3 research outputs found
Multi-regression analysis between stable isotope composition and hydrochemical parameters in karst springs to provide insights into groundwater origin and subsurface processes: regional application to Lebanon
No full textJoint applications of isotope characterization using δ2H, δ18O and geochemical analyses have allowed for a better conceptualization of hydrological systems and helped in the evaluation and management of water resources. Processes of infiltration, and evapotranspiration (ETP), as well as mixing in the unsaturated zone, incur changes in the meteoric δ2H-δ18O signal that is transferred to groundwater during recharge. Previous studies on the isotopic composition of atmospheric precipitation highlight the importance of rainwater differentiation in terms of chemical composition and isotopic signature as a function of topographical and orographic variations as well as natural and anthropogenic impacts and identified altitude gradients for both δ2H and δ18O. In this work, a comparative correlative analysis of stable oxygen and deuterium isotopes was conducted on selected Lebanese springs. At the first stage, a hydrochemical analysis allowed the characterization of the springs and their clustering according to their predominant ionic content and aquifer units. Additionally, a multi-regression analysis reveals a relationship between hydrogen and oxygen isotopes and other easily measured parameters at the spring such as temperature, electrical conductivity, elevation, and easting and northing. The obtained relationship validated on a second campaign was attributed qualitatively to the extent and elevation of the spring catchment, the depth of flow, mixing, the snow effect, and residence time. Moreover, outliers characterized by a very large catchment area or allochthonous recharge could be outlined in the set of investigated springs. The results show that the stable isotopic signature indicative of recharge areas can be inferred based on easily measured spring parameters and can, therefore, help in the identification of protection zones and direct areas of spring recharge from a regional dataset. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature
Integrated Numerical Modelling of Groundwater Flow in the Upper Litani Basin: Testing the Need of Managed Aquifer Recharge
No full textAlameddine, Ibrahim
Salah, MohamedGroundwater resources management has been a growing concern as the consequences of climate change and other anthropogenic forces have heavily impacted freshwater resources, especially in semi-arid regions. The adoptions of managed aquifer recharge (MAR) remains at its earliest stages of assessment in developing countries such as Lebanon. Regional conflicts and the current refugee status have amplified the need for accessible uncontaminated freshwater resources in the semi-arid Bekaa region. At a pilot scale, this thesis investigates the hydraulic properties of a well drilled in the Miocene alluvial consolidated deposits in the Litani Basin, Bekaa in Lebanon, which is
devised to store surface runoff during the winter, to be utilized for agricultural irrigation purposes in the summer (Aquifer Storage and Recovery scheme). The small scale subsurface characterization of aquifer properties was done using grain size analysis of borehole cuttings and several pumping tests to assess transmissivity in the recharged aquifer at the borehole scale. In the latter case, water availability poses a challenge on the sustainability of MAR. To answer this question, an integrated hydrological model was constructed and calibrated using MIKE SHE (DHI, 2017a) for the entire Upper Litani Basin (ULB) catchment to simulate flow in steady-state for the years 1970 and 2010 based on existing water level data to evaluate the water balance in the area including lateral and return flow and recharge to groundwater) in comparison to pumping and river exchange. Transient flow was simulated to assess the degree of groundwater depletion, the availability of water resources, and recharge during high
flow periods while accounting for the different hydrological components; namely climate, river, saturated and unsaturated zone. The model serves as an integrated decision support tool to predict the change in groundwater levels in the future under climate change scenarios and to ensure proper sustainable water management. Additionally, the testing of the sensitivity of model output to model parameters will help refine model uncertainty and identifies the need for specific additional measurements to be implemented on the ULB
Hybrid modeling of evapotranspiration: Inferring stomatal and aerodynamic resistances using combined physics-based and machine learning.
No full textScripts for the Hybrid Models used in the paper " Hybrid Modeling of Evapotranspiration: Inferring Stomatal and Aerodynamic Resistances Using Combined Physics-Based and Machine Learning"
By ElGhawi, R., Kraft, B., Reimers, C., Reichstein, M., Körner, M., Gentine, P., & Winkler, A. (2022)
Preprint can be found here: https://doi.org/10.1002/essoar.10512258.1
The repository can be accessed here: https://github.com/relghawi/Hybrid_ET.git
The datasets used cannot be shared but all datasets are referenced in the paper. The simulated variables are available and linked in the paper.
We share the code for transparency and to demonstrate the concept of hybrid modeling. However, the code is tweaked to our environment and data infrastructure, it cannot be run without adaptions.
All data paths need to be adapted to your data infrastructure.
Structure
Data preprocessing of the individual datasets: `Hybrid_ET/Preprocessing/`
Data is compiled into a "netcdf" files using `Hybrid_ET/Preprocessing/Flux_mult.py`.
The standard hybrid model can be found here: `Hybrid_ET/Models/Under-constrained hybrid model.py`
The hybrid model is trained `Hybrid_ET/Training/train_hyb_uncon.py
