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BPSC Mains GS-2 Masterclass · Science & Technology

Bihar's Water ResourcesAbundant Water, Used Unwisely

Bihar has generous rain, the Ganga and its great tributaries, and deep alluvial aquifers. Yet some of its districts face drought, its cities' water tables are falling and most of its ponds have vanished. This page shows what Bihar has, how it is being wasted, and what is being done.

Rain~110 cmAverage annual rainfall

Purnia and Kishanganj about 200 cm.

Monsoon85%+Monsoon share

of rain, June to September.

Groundwater45.8%Groundwater extraction

against the all-India 63.3%.

Ponds70%+Water bodies dead

in three decades (satellite data).

Decline2.5 lakh → <90,000Ponds

since the late 1980s.

Sewage290 MLDPatna's sewage

half flows straight into the Ganga.

Part 1 · Water resources in Bihar

Bihar's Water Wealth and Its Uneven Rain

Abundant surface and groundwater, but rain that comes in four months, falls far more in the north than the south, and is changing with the climate.

Illustration of a north Bihar landscape with a wide river, a village pond, paddy fields and monsoon clouds

Water resources in Bihar

The state of Bihar is endowed with abundant surface and groundwater resources, enough to meet the growing demands of different sectors such as agriculture, industry, household, and environment.
Though water is considered as a renewable resource because of regular replenishment by the rain spells, the growing population and indiscriminate development is inducing stress on the natural water ecosystems.
Bihar is also prone to excessive flooding, where more than 70 percent of the population are living under the constant threat of floods.

Rainfall

Average annual rainfall in Bihar is around 110 cm with Purnia and Kishanganj getting around 200 cm annual rainfall.
The climate change altering the patterns of precipitation around the globe is also a challenge for Bihar.
More than 85% of rain is due to the south-west monsoons, occurring during the four months of June to September.
Besides temporal variations, the rainfall distribution is also uneven across the districts of Bihar, as they fall under different agro-climatic zones. The agroclimatic Zones I (North-West) and II (North-East) form the wet zones in the state, which receive higher proportion of rainfall compared to the dry zone in the southern part of the state.
- During 2018-19, Kishanganj received the highest annual rainfall of 152 cms, while the lowest rainfall was observed in the district of Jehanabad (403 mms.).
- In case of south-west monsoons, there is no uniform distribution of rain as it varies from 1581 mms. in Kishanganj to 545.4 mms. in Arwal during 2019.
The lower intensity of rainfall in the southern districts is a cause of concern for groundwater level, compared to the northern counterparts. Such extreme rainfall variability in the state over time and space leads to low crop yields and the risk of crop failures in both flood and drought-prone areas.

Highest vs lowest district rainfall, 2018-19 (mm)

Kishanganj1,520 mm
Jehanabad403 mm

Kishanganj: 152 cm.

South-west monsoon rain, 2019 (mm)

Kishanganj1,581 mm
Arwal545.4 mm

Part 2 · Surface water, groundwater and wetlands

Rivers, Aquifers and Wetlands of Bihar

Fifteen river basins led by the Gandak and Kosi, alluvial aquifers that are drawn on more each year, and wetlands that help tame floods.

Surface water resource

Other than the rain water, the river systems in the state form the basis for surface water. Bihar is endowed with a favourable river system, comprising the river Ganga, its tributaries, and other rivers, some of which are perennial and others seasonal in nature.
The alluvial tract in the northern part of Bihar and some areas in the south have enough water available throughout the year.
In Bihar, the river Ganga has a total length of 445 kms and catchment area of 5473 sq. kms.
Among other rivers in Bihar, the Ghaghra river system is the biggest one with a catchment area of about 1.27 lakh sq.kms. and having a total length of 1116 kms.
Other major rivers are: Kosi, Sone, Gandak, Punpun, Bagmati, Mahananda etc.
Despite housing fifteen river basins, there has been a growing concern in the state over the quality of river water due to depleting water levels of subsurface resources.
As per the estimates, the basin-wise average water potential was the highest in the Gandak Baya river basin (47,350 MCM), followed by the Kosi river basin (41,615 MCM). On the other hand, the lowest water potential was observed in the river basin of Kiul (710 MCM).
In recent years, the quality of river water has become a major environmental concern. Owing to population growth and growing demand of water (for irrigation, industry, domestic consumption and other purposes), the water levels of subsurface resources have depleted. Secondly, there has also been a decline in flow of river waters. These two factors together have affected the quality of river water.

Average water potential by river basin (MCM)

Gandak Baya47,350 MCM
Kosi41,615 MCM
Kiul (lowest)710 MCM

Groundwater resource in Bihar

The water collected in aquifers, the porous layers of the underground formations, form the basis of groundwater resource.
The groundwater acts as major reservoir, especially in the drought prone regions of Bihar, making the water available for agricultural purposes.
In recent years, the dependency on groundwater resources has been rising on account of rapid economic and urban growth. Such growths lead to a decline in groundwater table, discharges and water quality. The impending water crisis is particularly severe, especially for food supply and healthy life of the poor.
Bihar's stage of groundwater extraction stands at 45.8 percent, which is lesser than the all-India average of 63.3 percent.
It is alarming to note that nearly 19 districts had the stage of groundwater extraction higher than that of the state's average of 45.8 percent. The dependency of irrigation on groundwater resource is one of the leading causes for depletion of water tables.
In Bihar, the commonly observed ground water contaminants include fluoride, nitrate, arsenic, and iron, which are harmful for drinking purposes.

Wetland

As one of the most productive ecological systems, the wetlands provide diverse ecosystem goods and services — assisting in erosion control, replenishment of land, regulation of life of habitats, and providing recreational and educational benefits.
In a flood-prone state like Bihar, wetlands are extremely beneficial, as they help in controlling flood by regulating the hydrological process.
The area estimates of wetlands reveal that Bihar has about 285 wetlands, with a total area of 3992 hectares.

Part 3 · Bihar is not utilizing her water resources rationally

Plenty of Rain, Yet Drought and Falling Water Tables

Floods and droughts in the same state, water tables down by 10–15 feet, cheap diesel pumping, contamination and cities heading for a water crisis.

Bihar is not utilizing her water resources rationally

According to India Meteorological Department, Bihar gets 1,027.6 mm rainfall in a normal monsoon year.
- While Average annual rainfall for India is 650 millimetres.
In spite of being endowed with many rivers like Ganga, Gandak, Kosi, Punpun etc Bihar still faces problem of water resource.
Part of Bihar experiences drought even though every part of the state receives decent amount of rainfall. Uneven rain patterns cause the flooding in large part of the state in almost every year.
- Most districts in the State received poor rains during the previous southwest monsoon season, prompting the State government to declare agricultural drought in 280 blocks of 25 districts.
The water scarcity is real and groundwater table has gone down significantly in most of these areas because of excessive withdrawal of water.
- Water levels have dropped by 10-12 feet in most parts of the State.
Diesel subsidies to farmers: cheap extraction of water.
Hard rock areas of South Bihar: less recharging.
Contaminants: Fluoride, Iron, Nitrate and Arsenic in many parts of the state. Uranium contamination found recently.

Cities running dry

At least 8 cities, including Patna, are likely to face severe water crisis soon. Gaya and Bhagalpur are already experiencing declining groundwater levels and consequent water scarcity. Muzaffarpur, Darbhanga, Ara, Munger and Biharsharif are likely to face the crisis in near future.
According to a study conducted by the CGWB, groundwater reservoirs in as many as 11 blocks of the state e.g. Gaya Sadar, Rajgir, Sampatchak (Patna) etc are in semi-critical condition.

Patna

So far as Patna is concerned, the water table has reportedly gone down 10 to 15 feet in recent years. Over-exploitation through deep tubewells is forcing the groundwater reservoir to deplete faster than it is being replenished.

For a city of nearly 25 lakh people already facing a major water crisis, the rapid depletion of groundwater will spell doom.
In the last few years, many shallow tubewells dried up during the summer season.
Although the average annual rainfall over Patna is about 1,000mm per annum, which is fairly high, the bulk of the rainwater is lost through surface run-off.
Things have come to such a pass due to the gradual disappearance of ponds and other open surface water bodies that helped recharge the groundwater reservoir through slow seepage.

Example: A pond is a recharge well that nature built: water stands in it for months and slowly seeps down to the aquifer. Fill the pond for a housing plot and the rain that fell on it runs off into a drain within hours, which is how a rainy city like Patna still loses its groundwater.

Part 4 · Vanishing water bodies, unfinished plans and sewage

Vanishing Ponds, Unfinished Plans and Untreated Sewage

Most of Bihar's ponds have been lost to silt, encroachment and neglect; plans to revive them, a groundwater bill and a regulator never came through.

Water availability and water bodies

The gross per capita water availability in Bihar will decline from about 1,950 m3/yr in 2001 to as low as about 1,170 m3/yr in 2050.
Surface water coverage in Ghagra-Gandak & Gandak-Kosi Zones decreased by 43.4% and 37.8% respectively.
Massive sedimentation affects the channel flow.
More than 70% water bodies in Bihar have died an unnatural death during the last three decades (using satellite data).
- There were more than 2.50 lakh ponds in the state till the late 1980s, but the number has reportedly declined to less than 90,000.
- Thousands of ponds, which are essential to store rainwater during the eight dry months of the year, have disappeared during the period owing to the alleged government apathy and increasing real estate activities.
- Most of the ponds and lakes have been encroached upon by the vested interests for construction purposes.
The distribution of water bodies varies from one district to the other.
- The perennial water bodies are maximum in Madhubani (902), followed by East Champaran (267) and Darbhanga (250).
- Large water bodies with area more than 1000 hectares are seen in only Samastipur, Vaishali and Patna districts and 60% of these are seasonal.
Satellite imageries also reveal that the seasonal water bodies are either utilized for agriculture or they are weed-infested after monsoon.

Perennial water bodies by district

Madhubani902
East Champaran267
Darbhanga250

Per capita water availability in Bihar (m³/yr)

20011,950 m³
2050 (projected)1,170 m³

Lack of implementing the plans

In 2016, the state revenue and land reforms department had undertaken a project to make all water bodies encroachment-free and renovate them so that they are fit for water conservation. It had also directed the officials concerned to lodge cases against those who have encroached upon ponds, lakes and rivers in the state.
Under the water bodies' conservation project, which is part of the disaster risk reduction road map (2015-30) of the state government, the department was first supposed to identify all community water bodies in the state and then remove encroachments, if any.
Finally, all water bodies were to be renovated under various schemes of the government and made fit to conserve water. This was also supposed to help in groundwater conservation.
But it is yet to be done.
The state government planned to introduce the Bihar Groundwater Conservation Bill, 2019. But it did not happen.
- The proposed Bill was supposed to ensure better management and conservation of groundwater, the level of which is going down fast. Its passage would not only regulate water use, but also focus on its conservation by digging out ponds and cleaning choked water bodies to recharge the groundwater.
In 2006, the state minor irrigation department had proposed to set up a state-level authority on the pattern of the (CGWB) to regulate the exploitation of groundwater resources, but it did not materialize yet.

Need of more sewage treatment plants

e.g. Patna generates around 290 MLD of sewage, of which half flows into the Ganga directly; the rest seeps underground polluting the groundwater. It has four sewage treatment plants with a combined capacity of 121 MLD but only a little over 50 MLD of sewage reaches these plants since the sewage system is completely dilapidated.

The plants also perform poorly on account of power failures, poor maintenance and non-functional treatment zones. The STP's treated water can also be used for power generation and irrigation purposes.

“The state of Bihar is endowed with abundant surface and groundwater resources, enough to meet the growing demands of different sectors.”

— BPSC Mains answer · Water resources of Bihar

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