River hydrology

The calibration of a hydrological model to river flow gauging data is often a time consuming task. Manual (trial-and-error) and numerical calibration techniques both have disadvantages. The numerical methods do not make use of experience-based information. The manual methods are very time consuming and not objective. Therefore, a transparent physically-based method is proposed. In this method, physical information is derived from the river discharge data in a step-wise way (based on data-mining techniques). It is used for the calibration of the submodels of the hydrological model in a step-wise and separate way. The method makes use of filtering techniques to separate the total discharge series in different subflows and reverse river routing techniques to transform the river discharge series in equivalent rainfall-runoff discharge series. For the calibration of the separate submodels, 'maximum likelihood' statistical measures are used.
This procedure is worked out in a Ph.D. study, and applied to a generalized structure of lumped conceptual rainfall-runoff model in combination with a model-structure identification procedure. As part of a project for AMINAL - division Water, the procedure is refined for the specific model-structures of NAM (Danish Hydraulic Institute) and PDM (HR Wallingford, UK Institute of Hydrology).
The procedure has been applied to river (sub)basins in Flanders-Belgium (Dender and Nete basins), as well as selected catchments in Ecuador (Paute basin) and the Nile basin.

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At least half of the global fresh water resources derive from mountains; they play a critical role in the global water cycle and are a main source for hydropower and irrigation. Mountainous basins are characterized by showing variations in meteorological, hydrological and ecological conditions over short distances due to the effects of altitudinal gradients. For this reason, hydrological processes in these catchments are highly variable in space and time. However, despite its importance, mountain hydrology is still poorly understood and therefore the sustainable development of water resources for mountain communities cannot be properly addressed.
The study area is the Paute basin in Ecuador. The purpose of the study is to obtain a better understanding of rainfall patterns, space-time variability of rainfall, and hydrological processes at various space and time scales in a complex mountain basin.

Publications:

Celleri, R., Willems, P., Buytaert, W., Feyen, J.(2007), 'Space-time rainfall variability in the Paute basin, Ecuadorian Andes, Hydrological Processes, doi: 10.1002/hyp.6575

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The last century has witnessed a change in the landscape of Flanders, and an increase in flooding intensity and frequency that has been observed in Europe over the last decade. Reverting to states existing prior to the introduction of intensive farming practices is being considered as a potential remedy for mitigating these flood events. Rewetting is one such, which is believed to have environmental benefits including increased infiltration and flood mitigation. However, such actions need to be built on sound scientific arguments, and here there exists a gap. This research study builds on the need for scientific arguments for or against restoration. The hydrological effects are investigated by means of a MIKE-SHE model.

MIKE SHE is a fully distributed hydrological modelling tool developed by the Danish Hydraulic Institute (DHI Water & Environment), which simulates the entire land phase of the hydrological cycle. In cooperation with the Bio-engineering faculty of K.U.Leuven, it has been used to build a model of the Nete basin in Belgium. The model is composed of a root zone component for estimating the net precipitation, a comprehensive three-dimensional groundwater component for estimating recharge to and hydraulic heads in different geological layers, and a river component for streamflow routing and calculating stream-aquifer interaction

In a first research study (M-H Rubarenzya), the flood mitigation effect of the restoration of wetlands is investigated. Restoration scenarios are defined in cooperation with Antwerp University (Prof. P.Meire).
In a second study (T.Vansteenkiste), the MIKE-SHE model is adopted for an infiltration project by surface water regulations and to investigate the effects of increased groundwater pumping for drinking water production, and for climate change impact investigations.

Publications:

Rubarenzya, M.H., Willems, P., Berlamont, J., Feyen, J.(2006), 'Modelling of river valley rewetting and extreme events in the Nete chatchment (Belgium)', in Floods, from defence to management' (Ed. J. van Alpen, E. van Beek & M. Taal), Taylor & Francis Group, London, 757-761 (ISBN 0 415 39119 9)

Rubarenzya, M.H., Willems, P., Berlamont, J.(2007), 'Identification of uncertainty sources in distributed hydrological modelling. Case study of the Grote Nete catchment in Belgium', Water SA, 33(5), 633-642

Rubarenzya, M.H., Graham, D., Feyen, J., Willems, P., Berlamont, J.(2007), 'A site-specific land and water management model in MIKE SHE', Nordic Hydology, 38(4-5), 333-350

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A joint Sino-Belgian research project for the Belgian Federal Science Policy Office is carried out with main objective the set-up of a regional surface water model. This model will take the form of a conceptual model for the subbasin's rainfall-runoff processes and the river network in the entire Tarim basin. As secondary objective, preliminary modelling activities will be started up in order to investigate the surface water - groundwater interactions, and relations between the basin's ecological status and hydrological variables such as the groundwater depth, the flooded areas, etc. Remote sensing data will be used to produce rainfall, evaporation, soil moisture and land use data, and to produce earth observation input data for the hydrological models. They also will be applied to analyse indications of historical trends in land use, and to investigate the impact these changes had on the hydrology of the basin.
The modelling products developed by the project will grow into elements of an envisaged integrated water resources management system. The decision support system can be used for scenario-analysis and the evaluation of water management alternatives in order to solve the dry-out and ecosystem deterioration problems in the basin.
The project is being carried out in collboration with the Flemish Institute for Technological Research (VITO), the Xinjiang Institute for Ecology and Geography in China, the Tarim Water Resources Management Bureau, and the Xinjiang Meteorological Administration.

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