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Global water-balance modelling with WASMOD-M: parameter estimation and regionalisation
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science. (Hydrologi)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science. (Hydrologi)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science. (Hydrologi)
2007 (English)In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 340, no 1-2, 105-118 p.Article in journal (Refereed) Published
Abstract [en]

Limitations in water quantity and quality are among the greatest social and economic problems facing mankind. However, difficulties in estimating the global long-term average runoff have led to differences of as much as 30% when integrated to the whole earth. Model estimates of runoff are especially uncertain for the 50% of the global land surface lacking consistent runoff data. In this study, we present the WASMOD-M global water-balance model, constructed to provide robust runoff estimates both for gauged and ungauged basins. WASMOD-M is a conceptual water-budgeting model with two state-variables and five tunable parameters. A simple parameter-value estimation procedure allowed “acceptable” parameter values to be identified both for the majority of gauged basins, and for most ungauged basins. Acceptable global simulations could be accomplished with continentally constant parameter values but at the cost of compensating errors on a basin scale. A “standard”, spatially-distributed parameter-value set was derived for a ”best” global simulation. Of the simulated 59132 0.5° × 0.5° cells, 45% got “good” parameter values as a by-product of regionalisation, 41% from regionalisation, whereas 14% were given a default value set. This global set allowed simulation of the 1915–2000 world water balance. The simulation was in the same range as previously published model results and compilations of runoff measurements. Long-term average within-year runoff variations agreed well with previously published results for most of the studied runoff stations although WASMOD-M was only calibrated against long-term average runoff. Improvement of WASMOD-M and other global water-balance models should be simplified by a common definition of basin boundaries and areas, as well as runoff. Further, modelling progress will depend on improved global datasets of precipitation and runoff regulation.

Place, publisher, year, edition, pages
2007. Vol. 340, no 1-2, 105-118 p.
Keyword [en]
Global model, Water balance, Runoff, Regionalisation, Distributed
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-96556DOI: 10.1016/j.jhydrol.2007.04.002ISI: 000247704100009OAI: oai:DiVA.org:uu-96556DiVA: diva2:171170
Available from: 2007-11-23 Created: 2007-11-23 Last updated: 2011-02-02Bibliographically approved
In thesis
1. Global-Scale Modelling of the Land-Surface Water Balance: Development and Analysis of WASMOD-M
Open this publication in new window or tab >>Global-Scale Modelling of the Land-Surface Water Balance: Development and Analysis of WASMOD-M
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Global modellering av landområdenas vattenbalans : Utveckling och analys av WASMOD-M
Abstract [en]

Water is essential for all life on earth. Global population increase and climate change are projected to increase the water stress, which already today is very high in many areas of the world. The differences between the largest and smallest global runoff estimates exceed the highest continental runoff estimates. These differences, which are caused by different modelling and measurement techniques together with large natural variabilities need to be further addressed. This thesis focuses on global water balance models that calculate global runoff, evaporation and water storage from precipitation and other climate data.

A new global water balance model, WASMOD-M was developed. Already when tuned against the volume error it reasonable produced within-year runoff patterns, but the volume error was not enough to confine the model parameter space. The parameter space and the simulated hydrograph could be better confined with, e.g., the Nash criterion. Calibration against snow-cover data confined the snow parameters better, although some equifinality still persisted. Thus, even the simple WASMOD-M showed signs of being overparameterised.

A simple regionalisation procedure that only utilised proximity contributed to calculate a global runoff estimate in line with earlier estimations. The need for better specifications of global runoff estimates was highlighted.

Global modellers depend on global data-sets that can have low quality in many areas. Major sources of uncertainty are precipitation and river regulation. A new routing method that utilises high-resolution flow network information in low-resolution calculations was developed and shown to perform well over all spatial scales, while the standard linear reservoir routing decreased in performance with decreasing resolution. This algorithm, called aggregated time-delay-histogram routing, is intended for inclusion in WASMOD-M.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 76 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 377
Hydrology, Global, Water balance, Runoff, Regionalisation, Model uncertainty, Multi-objective, Parameter, Evaluation criteria, Routing, Climate change, Hydrologi
urn:nbn:se:uu:diva-8352 (URN)978-91-554-7051-7 (ISBN)
Public defence
2007-12-14, Axel Hambergsalen, Geocentrum, Villavägen 16, Uppsala, 10:00
Available from: 2007-11-23 Created: 2007-11-23Bibliographically approved

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