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Developing groundwater and surface water interaction methods for complex hydrological systems

Methods and models associated with the interaction of surface-subsurface water flow have been widely employed in many environmental studies over the last decade. However, in spite of considerable effort, understanding the impact of both artificial and natural aspects of the connection between surface water and groundwater systems still remains a challenge for groundwater and surface water models. In this doctoral study, two types of complex and integrated problems are identified as knowledge gaps in coupled surface and subsurface flow studies (i) interaction situations that arise from use of artificial drains in agricultural catchments, and (ii) complex flow situations that sometimes arise as a result of a combination of near surface aquifers which are both perched and leaky. The specific objectives of this research project were (1) to improve classical tile drain spacing design methods; and (2) via a case study, to assess the role of semi-impermeable layers influencing the interaction between surface water and a regional groundwater system. To meet the first objective the DrainFlow code is developed. DrainFlow is a new, fully distributed, physically based and integrated surface-subsurface flow code that is designed for water movement in tile/mole drains, open drains, and saturated/unsaturated zones. DrainFlow, applied to examples of drainage studies, is found to be quite flexible in terms of changing all or part of the model dimensions as required by problem complexity, scale, and data availability. This flexibility gives DrainFlow the capacity to be modified to meet the specific requirements of varying scale and boundary conditions as often encountered in drainage projects. In addition, the classical well-known Hooghoudt drain spacing equation is modified. It is shown via comparison with numerical models that the Hooghoudt equation can overestimate water table height and therefore yield drain spacings which may be too wide. The modified expression yields improved accuracy as measured against the numerical reference model. To meet the second objective, the effect of a thin semi-impermeable and fractured layer between two relatively permeable volcanic formations is investigated in an industrial catchment system at Kawerau, New Zealand. It is concluded that subtle near-surface geological features may have a critical role on controlling the volume and pattern of the flow exchange between the surface, subsurface flow and regional groundwater systems. This doctoral thesis overcomes some weaknesses of isolated surface and subsurface flow models and some constructive and practical approaches are developed to enhance the previous methods.
Type of thesis
Shokri, A. (2016). Developing groundwater and surface water interaction methods for complex hydrological systems (Thesis, Doctor of Philosophy (PhD)). University of Waikato, Hamilton, New Zealand. Retrieved from https://hdl.handle.net/10289/10689
University of Waikato
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