Agriculture greatly impacts water resources due to the high volumes of irrigation water consumed in crop production. Additionally, agricultural activities affect hydrological cycles through land-use changes and soil modifications, which may lead to pollution of water bodies. On a local level, these impacts and specific improvement options can be assessed by risk assessment and integrated water resource management. Modelling the impacts of agriculture on freshwater comprehensively is a difficult task as freshwater can be impacted by water consumption and also by water pollution. These are influenced by direct agricultural activities (e.g. irrigation) as well as by indirect activities for the production of agricultural inputs (e.g. fertilizers, agrochemicals). This chapter looks at modelling the impacts of agriculture on freshwater. Following an introduction, the authors go on to look at modelling in relation to water consumption, water quality and salinization. The chapter also covers soil quality, land use and both geographical and temporal variation. Case studies are also included.