The Lowland Groundwater Surface water Interaction model: a new runoff model for high flow and low flow conditions

Dimmie Hendriks1, Marijn Kuijper1
1 Deltares

O 6.4 in Grundwasser-, Boden- und Oberflächenwasser-Interaktionen

30.05.2014, 12:00-12:20, H19, NW II

A main challenge in forecasting stream discharge is to develop a model that performs well in both high flow and low flow conditions. Until recently, the interaction of groundwater and surface water was either modeled in a simplified way disregarding the changing groundwater storage capacity, or in rather complex ways involving time-consuming coupling of groundwater and surface water models. The latter can be very useful when one aims to understand the flow processes, but is not feasible in hourly runoff simulations.

The Lowland Groundwater Surface water Interaction model (LGSI), is an innovative modeling concept that facilitates both (Van de Velde et al., 2009). LGSI uses the changes in groundwater storage through time, because these influence not only a delay in rainfall discharge, but also the amount of active rivers and ditches in the drainage network. LGSI is unique in involving this non-linear behavior of the drainage system in its discharge calculation by capturing the dynamics of groundwater-surface water interaction in the distribution of groundwater depths. For each time step this distribution is drawn from an existing, numerical groundwater model, and the active discharge system is determined by the part of the distribution that represents groundwater levels above drainage level. As a result, both the occurrence and the amount of groundwater discharge to ditches and streams are calculated dynamically, explicitly taking into account spatial variations within the catchment.

Results in the Drentsche Aa catchment, the Leijgraaf catchment, and the Dinkel catchment (the Netherlands), showed that in average and high discharge periods LGSI reaches similar results as traditional in rainfall-runoff models (Wanders et al., 2011). However, its benefit lies in the simulation of low flows. Especially low groundwater levels and resulting low discharges are simulated very well with LGSI, as it takes into account the spatially distributed changes in groundwater storage. Recently, the LGSI model concept was added to the Rainfall-runoff model suite of Sobek. The next step is to apply LSGI in a DELFT FEWS decision support system, making LGSI available for early warning on floods and droughts.

Van der Velde, Y., G. H. De Rooij, et al. (2009). "Catchment-scale non-linear groundwater-surface water interactions in densely drained lowland catchments." Hydrology and Earth System Sciences 13: 1867-1885

Wanders, N., D.M.D. Hendriks and Y. van der Velde (2011) Combined groundwater – surface water modeling with a lumped hydrological model. Deltares-report 1203833-000-BGS-0001, Utrecht.

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Letzte Änderung 01.11.2013