A gravity dam is designed to hold back water by relying primarily on its own weight to resist the horizontal pressure exerted by the reservoir. The massive structure creates a downward force that generates sufficient frictional resistance at the base to prevent sliding and overturning. While uplift pressure and water pressure are forces acting on the dam, they are destabilizing forces, not sources of resistance.

The maximum probable flood represents the upper limit of flood magnitude that is physically possible in a given drainage basin. It is calculated by analyzing the most severe combination of meteorological factors, such as intense rainfall and snowmelt, and hydrological conditions, such as saturated soil, providing a conservative estimate for critical infrastructure safety.

The dominant discharge, often associated with the bankfull discharge, is the flow rate that is considered most responsible for shaping the river channel's morphology over time. It is the discharge that effectively transports the sediment load and maintains the channel's characteristic meandering pattern, rather than extreme flood events or average annual flows.

The irrometer is used to measure soil water tension, which relates to hygroscopic humidity and the energy required for roots to extract water. Canopy temperature is measured using an infra-red thermometer, which detects thermal radiation emitted by plant leaves. Atmospheric pressure is measured using a barometer, which balances the weight of a mercury column against the pressure of the atmosphere. These instruments are essential for precision agriculture and environmental monitoring.

An instantaneous unit hydrograph (IUH) is a theoretical hydrograph resulting from an effective rainfall pulse of infinitesimal duration. It represents the response of a watershed to a unit volume of rainfall excess applied instantaneously over the entire drainage area.

An aqueduct is a cross-drainage work where the canal is carried over the drainage. In this configuration, the drainage water flows freely under the canal bed without being under pressure. This is distinct from a syphon-aqueduct, where the drainage water is forced to flow under the canal under pressure.

Irrigation intensity refers to the percentage of the total cultivable command area that is actually irrigated during a specific cropping season. It is a key metric used in irrigation engineering to assess the efficiency of water utilization and the extent of land coverage provided by a given water source or canal system, helping in planning water distribution and infrastructure requirements.

A breast wall is a heavy structural wall placed above the gates of a regulator. Its primary purpose is to act as a barrier against high flood levels, preventing water from spilling over the top of the gates. By utilizing its substantial weight, it resists the hydrostatic pressure exerted by the floodwater, ensuring the stability of the regulator structure.

Khosla's theory is used to analyze the seepage flow under hydraulic structures. The exit gradient, which determines the safety against piping, is calculated based on the geometry of the structure, specifically the ratio of the depth of the cut-off wall to the width of the floor or the base length, often expressed as a ratio involving depth.

Sensitivity is defined as the ratio of the rate of change of discharge of an outlet to the rate of change of the water level of the distributary channel. It measures how effectively an outlet responds to fluctuations in the water level of the parent channel, which is crucial for maintaining equitable water distribution in irrigation systems.