Case studies and the design practice driven by digital technologies in public service about environmental protection are probed. The common feature in this field is proposed based on the analysis of five foreign case studies, and then, during the "New Channel•Sanjiangyuan" project, we use observation and face-to-face interviews to understand service users' needs, and conversations among stakeholders are carried out to promote collaborative service system in Qinghai. We finally output the public service system for Qinghai's water management by using digital technologies, and this system includes the product-service system design for local water monitoring, the service platform design and the "water ecology" service network design, and "4open" design method driven by digital technologies is put forward based on previous case studies and design practice.