in the world. The estimated crop calendar showed good agreement with earlier reports for wheat, maize, and rice in major countries of production. The estimated irrigation water withdrawal also showed fair agreement with country statistics, but tended to underestimate countries in the Asian monsoon region. In the reservoir operation module, 452 major reservoirs with more than 1 km³ each of storage capacity store and release water according to their own rules of operation. Operating rules were determined for each reservoir using an algorithm that used currently available global data such as reservoir storage capacity, intended purposes, simulated inflow, and water demand in the lower reaches. The environmental flow requirement module was newly developed based on case studies from around the world. The integrated model closes both energy and water balances on land surfaces. Global water resources were assessed on a subannual basis using a newly devised index that locates water-stressed regions that were undetected in earlier studies. These regions, which are indicated by a gap in the subannual distribution of water resources and water use, include the Sahel, the Asian monsoon region, and southern Africa. The integrated model is applicable to assess various global environmental projections such as climate change.

scholarly journals An integrated model for the assessment of global water resources – Part 1: Model description and input meteorological forcing

2008 ◽  
Vol 12 (4) ◽  
pp. 1007-1025 ◽  
Author(s):  
N. Hanasaki ◽  
S. Kanae ◽  
T. Oki ◽  
K. Masuda ◽  
K. Motoya ◽  
...  
Keyword(s):  
Water Resources ◽  
Land Surface ◽  
Reservoir Operation ◽  
Storage Capacity ◽  
Environmental Flow ◽  
Surface Hydrology ◽  
Meteorological Forcing ◽  
The World ◽  
Land Surface Hydrology ◽  
Global Water

Abstract. To assess global water availability and use at a subannual timescale, an integrated global water resources model was developed consisting of six modules: land surface hydrology, river routing, crop growth, reservoir operation, environmental flow requirement estimation, and anthropogenic water withdrawal. The model simulates both natural and anthropogenic water flow globally (excluding Antarctica) on a daily basis at a spatial resolution of 1°×1° (longitude and latitude). This first part of the two-feature report describes the six modules and the input meteorological forcing. The input meteorological forcing was provided by the second Global Soil Wetness Project (GSWP2), an international land surface modeling project. Several reported shortcomings of the forcing component were improved. The land surface hydrology module was developed based on a bucket type model that simulates energy and water balance on land surfaces. The crop growth module is a relatively simple model based on concepts of heat unit theory, potential biomass, and a harvest index. In the reservoir operation module, 452 major reservoirs with >1 km3 each of storage capacity store and release water according to their own rules of operation. Operating rules were determined for each reservoir by an algorithm that used currently available global data such as reservoir storage capacity, intended purposes, simulated inflow, and water demand in the lower reaches. The environmental flow requirement module was newly developed based on case studies from around the world. Simulated runoff was compared and validated with observation-based global runoff data sets and observed streamflow records at 32 major river gauging stations around the world. Mean annual runoff agreed well with earlier studies at global and continental scales, and in individual basins, the mean bias was less than ±20% in 14 of the 32 river basins and less than ±50% in 24 basins. The error in the peak was less than ±1 mo in 19 of the 27 basins and less than ±2 mo in 25 basins. The performance was similar to the best available precedent studies with closure of energy and water. The input meteorological forcing component and the integrated model provide a framework with which to assess global water resources, with the potential application to investigate the subannual variability in water resources.

scholarly journals Simulating human impacts on global water resources using VIC-5

2020 ◽  
Vol 13 (10) ◽  
pp. 5029-5052
Author(s):  
Bram Droppers ◽  
Wietse H. P. Franssen ◽  
Michelle T. H. van Vliet ◽  
Bart Nijssen ◽  
Fulco Ludwig
Keyword(s):  
Water Resources ◽  
Human Impacts ◽  
Anthropogenic Impacts ◽  
Environmental Flow ◽  
Water Withdrawal ◽  
Groundwater Depletion ◽  
Vic Model ◽  
Water Withdrawals ◽  
Surface And Groundwater ◽  
Global Water

Abstract. Questions related to historical and future water resources and scarcity have been addressed by several macroscale hydrological models. One of these models is the Variable Infiltration Capacity (VIC) model. However, further model developments were needed to holistically assess anthropogenic impacts on global water resources using VIC. Our study developed VIC-WUR, which extends the VIC model using (1) integrated routing, (2) surface and groundwater use for various sectors (irrigation, domestic, industrial, energy, and livestock), (3) environmental flow requirements for both surface and groundwater systems, and (4) dam operation. Global gridded datasets on sectoral demands were developed separately and used as an input for the VIC-WUR model. Simulated national water withdrawals were in line with reported Food and Agriculture Organization (FAO) national annual withdrawals (adjusted R2 > 0.8), both per sector and per source. However, trends in time for domestic and industrial water withdrawal were mixed compared with previous studies. Gravity Recovery and Climate Experiment (GRACE) monthly terrestrial water storage anomalies were well represented (global mean root-mean-squared error, RMSE, values of 1.9 and 3.5 mm for annual and interannual anomalies respectively), whereas groundwater depletion trends were overestimated. The implemented anthropogenic impact modules increased simulated streamflow performance for 370 of the 462 anthropogenically impacted Global Runoff Data Centre (GRDC) monitoring stations, mostly due to the effects of reservoir operation. An assessment of environmental flow requirements indicates that global water withdrawals have to be severely limited (by 39 %) to protect aquatic ecosystems, especially with respect to groundwater withdrawals. VIC-WUR has potential for studying the impacts of climate change and anthropogenic developments on current and future water resources and sector-specific water scarcity. The additions presented here make the VIC model more suited for fully integrated worldwide water resource assessments.

scholarly journals Simulating human impacts on global water resources using VIC-5

2019 ◽  
Author(s):  
Bram Droppers ◽  
Wietse H. P. Franssen ◽  
Michelle T. H. van Vliet ◽  
Bart Nijssen ◽  
Fulco Ludwig
Keyword(s):  
Water Resources ◽  
Water Use ◽  
Water Resource ◽  
Human Impacts ◽  
Anthropogenic Impacts ◽  
Environmental Flow ◽  
Hydrological Models ◽  
Macro Scale ◽  
Water Withdrawals ◽  
Global Water

Abstract. Questions related to historical and future water resources and water scarcity have been addressed by several macro-scale hydrological models over the last few decades. However, further advancements are needed to improve the integration of anthropogenic impacts and environmental flow requirements into hydrological models. The newly developed VIC-WUR model aims to increase the applicability of the VIC-5 model for water resource assessments, specifically by including human impacts and environmental flow requirements. To this end, VIC-WUR extends VIC-5 with modules for irrigation, domestic, industrial, energy and livestock water-use, environmental flow requirements for surface and groundwater systems, and dam operation. Model inputs of sectoral water demand were estimated independently and correlated well to reported national water withdrawals. VIC-WUR results, based on the newly developed modules, corresponded with results from reported global water withdrawals and other hydrological models, although differences exist. The VICWUR irrigation withdrawals were high compared to the other models but closer to the reported values, decreasing the gap between simulated and reported withdrawals. Irrigation withdrawals were probably high due to the inclusion of groundwater withdrawals and paddy irrigation in the model. Domestic and industrial water withdrawals were slightly lower than the reported values. Domestic and industrial withdrawals were probably insufficient due to low water availability, as the potential water withdrawals are more in line with reported values. Livestock water withdrawals were within the range of reported values and other models. The model additions comprehensively incorporate anthropogenic and environmental water use, which provides new opportunities for global water resource assessments. A preliminary assessment of environmental flow requirements shows competition between water resources allocated for human consumption and the environment, from ground and surface water sources. The improvements made here are a first step towards integrated water-food-energy nexus modelling.

scholarly journals A global water scarcity assessment under shared socio-economic pathways – Part 2: Water availability and scarcity

2012 ◽  
Vol 9 (12) ◽  
pp. 13933-13994 ◽  
Author(s):  
N. Hanasaki ◽  
S. Fujimori ◽  
T. Yamamoto ◽  
S. Yoshikawa ◽  
Y. Masaki ◽  
...  
Keyword(s):  
Water Use ◽  
Water Availability ◽  
Water Scarcity ◽  
Climate Models ◽  
Water Cycle ◽  
Water Withdrawal ◽  
Electricity Production ◽  
Daily Water ◽  
Consumption Demand ◽  
Global Water

Abstract. A global water scarcity assessment for the 21st century was conducted under the latest socio-economic scenario for global change studies, namely Shared Socio-economic Pathways (SSPs). SSPs depict five global situations with substantially different socio-economic conditions. In the accompanying paper, a water use scenario compatible with the SSPs was developed. This scenario considers not only quantitative socio-economic factors such as population and electricity production but also qualitative ones such as the degree of technological change and overall environmental consciousness. In this paper, water availability and water scarcity were assessed using a global hydrological model called H08. H08 simulates both the natural water cycle and major human activities such as water withdrawal and reservoir operation. It simulates water availability and use at daily time intervals at a spatial resolution of 0.5° × 0.5°. A series of global hydrological simulations were conducted under the SSPs, taking into account different climate policy options and the results of climate models. Water scarcity was assessed using an index termed the Cumulative Withdrawal to Demand ratio, which is expressed as the accumulation of daily water withdrawal from a river over the potential daily water consumption demand. This index can be used to express whether renewable water resources are available from rivers when required. The results suggested that by 2071–2100 the population living under severely water stressed conditions for SSP1-5 will reach 2588–2793 × 106 (39–42% of total population), 3966–4298 × 106 (46–50%), 5334–5643 × 106 (52–55%), 3427–3786 × 106 (40–45%), 3164–3379 × 106 (46–49%), respectively, if climate policies are not adopted. Even in SSP1 (the scenario with least change in water use and climate) global water scarcity increases considerably, as compared to the present day. This is mainly due to the growth in population and economic activity in developing countries, and partly due to hydrological changes induced by global warming.

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

2016 ◽  
Vol 20 (7) ◽  
pp. 2877-2898 ◽  
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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