Water resources, and several water-related sectors such as energy, fuels, industry, agriculture, and the economy are increasingly affected by the evident impacts of climate change on environmental resources and extreme events, issues of ageing and mismanaged infrastructure, natural and qualitative water scarcity, and recent changes such as recession, wars, population movements, increased energy and resources demand, Covid-19.

A multi-objective optimization model for the water allocation from limited resources to meet increasing demands in multiple sectors has been developed, in an attempt to conceptualize the situation described above and balance different goals. We present the conceptual model with its detailed structure, which can be applied for any timespan at a monthly or annual time step. The model considers the following available water supply sources: groundwater, surface water, desalinated water, and treated wastewater. The water uses considered are: domestic (urban), agricultural and industrial sectors. The Goal Programming technique has been used to solve the optimization model, considering different maximization and minimization objectives, as well as the input of stakeholders, as weights of importance to these goals. The decision variable is the volume of water from each source allocated to each user, in a way that minimizes water demand deficits, overproductions in water supply, and exceedances on the available economic resources, based on the supply costs. The water quality is controlled through the allowable quality parameter thresholds per use. The model can be coupled with hydrological models that will estimate the water supply available per source and its quality, the water demand per use, and economic models accounting for the relevant costs.

This model can be tested under different management strategies, or future scenarios (e.g. climate change), by altering certain parameters. The code has been developed in Python, and is expected to be a useful resource for modelers and water planners.