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Assessment of the Groundwater in Erbil Basin with Support of Visual MODFLOW

Mustafa Jwan Sabah, Mawlood Dana Khider

Journal of Ecological Engineering

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2024

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Vol. 25, nr 4

203--227

EN

Groundwater stands as a crucial lifeline in numerous regions across the globe, a significance magnified in water-scarce locales like the Middle East. With depleting water resources exacerbated by global climate change, the imperative for sustainable groundwater management becomes increasingly urgent. This research employs a groundwater flow modeling approach, utilizing Visual MODFLOW (version 4.6.0.166), to scrutinize the present state and future security risks of groundwater resources in the Erbil basin. A distinct aspect of this study involves investigating the interaction between the groundwater aquifers of Greater Zab and Lesser Zab Rivers, along with an exploration of the Erbil aquifers, rivers interaction and recharge zones as a second novelty in this research. The model, calibrated for heterogenous anisotropic unconfined aquifer transient conditions, exhibits a high correlation coefficient (CC) of 0.997 during calibration and 0.985 in the validation process respectively. Findings indicate a general groundwater flow direction from northeast to southwest in the Erbil basin, aligning with surface observations. Despite groundwater aquifers supplying only 55% of the current water demand from the existing wells, the computed balance reveals river leakages of 33,432 m3/day into the aquifers. The study forecasts a substantial increase in the dry area of the groundwater aquifer under climate change scenarios, especially when recharge rates diminish. To mitigate these impacts, the study recommends preventing illegal well drilling and implementing continuous monitoring using distributed sensors. The insights gleaned from this research are anticipated to furnish essential information for sustainable planning and effective management of groundwater resources in the Erbil basin and its environs.

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Problem zasobów wód podziemnych

Sadurski A., Śmietański L.

Przegląd Geologiczny

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2015

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Vol. 63, nr 10/2

1047--1052

EN

The term of groundwater resources was introduced to hydrogeology from economic geology similarly to the resources of ore bodies almost hundred years ago. It results years ago from the needs of physical planning, investment in new water intakes and water management. Discussion on the groundwater resources was started in the past after new method of their evaluation, e.g. analytical approaches, physical and then numerical modeling techniques implementation. The ecological aspects of water demands obliges to introduce new idea of quantities of groundwater resources estimation. This idea is also presented in the Water Framework Directive and in the water management planes in the water catchment areas.

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Wpływ uproszczeń modelu numerycznego na symulację odwodnienia budowlanego

Burzyński K., Szpakowski W.

Biuletyn Państwowego Instytutu Geologicznego

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2010

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nr 442 Hydrogeologia z. 11

9--13

PL

Wiele inwestycji budowlanych wymaga przygotowania odwodnienia budowlanego. Najczęstszym sposobem odwodnienia, zwłaszcza rejonów nadbrzeżnych, jest wykorzystanie studni wierconych. Postępowanie takie wymaga zazwyczaj opracowania projektu odwodnienia budowlanego wykopu fundamentowego oraz odprowadzenia wód z odwodnienia w celu uzyskania decyzji wodnoprawnej w trybie ustawy Prawo wodne z dnia 18 lipca 2001 (Dz.U. 2005 nr 239, poz. 2019 z późn. zm.). Obecnie do obliczeń najczęściej wykorzystywane są programy komercyjne wykorzystujące metody rozwiązań numerycznych. Wiarygodność obliczeń wynika z przyjętych uproszczeń zarówno w modelu hydrogeologicznym, jak i modelu numerycznym, a także informacji z badań polowych. W pracy dokonano analizy wpływu zmian parametrów siatki obliczeniowej na ewolucję zwierciadła wód gruntowych podczas odwodnienia.

EN

Many building constructions require a building dewatering. Generally drilled wells are used for dewatering in excavation sites localized near the sea shore. According to the Polish Water Law 2001 (D.U. 2005 no. 239, 2019) elaboration of concrete project of dewatering is required. In actual calculation the governing equations are converted into applicable partial differential equations using a finite-difference approach. The credibility of calculations based on the assumed hydrogeological and numerical simplifications. In this paper the impact of grid dimension on groundwater table was studied.

4

The velocity oriented approach revisited

Nawalany M., Zijl W.

Biuletyn Państwowego Instytutu Geologicznego

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2010

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nr 441 Hydrogeologia z. 10

113--121

EN

A great deal of hydrogeological situations requires an extremely accurate calculation of the 3-dimensional groundwater discharge rates in the subsoil. Examples are: hydrology of wetlands, water balances of aquatic ecosystems depending on groundwater recharge, river-groundwater interaction, advective transport of pollution underneath waste disposal sites, particle trajectories in aquifer-aquitard systems with contrasting heterogeneities and many others. Numerical determination of the vertical groundwater velocity is a notoriously difficult problem. In nature this component may be two or three orders of magnitude smaller than the horizontal velocity components. In such cases application of Darcy’s law to the numerically calculated hydraulic heads obtained from a finite difference or finite element model may lead to relatively inaccurate vertical velocities. More specifically, when estimating vertical velocity components in cases where the Dupuit approximation – negligible vertical head gradient – holds, numerical differentiation of hydraulic heads yields zero vertical velocity. In the 1980s of the last century Zijl and Nawalany proposed to invert the order of calculating the velocity field by eliminating the head from Darcy’s law and to consider the Darcy velocity as the primary variable. For 2-dimensional flow this was already common practice and the challenge was a 3-dimensional extension, which was called the Velocity Oriented Approach (VOA). In two dimensions such methods were conventionally based on a stream function as primary variable. However, at that time application of a 3D stream function was not feasible and, therefore, the Darcy velocity itself was considered as the primary variable. This approach has been proven to yield a high accuracy for all three components of the specific discharge, including the relatively small vertical component, especially in cases where the subsoil is smoothly heterogeneous in the horizontal directions. In the 1990s the mixed-hybrid finite element method was developed. The physical interpretation of this method shows the way how to liberate the VOA from its smoothness requirement by introduction of a practical applicable 3D stream function. In conclusion, the velocity oriented approach indicates a change in paradigm regarding the accurate calculation of specific discharge in groundwater flow.