water and its unique properties Flashcards
define hydrosphere
refers to all groundwater present on above or below earth’s surface (oceans ,seas , lakes ,river)
facts about water
1) water exist on earth over a wide temperature range
2) it takes a lot of heat to evaporate liquid water (effective cooling medium )
3) a high surface tension and high wetting ability
4) dissolves a variety of compounds (carries dissolved nutrients and remove dissolved waste product )
5) liquid water expands rather than contracts on freezing - therefore ice water floats
the hydrological cycle
refers to the circulation of water between atmosphere ,land and the oceans - driven by the sun
summary of the hydrological cycle
1) water evaporates from lakes, rivers and oceans
2) transpiration - is the loss of water vapour from pores
(stomata) in the leaves of plants
3) when the temperatures fall - water vapour condeses forming clouds or fogs
4) condensation - the conversion of water vapour into droplets of liquid water ; this occurs because cool air holds less water than warm air .
5) precipitation - any form of water resulting from condensed atmospheric water vapour being returned to Earth’s surface under gravity
6) interception - precipitation that collects on leaves and stems of plants - will reach the ground
residence time
average time that a water molecule spends in any part of the hydrological cycle
Runoff
the visible flow of water in rivers , creeks and lakes at the water stored in the basin drains out
infiltration
the process whereby water enters soil and porous rocks
percolation
the downward movement of water through soil or porous rock
groundwater
water that occurs below Earth’s surface where it fills up pores and cracks within rocks and sediments
aquifer
a layer of rock or sediment saturated with groundwater
water table
upper most surface of aquifer
surface runoff
water from precipitation that flows on the surface - occurs because the amount of water falling is greater than the rate of infiltration of the ground-Surface runoff erodes and transports soil. It dissolves and transports nutrients as well as undesired substances within and between ecosystem
what does the hydrological cycle help with ?
The hydrological cycle is a cycle ofnatural renewal and purification of earth’s water resources. Evaporation and precipitation act as a distillation process, removing impurities dissolved in water. Water flowing through streams and in aquifers is also filtered and purified by various processes, both chemical and biological
causes of water scarcity
1) uneven distribution - Canada - abundant water whilst highly populated region lack water
2) the lack of economic means to create adequate water collection and storage infrastructure
3) available water - polluted
4) unsustainable use of aquifers
surface water
Surface water-Precipitation that does not infiltrate the ground or return to the atmosphere by evaporation, but collects in ponds,lakes, streams and rivers. In other areas much surface water is lost since it ends up in the sea
strategies for increasing freshwater availability
being dams across rivers to divert surface water
2) using ground water (pumped through bore holes and pumping stations )
3) desalination
recharge area/zone
The area of land through which water passes into the aquifer. It is the areathat replenishes the aquifer
the unsustainable water extraction ;
1) can cause lowering of water table - more difficult to extract water
2) contamination of water through salt -water intrusion
3) Subsidence(downward movement of the overlying rock) can occur since water extraction can result in compression of the aquifer material particularly if it is clay or s
desalination
the removal of salt from sea water or from salty groundwater- distillation or from salty groundwater
distillation
the heating of saltwater until the water evaporates. This leaves the salts behind. Water vapour is condensed forming pure water. used in united arab Emirates - very costly
reverse osmosis
involves pumping seawater at high pressures through semi-permeable membranes that allow water molecules to pass through but do not allow the passage of dissolved salts.
osmosis
Osmosis–the movement of water from a region of high-water concentration (low solute concentration) to a region of lower-water concentration (higher solute concentration) across a semi-permeable membrane.It is a passive process that occurs naturally and does not require an external energy source
disadvantages of reverse osmosis
Reverse osmosis can result in the seawater in the vicinity becoming more saline. The membranes used for reverse osmosis are expensive and can easily be damaged by pollution such as floating oil patches
efficient use of water resources
Water saving crop irrigation systems➢Treatment and reuse of wastewater➢Early detection and repair of leaks➢Realistic pricing of water➢More efficient appliances that use water
name the two local aquifers
the mean sea level aquifer and the perched aquifer.
the mean sea level aquifer
his is present in the pores of lower coralline limestone and globigerina limestone at sea level. Seawater also penetrates into these pores, but the less dense freshwater ‘floats’on the denser saltwater. The mean sea level is lens shaped and is thickest in the central regions of the island- y loses some of its freshwater through discharge into the sea at the coastal zone.
collected from;
underground gallaries - ta’Kandja
overuse of this aquifer
y loses some of its freshwater through discharge into the sea at the coastal zone.
The perched aquifer
formed above the clay - impermeable - water collects on top of it -y loses some of its freshwater through discharge into the sea at the coastal zone.
spring water
The perched aquifer is the source of the few freshwater springs present on the island-ut many have been diverted to reservoirs built by farmers.Only the names remain (Ghajn Zejtuna, Ghajn Dwieli etc.).
local rare freshwater species
the endemic Maltese freshwater crab
Sea water is an excellent medium for supporting life:
1) contains dissolved oxygen and carbon dioxide
2) has a high specific capacity - stable environment
3) allows light penetration - photosynthesis
the marine biome is made up of 2 main habitats:
the pelagic environment (water itself ) benthic environment (seabed )
a biome
a biome is a major ecological habitat)
marine zones can be distinguished ;
- The coastal zone is closest to land, extending from the coastline to the end of the continental shelf. This is the shallow seabed surrounding a continent
- The water tends to be sunlit, warm and rich in nutrients
the open sea is divided into zones
the upper zone - photic zone - enough light penetration for photosynthesis - up to 200m deep- the light penetration depends on the water clarity and angle of incidence - poor in nutrients
- the bathyal zone -insufficient for photosynthesis- low amounts of dissolved oxygen -zooplankton and various species live here
the abyssal zone -1500m deep and more - completely dark and cold- rich in nutrients due to debris
aquatic producers
algae and plants
oceanic circulation
driven by temperature changes and density(warm water is less dense than cold ) and prevailing winds which are ultimately powered by the sun
what do ocean currents transport?
warm water from equatorial region towards towards the poles whilst colder water flows from the poles to the tropics.
what is oceanic circulation responsible for ?
transportation of heat , salt and nutrients, dissolved gases and living organism
ocean temperature change with
depth and latitude
the thermocline
Below the mixed surface waters, there is a thin layer of water where the temperature falls rapidly.
density difference
prevents mixing between the surface waters and deep water - thermocline acts as a lid
upwelling zones
deep water returns here - strong currents -water - up to surface again full of nutrients important for primary productivity
tides
a periodic rise and fall of sea level caused by the gravitational pull exerted on earth by moon and sun
moon’s gravity
ocean bulge out in the direction of moon and on the other side too - earth pilled towards the moon
the sun’s gravity
whether the tides are strong or weak depends on the sun’s position and moon relative to earth
when are the strongest spring tides
when earth , sun,and moon are in line with each other
weakest spring tides
when moon and sun are perpendicular
tidal range -
the different water levels on different days
tidal range in Malta
small
canada
exceeds 15 m
in france
generate electricity - early stages of development
- suitable sites are limited , corrosion and expensive but might become a realistic operation in uk
