Morphogenic setting and diversity of processes and landforms: The geomorphological regions of Belgium

peer reviewe

Exploring the Role of Land Use evolution in Groundwater Modeling for Sustainable Management: A Case Study of the Lille Metropolitan Area

International audienceGroundwater represents a crucial source of drinking water in the Lille metropolitan area. Despite its importance, the resource is vulnerable to potential evolution of land use: recharge, runoff and evapotranspiration processes in a soil-sealing context and cultural practices, etc... As a result, stakeholders emphasized the importance of exploring the influence of land use on groundwater to ensure sustainable management of the resource and enhance territorial planning. The actual 3D hydrodynamic model useful for the management of groundwater resources (MARTHE code) has a significant limitation in that it does not consider the impact of land use evolution. We propose here to investigate the contribution of a hydrological distributed numerical approach that incorporates land cover data in the groundwater modeling compared to a global approach at the scale of a peri-urban territory. To do so, we use the HELP code by considering the temporal and spatial evolution of land use and their associated characteristics such as vegetation, soil properties to detail recharge and runoff over more than 20 years that we incorporate to the initial groundwater model. At a global scale of the Lille Metropolitan Area, we observed quite similar results on the water balance between the two approaches. However, the hydric components calculated by the model taking into account the land use evolution are drastically different at a local scale. The pertinent modelling approach depends on the study scale and it becomes essential to consider the land use evolution and its associated characteristics to quantify the impact of urban planning

Multi-Annual Dynamics of a Coastal Groundwater System with Soil-Aquifer Treatment and Its Impact on the Fate of Trace Organic Compounds

The combination of managed aquifer recharge (MAR) with soil-aquifer treatment (SAT) has clear advantages for the future sustainable quality and quantity management of groundwater, especially when using treated wastewater. We built a Marthe flow and transport model of an MAR–SAT system located in a near-shore sand aquifer, for quantifying the influence of environmental factors (climate, tides, and operational conditions) on the coastal hydrosystem with regard to the fate of trace organic compounds (TrOCs). The simulations show the impact of these factors on flow rates and dilution, and thus, on the potential reactivity of TrOCs. The dilution of secondary treated wastewater (STWW) is variable, depending on the operations (feeding from infiltration ponds) and on shore proximity (dilution by saltwater). We show that, close to the ponds and during infiltration, the attenuation of TrOC concentrations can be explained by reactivity. At the natural outlet of the aquifer, the simulated average residence times ranged from about 70 to 500 days, depending upon seasonal dynamics. It is important to study TrOCs at site scale in order to anticipate the effect of natural variations on the SAT and on the fate of TrOCs.</jats:p

Comparison of surface and groundwater balance approaches in the evaluation of managed aquifer recharge structures: Case of a percolation tank in a crystalline aquifer in India

International audienceTo face the problem of groundwater depletion, the Indian Government relies on large projects of Managed Aquifer Recharge (MAR). Numerous recharge structures such as percolation tanks exist but the impact of these structures on groundwater resources remains poorly understood. Although the evaporation/infiltration ratio of percolation tanks was determined in several studies in semi-arid contexts using surface water balance methods, few studies evaluated the impact on the aquifer recharge. However, knowledge on recharge dynamics over time and space is essential for (1) the quantitative evaluation of stored water volumes, (2) the identification of beneficiaries (farmers) and (3) the estimation of percolation tanks recharge zone to the extent that is required to define proper management regulations at basin scale. These three points are of prime importance in the case of semi-arid regions where a limited number of rain events determine the water stored over the entire year. Assessment of the stored groundwater is even more difficult in crystalline aquifers due to the heterogeneous structure of flow paths.To date no methodological guidelines exist for local assessment of percolation tanks in crystalline aquifers. In this paper, we develop a method for calculating a local groundwater budget and we compare it with a computed surface balance. The method is applied to a case study in semi-arid crystalline context. From the groundwater balance we draw conclusions on (1) the limited amount of stored water in the aquifer, (2) the delayed recharge of the aquifer highlighting temporary storage/slow groundwater movement in the unsaturated zone and (3) the limited number of beneficiaries in years of medium monsoon rainfall.These results complement the understanding of the hydrodynamic functioning of percolation tanks, and their impact on the local groundwater balanc