In this paper we aim to present why catchment systems science is required for understanding and managing catchments to provide multiple benefits; what is required for catchment systems science and how greater levels of catchment system science can be delivered. Catchment systems science requires systems based understanding, monitoring and modelling approaches that provides improved linkages between catchment functioning and facilitate the decision making process through integrative problem solving frameworks. Integrated Water Management is the backbone to the natural system and is key to many catchment functions but as this system sits within a wider 'nexus' of food, energy and social systems it can not be treated separately. To deliver catchment systems science requires systems based integrative research that develops collaborative knowledge based on shared experimental platforms that directly support decision making and problem solving. There is a need to create and support processes that facilitate and harness existing and novel knowledge infrastructure that spans physical, social and digital to help ensure team based integrative research across the natural, social and computer sciences support better decision making in catchments. Good ideas and practise can be expressed through proactive co-designed problem solving. Here we will show examples of in-situ problem solving driven by well-informed local stakeholders and regulators who, by calling on internet technologies, community monitoring and proactive interventions in their own catchments, can start to solve a range of complex issues. Information and debate within a catchment based community can lead to the design, implementation and evaluation of problem solving interventions in the landscape. Understanding where water, food and energy comes from is the first step in shaping this catchment system paradigm. Enlightened and empowered residents can then work within a regulatory framework to address their own issues whilst being sympathetic to other upstream and downstream in the wider system. Examples will be shown include of the establishment wetlands and water storage zones for flood, drought and pollution control. Lessons learned can be quickly taken up and transferred as 'best practise' to others and it can create the evidence base to influence policy making. Even though there is no direct method of evaluating the real impact of on the whole system there is growing confidence that the whole system starts to function better for all who live within that catchment community. Inevitably water resources management and catchment system science is very complex, in fact it is too complicated to characterise in detail or to simulate with accuracy. Uncertainty in decision making and problem solving is currently in-effective as it is not an inclusive or transparent process and mistakes and misapplications are common. Essentially catchment system science and water resources management is lost in a conceptual muddle where information and models confuse rather than empower stakeholders. Here we will present a vision for catchment system science based on a worked example of land use change impacts for flood and pollution control. The need for simple and clear conceptual understanding of the functioning of catchments is key to the approach. Water and its movement in time and space is fundamental to the operation of many aspects of the catchment system and its ultimate health. Policy makers and stakeholders need to understand simple concepts relating to water movement, storage, attenuation and buffering capacity in a catchment. Hence by knowing why and where processes can be changed and by demonstrating that change is viable then catchment science and water management move forward. The system itself may be too complex to quantify or control at the broad scale but numerous small interventions by the residents of the catchment system can slow degradation, balance the need of water, food and energy production, anticipate climate impacts and create local sustainable landscapes. The emergent property is a healthy catchment system.