The Great Lakes are surface-water bodies that influence and are influenced by ground water. Ground-water/surface-water systems that were fairly stable under natural, pre-pumping, conditions, often change dramatically when subjected to pumping. In the introductory material linked to this page, the behavior of natural ground-water systems and their connection to surface-water bodies are first presented, then the effects of pumping wells on natural flow are illustrated.

• Schematic flow system
• Natural recharge to ground water
• Natural discharge of ground water
• Surface-water and ground-water divides
• Effects of pumping on shallow and deep water levels (drawdown)
• Sources of water to wells
• Effect of pumping from wells on ground-water divides
• Effect of pumping from wells on direct and indirect ground-water flow to a Great Lake

Each conceptual discussion is linked to corresponding material from the case study.

To first concept -- > Schematic flow system