- Title
- Improving the simulation of surface water and groundwater interactions using a couple modelling approach and insights from water isotopes
- Creator
- Jafari, Tina
- Resource Type
- thesis
- Date
- 2021
- Description
- Professional Doctorate - Environmental Sciences
- Description
- With a growing global population driving increasing demand, water has become even more critically important than it already was, particularly for arid and semi-arid countries like Iran. To meet the growing need for water, proper management of water resources is required. To successfully manage water resources, an understanding of the temporal patterns of surface water (SW), distribution of groundwater (GW) resources, and interaction between SW and GW are essential. To obtain insights into SW and GW resources, a comprehensive assessment of all water cycle components is required. The physical processes that govern water interactions between SW, GW, and other water cycle components are highly nonlinear. Sustainable management water resource systems requires characterisation of the complex, integrated surface–subsurface water interaction processes in a united water cycle system. However, assessing water components and understanding the interaction between them is challenging because of (i) the lack of field information available and (ii) the complexity of the processes involved makes it difficult to realistically estimate SW and GW model parameters which results in poor accuracy and low reliability of SW-GW model simulations. To understand SW-GW interactions and comprehensively assess all water cycle components in a catchment, a fully integrated model that jointly simulates SW and GW in a holistic way is required. In this thesis, the interaction between SW and GW is investigated and simulated using a combination of a fully integrated numerical modelling and isotope hydrology techniques. We use a coupled SWAT-MODFLOW model for numerical modelling and stable isotopes (2H and 18O) for isotope investigations. SWAT-MODFLOW is used to simulate SW, GW, and the interaction between them at the 1452 km2 Shiraz catchment, located in southwestern Iran, for the period 2006–2019. The integrated SWAT-MODFLOW model was compared with the original SWAT to determine the importance of SW-GW interactions in hydrological simulation in the Shiraz water basin. In the absence of filed measurement data, we introduced and use water isotopes as an additional tool to obtain insight into the SW-GW relationship to ultimately improve the model’s performance. We carried out stable isotope investigation to determine aquifer recharge sources and investigated whether insights into the exchange of water fluxes between SW and GW revealed by isotopes improves SWAT-MODFLOW simulation performance. 2H and 18O analysis determined the relative contribution of different sources to aquifer recharge and identified areas with high SW-GW interaction. The critical information obtained from the isotope investigations was then embedded into SWAT-MODFLOW and used to calibrate SWAT-MODFLOW parameters related to interchange fluxes between SW and GW. The results show that (1) SWAT-MODFLOW not calibrated with isotope data performs better than SWAT alone (R2 improvement from 0.50 to 0.54), and (2) SWAT-MODFLOW calibrated with isotope data (SWAT-MODFLOW-ISO) performs significantly better than SWAT-MODFLOW (R2 improvement from 0.54 to 0.68 and RMSE reduction from 1.67 m to 1.33 m). This demonstrates that insights from isotopes can improve our conceptual understanding of SW-GW interactions and, consequently, improve the accuracy and reliability of SW-GW model simulations. This thesis also introduces a ‘GW Calibrator’ (GWCal), which is a code to calibrate GW parameters in SWAT-MODFLOW. GWCal significantly reduces the time and effort involved in calibrating SWAT-MODFLOW meaning it is efficient to conduct a comprehensive sensitivity analysis (SA) for both SW and GW parameters which provides useful insights into what controls runoff and GW levels in the study catchment. The SA reveals that the curve number (CN) and GW hydraulic conductivity (K) parameters have the most significant impact on runoff and GW level simulation. This enabled the development of a framework to conduct a site-specific test of the physical as well as statistical ‘reality’ or ‘accuracy’ of the SW-GW simulation. The insights and tools developed from this thesis will assist decision-makers when developing policies and programs aimed at sustainable water management under current and future hydroclimate conditions as well as current and future demand for water. The approach developed in this research is transferable and can be readily applied in other locations.
- Subject
- surface water; groundwater; interactions; water isotopes
- Identifier
- http://hdl.handle.net/1959.13/1509528
- Identifier
- uon:56255
- Rights
- Copyright 2021 Tina Jafari
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 8 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 341 KB | Adobe Acrobat PDF | View Details Download |