Land degradation: waterlogging, salinity and desertification

Detail

What soil degradation means

• Soil degradation means the soil gets worse in quality and the land produces less.
• It has five main causes:
• erosion, where wind or running water carries away the fertile topsoil
• loss of nutrients and organic matter (humus, the dark material made from rotted plants and animals)
• salinity, too much salt in the soil
• waterlogging, where the soil stays soaked with water

• chemical pollution from industry, mines and farm chemicals

• Land degradation is the wider term. It covers soil and also the vegetation and water on the land.

Regional causes of land degradation in India

Cause	Main states	How it damages land
Mining	Jharkhand, Chhattisgarh, Madhya Pradesh, Odisha	Forests are cut down. Deep pits are left open after mining ends. Overburden (the waste rock and soil dug out to reach the ore) is dumped on nearby land.
Overgrazing	Gujarat, Rajasthan, Madhya Pradesh, Maharashtra	Too many animals eat the grass faster than it can grow back. The bare soil is then blown or washed away.
Over-irrigation	Punjab, Haryana, western Uttar Pradesh	Too much water causes waterlogging, which then raises salinity and alkalinity in the soil.

• Mineral-processing dust:
• Limestone is ground to make cement. Calcite and soapstone are ground for the ceramics industry.
• The grinding makes fine dust. The dust settles on nearby land.

• The dust layer stops water from soaking into the soil (infiltration). Plants then cannot grow well.

• Industrial effluents: effluents are the liquid waste that factories release. They pollute both the land and the water around it.

• NCERT exercise point: over-irrigation is the main cause of land degradation in Punjab. Mining and overgrazing are not.

Waterlogging: how it happens

• Waterlogging means the water table rises into the root zone, so the soil around the roots stays soaked.
• The water table is the top level of the groundwater.
• The root zone is the top part of the soil, where plant roots grow.

• Roots in soaked soil cannot get air, so crops become weak or die.

• There are two main causes:

• Over-irrigation: farmers give the fields more water than the crops need. The extra water sinks down and adds to the groundwater.

• Seepage from unlined canals: the canal bed is bare earth, not lined with concrete or brick. Water leaks out of the canal and raises the water table on both sides of it.

• Result: the water table keeps rising year after year until it reaches the roots.

Salinisation and alkalisation: the next stage

• Salinisation means salts build up in the topsoil.
• Alkalisation means sodium carbonate builds up in the soil and makes it alkaline. The soil's pH (a scale that measures how acidic or alkaline something is) goes up.
• Such soil is also called sodic soil.

• It turns hard, sticky and cannot let water through.

• How it happens, step by step: 1. The water table comes close to the surface. 2. Groundwater moves upward through tiny pores in the soil, the way oil climbs up a lamp wick. This is called capillary action. 3. In the hot, dry climate of north-west India, the water evaporates from the surface. 4. The salts that were dissolved in the water stay behind and form a white crust on the soil. 5. If the salt is mostly sodium carbonate, the soil also becomes alkaline.

• Local names for these salty, barren soils are reh, kallar and usar.

Classic waterlogged and salt-affected areas in India

Area	Where it is	Why it suffers
Indira Gandhi Canal command	Western Rajasthan, in the Thar Desert	The canal starts at the Harike Barrage in Punjab, where the Sutlej and Beas rivers meet. It carries water deep into the desert. Desert soil sits on hard layers below, so the extra water cannot drain away and the water table rises.
Punjab–Haryana plains	North-west alluvial plain (alluvial means made of soil laid down by rivers)	Heavy canal and tube-well irrigation for the rice–wheat cropping system.
Sharda Sahayak command	Central and eastern Uttar Pradesh	The canal system takes water from the Sharda river. Canal seepage and flat land with poor drainage raise the water table.
Chambal command	Kota region of Rajasthan and the Chambal area of Madhya Pradesh	Heavy black and alluvial soils drain slowly, so irrigation water collects in them.

• A command area is the land that a canal or dam project can irrigate.
• Elsewhere in the world, the same canal-irrigation problem is seen in the Indus basin of Pakistan and the Aral Sea basin of Central Asia.

Remedies for waterlogging and salinity

• Canal lining: the canal bed and sides are covered with concrete or brick, so less water leaks out.
• Drip irrigation: water is given drop by drop at the roots. Little water is wasted, so less extra water sinks into the ground.
• Sub-surface drainage (SSD): perforated pipes (pipes with small holes) are laid underground. They collect the extra salty water and carry it away from the field.
• In waterlogged and saline areas of Haryana, SSD brought fallow land (land left unused) back under farming. Crop yields and farm incomes went up, and farmers moved to more profitable crops [3].

• SSD works only when there is a safe way to dispose of the salty drainage water and enough fresh water to wash salts out of the soil [3].

• Gypsum (calcium sulphate):

• The calcium in gypsum takes the place of sodium on the soil particles.
• Irrigation water then washes the freed sodium down and out of the root zone.

• This is the main way to reclaim alkaline (usar) soils.

• Salt-tolerant crop varieties: crops bred to grow even in somewhat salty soil.

Scale of land degradation in India

• The Desertification and Land Degradation Atlas of India (2021) was made by ISRO's Space Applications Centre (SAC), Ahmedabad, using satellite data.
• 2018-19: about 97.85 million ha was degraded. This is roughly 30 per cent of India's land.

• Ranking of the processes: 1. Water erosion, the largest 2. Vegetation degradation, meaning the loss of plant cover 3. Wind erosion

• States with the largest degraded areas: Rajasthan, Maharashtra, Gujarat, Jharkhand and Odisha are among them.

Desertification and the UNCCD

• Desertification is land degradation in drylands: arid, semi-arid and dry sub-humid areas.
• It is caused by changes in climate and by human activity.

• It does not mean sand dunes moving forward. It means that once-productive dry land loses its fertility.

• UN Convention to Combat Desertification (UNCCD):

• It was adopted on 17 June 1994 in Paris and came into force in 1996.
• 17 June is marked every year as Desertification and Drought Day.

• It is one of the three Rio Conventions. The other two are the UNFCCC (climate change) and the CBD (Convention on Biological Diversity).

• COP14:

• COP means Conference of the Parties, the meeting of all member countries.
• COP14 was held in Greater Noida (Delhi NCR) on 2–13 September 2019. It had 197 Parties and the theme "Investing in Land, Unlocking Opportunities" [2].
• India held the COP Presidency for two years after it [2].
• The New Delhi Declaration (2019) made achieving land degradation neutrality by 2030 a national target for each country. It also covered land tenure (secure rights over land), gender equality in land rights, and drought [2].

• COP14 adopted a decision to reduce and manage drought risk. The decision recognised that climate change will make droughts more frequent and more severe [2].

• India's pledge:

• India will restore 26 million ha of degraded land by 2030.

• This raised its earlier target of 21 million ha [2].

• Land degradation neutrality (LDN): the total area of healthy, productive land stays the same or grows over time. Any new degradation is balanced by restoring land somewhere else. It is SDG target 15.3 (SDG means Sustainable Development Goal).

• Links to other topics:
• The Aravalli Green Wall, a green belt being planted along the Aravalli hills to stop the Thar Desert spreading east (see natural-vegetation-forests).
• Drought (see natural-hazards-disasters).

Prelims Hooks

• Over-irrigation is the main cause of land degradation in Punjab, Haryana and western Uttar Pradesh. Mining is the main cause in Jharkhand, Chhattisgarh, Madhya Pradesh and Odisha.
• Overgrazing states: Gujarat, Rajasthan, Madhya Pradesh, Maharashtra. Madhya Pradesh appears in both the mining and the overgrazing lists.
• Mineral and use matches: limestone → cement; calcite and soapstone → ceramics. Their dust blocks water from soaking into the soil.
• Order of processes: waterlogging → capillary rise → evaporation → salinisation. Sodium carbonate causes alkalisation. Gypsum is the remedy for alkaline soil.
• Indira Gandhi Canal: starts at the Harike Barrage (Sutlej–Beas confluence, Punjab) and waterlogs parts of western Rajasthan.
• ISRO-SAC Atlas (2021): 97.85 million ha (about 30 per cent of India) was degraded in 2018-19. Ranking of processes: water erosion > vegetation degradation > wind erosion.
• UNCCD: adopted 17 June 1994 in Paris, in force 1996. 17 June is Desertification and Drought Day.
• COP14: India, September 2019, 197 Parties. India raised its restoration target from 21 to 26 million ha by 2030 [2].
• Trap: UNCCD COP14 was held in India. UNFCCC COP8 (2002) was held in New Delhi. Do not mix them up.

Mains Points

• Green Revolution cost (GS-III):
• Free or cheap power and water, unlined canals and the rice–wheat cropping system in Punjab–Haryana → the water table rose → waterlogging, salinity and alkalinity.

• Fixes: canal lining, drip and sprinkler irrigation, sub-surface drainage (shown to work in Haryana [3]), gypsum for alkaline soil, crop diversification, and water-pricing reform.

• Regional pattern:

• Mining degradation is concentrated in the mineral-rich Chotanagpur and Chhattisgarh plateaus.
• Overgrazing is concentrated in the dry western and central states.
• Irrigation-induced degradation is concentrated in the north-west plains.

• So each region needs its own remedy: mine reclamation, grazing control, or water management.

• Policy response: UNCCD commitments (LDN, 26 million ha by 2030 [2]), the Aravalli Green Wall, watershed development and the Soil Health Card scheme together form India's strategy against desertification. Use ISRO-SAC satellite atlases to track progress.

• Link to climate and disaster: land degradation and drought feed each other. The COP14 drought decision noted that climate change will make droughts more frequent and severe [2]. This is useful for GS-III disaster-management answers.