Upstream Our Client is seeking a Senior Groundwater Modeler for a project in Saudi Arabia.
This is 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 SLB-led program team responsible for monitoring, database/GIS, tender packages and water-balance studies.
Reporting & Deliverables
The Senior Groundwater Modeler reports to the Program Team Leader and is accountable for the Model Assessment Report, conceptual and preliminary models, twelve calibrated child models, sensitivity and validation reports, calibration and scenario reports, the reliability report, the 2050 Master Plan and action plan, the decision-support emulator, and the Task Completion Report — each delivered per the project milestone schedule and to the client’s acceptance.
Core Responsibilities
Model Assessment, Conceptualization & Preliminary Models
- 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.
Neighborhood Child Models & Recharge
- 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.
Sensitivity, Detailed Construction & Validation
- 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.
Integrated Dewatering, Network & Overland-Flow Modeling
- 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 lumped elements for pluvial-flood and early-warning assessment.
Measures, Mega-Structures, Calibration & Reliability
- Assess individual dewatering measures and combine effective ones into approved scenarios, incorporating climate-change impacts.
- Build dedicated sub-models for the Riyadh Metro (~50 stations to ~40 m) and other deep structures, capturing barrier/drain effects and construction dewatering.
- Calibrate detailed models after the first monitoring year using PEST++ regularized inversion; document every calibration step and justify any unmet criteria.
- Run the preferred scenario and deliver a reliability (uncertainty) analysis reporting P5/P50/P95 predictive bounds.
Master Plan, Emulator, Handover & Training
- Produce the 2050 Master Plan: five-year-interval level predictions, critical-area identification, a five-year rolling mitigation project list, and an adaptive management tool.
- Deliver the governance-controlled decision-support emulator (stress-only interface on the calibrated model with archived, traceable runs).
- Install and test all models and software at the client’s head office, verify reproducibility, and train up to five client staff; assess the real-time early-warning system approach.
Technical Environment
The delivered stack is open-source and free of license cost:
- Groundwater core: MODFLOW-USG (unstructured grid, Newton solver, CLN package).
- Automation & coupling: Python / FloPy.
- Calibration & uncertainty: PEST++ (IES / ENSI ensemble methods).
- Surface/network: 1D/2D representation within MODFLOW-USG (CLN/DRN/RIV) or an approved coupled code.
- Deliverable formats: PDF plus editable Word/Excel; GIS/CAD (ArcGIS/AutoCAD, WGS 1984); Primavera schedules.
Key Competencies
Technical depth – Independent construction, calibration and validation of regional + nested urban groundwater models in complex carbonate/fractured settings.
Uncertainty – Fluency in ensemble methods and risk-informed reporting of predictive bounds for decision-making.
Integration – Ability to couple groundwater with piped-network and overland-flow systems rather than treating recharge as assumed.
Tooling – Strong Python/FloPy scripting for reproducible, automated, auditable workflows.
Delivery – Review-ready documentation, adherence to the project sequence, and on time milestone delivery.
Communication – Client engagement, workshop support, and effective training of non-specialist staff.
Minimum Qualifications & Experience
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 / FloPy 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.
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