Anglian Water Services used Hydro-Logic® Aquator to run the Third Dry Winter modelling project, resulting in drought impact analysis that informed water supply and resilience planning for the Ruthamford supply network. 

Situation

The Ruthamford water supply network was originally developed during the 1970’s to accommodate the growth areas around the town of Milton Keynes, the largest town in Buckinghamshire. However, with the East of England being the driest part of the UK and also one of the fastest growing, Ruthamford faces additional pressure to supply population in the Anglian region.

The Ruthamford system is a “conjunctive use water resource system”; such systems contain multiple sources of supply, impounding reservoirs, pumped storage reservoirs, river networks, water transfers, abstractions, treatment, and delivery to multiple demand centres. When the region experienced a severe drought in 2011/12, there were severe impacts on the reservoirs that feed the Ruthamford supply system, including Rutland Water, Grafham Water and Pitsford reservoir.

Prompted by this drought, which affected the entire Anglian region, Anglian Water Services (AWS) determined the need for a project to model drought scenarios to enable planners to manage water supply and drought resilience in the event of future, more severe drought events.

Problem

In response to the drought, AWS launched the “Third Dry Winter” modelling project, intended to examine the impact of severe and extreme third dry winter droughts on the company’s Ruthamford system and the relative deployable output (DO).

There were a number of specific characteristics that made the project particularly challenging, however:

• The model had to be built and validated entirely using observed data
• The analysis needed to assess the impact of a completely new resilience system in Ruthamford
• In order for the analysis to be reliable a very high number of scenarios had to be investigated, with some 200 drought scenarios across three different DO assessment scenarios had to be considered (E&W DO without LoS restriction, E&W DO with LoS restriction and Scottish DO with LoS restriction)

Solution 

AWS engaged the Hydro International Data, Insight & Analysis team to run a Hydro-Logic® Aquator modelling project. The team adopted a stage approach to the problem, identifying three major steps: model construction and validation; model verification and DO assessments; and third dry winter DO assessments and evaluation.

Stage 1

The model was built using information from the existing MISER model, technical maps and records of time dependent and non-time dependent parameters. This stage also included the validation of the model for the dataset from 1994 to 2009.

The validation was based on the comparisons of model results and observed time series data associated with reservoir storage / drawdowns, water treatment works and supply, and river flows.

Stage 2

In addition to initial comparisons of model fit to develop the model in Stage 1, the Hydro International consulting team also carried out further model verification specifically against records during the 2011/12 drought.

For the model verification, the team made use of observed storages, inflows and demands during the two dry winter drought of 2010/12. The validated Aquator model was used to generate baseline deployable output (DO) estimates for the Ruthamford system, and the Ruthamford North and South resource zones.

Stage 3

Using the Standard Evaporation and Precipitation Indices (SEPI) metrics provided for the project, the team developed a project drought classification scheme to facilitate screening of the key drought scenarios investigated through the project.

A total of 600 DO analyses was used to complete the third dry winter evaluation. The team used Hydro-Logic® Aquator XM, which allows batching of model runs and scenarios, to generate hundreds of remote virtual machines to work in parallel, completing the analysis in a fraction of the time that would have been required using a single local Aquator machine.

About Hydro-Logic® Aquator XM 

The prior screening of drought scenarios is often a sensible approach that can save a significant amount of money and time in completing assessments of severe or extreme drought resilience. This allows shorter model runs, by grouping droughts of similar length, severity and geographical spread, to allow a representative sequence with a range of events to be developed (as opposed to running lots of separate scenario sets).

The distributed computing operated through Hydro-Logic® Aquator XM, enhanced by the cloud capacity to generate several virtual machines, allowed this analysis to be delivered on time and with a reasonable cost. For example, a single analysis was completed in an average time of 50-60 minutes versus the 1 day estimated for the E&W DO assessments without XM, while for the Scottish DO analysis an average time of 300 minutes has been registered against the 5 days estimated for the analysis without XM.

Hydro-Logic® Aquator XM (eXecution Manager) is a control program add-on for undertaking different types of analysis based on Hydro-Logic® Aquator water resource system models. XM can execute multiple instances of Hydro-Logic® Aquator simultaneously to complete the analysis in a shorter time than would be possible using a single instance of the software. Aquator XM has also proved to be a fundamental tool to integrate Aquator for climate change investigations in other projects.

Outcome

Hydro-Logic® Aquator proved to be a remarkable tool to support water supply companies in estimating the impacts of different droughts and the recovery effect of system resilience.

The modelling project concluded that the impact of severe and extreme third dry winter droughts on the Company’s Ruthamford system was significant. Drought impact on the system’s supply capability ranges from 72 Ml/d (severe drought) through 96 Ml/d (extreme drought) to 186 Ml/d (very extreme drought).

This knowledge was then in turn used to inform ongoing planning activities.