A farmer standing beside a dry canal does not measure water in million acre-feet. He measures it by the crop wilting in his field, the diesel he has spent running a pump and the number of days he has waited for water that was supposed to arrive through the canal.
The Son is being described in official calculations as having more water than it did five decades ago. Yet farmers at the tail end of the irrigation system continue to wait for water. The river may be carrying water, but that does not necessarily mean the water is reaching the field.
That contradiction should be at the heart of any discussion about the latest Son water-sharing agreement between Bihar and Jharkhand.
In a letter to the Union Jal Shakti Minister, MP Sudhakar Singh has questioned the basis of the latest assessment of water availability in the Son basin. In 1973, the basin’s availability was assessed at 14.25 million acre-feet (MAF). A communication from Bihar’s Water Resources Department dated August 20, 2026, reportedly puts the figure at 19.6335 MAF.
That is an increase of nearly 5.38 MAF.
The obvious question is: How did this additional water enter the calculation?
Has rainfall increased? Has the hydrology of the basin changed? Has the catchment area altered? Have additional sources been included? Or does the revised figure include flows that are technically present in the river but cannot be reliably stored, regulated or delivered for irrigation?
The distinction is crucial.
Water flowing through a river is not automatically water available to a farmer.
On August 31, Bihar and Jharkhand signed an agreement in New Delhi to settle the division of the 7.75 MAF that had been assigned to undivided Bihar. Under the new arrangement, Bihar will receive 5.75 MAF and Jharkhand 2 MAF.
The agreement addresses a long-standing issue created by the formation of Jharkhand in 2000. For nearly 25 years, the two states have had to negotiate how the water share of undivided Bihar should be divided.
Settling that dispute is important. But an agreement on paper does not settle the larger question of water security.
Because allocation is not delivery.
A river may carry a certain volume of water. A barrage may receive another volume. A certain quantity may be released into canals. Yet the quantity that finally reaches a farmer’s field can be substantially smaller.
This gap between hydrological availability and usable irrigation water lies at the heart of much of India’s water-management problem.
The Son is a particularly important example.
The Indrapuri Barrage and the Son canal system serve a large agricultural region of Bihar, including Rohtas, Kaimur, Bhojpur, Buxar, Aurangabad, Arwal, Gaya and adjoining areas. For farmers in these districts, the Son is not an abstract figure measured in MAF. It can be the difference between a crop surviving and a crop failing.
Yet the history of irrigation in the region shows that water reaching the head of a canal does not necessarily mean water reaching its tail.
This is why the debate over 14.25 MAF versus 19.6335 MAF cannot be reduced to a dispute over numbers.
The first requirement should be to establish what those numbers actually represent.
For example, flow data generated through monitoring systems such as SCADA at the Indrapuri Barrage can provide valuable information about river discharge. But a period of high flow does not automatically translate into dependable irrigation availability. Floodwater that arrives in excess of the capacity of a barrage or canal system may simply pass downstream.
Such flows cannot necessarily be treated in the same way as water that can be regulated and delivered during the agricultural season.
This is the significance of the reference to “unmanaged surplus discharge” in Singh’s letter.
The terminology may sound technical, but the policy question is simple:
Should water that cannot realistically be captured and delivered to farms be counted in the same category as dependable irrigation water?
If the answer is yes, the official balance sheet may look healthier while the farmer sees no additional water.
That is the central problem with treating basin water as a single number.
The Son of 2026 Is Not the Son of 1973
The Son basin of 2026 is not the Son basin of 1973.
Population has increased. Cropping patterns and irrigation requirements have changed. Urban and industrial demand has grown. Energy requirements have expanded. Climate change has made rainfall increasingly erratic, with intense rainfall often concentrated over shorter periods followed by prolonged dry spells.
These changes make periodic reassessment necessary.
But reassessment must work both ways.
Old estimates should not be treated as permanently valid simply because they are old. Nor should a substantially higher new estimate be accepted merely because it appears in an official document.
The revised figure must be independently tested.
That requires a basin-wide water audit.
The audit should answer a sequence of basic questions: How much rainfall does the basin receive? How much becomes runoff? How much enters reservoirs? How much reaches the Indrapuri Barrage? How much is released? How much enters the canal network? How much is lost during transmission? And, most importantly, how much actually reaches the agricultural fields?
The last question is often the least visible in official water accounting.
It should be the most important.
A credible water audit should therefore be placed in the public domain and subjected to independent scrutiny by hydrologists, scientific institutions, farmers’ organisations and representatives of affected regions.
Transparency here is not merely a matter of administrative procedure. It is essential to building trust between states.
Jharkhand needs water. Bihar needs water. The solution cannot be to present one state’s requirement as a threat to the other.
The two states share a river system. They therefore need a common scientific basis for determining how much water is dependable, how much is seasonal, how much is actually usable and how much must remain in the river.
That last category is often overlooked.
Not all water left in a river is surplus.
The river needs water for its ecological functions, aquatic life, fisheries and groundwater recharge. Any water-sharing arrangement that allocates every available unit to irrigation, industry or energy without accounting for environmental flows risks damaging the very river on which the allocation depends.
The Question of New Projects
The same caution is necessary when considering future projects.
Singh’s letter raises questions about the water requirements of proposed pumped-storage projects in Uttar Pradesh. Such demands should be subjected to transparent technical scrutiny before they are factored into future allocations.
For every new project, three basic questions should be answered:
Where will its water come from?
Will it affect existing allocations?
What will be its impact on agriculture and the river’s ecological needs?
The Son agreement should therefore not be viewed as a final settlement carved in stone.
Water availability is dynamic. Rainfall changes, river flows fluctuate and demand grows. A durable arrangement needs mechanisms for periodic review, transparent monitoring and clear rules for years when water availability falls below expectations.
But there is another issue that cannot be postponed: accountability.
Governments can sign agreements. Departments can produce statistics. Ministers can announce allocations.
None of these, by themselves, puts water in a farmer’s field.
The governments of Bihar and Jharkhand must therefore disclose not only their respective allocations but also the assumptions behind them.
If the Son basin’s estimated availability has risen from 14.25 MAF to 19.6335 MAF, the public deserves to know precisely why.
How much of the increase is dependable water?
How much is actually usable for irrigation?
How much is lost as uncontrolled or unmanaged discharge?
How much of Bihar’s 5.75 MAF actually reaches farms?
And where water does not reach the fields, who is responsible?
These are not questions that can be answered by another allocation table.
They require measurement from the river to the canal—and from the canal to the field.
The Real Test Is at the Field Boundary
This is where the real test of the August 31 agreement begins.
The purpose of a water-sharing agreement is not merely to divide a number between two governments. Its purpose is to ensure that water is equitably and efficiently available to the people whose livelihoods depend on it.
For Bihar’s farmers, the measure of success will not be 5.75 MAF.
It will be whether the canal runs when the crop needs water.
It will be whether water reaches the tail-end farmer.
It will be whether a farmer who has been promised irrigation can actually see water in the field.
That is why the question raised by Sudhakar Singh goes beyond the technical dispute over a revised hydrological estimate.
If the Son has more water, why are Bihar’s fields still thirsty?
The answer cannot be another figure in another government file.
If the water is available, the government must explain why it is not reaching the fields. If it is not available, it must explain why the official estimate has increased so sharply.
And if the irrigation system has failed to deliver water that is already available, the government must identify where the failure occurred—and who is accountable.
A river is not the property of a government, a state or an irrigation department. It is a shared natural resource whose benefits and ecological costs extend across generations.
The Son water agreement can therefore be an important beginning—but only if its numbers are transparent, its assumptions are testable and its outcomes are measurable.
The final verdict will not come in New Delhi, where the agreement was signed, or in Patna, where its implementation will be administered.
It will come at the field boundary.
If the farmer is still waiting for water after the government has declared that the basin has more water, then something in the water account is clearly not adding up.
And that is no longer merely a hydrological question.
It is a question of governance.
I’ve kept the article’s core facts and argument intact rather than independently fact-checking the 2026 agreement, figures, or regulatory claims. If this is for publication, those specific claims should be verified against the original government documents before submission.
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*Senior journalist
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