Integrated river catchment management planning seeks to balance many demands on the water and land, to protect water resources and ecology for the benefit of the economy, society and the natural world. Third sector organisations have a key role in this process - providing both the practical delivery of river restoration work, and an 'honest broker' role between government, private sector interests and local communities, to try and balance these often conflicting interests in a sustainable catchment plan. However, access to the complex evidence, software models and datasets, which are required for strategic environmental management planning, can be difficult for the third sector and community groups, due to reasons such as cost, licensing restrictions or technical capability. As the umbrella organisation of the rivers trusts movement in England, Wales and Northern Ireland, The Rivers Trust has been exploring the potential for open source software and datasets to improve the sharing of information and evidence with a range of stakeholders in the catchment management planning process. A web GIS application for identifying and prioritising barriers to migratory fish (based on Geoserver) and an application to identify sources of diffuse sediment pollution (built on SAGA GIS) will be demonstrated, and plans for future development of open source tools and data sharing is discussed.