Senior Groundwater Modeler

We are seeking a Senior Groundwater Modeler to lead the numerical groundwater modeling and Master Plan works of a major urban rising-groundwater program.

The role owns the integrated modeling system in which a groundwater model is coupled to the dewatering, water-supply, wastewater and overland-flow systems that drive rising shallow water tables, delivering the calibrated model, reliability analysis, the 2050 Master Plan and the governance-controlled decision-support tool handed over to the client.

The modeler reports to the Program Team Leader and interfaces with the wider program team responsible for monitoring, database/GIS, tender packages and water-balance studies.

A minimum of fifteen (15) years of professional experience in regional and nested numerical groundwater modeling is required. Candidates below this threshold will not be considered.

• 15+ years delivering regional and nested (parent-child) groundwater models for government, urban-water, mining or infrastructure projects.
• Postgraduate degree (MSc or PhD preferred) in hydrogeology, hydrology, water resources or a closely related discipline.
• Demonstrated expertise in MODFLOW-USG (or an approved equivalent): unstructured-grid support, Newton solver, and the Connected Linear Network (CLN) package for 1D pipe/canal coupling.
• Proven PEST++ highly-parameterized ensemble calibration and uncertainty analysis (IES / ENSI); reporting predictive uncertainty as P5 / P50 / P95 bounds.
• Hands-on Python / Flo Py automation for model construction, coupling, batch execution and post-processing across multiple child models.
• Direct experience with carbonate, fractured and urban aquifer systems and representing infrastructure leakage and drainage as explicit model stresses.
• Experience building governance-controlled emulators / decision-support tools for non-specialist users, with protected calibrated parameters and full run auditability.
• Track record of client-facing delivery, review-ready model documentation, and training of client staff.

• Assess and select the model suite (water-balance, groundwater, 1D dewatering/wastewater/water-supply, 2D-overland, integrated) and document a Model Assessment Report for client approval.
• Consolidate the Riyadh hydrogeological conceptual model (regional hydrostratigraphy, gaining/losing wadi behavior, fracture corridors, urban recharge/drainage) defining layout, model area and input parameters.
• Select and secure approval of open-source modeling software provided to the client free of license cost; build preliminary (uncalibrated) models to expose data gaps and inform the survey plan.

• Develop twelve high-resolution child models — one per water-balance area — nested in the regional parent to quantify urban recharge and produce a defensible city-wide recharge parameterization.
• Calibrate child models against groundwater levels, drainage flows and water-balance consistency, focusing on leakage fractions, hydraulic conductivity and drain conductance.

• Run sensitivity analysis on all input parameters (local Jacobian-based and global ensemble screening) to rank controls and prioritize data acquisition.
• Construct the detailed integrated models and validate them against existing observations and known system behavior prior to calibration.

• Couple the groundwater core to 1D dewatering pipes/canals (CLN / DRN / RIV) and represent water/storm/sewer network leakage so groundwater response to each network is explicitly defined.
• Route rainfall-runoff via 2D-overland or…