Research School for Socio-Economic and
Natural Sciences of the Environment
Research School for Socio-Economic and
Natural Sciences of the Environment

WALRUS shows rainwater discharge in lowland river catchments

Claudia BrauerThe Hydrology and Quantitative Water Management chair group of Wageningen UR hosted a users' day in cooperation with Deltares for representatives of water boards, Rijkswaterstaat, consultancy firms and knowledge institutes. The central focus of the day was the Wageningen Lowland Runoff Simulator (WALRUS), a rainfall-discharge model for lowland river catchments. This model was developed by SENSE PhD graduate Claudia Brauer as part of her PhD research. ‘Our model is already being used by five water boards, for example as a prediction model for high water or as a reference model,’ explains Claudia Brauer. ‘There were 30 people at the users’ day, including hydrologists from 13 water boards, and they were able to practice with the model themselves. There is therefore a good chance that it will be used even more in the future.’

Many different hydrological models exist for the modelling of the discharge from a river catchment, with varying degrees of complexity, depending on the purpose for which the model is used. Hydrological systems are simplified into a collection of reservoirs and river flow routes in what are referred to as conceptual models, capturing the essence of the hydrological processes while limiting the number of parameters. However, most conceptual models are developed for sloping river catchments and may provide unreliable results for lowland catchments such as those in the Netherlands. Processes such as capillary rise and interactions between groundwater and surface water are important to the Netherlands. ‘That is why we have developed WALRUS especially for the circumstances in the Netherlands; it is an entirely new parametric model that simulates the discharge from lowland catchments.

WALRUS fills the gap between complex, spatially-distributed models often used in lowland catchments and simple, spatially-integrated parametric models developed primarily for sloping river catchments. WALRUS explicitly takes into account the hydrological processes that are important in low-lying areas. In this regard, the focus is on the link between groundwater and the unsaturated zone, flow routes that are dependent on moisture conditions, the feedback between groundwater and surface water and the question of seepage, drainage and supply or extraction of surface water. ‘The strength of WALRUS is that it is a model suitable for operational applications as it calculates efficiently and is numerically stable,’ explains Claudia Brauer. Standard relationships have been implemented in the freely-accessible model code, leaving only four parameters that need to be calibrated. The model is suitable for the operational simulation of floods and droughts for the purposes of risk analyses and scenario analyses, for the design of infrastructure and for imputing missing data in discharge measurement series.’

Click here for additional information on WALRUS.

Source: intranet Wageningen UR

Wednesday 4 April 2018