The University of Tokyo · Environmental Science
Professor Taikan Oki's research lab specializes in global hydrology, water resources assessment, and the integration of land surface processes within Earth system modeling. The lab focuses on understanding the dynamics of freshwater circulation, river flow, and water availability under climate change, using advanced modeling frameworks such as the TRIP (Total Runoff Integrating Pathways) river network. A key research direction involves quantifying virtual water trade and water scarcity to support sustainable water management and policy planning on a global scale. The lab also investigates the diurnal and seasonal variability of precipitation and atmospheric water fluxes to improve the accuracy of hydrological and climatological models.
Figures are computed from collected data and may differ slightly.
Water is a naturally circulating resource that is constantly recharged. Therefore, even though the stocks of water in natural and artificial reservoirs are helpful to increase the available water resources for human society, the flow of water should be the main focus in water resources assessments. The climate system puts an upper limit on the circulation rate of available renewable freshwater resources (RFWR). Although current global withdrawals are well below the upper limit, more than two bil
As a first step toward designing a comprehensive model for validating land surface hydrology and river flow in Earth system models, a global river channel network has been prepared at 1° latitude × 1° longitude resolution. The end product is the Total Runoff Integrating Pathways (TRIP) network. The aim of TRIP is to provide information of lateral water movement over land following the paths of river channels. Flow directions were determined from vector data of river channels and river pathways a
Global virtual water trade was quantitatively estimated and evaluated. The basic idea of how to estimate unit requirement of water resources to produce each commodity is introduced and values for major agricultural and stock products are presented. The concept of virtual water and the quantitative estimates can help in assessing a more realistic water scarcity index in each country, projecting future water demand for food supply, increasing public awareness on water, and identifying the processe
Abstract The anticipated water scarcity in the first half of this century is one of the international issues of most concern, which needs to be adequately addressed. However, even though the issue has an international impact and worldwide monitoring is critical, there are limited global estimates at present. In this study, annual water availability has been derived from annual runoff estimated by land surface models using total runoff integrating pathways (TRIP) with 0.5° by 0.5° longitude/latit
Abstract Atmospheric vapour flux convergence is introduced for the estimation of the water balance in a river basin. The global distribution of vapour flux convergence, ‐ Δ H · Q is estimated using the European Centre for Medium‐Range Weather Forecasts global analysis data for the period 1980‐1988. From the atmospheric water balance, the annual mean ‐ Δ H · Q can be interpreted as the precipitation minus evaporation. The estimated ‐ Δ H · Q is compared with the observed discharge data in the Cha
Abstract The diurnal cycle of precipitation is investigated using ground-based hourly observations for more than 10 years both in Japan and Malaysia. The diurnal cycle of precipitation in Japan is classified into three clusters. The first one has a peak in the morning, and the stations categorized into this cluster are located in coastal regions. The second cluster has two peaks in the morning and in the evening. These stations are located in an inland region. The morning peak in the above two c
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