One of the results of the European project "PIRAGUA - Assessment and prospective evaluation of water resources in the Pyrenees in the context of climate change, and adaptation measures with territorial impact" was the implementation of the WEAP-Andorra model. This model represents the hydrological cycle and the management of the country's water resources, making it possible to estimate flows at different points in the Valira river basin [1]. The current project focuses on maintaining, updating and using the WEAP-Andorra model to support water resources planning in Andorra.

Modelling of water resources and their future development is addressed using the integrated hydrological simulation tool WEAP (Water Evaluation and Planning), developed by the Stockholm Environment Institute. WEAP allows analysis of sectoral demand, water conservation, water rights, allocation priorities, streamflow simulations, reservoir operations, hydropower generation, pollution loads and cost-benefit analysis of projects. Based on the fundamental principle of water balance, WEAP can be applied to a single basin or to complex transboundary river basin systems. In addition, WEAP can simulate a wide range of natural and engineered components within these systems, including rainfall runoff, base flow and groundwater recharge from precipitation.

In the case of WEAP-Andorra, it estimates the water balance in the Valira river basin (considering second-level basins) from 2015 to 2050 at a monthly time interval. The main algorithm of WEAP is a spatially resolved water balance that balances water supply and demand at each node and connection within the system [2].

Currently, WEAP-Andorra allows for future flow projections under different scenarios. Some examples of these scenarios are the increase or decrease in population and consumption, changes in temperature, fluctuations in demand from the tourism sector, the regulation of different ecological flows and the introduction of drought periods, among others.

This is a live model designed to study the effects of global change on the streamflow of Andorran rivers, water demand and supply [3]. The aim of this project is to maintain and improve it over time, providing useful results not only in the field of research, but also to support studies by consultants or engineers in the country, as in the case of carrying capcity studies in the andorran municipalities [4], [5].



[1] O. Travesset-Baro, M. Domènech, C. Pesado-Pons, M. Pons, "Evolución de los usos de los recursos hídricos y posibles tensiones bajo escenarios de cambio climático en Andorra", Actividad 4.7- Desarrollo y puesta en marcha de estrategias de adaptación, 2022.

[2] B. Höllermann, S. Giertz, and B. Diekkrüger, “Benin 2025—Balancing Future Water Availability and Demand Using the WEAP ‘Water Evaluation and Planning’ System,” Water Resour. Manag., vol. 24, no. 13, pp. 3591–3613, Oct. 2010, doi: 10.1007/s11269-010-9622-z.

[3] M. Domènech, O. Travesset-Baro, C. Pesado-Pons, J. I. López-Moreno, and M. Pons, “Effects of global change on streamflow, water demand and supply: a case study from the Pyrenees”, In review at Water Resources Management, 2024.

[4] M. Domènech, O. Travesset-Baró, Projeccions de cabal a l’horitzó 2050 a diferents conques segons el model hidrològic WEAP-Andorra, 2023.

[5] M. Domènech, O. Travesset-Baró, Projeccions de cabal a l’horitzó 2050 a diferents conques segons el model hidrològic WEAP-Andorra - La Massana, Encamp, Sant Julià de Lòria i Andorra la Vella, 2024.