Hydrological Modelling for Informed Water Resource Planning and Investments

Water security
Yemen

Yemen faces declining agricultural productivity and rising malnutrition of people due to an extreme pressure on water resources. This is caused by the arid climate, limited and uneven rainfall, and increasing water demand. A basin-wide SWAT model (Soil Water Assessment Tool) was developed for the Wadi Tuban catchment in southern Yemen. The applied modelling approach provides a first estimate of the water balance and key hydrological processes.

Observed streamflow conditions in the wadi during the field visit in Tuban, Yemen.

Key Takeaways

  • Targeted monitoring is essential to resolve groundwater sources and dynamics.
  • Rapid groundwater decline and salinization threaten water security in the coastal delta.
  • Managed Aquifer Recharge and water harvesting offer promising solutions to increase water resilience.
  • Field surveys and stakeholder engagement improved models and identified interventions.
  • The hydrological models provide valuable first estimate of the water balance and key hydrological processes.

Project Details

Started: 2024 – Completed: 2025
Ref: 251590| Status: Completed
Title: Hydrological Study for Tuban Catchment in Yemen

Background

Identifying areas with potential for water harvesting interventions was one of the objectives in this project, focusing on four key districts. Additionally, the likely impacts of these interventions were evaluated on both upstream and downstream water availability.

The study combined spatial data collection, field surveys, and stakeholder workshops. Local knowledge was integrated into the modelling process to improve model accuracy and relevance. Fieldwork not only refined hydrological simulations but also fostered social acceptance and stakeholder support for defining appropriate water harvesting strategies.

By simulating hydrological processes and estimating water balances under different scenarios, the study provides actionable insights to guide sustainable water resource planning, prioritize water harvesting interventions, and support future investments across the Tuban Basin.

Activities

Given the limited availability of consistent hydrological data across the region, a tiered modelling approach was adopted. This includes both a model covering the entire Tuban catchment, and more detailed models for four targeted districts.

This modelling study combined a reconnaissance-level SWAT model for the entire basin with detailed models for four priority districts: Al-Mawaset, Al-Selw, Al-Musaymir, and Tuban. A coupled SWAT–MODFLOW model in Tuban district further supports analysis of aquifer behaviour. Global datasets and satellite-derived inputs are used for topography, land use, soil descriptions, weather inputs, and evaporation data for model calibration. The detailed district models incorporate field data and stakeholder input, obtained from an intensive 14 day field survey for a deeper analysis, to better represent irrigation practices, crop patterns, and water infrastructure. They help identify potential zones for water harvesting and groundwater recharge, and offer a strategic basis for planning future interventions.

The models are designed to simulate the effects of water management decisions on water quantity and quality. While not yet ready for site-specific planning, they provide essential guidance for prioritising water resource management actions.

Findings

The modelling results show a strong decline in water availability from the wetter northern uplands to the arid coastal zone, with most rainfall lost to evapotranspiration, underscore the urgent need for water harvesting, storage, and more efficient irrigation practices.

The reconnaissance-scale SWAT model provides the first basin-wide overview of hydrological processes, water availability, and losses in the Tuban Basin. Despite limited field data and restricted access in some areas, the model results supported the development of more detailed district-level analyses, including a coupled surface–groundwater model for the Tuban District.

The study also highlights significant groundwater depletion and increasing salinity risks in the coastal delta area. These challenges underline the need for improved water management practices, including water harvesting, storage, and more efficient irrigation methods.

Although further calibration and monitoring are needed, the models provide a strong foundation for future water planning, research, and capacity development in Yemen.

Project Areas

The Wadi Tuban catchment covers around 7,169 km², including about 700 km² of delta area along the coast. Elevation ranges from 3,209 m above sea level in the highlands down to sea level at the Arabian Sea. The wadi is about 156 km long, running from Ibb in the north, through Taizz in the west, and toward Abawil in the east. It flows into the Arabian Sea near Aden.

The basin includes a wide range of climatic and hydrological conditions, from relatively wetter upland areas to extremely arid coastal environments.

Geographic scope: Regional

Downloads and Links

No downloads or links are available for this project.

In Cooperation With

Commissioned by:

United Nations Development Programme (UNDP)

Funded by:

German Ministry for Economic Cooperation and Development (BMZ)

Project partners:

Acacia Water MetaMeta

Contact

Natalia Ulribe

Hydroinformatics and Water Resources Specialist

+31 6 83 55 95 48
natalia.uribe@acaciawater.com
natalia-uribe-rivera

Related topics

Catchment, Hydrological model, Modelling, SWAT, Stakeholder engagement, Water harvesting, Water interventions

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