ADVERTISEMENTS:
In this article we will discuss about the denudation and depositional work of underground water.
Denudation Work of Underground Water:
Water plays an important role in changing shapes over the land although. Its amount is not uniform at all places. At some places it is found an abundance and at other its quantity is very small. When Surface water seeps into Earth through porus rocks, it is known as underground water.
Although flow of underground water is similar to that of over ground water yet, the speed of flow of underground water is too less and because of this its geographical weathering activity is also low while chemical weathering activity is high. Moreover, clean water does not involve in any activity but while sieving into Earth various chemicals get mixed in it. We find the work of underground water in the regions with rich chalk, Limestone and Dolomite contents.
ADVERTISEMENTS:
A geographical distribution of the location of water on earth:
Works of underground water are not much visible on the upper layer of Earth. Mankind extracts it out to fulfill their various needs. e.g. Agricultural and house hold, etc. Sometimes it naturally comes out from Earth through natural openings like springs, wells, Geysers, etc.
If in any region, rainfall is high and rate of evaporation is low then the level of underground water will be high.
(A) Springs:
When the water oozes out naturally from Earth i.e. on the upper and outer most surface, that flow is known as ‘spring’. Mostly springs are found at the junction or fissures and joints of Porus and Nonporus rocks. In India these are found in hilly regions of Jammu Kashmir, Manikaran (Himachal Pradesh), Bihar and Assam.
ADVERTISEMENTS:
There are various kinds of springs:
(i) Hot Water Spring/Thermal Water Spring:
These springs have hot water and are found in volcanic regions. In Himachal Pradesh, langar is cooked with the help of heat generated by such springs at Manikaran Sahib.
(ii) Cold Water Springs:
These springs provide cold water and are mainly found in Himalayas, Western Ghats and Mountains of Chhota Nagpur Plateau.
(iii) Mineral Springs:
These springs have mineral and salts in their water. These are very helpful in the treatment of skin diseases. Such springs are found in Manikaran, Manali (District Kullu), Sahashtradhara (Dehradun), Tilsma Rajasthan when water flows continuously from a spring, it is known as Permanent spring.
(iv) Geysers:
When lots of steam oozes out as fountain along with hot water, such form is known as geyser. These might raise 30 to 60 meters high. The old faithful geysers of Yellow Stone National Park, Situated in Rocky Mountains of USA, comes active for four minutes after sleeping for 65 minutes at average. Iceland, parts of Rocky Mountains of USA, North Island of New Zealand and Yellow stone park of Wyoming state in USA are known for Geysers and Hot water springs. Total number of geysers in the world is 425 and out of these, 225 are situated in Yellow Stone Park of (USA America) this region has 24000 springs of hot water and around 100 geysers.
Some Geysers continuously ooze out on the Earth’s surface and their temperature is 100°C (or 212°F). Some Geysers collect very less debris and some of them make a cone like nozzle. Most of the Geysers spread mineral deposits on the area around them.
(B) Well:
When underground water flows beneath the surface through a hole that is known as ‘well’. If the well is not deep then the water does not come out continuously and that is known as ‘Intermittent well’.
(C) Aquifer:
This is a word of Latin language which means ‘to bear water’. An underground permeable rock is present which contains water and an impermeable rock is situated below the permeable rock, thus a reservoir of underground water is created. ‘Aquifer’ is a natural filter which purifies various types of sediments and bacteria.
‘Aquifers’ get polluted if waste material is thrown in them and moreover septic tanks, medical waste (Injections, Medicine), Fertilizers etc. also create problems if constructed or piled near the aquifers.
(D) Artesian Well:
The word Artesian has been derived from the word ‘Artois’, which was the name of a province of France where first Artesian well on the Earth was dug in 1126. It is a limited Aquifer in which water comes out through well because of pressure even without using a pump.
Great Artesian basin is the world’s largest and deepest Artesian basin, which extends over 23% part of Australian continent. Australia has 9000 Artesian wells, maximum in the world. In India these are found in Indora Tehsil of District Kangra (HP), Mukerian Tehsil of District Hoshiarpur (Punjab), Tarai, Pudduchery, Tamilnadu, Alluvial soil areas of Gujrat etc.
Underground Water as an Agent of Denudation:
Underground water also performs erosion, transportation and deposition activities. The speed of underground water is very low. If ‘KM/Hr’ unit is used for speed of river then ‘meter per day’ is used for underground water. Because of this its activities may be seen only in regions having soft rocks or regions with Limestone, Dolomite etc.
As topography, underground water forms ‘Karst topography’ in areas which have limestones. In India this is found in Cherapoonji, Jammu-Kashmir, Himachal Pradesh, Panch Marhi (M.P.), Bastar Chattisgarh and Coastal areas near Vishakhapatnam.
‘Karst topography’ is also found in the areas having Dolomite, Gypsum or Halite, (Rock-salt).
Following land forms are formed by denudation activity of underground water:
1. Lapies:
In German language these are known as ‘Karren’ and in English these are known as ‘clint’ while Lapies is a french word. When underground water contains Carbon-dioxide in it, dissolving process of ‘lime stone’ rocks begins. Because of this breadth of cracks and joints increases, which are known as ‘Lapies’.
2. Sink Holes:
Sometimes Lapies gets deep like funnel forming a sink hole. Its depth may vary from a few centimeters to some meters.
3. Swallow Holes:
When the size of sink holes increases, these are called swallow holes.
4. Doline:
Due to high chemical activity on swallow holes, their size and depth increases. Its diameter may extend upto some kilometers and depth may run upto 100 meters. Mostly such forms are found in tropical regions.
5. Karst Lakes:
When the lower part of Dolite is blocked because of debris formed by its own erosion, water gets collected as reservoir. This is known as ‘Karst Lake’.
6. Uvalas:
A reservoir is formed with the conjugation of many sink holes. This is known an Uvala.
7. Ponar:
When Uvalas are filled with water, high erosion activity converts it into a tunnel like structure, which is known as ponar.
8. Caverns:
In lime stone regions the flow of rivers are not outwards but is inwards. it dissolves its own bed and forms a large cave called ‘cavern’. The roofs of such structures are called Chambers. In India these are found in Chattisgarh and Chirapoonji.
9. Natural Bridge:
When roofs of caverns collapse, some of its parts are left behind, which look like a bridge. This is called natural bridge.
Depositional Work of Underground Water:
Underground water dissolves the rocks but when it deposits this dissolved materials various types of forms are created:
1. Stalactite and Stalagmite:
These are formed in a region rich with lime stone, where caverns have been formed. Lime water seeps down-ward from these caverns during this activity some of drops hang with the ceiling of cavern. Due to evaporation, water gets evaporated and the hanging structure of lime is left, which is known as ‘stalactite’. Its breadth is more near the ceiling as compared to its tip.
The drops of lime water which fell on ground, get evaporated and only a structure made of lime is left behind. This is known as ‘Stalagmite’. Its width on the ground is more as compare to its tip.
Sometimes both stalactite and stalagmite combine to form a pillar which gives an impression of a cavern on the whole. ‘Zenolan lane’ in Sydney (Australia) is its fine example which is around 100 kms deep. Another natural cave or cavern is at Tirlokpur falling on Pathankot-Dharmshala Highway, which is thousands of years old.
Underground water is very important and it must be used properly. In Punjab the level of underground water is decreasing day by day (continuously). Its level is extremely down in 85% part of the state. Low rainfall is one of the primary reasons behind the situation. Annual average rainfall has been decreased upto 45-50%. Annual rainfall in 1990 was 755 mm. which has come down to 375 mm in year 2004. In 2009 it was 420 mm and in 2014 it was recorded 600 mm.
Cultivation of ‘Rice’ is another reason. Rice is planted on 2/3 part of Punjab before June 15 ever year, which increases the need of irrigation and moreover during this period evaporation is also fast due to hot weather. In these conditions underground water is used to fulfill the requirement of water. Around 73% Irrigation depends on the underground water and all this has resulted in banning of use of underground water at a few places. Hence it is our duty to use underground water properly.