Rain is liquid water that falls from clouds when water vapor condenses and becomes heavy enough to fall. It is a major part of the water cycle, depositing fresh water on Earth. Rain sustains many ecosystems and provides irrigation and hydroelectric power. The primary causes of rain include moisture moving along weather fronts and convection from clouds, as well as upslope flow in mountainous areas. Rain nourishes plants and replenishes drinking water sources, but can also cause erosion if too much falls at once.

2. RAIN
• RAIN IS LIQUID WATER IN THE FORM OF DROPLETS THAT HAVE CONDENSED FROM ATMOSPHERIC WATER
VAPOR AND THEN BECOME HEAVY ENOUGH TO FALL UNDER GRAVITY.
• RAIN IS A MAJOR COMPONENT OF THE WATER CYCLE AND IS RESPONSIBLE FOR DEPOSITING MOST OF THE
FRESH WATER ON THE EARTH.
• IT PROVIDES SUITABLE CONDITIONS FOR MANY TYPES OF ECOSYSTEMS, AS WELL AS WATER FOR
HYDROELECTRIC POWER PLANTS AND CROP IRRIGATION.

3. CAUSE OF RAIN PRODUCTION
• THE MAJOR CAUSE OF RAIN PRODUCTION IS MOISTURE MOVING ALONG THREE-DIMENSIONAL ZONES OF
TEMPERATURE AND MOISTURE CONTRASTS KNOWN AS WEATHER FRONTS
• IF ENOUGH MOISTURE AND UPWARD MOTION IS PRESENT, PRECIPITATION FALLS FROM CONVECTIVE
CLOUDS (THOSE WITH STRONG UPWARD VERTICAL MOTION) SUCH AS CUMULONIMBUS (THUNDER
CLOUDS) WHICH CAN ORGANIZE INTO NARROW RAINBANDS.
• IN MOUNTAINOUS AREAS, HEAVY PRECIPITATION IS POSSIBLE WHERE UPSLOPE FLOW IS MAXIMIZED
WITHIN WINDWARD SIDES OF THE TERRAIN AT ELEVATION WHICH FORCES MOIST AIR TO CONDENSE AND
FALL OUT AS RAINFALL ALONG THE SIDES OF MOUNTAINS.

4. • ON THE LEEWARD SIDE OF MOUNTAINS, DESERT CLIMATES CAN EXIST DUE TO THE DRY AIR CAUSED BY
DOWNSLOPE FLOW WHICH CAUSES HEATING AND DRYING OF THE AIR MASS.
• THE MOVEMENT OF THE MONSOON TROUGH, OR INTERTROPICAL CONVERGENCE ZONE, BRINGS RAINY
SEASONS TO SAVANNAH CLIMES.

5. THE POSITIVE EFFECTS OF RAIN

6. • WATER IS ONE OF THE MOST VALUABLE RESOURCES ON EARTH. RAINWATER FILLS RESERVOIRS THAT
SUPPLY DRINKING WATER, PROVIDE A HABITAT FOR FISH TO LIVE, AND NOURISHES THE SOIL WITH WATER
NECESSARY FOR VEGETATION. RAIN WATER, HOWEVER, CAN ALSO HAVE A NEGATIVE EFFECT ON THE EARTH
WHEN IT CAUSES EROSION OR WHEN IT HAS A HIGH PH.

7. HUMAN LIFE
• HUMANS NEED A CONSTANT SOURCE OF FRESH WATER TO SUSTAIN THEIR LIVES, AND THIS OCCURS AS A
DIRECT RESULT OF ADEQUATE RAINFALL. THE HUMAN DIGESTIVE SYSTEM NEEDS WATER TO BREAK DOWN
SOLIDS. WATER FLUSHES THE HUMAN SYSTEM OF TOXIC SUBSTANCES, BY EXPELLING SWEAT, URINE AND
FECAL MATTER. WATER CUSHIONS THE HUMAN JOINTS, ALLOWING MOVEMENT WITHOUT FRICTION.
WATER REDUCES THE HUMAN BODY TEMPERATURE, HELPS BLOOD TO FLOW AND TRANSPORT OXYGEN
AND NUTRIENTS. THE LYMPH SYSTEM IN THE HUMAN BODY,COMPOSED OF WATER, CONTAINS
IMMUNITIES TO HELP FIGHT DISEASES.

8. PLANTS
• PLANTS, TREES, GRASS AND FLOWERING SHRUBS ALL DEPEND UPON RAINFALL TO LIVE AND REPRODUCE.
PLANT ROOTS ABSORB WATER AND TRANSPORT IT TO THE LEAVES AND STEMS, ASSURING GROWTH
FROM SEEDLINGS TO MATURE STAGES OF DEVELOPMENT. PLANTS TAKE IN CARBON DIOXIDE AND EXPEL
OXYGEN, AS A RESULT OF PHOTOSYNTHESIS, WHICH SUPPLIES THE NEEDED OXYGEN TO THE ATMOSPHERE
FOR ANIMAL RESPIRATION. AS A RESULT OF ADEQUATE RAINFALL, PLANT ROOTS GROW LONG AND STURDY,
WHICH ENABLES THEM TO HOLD THE TOPSOIL TOGETHER. STRONG PLANT ROOTS REDUCE SOIL EROSION.

9. RAINWATER CONSUMPTION
• A STUDY BY THE MEDICINE, NURSING AND HEALTH SCIENCES DEPARTMENT AT MONASH UNIVERSITY
FOUND THAT DRINKING UNTREATED RAINWATER DOES NOT POSE AN INCREASED RISK OF ILLNESS. THE
STUDY FOLLOWED TWO GROUPS, THOSE THAT DRANK TREATED WATER AND THOSE THAT DRANK
UNTREATED RAIN WATER. ACCORDING TO THE STUDY, DRINKING RAINWATER DOES NOT POSE HEALTH
RISKS AND COULD POSE AS A SOLUTION IF WATER BECAME SCARCE. IT COULD ALSO DECREASE THE NEED
FOR PEOPLE TO DRINK BOTTLED WATER, WHICH HAS LED TO WASTE THAT OVERRUNS LANDFILLS.

10. EROSION
• WHEN SOIL MOVES FROM ONE LOCATION TO ANOTHER, IT IS REFERRED TO AS EROSION. THE IMPACT OF
RAIN WATER STRIKING THE SURFACE CAN CAUSE SOIL EROSION. EROSION IS A CONCERN FOR FARMERS
AS THEIR VALUABLE, NUTRIENT RICH TOP SOIL CAN BE WASHED AWAY FROM RAIN WATER. IT CAN ALSO
WEAKEN STRUCTURES SUCH AS BRIDGES OR WASH OUT ROADS. VEGETATION CAN DECREASE THE
AMOUNT OF SOIL THAT IS ERODED DURING A RAIN.

11. NATURAL WATER STORAGE
• RAINWATER FALLS TO THE GROUND AND IS ABSORBED INTO THE SOIL, REACHING LOCATIONS IN THE
BEDROCK KNOWN AS AQUIFERS. AQUIFERS HOLD HUGE VOLUMES OF WATER IN THE WATER TABLE. MANY
MAN-MADE WELLS FEED DIRECTLY FROM THE WATER TABLE, PROVIDING DRINKING AND BATHING WATER.
WATER IN THE AQUIFERS TRAVEL THOUGH THE SEDIMENTARY ROCK TO OTHER LOCATIONS, PROVIDING
PLANTS AND TREES WITH A CONSTANT SOURCE OF WATER. HUGE AMOUNTS OF RAINFALL OVER THE
ARCTIC REGIONS DROP SNOW, LOCKING UP TRILLIONS OF GALLONS OF FRESH WATER IN THE SNOW
SHEETS AND GLACIERS.