It is a branch of civil engineering concerned with water resources. It includes the

study of water quality, quantity, flow, and distribution (hydrogeology) but most commonly refers to flood safety and prevention.

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In the construction industry refers to identifying and understanding how water can affect a building from different sources.

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It can wreak havoc by eating away at a structure over time, costing homeowners even more money.

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It is the science of water.

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It came from the Greek word hudor meaning "water"

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It came from the Latin word logia meaning "science or study of"

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It is the science that deals with the occurrence, circulation, and distribution of water of the earth and its atmosphere.

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It is concerned chiefly with academic aspects.

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It is concerned with engineering application.

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It is based on the sciences of hydrology and hydraulics.

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It is a fundamental factor in designing a drainage system within a specific area.

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This involves studying rainfall patterns, watershed characteristics, soil types, land use, and topography to understand how water moves across the landscape and where it accumulate

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It involves accounting for the inputs, outputs, and changes in water storage within a defined system over a specific period.

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Start by identifying all sources of water entering the system.

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Determine all the ways water leaves the system. OUTPUTS may include evaporation from the soil and water surfaces, transpiration from plants, surface runoff, groundwater discharge, and human withdrawals for irrigation, industrial use, or municipal supply.

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It consider any changes in water storage within the system. This includes changes in soil moisture, groundwater levels, surface water storage in lakes or reservoirs. Changes in storage can be positive (ex. Water accumulation) or negative (ex. Water depletion).

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It plays a crucial role in designing irrigation systems by providing the necessary

information to efficiently manage water resources for agricultural purposes.

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It plays a significant role in assessing the impacts of natural and human-induced environmental changes

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It is a fundamental concept in Earth sciences, explaining the circulation and conservation of water throughout the planet.

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The Italian polymath made significant contributions to the field of hydrology, particularly in conceptualizing the hydrological cycle

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The English chemist and physicist provided

further insights into the hydrological cycle through his research on the behavior of gases and the principles of evaporation and condensation.

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A French Huguenot potter and hydrologist, proposed one of the earliest scientific theories of groundwater movement and the role of precipitation in replenishing underground water sources.

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An American engineer and hydrologist, developed the concept of the "infiltration capacity" of soils and pioneered the quantitative

study of surface runoff and streamflow

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He made significant contributions tom meteorology and hydrology. He proposed a theory of the global circulation of moisture, which laid the groundwork for modern understanding of the hydrological cycle.

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It is the movement of water on Earth and in the atmosphere between

different states.

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The percentage of water on the Earth's surface

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It occurs when water is heated by the sun, changing it from a liquid to a gas that is

known as water vapor.

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The combined process of water evaporation from the Earth's surface, such as soil, water bodies, and vegetation, along with transpiration from plants. Essentially, it's the movement of water into the atmosphere from both the natural surface and vegetation.

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It is the process by which liquid water transforms into water vapor or gas and

enters the atmosphere. It occurs when energy, usually in the form of heat, is transferred to

the liquid water, increasing the kinetic energy of the water molecules. As a result, some of

these molecules gain enough energy to break free from the liquid surface and escape into the

air as vapor.

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It is the process of water vapor being released from plants and soil. Plants

release water vapor through microscopic pores called stomata.

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The process by which water vapor in the air is changed into liquid water; it's

the opposite of evaporation. Condensation is crucial to the water cycle because it is responsible for the formation of clouds

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Provides the input of water to watersheds

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It is the process by which water on the ground surface enters the soil.

Infiltration rate in soil science is a measure of the rate at which soil is able to absorb rainfall or irrigation. It is measured in inches per hour or millimeters per hour.

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It begins when the precipitation rate exceeds the infiltration rate, and retention and

surface storage are filled.

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it is precipitation that soaks into the soil.

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It is precipitation that does not soak into the soil but instead moves on the Earth's

surface toward streams.

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It is water moving across the Earth's surface in streams.

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It is an area of land that drains all the streams and rainfall to a common outlet

such as the outflow of a reservoir, mouth of a bay, or any point along a stream channel. It consists of surface water--lakes, streams, reservoirs, and wetlands and all the underlying groundwater.

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Their important because the streamflow and the

water quality of a river are affected by things, human-induced or not, happening in the land area "above" the river-outflow point.

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It refers to a contiguous area, such that the net rainfall or runoff over that area will contribute water to the outlet. Rain that falls outside the watershed boundary will generate runoff to some other outlet.

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It nourish and connect ecosystems throughout the watershed

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It help to store and filter water, and provide habitat for fish and wildlife.

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It provide habitat for wildlife and nutrients for aquatic ecosystems, and encourage infiltration of rainwater into the ground.

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Their mainly covered in impermeable surfaces (parking lots, buildings, roads,

etc.) causing water to flow quickly across surfaces, picking up debris and pollution, and draining into storm drains which lead directly to waterways including our creeks, rivers and ocean.

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It consist of mature forests, sometimes interspersed with open

meadows. The soil in forests consists of plants, fungi and decaying organic material that soaks up moisture and encourages infiltration.

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t is a plot of flow rate vs. time for a given location within a stream and represents the main hydrologic response function.

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It reflects the rate of change of elevation with distance along the main channel or within an overland flow area. Both slope measures are used in performing unit hydrograph, flood routing, and time of travel calculations.

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It is responsible for developing soils maps to provide information on soil type, soil texture, and hydrologic soil groups.

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It is important in determining water-holding capacity and infiltration capacity of a

soil layer. Thus, sands generally infiltrate water at a greater rate than do silts or clays. Of course, there can be mixtures of sizes, which can complicate the overall soil structure.

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These are in the form of parking lots and urban development, can have profound effects on watershed response. In fact, many of the methods described later were developed to address urban development impacts in a watershed.

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It uses a coefficient C to reflect the runoff potential of a watershed. The value of C for

commercial (0.75) is greater than residential (0.3), which is greater than forested (0.15),

indicating that more intense development generates 90 Urban development is also

characterized by the percent imperviousness, or paved area, which can range from

50% to 90% for commercial compared to 20% to 40% for residential areas. Several of

the unit hydrograph methods contain parameters that relate to urban land use effects.

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It provide a means for evaluating availability and sustainability of a water

supply. It simply states that the rate of change in water stored in an area, such

as a watershed, is balanced by the rate at which water flows into and out of the area.

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It refers to the way snow, droplets of water, sleet, and even hail form and fall out of the

atmosphere to land on the surface of the planet. When warm air rises and cools, water vapor in the sky condenses into minuscule water droplets or ice crystals, starting the precipitation process. Following their collisions, these droplets or crystals may enlarge until they are heavy enough to fall under the force of gravity.

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The temperature of the air affects its capacity to retain water vapor; the colder the air, the less water vapor is held in suspension. A body of warm, humid air that is cooled will eventually become saturated with water vapor, which will condense into liquid or solid water.

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The most common form of cooling is from the uplift of air through the atmosphere. As air rises the pressure decreases; Boyle’s Law states that this will lead to a corresponding cooling in temperature.

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Tiny particles floating around in the air. They could be dust, pollen, smoke, or even salt from

the ocean. When water vapor in the air meets these particles, it latches onto them and forms

droplets or ice crystals. They are commonly less than a micron (i.e. one-millionth of a meter) in

diameter.

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Water or ice droplets formed around condensation nuclei are normally too small to fall directly to the ground; that is, the forces from the upward draught within a cloud are greater than the gravitational forces pulling the microscopic droplet downwards.

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The spatial and temporal distribution of precipitation over a given region results from several

complex causes and interacting processes that are themselves time and space dependent.

Therefore any discussion of precipitation distribution must of necessity address these variations

both in time and space. This can be accomplished by examining the major features of global

patterns of precipitation and the factors that combine to influence those patterns, by looking at

seasonal variations in precipitation distribution to discern major seasonal regimes and their forcing

mechanisms, by considering the nature and causes of the diurnal distribution, and, finally, by

examining distribution from a statistical perspective rather than from a purely climatological one. In

this last case, distribution characteristics such as variability, persistence, frequency, and intensity

become important.

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It has already been explained that temperature is a critical factor in controlling the amount

of water vapor that can be held by air. The cooler the air is, the less water vapor can be held. As

temperature decreases with altitude it is reasonable to assume that as an air parcel gains altitude it

is more likely to release the water vapor and cause higher rainfall.

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The influence of aspect is less important than altitude but it may still play an important part in the distribution of precipitation throughout a catchment. The predominant source of rainfall is through cyclonic weather systems arriving from the west.

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The influence of slope is only relevant at a very small scale. Unfortunately the measurement

of rainfall occurs at a very small scale. The difference between a level rain gauge on a hillslope,

compared to one parallel to the slope, may be significant. It is possible to calculate this difference if

it is assumed that rain falls vertically – but of course rain does not always fall vertically.

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It is an area of significantly reduced rainfall behind a mountainous region, on

the side facing away from prevailing winds, known as its leeward side. Evaporated moisture from water bodies is carried by the prevailing onshore breezes towards the drier and hotter inland areas.

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This is the water that falls to the ground either directly, through gaps in the canopy, or

indirectly, having dripped off leaves, stems or branches. The amount of direct it is controlled by the canopy coverage for an area, a measure of which is the leaf area index.

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It is the rainfall that is intercepted by stems and branches and flows down the

tree trunk into the soil. Although measurements of stemflow show that it is a small part of the hydrological cycle.

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While water sits on the canopy, prior to indirect throughfall or stemflow, it is available

for evaporation, referred to as interception loss. precipitation which is returned to the.

Atmosphere through evaporation from plant. surfaces or is absorbed into the plant.

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In some circumstances it is possible that there is an interception gain from vegetation.

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It is the depth of water that would accumulate on the surface if all the rain

remained where it had fallen.

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A technique refer to the methods used to quantify the volume of

water present, as opposed to estimation techniques where another variable is used as a surrogate for the water volume.

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It measures the volume of water that falls onto a horizontal surface delineated by the rain gauge rim. the volume is converted into a rainfall depth through division by the rain gauge surface area. any errors in measurement will be amplified hugely because the rain gauge collection area represents such a small sample size.

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A rain gauge can be any collector of rainfall with a known collection area; however, it is important that any rainfall that does collect is not lost again through evaporation.

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As the water trickles down the funnel it is inevitable that some water will stay on the surface of the funnel and can be lost to evaporation or not measured in the collection tank. This is often referred to as a wetting loss.

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The perfect rain gauge should measure the amount of rainfall that would have fallen on a

surface if the gauge was not there. This suggests that the ideal situation for a rain gauge is

flush with the surface. In extreme situations it is even possible that the rain gauge could be flooded by water flowing over the surface or covered by snow.

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If a rain gauge is raised up above the ground (to reduce splash) another problem is created due to air turbulence around the gauge.

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Once the best measurement device has been chosen for a location there is still a considerable measurement error that can occur through incorrect siting. It is extremely important that the measurement location is an appropriate surrogate for the larger area. If the area of interest is a forested catchment then it is reasonable to place your rain gauge beneath the forest canopy; likewise, within an urban environment it is reasonable to expect interference from buildings because this is what is happening over the larger area. The rule-of-thumb method for siting a rain gauge is that the angle when drawn from the top of the rain gauge to the top of the obstacle is less than 30°

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It refers to the rate at which precipitation falls over a specific area during a

given period of time. It is typically measured in units like millimeters per hour (mm/h) or inches per

hour (in/h). Higher rainfall intensity indicates a greater volume of precipitation falling within a

shorter time frame. This parameter is crucial for understanding the potential for flooding, erosion,

and other impacts on the environment and infrastructure during a storm event.

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It refers to the length of time that a storm system persists over a particular

area. It measures the duration of significant weather conditions associated with a storm, such as

rainfall, strong winds, or thunderstorms. Storm duration can vary widely, ranging from just a few

minutes to several days, depending on factors such as atmospheric conditions, the movement of

weather systems, and the local topography.

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It is in weather forecasting where it is used to track the

movement of rain clouds and fronts across the earth’s surface, but does not provide the hydrological requirement of estimating how much rain is falling over an area.

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A method of collecting data about Earth's surface, atmosphere, and oceans using sensors on

satellites orbiting the planet. These sensors detect electromagnetic radiation emitted or reflected by

Earth's surface and atmosphere. Satellites can capture images and measurements across various

wavelengths of the electromagnetic spectrum

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It plays a vital role in water quality by scavenging airborne pollutants, which are

then dissolved by the rain. In forested areas, trees act as surfaces for these pollutants. When rain

falls onto trees, salts formed on leaves and branches may dissolve, resulting in pollutant-rich

stemflow and throughfall.

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It occurs when precipitation in polluted areas dissolves gases and absorbs particles, lowering the rain's acidity. Naturally, rain is slightly acidic, with a pH between 5 and 6, due to the dissolution of carbon dioxide to form weak carbonic acid.

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The movement of water through the soil surface. Affects the timing, distribution and magnitude of the runoff.

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There is a two-way relationship between infiltration and base flow. Infiltration

contributes to base flow by replenishing groundwater, while base flow provides infiltration by allowing some water to infiltrate riverbeds as rivers flow downstream.

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Different soils behave differently. Its porosity (amount of empty space

within the soil) and permeability (how well-connected the pore spaces are) influence

infiltration. Coarse subsoils with large pore spaces allow faster water entry. Well-connected pores enhance water flow.

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When soil becomes saturated, there will be no space available for

further infiltration, leading to more surface runoff or ponding.

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Note that water needs time to infiltrate. Steeper slopes result in faster water flow compared to low-lying areas.

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Impervious surfaces like paved areas reduce infiltration, whereas pervious

surfaces like forests promote infiltration due to greater soil exposure.

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Measures the movement of water into, and through, the soil. The measured value from an infiltrometer is known as hydraulic conductivity

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It is the graphical representation of the variation of infiltration

capacity with time, during and a little after rainfall. Since the curve is reaching a constant value and therefore it is a curve of the exhaustion type.

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This method is based on Darcy’s law and is now employed in an extensive range of usages.

MON-AY, JMP. Named after Herber Green and Gustav Adolf Ampt (1900s).

Green and Ampt assumed that the soil surface was covered by ponded water of negligible

depth in the original formulation. Water infiltrated a homogenous soil with uniform water

content.

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