What is the purpose of well casing?

The primary purpose of well casing is to support the borehole. Well casings are typically made of steel or other durable materials and are installed to prevent the collapse of the surrounding soil and rock formations into the well. This structural support is essential for maintaining the integrity of the well, ensuring that it remains open for water withdrawal and does not become contaminated by surface runoff or other environmental factors.

In addition to supporting the borehole, the casing also serves several other functions such as providing a barrier to prevent contamination and allowing for the installation of pumps and other equipment within the well. However, the most fundamental role is to ensure the well remains stable, which is why this choice is the correct answer. Enhanced water pressure, drilling facilitation, and contaminant filtration are secondary functions or consequences of proper well casing design but are not its primary purpose.