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

Abstract

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 sitespecific 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 Correspondence to: N. Hanasaki (hanasaki@nies.go.jp) 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 km 3 ) 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.

Water availability in +2°C and +4°C worlds

“…[11,31]), economic and technological advancement (e.g. [6,27]) as well as access to water sources (e.g. [32]).…”

Analysis of Water Resources in Horqin Sandy Land Using Multisource Data from 2003 to 2010

“…However, overexploitation or persistent depletion of groundwater occurs if its abstraction exceeds its natural recharge rate over extensive areas for a long period [3,4]. This situation has led to water stress in several parts of the world, including South Africa, central and western U.S., Australia, India, Pakistan, and North China [1,3,[5][6][7][8][9]. Groundwater depletion poses a serious threat to the water supply of local residents because it can lead to soil salinization and land subsidence; consequently, it can restrict the social development and economic growth of the affected regions.…”

Balancing water resource conservation and food security in China

“…The VWC of unprocessed livestock products is defined as water consumption per head of livestock (kilograms of water per head), involving the feed's VWC, drinking, and cleaning water divided by the livestock production per head (kilograms of meat per head). The VWC value of each commodity was calculated using provincial crop yield estimates from CHINAGRO (17) (for rainfed and irrigated lands) and ET simulated with the H08 global hydrologic model (18,40). The ET simulation used meteorological forcing data (41) covering the whole globe at 0.5°s patial resolution, from 1948 to 2008 at daily intervals; the average from 2003 to 2007 was used in this study (circa 2005) to isolate the effects of policy and socioeconomic changes from climate change effects; the latter are not considered here.…”