A large majority of national responses (80%) also note that groundwater management is at least partially linked with surface water. It is systematic for most countries or regions with mandatory management plans, but there are exceptions. Countries with no management plans can also have systematic connections, and some regions with mandatory plans only link the two in a limited fashion. Historically, water laws started to focus on surface water because groundwater was less visible and subject to pressure, but as some countries evolved, others lagged behind (Mechlem, 2012).