According to the agreement of the 1351 treaty between Iran and Afghanistan

According to the agreement of the 1351 treaty between Iran and Afghanistan

Iran has a share of nearly one million three hundred thousand cubic meters of Hirmand water every year
This amount is effective if Afghanistan itself is not facing a water shortage.
According to this treaty, Iran has consumed more water than the specified consumption during 40 years, but due to crises and instability, the additional cost of this consumption was never calculated.
Iran’s annual consumption from Hirmand reaches nearly four million cubic meters of Iran per year. If this additional amount of Hirmand’s water consumption is calculated according to the price of water in the world market, which is 1.5 dollars, Iran will spend nearly 75 billion dollars during 40 years. ) is indebted to Afghanistan.
This calculation was accurately calculated by the president of Afghanistan at the time, and it was reported to the international institutions, which at the same time cut off the water supply to Iran until the payment of its debt amounting to 75 billion dollars.

During the government of Mohammad Ashraf Ghani, many delegations went back and forth between Iran and Afghanistan to solve the water issue, the Afghan side wanted debt and instead of paying the debt, the Iranian side raised the issue of the presence of immigrants in Iran for several decades.
On the Afghan side, in response to the statement of the issue of immigrants by the Iranian delegations, while thanking Iran for hosting the immigrants with documents, they warned that first of all, the presence of immigrants is 100% in Iran’s favor, they are considered cheap labor for this country, and they are also an institution. International organizations receive heavy fees due to the presence of immigrants, similarly, Afghans living in Iran pay fees for living in Iran in different areas and also pay for their water consumption. It has been used both in the Iran-Iraq war and in the Syrian war, as well as the humiliation and harassment of immigrants in Iran.

In the current situation, Iran is trying to take advantage of the lack of a legitimate government in Afghanistan to both make water flow inside Iran and cover up the 40-year-old debt problem.