Infiltration is the process by which water enters the soil surface, and it is an important aspect to consider in various civil engineering projects such as drainage design, groundwater recharge, and stormwater management. Infiltration rates can vary depending on factors such as soil type, vegetation cover, slope, and land use. To measure infiltration rates accurately, field measurements are conducted using an instrument called an infiltrometer.

An infiltrometer is a device specifically designed to measure the rate at which water infiltrates into the soil. It consists of a metal or plastic cylinder with a known surface area that is inserted into the ground. The cylinder is filled with water and the water level is recorded over time to determine the rate of infiltration.

The field measurement of infiltration is done by an infiltrometer because:

1. Accuracy: Infiltrometers provide accurate measurements of infiltration rates by directly measuring the water infiltration into the soil. This helps in obtaining reliable data for various engineering calculations.

2. Ease of use: Infiltrometers are relatively easy to use and can be quickly installed in the field. They do not require complex procedures or specialized skills to operate, making them suitable for field measurements.

3. Versatility: Infiltrometers can be used in a variety of soil types and conditions. They can be used to measure infiltration rates in both saturated and unsaturated soils, allowing for a wide range of applications.

4. Cost-effectiveness: Infiltrometers are cost-effective compared to other methods of infiltration measurement. They are relatively inexpensive to purchase or construct, making them accessible to a wider range of users.

5. Time efficiency: Field measurements using an infiltrometer can be completed in a relatively short period, allowing for efficient data collection. This is particularly useful when conducting multiple measurements at different locations or during time-sensitive projects.

In conclusion, the field measurement of infiltration is done using an infiltrometer because it provides accurate, versatile, and cost-effective measurements of infiltration rates. This allows for better understanding and management of water infiltration in civil engineering projects.