SGLA LARE Grading, Drainage and Stormwater Management Practice Exam

The correct answer is the type of soil water known as hygroscopic water. This form of water is held tightly to soil particles due to the adhesive forces between water molecules and the surface of the soil particles. Hygroscopic water is usually found as a thin film surrounding the soil grains, which makes it unavailable for plant uptake because it is held too strongly for roots to extract.

In contrast, free water refers to water that exists in the larger pores of the soil and can move freely through gravitational force, making it available for drainage and plant use. Capillary water occupies the spaces between soil particles and is held by capillary forces, allowing for easy access by plant roots. Geosynthetics are synthetic materials used in various civil engineering applications, not a form of soil water.

Understanding the distinction between these different types of soil water is crucial for effective water management in grading and drainage practices, as it impacts both water availability to plants and the design of drainage systems.