Flow Building Blocks — Floyd Water Consulting

The building blocks

What they are and why they matter

The five UKTAG building blocks define the components of a naturalised flow regime that must be present downstream of a reservoir for a water body to achieve good ecological potential. They cover minimum baseflow, spring freshets, late summer pulses, autumn and winter flow elevations and annual flood events.

Together they set the standard that reservoir operators must demonstrate compliance with under the Water Framework Directive. This tool was built to make that demonstration faster, more consistent and fully auditable.

Compliance test

Pass or fail on every building block

Upload a daily flow time series and the tool tests it against all five building blocks instantly. Each block is assessed against its seasonal period, flow threshold, minimum event duration and required frequency.

Results show a clear pass or fail for each block with the full working behind every result, so you can see exactly where and why compliance is or is not being met.

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Options engine

Ranked options from failed blocks

Where a block fails, the options engine generates a ranked list of flow regime changes that could bring it into compliance. Options are tailored to your reservoir constraints and the ecological context of your catchment.

This turns a compliance report into an actionable starting point for operating rule development, giving you a structured basis for discussions with the regulator.

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Additional features

More from the tool

Beyond the compliance test and options engine, the tool includes a set of supporting analyses to help you understand your flow regime in full.

Baseline comparison

Runs your natural flow column through the same compliance tests and quantifies the gap between assessed and naturalised flow for each building block.

Year type analysis

Splits the record into dry, normal and wet years and shows how each block shifts across year types, revealing where compliance pressure is greatest.

Configurable periods

Seasonal windows are pre-filled with UKTAG defaults but fully editable so you can adjust to your licence conditions or specific catchment context.

Full audit trail

Export thresholds, daily compliance flags and monthly summaries as CSV. The methodology tab documents every calculation so results are transparent and reproducible.

Flow magnitude, frequency and event stats

For each building block the tool reports the number of qualifying events, their duration and how flow magnitudes compare to the threshold across the record, giving you the detail behind every pass or fail.

Reservoir cost breakdown

Quantifies the volume of water associated with meeting each failed block, giving an indicative cost of compliance in operational terms and a basis for comparing options.

FWC services

Need more than the tool?

The tool handles building block compliance. For full HMWB characterisation, designation review, ecological impact assessment or WFD reporting, FWC provides tailored consultancy including custom analysis built around your specific catchment, licence conditions and operating constraints.

Discuss your project

Flow Building Blocks Tool