Find out about stochastic modelling and how Hydro-Logic® Aquator uses it to deliver reliable, actionable water resource planning insights.
What is stochastic modelling?
Deterministic modelling is a technique in which a future prediction is calculated exactly based upon past events, and no randomness is involved.
By contrast, stochastic modelling is a technique that is used to simulate a range of potential different outcomes that incorporate a degree of randomness or uncertainty. This is particularly important when planning water resources far into the future, which is subject to ‘deep uncertainty’, and where historic datasets may be relatively short in the context of the risks being planned for.
A stochastic model incorporates random probability distribution that may be assessed statistically, but which cannot be used to provide a single, precise output.
Why is stochastic modelling beneficial for water resources modelling?
Water supply networks exist in the real world, which is a chaotic and unpredictable environment. It is simply not possible to predict future events with precision due to the number and complexity of the variables that could influence the shape of those future events.
Climate, population growth and water usage patterns, to name but a few, are all unpredictable factors that will influence future demand for water; these can only be modelled with any degree of reliability by using a statistical probability approach.
What are the strengths of stochastic modelling?
A stochastic model will not produce one single outcome, but instead provides a range of possible outcomes. This is valuable in that it shows analysts a spectrum of probable futures, ranging from best case to worst case scenarios, enabling them to consider and plan for the full extent of possible outcomes.
In addition, stochastic modelling enables meaningful simulation of large, complex systems such as the natural world where the number of variables is high and randomness is a fundamental part of the system.
What are the weaknesses of stochastic modelling?
One weakness of stochastic modelling is, perversely, that it is often prone to being used in a deterministic manner by analysts; this is particularly problematic when considering extremes such as floods and droughts. All statistical models exist as distributions and include some uncertainty, so understanding and using this uncertainty to your advantage is critical to effective modelling. Working with a good modelling partner or experienced specialist consulting team will help to ameliorate this risk.
How is stochastic modelling used for water resource planning?
Modelling tools such as Hydro-Logic® Aquator use vast amounts of data to simulate a range of future scenarios, allowing modellers and analysts to investigate different supply and demand conditions and run “what if” scenarios to inform current and future asset planning, investment and management decisions.
For context, over a series of projects for UK water companies, Hydro-Logic® Services analysts have used as much as 19,200 years of stochastic data to assess how a water system would respond to varying levels of demand across a number of different climatic situations. This vast amount of data improves the reliability of the outcomes.
Stochastic modelling in Hydro-Logic® Aquator
The Hydro-Logic® Services team has extensive experience in completing stochastic Deployable Output (DO) assessments within Aquator XV/XM through distributed computing and tailored setup. This not only includes undertaking baseline stochastic DO assessments, but also those under climate change, to assess the impact of drought measures and water resources options.
In addition to direct Aquator water resources modelling and DO assessments, Hydro-Logic® Services’ experience also extends to data management and post-processing to support the stochastic data process. Macros and post-processing tools have been created to handle the stochastic data / outputs, and bespoke VBA customisation has also been applied to reset the model state, record failure types each day, and to access emergency storage when reservoir levels are low.
Visit the Hydro-Logic® Aquator product page to discover more about how it can help you to make better planning, asset management and investment decisions.
Read our case studies to see how Hydro-Logic® Aquator has helped UK water companies to develop effective water resources plans:
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