Certified Professional Horticulturist (CPH) Practice Exam

What influences the rate of water flow in an irrigation system?

1. Water drag across the inside surface of a hose or pipe

2. Quality of water in the aquifer

3. Size of the garden to be irrigated

4. The water-soluble nutrients delivered by the irrigation system

The correct answer is: Water drag across the inside surface of a hose or pipe

The rate of water flow in an irrigation system is significantly influenced by the water drag that occurs across the inside surface of a hose or pipe. This phenomenon, known as friction loss, occurs as water moves through the system, encountering resistance from the surfaces it flows against. The roughness of the interior surface, along with the diameter and length of the hose or pipe, can greatly impact how quickly water can move through the system. A smoother interior surface allows for less resistance and, therefore, a higher flow rate, while rough surfaces increase drag and reduce flow. Additionally, the viscosity of the water and the flow rate itself also interact to affect the drag force, meaning that these factors must be accounted for in designing irrigation systems for efficiency and effectiveness. While the other aspects mentioned, such as the quality of water in the aquifer, the size of the garden, and the nutrients delivered, are important in their respective contexts (for example, water quality impacts plant health and nutrient uptake), they do not directly influence the mechanical movement of water through the irrigation system in the same way that the drag within pipes does.