Beyond the determination of who does what, the challenge lies in the problems of overlapping responsibilities generated by interpretation and implementation of water policy on the ground. In addition, both ministries are required to co-operate on some areas, given the interdependence of issues such as climate change, spatial planning, roles of water districts, agencies, organisations and the need to address issues of quantity and quality collectively. On average, domestic water services usually involve the highest number of ministries, public agencies and departments, because of the externalities of water supply on other policy areas (e.g. education, health, etc.)