Hydraulics & Water Management Flashcards

The soil infiltration rate determines:

Answer: The maximum rate at which water can be applied without causing surface runoff

The soil infiltration rate (also called intake rate) is the maximum speed at which soil can absorb water. If sprinklers apply water faster than this rate, the excess runs off the surface, wasting water and potentially causing erosion.

When designing a drip irrigation zone, the maximum recommended run length (from the supply point to the last emitter) is limited primarily by:

Answer: Pressure loss due to friction, which causes the last emitters to deliver significantly less water than the first emitters if the run is too long

Drip tubing run length is limited by friction loss along the tube. As water flows through the narrow tubing, pressure drops progressively. If the run is too long, the last emitters receive substantially less pressure and deliver less water, resulting in non-uniform irrigation.

A water audit reveals that an irrigation system is applying 1.5 inches of water per week to a turf area, but the turf's evapotranspiration (ET) rate is only 1.0 inch per week. This situation indicates:

Answer: The system is overwatering by 50%, wasting 0.5 inches per week that the plant cannot use and which may cause disease, runoff, or deep percolation loss

Applying 50% more water than the plant needs wastes water through deep percolation (below the root zone) or surface runoff. Overwatering also promotes shallow roots, fungal diseases, and nutrient leaching. Run times should be reduced to match the ET rate.

What is the 'available water capacity' (AWC) of soil in the context of irrigation?

Answer: The amount of water held in the soil between field capacity and permanent wilting point that is available for plant uptake

AWC is the amount of water stored in the soil that plants can actually extract — between field capacity (maximum water the soil holds after drainage) and permanent wilting point (the point where water is held too tightly for roots to extract). Sandy soils have low AWC; clay soils have high AWC.

A pressure-compensating emitter in a drip irrigation system is designed to:

Answer: Deliver a consistent flow rate across a range of inlet pressures, maintaining uniform application despite pressure variations

Pressure-compensating emitters use a flexible diaphragm or disc that restricts flow at higher pressures, maintaining a constant output (e.g., 1.0 GPH) across a wide pressure range (typically 10-50 PSI). This ensures uniform water delivery regardless of position in the system.

A reclaimed water (purple pipe) irrigation system requires which special considerations compared to a potable water system?

Answer: Purple-colored pipe and components, signage, no cross-connections with potable water, typically no overhead spray in some jurisdictions, and health department permits

Reclaimed water systems must use purple pipe, fittings, and valve box lids to clearly distinguish them from potable water systems. Signage is required, cross-connections with potable water are strictly prohibited, and local health codes may restrict spray methods and setback distances.