(SEM-VII) THEORY EXAMINATION, 2017-18 ENGINEERING HYDROLOGY

SECTION A

(Short questions – clear explanation)

1. What do you understand by precipitation?

Precipitation is the process by which water in the atmosphere falls to the earth’s surface in liquid or solid form. It includes rainfall, snowfall, sleet, and hail. Precipitation is the primary source of water for rivers, lakes, groundwater, and reservoirs. It plays a very important role in the hydrological cycle and directly affects runoff, infiltration, and water availability.

2. Distinguish between infiltration capacity and infiltration rate.

Infiltration capacity is the maximum rate at which soil can absorb water under given conditions. It depends on soil type, vegetation, and moisture content. Infiltration rate, on the other hand, is the actual rate at which water enters the soil during rainfall. The infiltration rate can never exceed the infiltration capacity and usually decreases with time during a storm.

SECTION B

(Medium questions – conceptual explanation)

3. What is meant by hydrological cycle? How can the parameters of the cycle be written in equation form?

The hydrological cycle is the continuous movement of water between the atmosphere, land surface, and underground. It includes processes such as evaporation, condensation, precipitation, infiltration, runoff, and groundwater flow. The hydrological cycle can be expressed using the water budget equation, which states that precipitation is equal to the sum of runoff, evapotranspiration, and change in storage. This equation helps in understanding and managing water resources in a catchment.

4. What is meant by design flood? Explain the factors affecting the flood hydrograph.

A design flood is the maximum flood discharge considered for designing hydraulic structures such as dams, bridges, and spillways so that they remain safe during extreme flood conditions. Factors affecting the flood hydrograph include rainfall intensity and duration, catchment area, shape and slope of the basin, soil type, land use, and drainage density. These factors influence the peak flow, time to peak, and shape of the hydrograph.

SECTION C

(Long questions – detailed explanation)

5. Explain both types of rain gauges: Automatic and Non-automatic rain gauges.

A non-automatic rain gauge measures only the total rainfall over a period and requires manual observation. Examples include the Symons rain gauge, which is widely used in India.
An automatic rain gauge records rainfall continuously and automatically. It provides information about rainfall intensity and duration. Examples include tipping bucket rain gauge and weighing type rain gauge. Automatic rain gauges are useful for flood forecasting and hydrological analysis.

6. What is meant by evapotranspiration? Explain the measurement of evapotranspiration.

Evapotranspiration is the combined loss of water from the earth’s surface through evaporation from soil and water bodies and transpiration from plants. It is an important component of the water cycle. Evapotranspiration can be measured using methods such as lysimeters, pan evaporation method, and empirical formulas like Blaney-Criddle method. Accurate estimation of evapotranspiration is essential for irrigation planning and water resource management.