An agriculture expert does a deep dive into the science
I have a question that no researcher, water expert or academic has been able to answer: how did Pakistan’s provinces share water from the River Indus before the 1991 agreement and the Indus River System Authority or Irsa? This question drives me crazy every year when people start griping about water shortages in Sindh.
The complaining stops when there is news of scattered rains in the north or the monsoon mid-June. And then people forget. Then they start again the next year but we are nowhere near any answers.
For what it is worth, I’ve gathered that Sindh’s water scarcity is caused by a few major problems, which no one is talking about. Allow me to make a case.
First, where the Indus River water comes from
Historically, the Indus River flows start in mid-April every year. There is a misconception that the Sindhu is a perennial or never-ending river. The truth is that the water in the river does not run constantly all year round because the source of that water ebbs and flows itself.
The water comes from two places: the Himalayan glaciers when they start melting as temperatures go up in March-April every year and monsoon rains, mid-July to mid-September. And so actually, the rest of the year the river is limited.
How Sindh waters its crops from the Indus River
So how did the people of Sindh get water for their early kharif crop sowing in March for the last forty years? For that we should thank the Tarbela Dam in KP commissioned in 1975. It used to store floodwater that would be used later on in the year for the Rabi winter crops sown in October. Even after water was used up in the winter, Tarbela could still save up to 3 million acre feet (MAF) which would then be used all the way down south in Sindh.
The reserves fed Sindh’s Nara and Rohri irrigation canals for early summer Kharif cropping starting April 1. These Sindh areas are famous for producing cotton and chillies because of their specific climate. In fact, these crops rise earlier than others in Pakistan.
The Tarbela link to Sindh’s water shortage
Unfortunately, Tarbela’s pond where the water is stored is 43% silted up. This means that it isn’t possible to save that extra water for the early kharif. With this backup plan gone, the Indus River is only left with glacier melt and rain supplies.
The people in the south-most part of Pakistan are the hardest hit. The people of Khyber Pakhtunkhwa and Punjab still have the advantage of receiving water from hill torrents and fresh groundwater to face the heat. In Sindh, according to careful estimates, only 15% of the underground water aquifer is fresh and whatever little exists is under serious stress because it is overexploited. People keep sucking groundwater out of the ground.
Sindh’s farming choices affect water use
This time of the year there is always a water crisis in Sindh’s Badin and Thatta which fall in the command area of or are fed by Kotri Barrage. A simple reason for this is that farmers have changed the time they sow their crops.
Historically, Thatta and Badin were famous for growing rice, which is flexible and was fed by flood irrigation. They could wait up till June and July. Even if you delayed supplying it with water, it would give you a good harvest. But now, this area is growing more cotton, sugarcane, wheat and tomatoes. These crops need perennial supplies of water—or water the whole year round. The problem is that Kotri Barrage’s canals were designed to be for just six months a year (non-perennial). Last year, the tomato crop was harvested in the Rabi season. This meant water was supplied more to the crop than for drinking from the canals. So, even in non-perennial canals, the irrigation department releases some water for drinking for the villages. But influential landowners take that water and use it for their new choice of perennial crops.
Water stealing, riverbed choking
Sindh seems to be increasingly facing conveyance losses in the riverbed between Tarbela Dam and Kotri Barrage. It is shrinking with encroachments for agriculture. The fields are irrigated with private lift machines and tube wells. A few experts have been talking about this, but it will take time for it to really sink in. The actual term for this problem is Conveyance Losses in River.
If you try to look up research on estimates of river losses, you
will find only two reports:
i. The Phenomena of Losses and Gains in Indus by S.S. Kirmani from 1956
ii. Lower Indus Development Plan 1966 by Hunting & Co and Mott Macdonald, with a chapter on Sukkur to Kotri
The first report is quite a consolidated piece of research. Engr. Kirmani was a senior engineer and member of the Pakistan Water Delegation to Washington D.C.
According to his report, in the summer, the water flow starts rising as the Himalayan glaciers melt. This flow moves from the mountainous ranges to the mud flats to saturate the dry riverbed. This process is called seepage which causes “losses” in surface flows. Sometimes, the hydrograph rises from rains in the basin and this increase in the flow is called a “temporary gain”.
In the winter, the usual flow from glaciers is stopped because of the freezing temperatures. As a result, the freed-up riverbeds get back a flow of seepage water from adjoining areas. This stage is called “gains”. It happens in KP and Punjab, where the riverbeds are lower than the ground surface.
In simple terms, this is a natural phenomenon whenever the level of a river or lake drops, the percolation towards its adjoining areas returns and the depression of the channel acts like a drain. This factor seems to have worked in the past, but now surface and ground water consumption have increased visibly. The Kirmani report elaborates five phases in the Indus River’s flows:
1. Rising Period-1 (1st April – 10th June) – Maximum Losses
2. Rising Period-2 (11th June – 31st July) – Medium Losses
3. Falling Period-1 (1st August – 10th September) – Minimum Losses
4. Falling Period-2 (11th September – 10th October) – Minimum Gains
5. Low Flow Period (11th October- 31st March) – Maximum Gains
This assessment is based on data from 1936 to 1946. When you do the math, on average there were 26% losses and 10% gains annually, which ends up as 16% losses yearly. If we compare this to present day data from 2012 to 2020, the annual losses have reached 32%. It is evident that this has happened because of encroachments and consumption in the riverine belt.
Today the irony is that the 1956 report was based on pure gauge readings and technical expertise. If we try to measure the same data today, it would be refuted and the authenticity of the readings would be questioned. Some irrigation managers will claim the gauges are outdated, others will claim that even if the gauges are good, the gate calibration is outdated.
If we cannot actually measure how much water is flowing, then how are the provinces fighting over water?
Last year, the problem was with IRSA and the prime minister removed its members. Punjab claimed they installed telemetry at their headworks and Sindh’s members said even if such a measuring system were installed, the gates are not calibrated, so the readings are not legitimate.
It is a shame that satellite remote sensing is not used for if we were measuring our river with it, ambiguities in the flow or cultivation stats would not matter anymore. Satellite imagery shows you everything—how much water is flowing in your rivers and canals, how much area is irrigated, what kinds of crops are cultivated, how much water is used and how much is wasted.
Here I am sharing an image as an example of how agricultural encroachments take place in a riverbed. On the main screen, the area to be assessed is demarcated with the help of river dykes. On the other side there is a graph of the vegetative index from 2000 to 2020. The trend line shows that the cultivated area has doubled in the last twenty years. The water consumed here is actually the right of the tail-end farmer in Sindh. (Imagery taken from a web platform, which is joint effort of Google and FAO. It is called Beta Earth.)
A recent land cover reports of KP, Punjab and Sindh says that farming encroaches on 1.93 million acres of the Indus riverbed. These riverine encroachers are freeloaders, using free land and free water. They are spoiling our natural resource base and creating water shortages at the tail-end of the system.
From last year, the Government of Sindh has been trying to free up encroached lands in the riverine area and the courts seem to be supporting it. The people of Sindh learned these lessons during the river floods of 2010, 2013, 2014, and 2015 and rain floods of 2011, 2012 and 2013. But who will ask the governments of Punjab and Khyber Pakhtunkhwa to start doing the same?
The writer is an agriculture and irrigation engineer. He tweets at @UmerKarim78