Water (H2O:
one molecule of water has two hydrogen atoms covalently bonded to a single
oxygen atom) is a transparent fluid which forms the world’s streams, lakes,
oceans and rain. Water is a tasteless, odorless liquid at standard temperature
and pressure. The color of water and ice is very slight blue hue, although
water appears colorless in small quantities. Water vapor is essentially
invisible as a gas.
The volume of water
one Earth would be about 332,500,000 cubic miles or 1,386,000,000 cubic
kilometers. Water also exists in the air as water vapor, lakes, rivers, icecaps,
glaciers, soil moisture, atmosphere, aquifer, and even in human’s body. About
71% of the Earth’s surface is water-covered, and the oceans hold about 96.5%
and freshwater has only about 3.5% of all Earth’s water. Over 68% of freshwater
is locked up in ice and glaciers, and other 30% is underground water. Fresh
surface-water sources, such as rivers and lakes, only constitute about 22,300
cubic miles (936,100 cubic kilometers), which is about 1/150th of
one percent of total water. he water is used for domestic, industrial, irrigation,
livestock, mining, public supply, thermoelectric power, and aquaculture.
Terminology
Condensation:
is the process by which water vapor in the air is changed into liquid water.
Condensation is crucial to the water cycle because it is responsible for the
formation of clouds.
Precipitation:
is the water released from the clouds in the form of
rain, freezing rain, sleet, snow, or hail. It is the primary connection in the
water cycle that provides for the delivery of the atmospheric water to the
Earth. Most precipitation falls as rain.
Evaporation:
is the process by which water changes from liquid to a
gas or vapor. Heat is necessary for evaporation to occur by breaking the bonds
that hold water molecules together, which is why water easily evaporates at the
boiling point (100°C),
but evaporate much more slowly at the freezing point.
Open channel flow: is
the flow with a free surface, such as flow in a river or in a partially full
pipe.
Transpiration:
is essentially evaporation of water from plant leaves. Studies have revealed
that transpiration accounts for about 10% of the moisture in the atmosphere,
with oceans, seas, and other water bodies providing nearly 90%, and a tiny
sublimation.
Evapotranspiration:
is the water lost to the atmosphere from the ground surface, evaporation from
the capillary fringe of the groundwater table, and the transpiration of
groundwater by plants whose roots tap the capillary fringe of the groundwater
table. Sublimation: is the conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage.
Infiltration:
is the process by which precipitation or water on ground surface enters the
subsurface soils and moves into rocks through cracks and pore spaces. Please visit our Facebook Page. Water Resources and Disaster Management
Hydrology is the scientific
study of the movement, distribution, and quality of water on the Earth
including the hydrologic cycle, water resources and environmental watershed
sustainability. The domains of hydrology include the fields of hydrometeorology,
surface hydrology, hydrogeology, drainage basin management, and water quality.
The hydrologist can engage with in various activities such as earth and
environmental science, physical geography, geology, civil and environmental engineering,
hydraulic modelling, flood mapping, catchment flood management plans, shoreline
management plans, estuarine strategies, coastal protection, and flood
alleviation.
The Water Cycle(Source: http://water.usgs.gov/edu/watercycle.html)
Branches of
Hydrology are:
☞ Chemical hydrology
is the study of the chemical characteristics of water.
☞ Ecohydrology
is the study of interactions between organisms and the hydrologic cycle.
☞ Hydrogeology
is the study of the presence and movement of groundwater.
☞ Hydroinformatics
is the adaptation of information technology to hydrology
and water resources applications.
☞ Hydrometeorology
is the study of transfer of water and energy between land and water body
surfaces and the lower atmosphere.
☞ Isotope
hydrology is the study of the isotopic signatures of
water.
☞ Surface
hydrology is the study of hydrologic processes that
operate at/near Earth’s surface.
☞ Drainage basin
management covers water storage, in form of reservoirs
and flood protection.
☞ Water quality
includes the chemistry of water in rivers and lakes, both pollutants and
natural solutes.
☞ Oceanography is
the study of water in oceans and estuaries.
☞ Meteorology
is the study of atmosphere and weather including precipitation as snow and
rainfall.
☞ Limnology
is the study of biological, chemical, physical geological of all inland waters.
Hydrological Models
Hydrological Models are simplified and
conceptual representations of a part of the hydrologic or water cycle for hydrologic
prediction and understanding hydrologic processes and behavior of hydrologic
systems to make better prediction and to solve the major challenges in water
resources management. There are two major types of hydrologic models can be distinguished:
☞ Stochastic Models are the black box
systems, based on data and using mathematical statistical concepts to link a
certain input to the model output. Commonly used techniques are regression,
transfer functions, neural networks and system identification.
Surface Water Concept (wikipedia)
☞ Process-Based Models (known as deterministic
hydrological models) represent the physical processes observed in the real
world including surface runoff, subsurface flow, evapotranspiration, and
channel flow.
Land Cover refers to the surface cover on the ground, whether vegetation, urban infrastructure, water, bare soil or other; it does not describe the use of land, and the use of land may be different for lands with the same cover type. For instance, a land cover type of forest may be used for timber production, wildlife management or recreation; it might be private land, a protected watershed or a popular state park. Land cover can be determined by analyzing satellite and aerial imagery. Land use cannot be determined from satellite imagery.
Land Use refers to the purpose the land serves, for example, recreation, wildlife habitat or agriculture; it does not describe the surface cover on the ground. For example, a recreational land use could occur in a forest, shrubland, grasslands or on manicured lawns. Land Use expresses how humans use the biophysical or ecological properties of land. Land use includes the modification and/or management of land for agriculture, settlements, forestry and other uses including those that exclude humans from land, as in the designation of nature reserves for conservation.
It is often impossible to observe land use by examining only land cover by remote sensing as illustrated in the figure. For example, the land cover type of trees might indicate a land use type of plantation or a land use type of conservation.
