What is a Flow and Load Survey?
A Flow and Load Survey measures the volume (flow) and pollutant concentrations (load) of influent entering wastewater treatment works, storm tanks, and catchment areas. It helps water companies and public authorities determine whether infrastructure is operating within capacity, and provides the accurate, high-resolution data needed to plan infrastructure, optimise treatment capacity, and meet regulatory requirements.
Cura Terrae Water delivers flow and load surveys for municipal and regulated utilities – from survey design and installation through to data collection, analysis, and reporting – helping build evidence for AMP, PR24, DWMPs, and WINEP schemes.
Menu of Services
- Feasibility assessment and scoping
- Catchment characterisation
- Equipment specification and deployment
- Flow monitoring (temporary and permanent)
- Load monitoring and composite sampling
- Laboratory analysis (COD, BOD, ammonia, etc.)
- Data validation and QA/QC
- Regulatory reporting
- Long-term trends and performance insights
- Support for WINEP, AMP and DWMPs
To discuss this service, contact Tim Rogers, Sales Manager – Industrial Water, on 0114 272 2270 or tim.rogers@cura-terrae.com.
Feasibility assessment and scoping
Cura Terrae Water begins with a detailed assessment of project goals, whether asset planning, compliance monitoring, growth forecasting or event-based catchment assessment. The team supports clients in designing a fit-for-purpose flow and load survey, aligned with Ofwat and Environment Agency expectations, including consideration of rainfall dependency, seasonal variability, flow balance needs, and access requirements.
Catchment characterisation
Understanding the nature of a catchment is critical to a reliable flow and load survey. Cura Terrae Water characterises inputs including population equivalents (PE), infiltration and inflow, industrial contributions, storm overflow activity, flow splits and returns, and potential misconnections, ensuring collected data reflects true operational performance and supports confident investment decisions.
Equipment specification and deployment
Cura Terrae Water deploys MCERTS-certified equipment to collect high-accuracy flow and quality data across multiple points, including ultrasonic or Doppler flow meters, level sensors, rain gauges, and refrigerated auto-samplers for 24-hour composite sampling. Equipment is installed with robust mounting, battery/solar options, and remote telemetry where needed, ensuring minimal disruption and maximum data integrity.
Flow monitoring: what does it measure?
Flow monitoring tracks both dry and wet weather flows using time- or event-based strategies to understand diurnal patterns, storm responses, and hydraulic loading. Typical flow types monitored include FFT (Flow to Full Treatment), DWF (Dry Weather Flow), storm overflow volumes, return liquors and sidestreams, infiltration contributions, and bi-directional flow conditions. Monitoring durations can range from a few weeks to several months depending on regulatory drivers or planning needs.
Load monitoring, composite sampling and laboratory analysis
To calculate pollutant loading, auto-samplers collect 24-hour composite samples representative of flow variations. These samples are sent to UKAS-accredited laboratories for analysis of determinands including BOD (Biological Oxygen Demand), COD (Chemical Oxygen Demand), ammonia, total suspended solids, total phosphorus and nitrogen, pH, conductivity, temperature, and other consented or site-specific parameters. All analysis follows standard methods and quality assurance procedures, with full traceability and chain-of-custody documentation, supporting load profiling, treatment optimisation, and compliance forecasting.
Data validation and QA/QC
Data validation ensures the integrity of results collected during a flow and load survey. This includes sensor drift checks, cross-verification of flow and rainfall data, statistical assessment of anomalies, and QA procedures aligned to MCERTS and WRc guidance, keeping data regulator-ready and robust for planning purposes.
Regulatory reporting
Cura Terrae Water provides clear, structured reports aligned to regulatory expectations and water company templates, covering a summary of monitoring approach, flow/load data tables, observations and anomalies, flow balance and performance analysis, and recommendations for further action. Reports are suitable for submission under WINEP, PR24 business cases, DWMPs and other statutory processes.
Long-term trends and performance insights
Beyond compliance, flow and load surveys help water companies understand seasonal and weather-related variations, network stress points and overflow behaviour, unaccounted-for flows and infiltration, treatment performance against design capacity, and growth impact on existing infrastructure. These insights feed into resilience planning and investment strategies, including support for WINEP submissions and needs statements, PR24 and future AMP funding cycles, DWMPs, CSO performance tracking and strategy, and treatment works reconfiguration or upgrades.
