The Water Model for SUNEX is a computer-based model to help assess future water demand position in a region using the end-user approach beside addressing its current supply options and their possible future development.

All data are considered as a region-specific and a model specific. The region-specific data include current population and its expected future growth rates, economic growth data and non-household customers data. The water model-specific data include also data related to water supply only and leakage data. These data are not directly linked with population´s figures.

Water Demand Side

Total Water demand is disaggregated into domestics (households) use, commercial (non-households) use and leakage.

Domestic Use

  • Measured Household – Population
  • Unmeasured Household – Population
  • Measured Household – PCC
  • Unmeasured Household – PCC
  • Measured Household – Consumption
  • Unmeasured Household -Consumption
  • Total Household Consumption
  • Heating Water Energy Consumption

Commercial Use

  • Measured Non-Household – Population
  • Unmeasured Non-Household – Population
  • Measured Non-Household – Consumption
  • Unmeasured Non-Household – Consumption
  • Total Non-Household Consumption


We will consider various scenarios including two baseline scenarios. The details of the proposed scenarios will be agreed during the stakeholders’ engagement meetings. The following two scenarios are considered as a baseline and will be run independently from any other agreed scenarios:

  1. Business as usual (central estimate)
  2. Sustainable development scenario

Running the model for the above scenarios will allow to contrast and compare the model results with any other scenarios proposed during the stakeholders’ engagement process. The model employs the scenario approach to estimate the water supply and water demand for various end-user in each sector/sub-sector of the economy and society. Each scenario will require estimation or modelling the demographic and economic input data.


Modelling environment and testing

The current model is built in the Excel environment. The model could be moved to the   R environment if required for integration purposes. We do not currently consider using one of the tools for system dynamics approach (i.e. Stella Architect)


Firstly, the model will be tested against Bristol Water forecasts submitted during the Water Resources Management Plan submission to national regulators. During the following model testing steps, data from Berlin, Vienna and Qatar will be inputted to the model and the model results compared and contrasted with Bristol Case study results.

Water Supply Side

There are various monetary costs and energy costs required to treat water from various sources, and these costs are a function of water treatment complexity. These data are available for Bristol Case Study and if possible will be used for other regions too. If the water treatment costs and energy consumption for water treatment data are not available for other cities / regions, then the average values will be used.

For Bristol Water Case study there is a possibility to divide water supply into “bio” water from Mendip and “normal” water from Purton. Mendip water is surface water and does not require very complex treatment whereas Purton Treatment Works treat water that comes from the river abstraction hence the complex and expensive treatment is required. Any other licence related costs for water supply should be included in the model too.

The model considers water transfer from and to the neighbouring water companies. Even if the region is assumed to be self- sufficient when water resources are considered, the potential import/ export options should be considered in proposed scenarios.

Water supply components included in the model


Raw water abstracted by sources

i.e. surface water, river abstraction groundwater


Total raw water imported


Total potable water imported


Total raw water exported

raw exports and non-potable uses


Total potable water exported


Raw water losses, treatment works losses and operational use


Baseline forecast changes to Deployable Output

if known by the company


Change in Deployable Output due to Climate change

if known by the company


Outage allowance

Outage is defined as ‘short-term losses of supply and source vulnerability’. Energy consumption is directly linked with raw water abstraction volume for each source.

Additional supply option

The model assumes that supply may not meet demand at some point over the planning horizon. Hence the following data are introduced:

  • Additional supply option

If the predicted demand is met over the planning horizon, then the above variable is equal to 0.

Additional supply options are any investments that will increase water available for use during the planning horizon and for these investments additional energy requirements, capital and operational costs are captured.

The proposed model is not an optimisation tool hence do not support any decision regarding the investment timings. Various additional supply options can be introduced as scenarios, i.e. additional desalination plant built in 2035, and the results of these scenarios can be compared within FEW nexus aspects.