Wastewater systems are increasingly challenged by tightening permits, emerging contaminants, and rising expectations for environmental protection, resilience, and sustainable performance. Conventional end-of-pipe treatment approaches are often capital-intensive and not always the most proportionate solution for complex, variable contaminant risks. This paper presents Catchment Control as a proven, science- and intelligence-led Source–Pathway–Receptor (SPR) control model that applies scientific method to wastewater systems — forming hypotheses, testing them through mass-balance and hydraulic analysis, and intervening only where evidence demonstrates risk. Integrating hydraulic modelling, flow-weighted load assessment, network intelligence, and investigative field techniques, the approach distinguishes structural (normal) contaminant behaviour from abnormal events, enabling defensible source attribution rather than correlation-based assumptions. Multiple intelligence streams — including operational data, monitoring analytics, site intelligence, and stakeholder insight — are triangulated to strengthen the evidence base and improve confidence, supporting a “food-factory” process-control mindset underpinned by control-room visualisation, early-warning indicators, and tiered escalation to enable timely, proportionate intervention across wastewater, catchments, and bioresources. Operational case studies at large wastewater treatment works, including Finham STW (Coventry) and Minworth, demonstrate how this approach has identified controllable upstream sources and stabilised regulatory performance, which we hope will enable the avoidance of costly end-of-pipe solutions through targeted intervention and site optimisation. At Finham STW, this included development of a combined catchment- and site-scale nickel mass balance across wastewater and sludge processing assets serving a population equivalent of approximately 500,000, enabling upstream interactions to be correlated with site sampling and operational data and supporting a wider range of proportionate intervention options beyond full end-of-pipe treatment. Catchment Control is designed as a continuous-improvement operating model, not a static solution. Baselines, assumptions, and controls are routinely refined to remain aligned with evolving regulation, scientific advancement, monitoring innovation, and changing catchment risk — integrating engineering, modelling, analytics, operations, and environmental protection into a single adaptive strategy that supports asset resilience, zero-pollution ambitions, and future-ready wastewater management.