What are the important parts of the water system?
- London Reservoirs
- Lee Reservoirs
- Groundwater abstraction
- Thames-Lee transfer abstraction
- Thames-Lee transfer connection
- Beckton desalination plant
Demand for water
How much water might we use in the future?
People use water for all sorts of things. If the population of London continues to grow, and if we all keep using more water, the amount of water that we take out of the water system will increase in the future.
Water Futures considers three scenarios of future water demand: low, central and high.
This is another important input to the model. River flows define the amount of water coming into the system. Demand defines the amount of water that we would like to take out of the system.
What could we do in response to how the world might change?
We could build or change different things in the water system. These are the interventions in the first table.
For example, we could build a new desalination plant, which would supply more water to the system. Or we could reduce how much water we use, which would put less demand on the system.
Then we need to make a plan which includes some of these interventions.
For example, in ‘Reuse and Reduce’ we plan to reuse 100 Ml of water per day, and reduce demand by 67 Ml per day.
The plans described in the second table can all be tested in the Water Futures model with near future flows and high demand – otherwise we assume no change from the current system.
Do we need to do anything different in the future? If so, what should we do?
After running the model hundreds of times, we can compare the various scenarios and plans.
The expected frequency of restrictions is calculated as the number of years in each scenario combination where a restriction level is met divided by the number of years simulated in all realisations of the scenario combination.
For example, we run 100 realisations of the near future, low demand, no change plan. Each realisation models 30 years, making 3000 modelled years. Level 4 restrictions only occur in 6 of those modelled years. So the expected annual frequency is 6 / 3000 = 0.002.
If we compare the no change plan across all other scenarios, we can see that only the low demand, near future scenario is close to meeting regulations. So we may need to do something different in the future.
If we compare how each of our plans perform under the high demand, near future scenario, we can see some variation in performance, with only Reuse, Reservoir and Desalination coming close to meeting regulations. So this plan might be worth exploring in more detail.