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UNESCO-IHE Institute for Water Education, Delft (2020)

Groundwater representation in WEAP models : A case study of the Upper Litani River Basin, Lebanon

Hackett, Caroline Croft

Titre : Groundwater representation in WEAP models : A case study of the Upper Litani River Basin, Lebanon

Auteur : Hackett, Caroline Croft

Université de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science (MS) 2020

Résumé
The Upper Litani River Basin (ULRB), Lebanon, plays an important role in the national economy, primarily in the agricultural sector. However, significant quantity and quality problems affect the surface water and groundwater resources in the upper Bekaa Valley, making the Litani a closing basin. Currently, demands that can’t be met by surface water are met using groundwater. The majority of these abstractions are unlicensed and unmetered. Groundwater levels are declining in parts of the basin, and some springs have already dried up. Increasing pressure from a growing refugee population, planned additional interbasin transfers from Qaraoun Reservoir, and climate change are likely to exacerbate the groundwater declines. Future water management of the basin must include policies to maximize conjunctive surface and groundwater use. The Lebanese Ministry of Energy and Water has chosen Water Evaluation and Planning (WEAP) software for water allocation planning, yet the current WEAP model for the Litani basin does not account for groundwater. The performance of the WEAP Groundwater Wedge method and the WEAP Two-Bucket method for the simulation of Litani River streamflow and groundwater levels were compared. The Two-Bucket model outperformed the Groundwater Wedge approach due to the more sophisticated routing of infiltration through the root zone before it recharges the aquifer. A distributed MODFLOW model of the ULRB was also built to compare to the semi-distributed parameter approach of WEAP. The MODFLOW performance was reasonable for a simplified conceptual model of the basin. In addition to the model accuracy, the ease of use of the models was compared. While MODFLOW has the potential to represent complex groundwater scenarios, the limited available data for the basin and the time and expertise required to set up a MODFLOW model make it a second-best choice for the ULRB. The WEAP Two-Bucket method is recommended for future conjunctive water use planning in the ULRB due to its relatively high accuracy in simulating groundwater levels, while minimizing the required human effort and data inputs.

Sujets  : river basins groundwater resources hydrological modelling water resources management Lebanon

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Page publiée le 22 avril 2021