Soil Moisture: Incorporating Antecedent Soil Moisture Conditions into Runoff Modelling in Green Urban Catchment Areas
Authors
Koscielska, Dominika ; Nomikou, Anna
Term
4. term
Publication year
2026
Submitted on
2026-06-01
Pages
91
Abstract
This project examines how antecedent soil moisture influences surface runoff in a green urban catchment in Lystrup, Aarhus. We collected and analyzed rainfall, runoff, a drought index (DI, an indicator of how dry the area and soils are), and volumetric water content (VWC, a measure of how much water the soil holds) for selected rain events. The results show that rainfall intensity alone does not explain runoff generation. Several rain events produced little to no runoff when soils were dry, while wetter prior conditions led to much larger runoff responses, making the initial wetness of the soil an important factor. A VWC classification and a runoff-ratio analysis indicated threshold-controlled behavior: higher soil moisture was associated with the most runoff. To further explore the catchment response, we set up a simple linear reservoir model, followed by a more advanced Nash linear reservoir model. Finally, we used the MIKE SHE model for baseline simulations to evaluate how accurately the catchment’s runoff response could be represented. The simple and Nash reservoir models reproduced the general timing of runoff events, while MIKE SHE, although not fully calibrated, suggested that infiltration and groundwater storage dominate within the catchment. However, none of the modeling approaches fully reproduced the observed runoff responses.
Dette projekt undersøger, hvilken betydning forudgående jordfugtighed har for dannelsen af afstrømning i et grønt byopland i Lystrup, Aarhus. Vi samlede og analyserede data for nedbør, afstrømning, et tørkeindeks (DI, et mål for hvor tør jorden og området er) og volumetrisk vandindhold (VWC, et mål for hvor meget vand jorden indeholder) for udvalgte regnhændelser. Resultaterne viste, at nedbørsintensitet alene ikke kan forklare, om der dannes afstrømning. Flere regnhændelser gav næsten ingen afstrømning, når jorden var tør, mens vådere forudgående forhold gav markant større afstrømningsrespons. Den indledende vådhed af jorden er derfor en vigtig faktor. En VWC-klassifikation og en analyse af afstrømningsratio pegede på tærskelstyret adfærd, hvor højere jordfugtighed var forbundet med mest genereret afstrømning. For at undersøge oplandets respons nærmere opstillede vi først en simpel lineær reservoirmodel og derefter en mere avanceret Nash lineær reservoirmodel. Til sidst brugte vi MIKE SHE til basissimuleringer for at vurdere, hvor præcist oplandets afstrømningsrespons kunne modelleres. De to reservoirmodeller gengav den overordnede timing af afstrømningshændelser, mens MIKE SHE, selv om modellen ikke var fuldt kalibreret, pegede på, at infiltration og grundvandslagring i oplandet er dominerende processer. Ingen af modellerne kunne dog fuldt ud genskabe de observerede afstrømningsrespons.
[This apstract has been rewritten with the help of AI based on the project's original abstract]