Quantifying Groundwater-Surface Water Interactions with Transfer Function Models
Publicerad
Författare
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
This project aims to develop and evaluate a data driven method for analysing
groundwater-surface water interactions. These interactions are analysed by using
time-series analysis and transfer function modelling to create models for ground water head, stream flow and stream level. The method is applied to a case study:
a tunnelling project in Kolmården, Sweden, where a recipient stream in a nature
reserve risks being affected by tunnel-induced groundwater drawdown due to leakage. The method consists of two modelling stages. In the first stage groundwater
head models (GWMs) are developed. In the second stage, the GWMs are used to
extend existing groundwater head time series and develop three types of models:
models that estimate baseflow (BFM), stream total flow (TFM), and stream level
(SLM). Additionally, the results are simulated using 18 different methods for estimation of potential evapotranspiration, to see how different methods impact results.
Results from the first modelling stage indicate higher model performance for models
representing groundwater level in soil, compared to rock, and for models using longer
calibration periods across all four seasons. Results from the second modelling stage
present very poor results for the stream baseflow models (BFMs), which is proba bly related to the baseflow separation procedure’s inability to account for specific
local conditions. Total stream flow models (TFMs) and stream level models (SLMs)
perform much better, with R2
-values around 0.6 in validation. However, all models
show signs of overfitting, with R2
-values above 0.8 in calibration. The contribution
from groundwater head to the variations seems to be higher for the SLMs.
The developed method constitutes a simplified and data driven approach for analysing
groundwater-surface water interactions, making it possible to study, e.g., how tunnel induced groundwater drawdown might affect a watercourse. Further development
is recommended, e.g., using additional model evaluation metrics and simulating different leakage rate scenarios with pump test data. The method shows promise for
allowing effective modelling of the dynamic response of groundwater-fed surface water to hydroclimatic variables, and can be seen as an additional tool for representing
hydrogeological systems.
Beskrivning
Ämne/nyckelord
hydrogeological modelling,, groundwater-surface water interactions, time series analysis, transfer-function models, impulse response models, Pastas, Python