Senior Groundwater Modeler

Client of Visuna; Medina; On-site; SAR 450,000 - 690,000; Full time

Job summary

Client of Visuna in Medina invites a Senior Groundwater Modeler to lead numerical groundwater modeling and master plan works for a major urban rising-groundwater program. The role owns the integrated modeling system, coupling groundwater with dewatering, wastewater, and overland-flow components, delivering calibration, reliability analysis, and the 2050 Master Plan.

Reporting to the Program Team Leader, you will supervise model assessment, nested child models, sensitivity analysis, and emulator

Qualifications

• 15+ years of regional/nested groundwater modeling experience.
• Postgraduate degree in hydrogeology, hydrology or closely related field.
• Hands-on with MODFLOW-USG and PEST++ for uncertainty analysis.

Responsibilities

• Lead conceptualization, calibration and validation of regional nested models.
• Couple groundwater with dewatering, wastewater and overland-flow systems.
• Develop and hand over a governance-ready decision-support emulator.
• Deliver model assessment, calibration reports and Master Plan outputs.

Skills

Groundwater modeling

Numerical modeling

Python FloPy

MODFLOW-USG

PEST++

Ensemble methods

Hydrogeology

Urban aquifers

Education

MSc or PhD in hydrogeology

Tools

MODFLOW-USG

FloPy

PEST++

ENSI

Job description

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.

Core Responsibilities

3 1 Model Assessment

Conceptualization amp 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

3 2 Neighbourhood Child Models amp 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

3 3 Sensitivity Detailed Construction amp 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

3 4 Integrated Dewatering Network amp 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

3 5 Measures Mega-Structures Calibration amp 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

3 6 Master Plan Emulator Handover amp 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 amp coupling Python FloPy Calibration amp 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

Area

Requirement

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

Reporting amp 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 Minimum experience requirement 15 years

Benefits

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.