Study of water resources by using 3d groundwater modelling in Al-Najaf region, Iraq

Groundwater is a vital water resource in many areas in the world, particularly in the Middle-East region where the water resources become scarce and depleting. Sustainable management and planning of the groundwater resources become essential and urgent given the impact of the global climate change. This research will use a new hydraulic conductivity estimation “Distributed Value Property Zones” approach, which is integrated into a state-of-the-art computer model—the Visual MODFLOW (version 4.6)—to assess the current state of groundwater resources and the risk of future water resource security in the region centred at Al-Najaf province, which is located in the mid-west of Iraq and adjacent to the Euphrates River. It will also explore and assess the groundwater aquifer-Euphrates River interaction. The impact of the interface soil layer located between the two soils of Al-Najaf region aquifer is studied, which is considered to be the second novelty in this research. The model is calibrated both statically and dynamically. The new hydraulic conductivity approach is highly improved the calibration process, particularly the dynamic process. Where, the application of the dynamic calibration with a 16.5 mm/year recharge rate shows the best correspondence with the field observations. After considering the new approach, sensitivity analysis and validation process are also carried out to evaluate the behaviour of the model, which reveals acceptable convergence. Ignoring the interface soil layer from the conceptualisation process and considering the aquifer as one layer only has affected the model’s results. Specifically, only 0.24 km2 dry area appears in the aquifer as compared with the current state’s results of the groundwater aquifer when the interface soil layer is modelled. In addition, the Euphrates River leakage results are different due to the impact of the interface soil layer when compared with those results when ignoring it from the modelling process. Calibration is also affected. The calculated heads were high and dispersed when compared with those heads when the interface soil layer is modelled. This affects the accuracy and acceptability of the model’s calibration results. The results of the current state of Al-Najaf region show a general flow pattern from the west to east of the study area, which agrees well with the observations and the gradient of the ground surface. With the current discharges taken from 69 wells in the study area, a dry area is found in the top and bottom layers, which equals 39 km2 and 1.32 km2, respectively. This indicated a degree of insufficiency of water resources in the study area because the groundwater aquifer supplies only 84% of the current water demand from the pumping schedules. The computed groundwater balance shows that the Euphrates River supplies water of 5354 m3/day into the groundwater aquifer, instead of gaining water from the recharge of 23527 m3/day if no water is pumped from the wells. The predicted impact of climate change cases concludes that the largest effect on the groundwater-Euphrates River connection is when reducing the recharge rate and the western constant head. In particular, the groundwater aquifer's dry area will increase dramatically and will reach 150 km2 and 120 km2 in the top and bottom layers, respectively. The Euphrates River will also suffer hugely through the loss of 14100 m3/day due to the reduction of either the recharge rate or the western constant head. Increasing the pumping schedule for future use will also impact on both the groundwater aquifer and the Euphrates River. Reducing the Euphrates River level by 0.5m or 1m will slightly affect the leakage from the river and the study area's dryness. To control the impact on the groundwater aquifer and its connection with the Euphrates River, it is highly recommended to remove some wells from the pumping schedule and reduce the pumping rate of the other wells, and constantly monitoring the behaviour of both over time. It is expected that the results obtained from the study can provide important information for the sustainable and effective planning and management of the groundwater resources for Al-Najaf City and the surroundi

Urban Hydrogeology Studies

Urbanization worldwide is a pervasive phenomenon of our time, and sustainable urban development is one of the greatest challenges faced by the contemporary world. The subsurface plays a range of roles in such developments through the complex processes of urbanization, including building development, constructing roads, and providing water supplies, drainage, sanitation, and even solid waste disposal.Urban groundwater problems are usually predictable; however, they are not predicted early enough. During recent decades, progressive advances in the scientific understanding of urban hydrogeological processes and the groundwater regimes of a substantial number of cities have been documented. This extensive array of subsurface challenges that cities have to contend with lies at the core of the sustainability of the urban water cycle. This is threatened by the increasing scale and downward extent of urban subsurface construction, including utilities (cables, sewage, and drainage), transportation (tunnels, passages), and storage (cellars, parking lots, and thermal energy). The cumulative impact of this subsurface congestion on the surrounding geology, and especially on the groundwater system, has to be constantly studied and addressed.In this volume, key connections amongst urban hydrogeology activities are identified as being consistent with scientific results and good practices in their relationship to subsurface data and knowledge on subsurface systems. The volume supports a useful dialogue between the providers and consumers of urban groundwater data and knowledge, offering new perspectives on the existing research themes