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Model performance and parameter behavior for varying time aggregations and evaluation criteria in the WASMOD-M global water balance model
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. (Hydrologi)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. (Hydrologi)
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Department of Geosciences, University of Oslo, Oslo, Norway.
2009 (English)In: Water resources research, ISSN 0043-1397, E-ISSN 1944-7973, Vol. 45, no 5, W05418- p.Article in journal (Refereed) Published
Abstract [en]

Global discharge estimates commonly range between 36.500 km(3) a(-1)  and 44.500 km(3) a(-1), i.e., around 20%, and continental estimates differ much more. Data uncertainties are assumed to be a main cause of simulated runoff uncertainties, but model performance must also be addressed. The parsimonious WASMOD-M global water balance model, using   limited input data, was used to assess data and model uncertainty  (contrary to models using much data but being modestly or not at all calibrated). A Monte Carlo technique based on 15,000 parameter value  sets was used to evaluate the model against four criteria: observed   snow and monthly, annual, and long-term discharge. WASMOD-M was overparameterized when evaluated only against long-term average discharge but not against monthly discharge, and its snow algorithm  could be simplified. Sequential calibration is suggested for confining  the behavioral parameter space and minimizing model equifinality starting with snow, followed by long-term volume error, and ending with discharge dynamics.

Place, publisher, year, edition, pages
2009. Vol. 45, no 5, W05418- p.
Keyword [en]
global water balance, model uncertainty, multiobjective
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:uu:diva-96557DOI: 10.1029/2007WR006695ISI: 000266367900003OAI: oai:DiVA.org:uu-96557DiVA: diva2:171171
Available from: 2007-11-23 Created: 2007-11-23 Last updated: 2017-12-14Bibliographically 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.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 377
Keyword
Hydrology, Global, Water balance, Runoff, Regionalisation, Model uncertainty, Multi-objective, Parameter, Evaluation criteria, Routing, Climate change, Hydrologi
Identifiers
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
Opponent
Supervisors
Available from: 2007-11-23 Created: 2007-11-23Bibliographically approved
2. Large-scale Runoff Generation and Routing: Efficient Parameterisation using High-resolution Topography and Hydrography
Open this publication in new window or tab >>Large-scale Runoff Generation and Routing: Efficient Parameterisation using High-resolution Topography and Hydrography
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Storskalig modellering av flödessvarstid ochavrinningsbildning : Effektiv parametrisering baserad på högupplöst topografi och hydrografi
Abstract [en]

Water has always had a controlling influence on the earth’s evolution. Understanding and modelling the large-scale hydrological cycle is important for climate prediction and water-resources studies. In recent years large-scale hydrological models, including the WASMOD-­M evaluated in the thesis, have increasingly become a main assessment tool for global water resources.

The monthly version of WASMOD-M, the starting point of the thesis, revealed restraints imposed by limited hydrological and climate data quality and the need to reduce model-structure uncertainties. The model simulated the global water balance with a small volume error but was less successful in capturing the dynamics. In the last years, global high-quality, high-resolution topographies and hydro­graphies have become available. The main thrust of the thesis was the development of a daily WASMOD-M making use of these data to better capture the global water dynamics and to parameter­ise local non-linear processes into the large-scale model. Scale independency, parsimonious model structure, and computational efficiency were main concerns throughout the model development.

A new scale-independent routing algorithm, named NRF for network-response function, using two aggregated high-resolution hydrographies, HYDRO1k and HydroSHEDS, was developed and tested in three river basins with different climates in China and North America. The algorithm preserves the spatially distributed time-delay information in the form of simple network-response functions for any low-resolution grid cell in a large-scale hydrological model.

A distributed runoff-generation algorithm, named TRG for topography-derived runoff generation, was developed to represent the highly non-linear process at large scales. The algorithm, when inserted into the daily WASMOD-M and tested in same three basins, led to the same or a slightly improved performance compared to a one-layer VIC model, with one parameter less to be calibrated. The TRG algorithm also offered a more realistic spatial pattern for runoff generation.

The thesis identified significant improvements in model performance when 1) local instead of global climate data were used, and 2) when the scale-independent NRF routing algorithm was used instead of a traditional storage-based routing algorithm. In the same time, spatial resolution of climate input and choice of high-resolution hydrography have secondary effects on model performance.

Two high-resolution topographies and hydrographies were used and compared, and new tech­niques were developed to aggregate their information for use at large scales. The advantages and numerical efficiency of feeding high-resolution information into low-resolution global models were highlighted.

Abstract [sv]

Vatten har alltid varit en nyckelfaktor för jordens utveckling. Att förstå och kunna modellera det storska­liga vattenkretsloppet är betydelsefullt såväl för klimatförutsägelser som för studier av vattenresur­ser. På senare år har storskaliga hydrologiska modeller, däribland WASMOD-M som utvärderas i denna avhand­ling, i ökande utsträckning kommit att användas som huvudverktyg för utvärdering av globala vattenresurser.

Den månatliga versionen av WASMOD-M, avhandlingens startpunkt, användes för att påvisa inskränk­ningar som låg i begränsande hydrologi- och klimatdata liksom behovet av att minska model­lens strukturella osäkerheter. Modellen simulerade den globala vattenbalansen med ett mycket litet volymfel (avrinningens långtidsmedelvärde) men var mindre lyckosam att efterlikna dynamiken. Under se­nare tid har globala topografiska och hydrografiska data med hög rumslig upplösning och kvalitet blivit tillgängliga. Avhandlingens huvudsakliga drivkraft var att utveckla WASMOD-M med hjälp av dessa data i syfte att bättre fånga den globala vattendynamiken och för att parametrisera lokala ickelin­jära processer i den storskaliga modellen. Under hela modellutvecklingen har skaloberoende, lågparametrise­rad modellstruktur och numerisk beräkningseffektivitet varit viktiga bivillkor.

En ny skaloberoende svarstidsalgoritm, benämnd NRF (network-response function), som utnyttjar två aggregerade högupplösta hydrografier, HYDRO1k och HydroSHEDS, utvecklades och provades i tre avrinningsområden med olika klimat i Kina och Nordamerika. Algoritmen bevarar den rumsligt fördelade informationen om koncentrationstider i form av enkla responsfunktioner för vattendragsnä­tet för godtyckliga lågupplösta beräkningsrutor in en storskalig hydrologisk modell.

En distribuerad algoritm för avrinningsbildning, benämnd TRG (topography-derived runoff genera­tion), utvecklades för att representera den höggradigt ickelinjära processen i större skalor. Algoritmen användes i den dagliga WASMOD-M och provades i samma tre avrinningsområden som ovan. Modellprestanda blev lika bra eller bättre än en enlagers VIC-modell fast med en parameter mindre att kalibrera. TRG-algoritmen gav ett rimligare rumsligt mönster för avrinningsbildningen.

Avhandlingen har identifierat påtagliga förbättringar i modellprestanda när 1) lokala i stället för globala klimatdata användes och 2) när NRF, den skaloberoende svarstidsalgoritmen användes i stället för en traditionell magasinsbaserad svarstidsalgoritm. Samtidigt har klimatdatas rumsliga upplösning och val av högupplöst hydrografi en andra ordningens inverkan på modellprestanda.

Två högupplösta topografier och hydrografier användes och jämfördes, och nya tekniker utveckla­des för att aggregera deras informationsinnehåll i stora skalor. Fördelarna och den numeriska beräkningsef­fektiviteten av högupplöst information i lågupplösta globala modeller har belysts.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2010. 71 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 725
Keyword
Parameterisation, runoff generation, routing, WASMOD-M, hydrography, data uncertainty, topographic index, scale, river network, response function, HydroSHEDS, HYDRO1k, Dongjiang basin, Parametrisering, avrinningsbildning, flödessvarstid, WASMOD-M, hydrografi, topografiskt index, dataosäkerhet, skala, flödesnät, svarstidssfunktion, HYDRO1k, HydroSHEDS, Dongjiang
National Category
Oceanography, Hydrology, Water Resources
Research subject
Hydrology
Identifiers
urn:nbn:se:uu:diva-121310 (URN)978-91-554-7757-8 (ISBN)
Public defence
2010-04-28, Hambergsalen, Earth sciences centre, Villavägen 16, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2010-04-01 Created: 2010-03-21 Last updated: 2010-07-27Bibliographically approved

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Gong, LebingHalldin, SvenXu, Chong-Yu

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