A water supply based on groundwater is often both economically and environmentally desirable, and many countries rely in part or solely on such a supply. The sustainable development and protection of groundwater resources include integrated groundwater and surface water assessments to ensure that sustainable exploitation of groundwater resources takes place. Model codes support authorities in their evaluations regarding:

• Identification of suitable well field locations, aquifer yields and their roles in the basin water balance
• Estimation of net rainfall and groundwater recharge, delineation of well head protection zones, and expected changes in groundwater recharge and capture zones with changes in water extraction patterns, land use, or climatic conditions
• Environmental impacts of groundwater developments on surface water depletion and degradation
• Evaluation of leaching risks for diffusive pollution (nutrients and pesticides) and leaching risks from point sources
• Seawater intrusion
• Impacts of industrial activities, e.g. mining.

Detailed groundwater models, which can simulate flow in two or three dimensions, provide the means to build large regional-scale models without losing local precision where necessary.

(GWP 2013b)