In his letter to the prime minister, Mr Kejriwal said the city has been receiving 1,133 cusecs of water from Haryana since 1996, but recently, for the first time in 22 years, the neighbouring state has contested Delhi's right over this water and partially stopped the supply to the national capital.
"The Supreme Court has directed Haryana to keep supplying the earlier quantity of water till May 21, which means the state could reduce water supply after Monday," he said.
If that happens, it would create an "unprecedented shortage of water" in Delhi and could lead to "serious" law and order situation, the chief minister said.
"I would urge you (PM) to kindly use your good offices to persuade Haryana to continue supplying same level of water that it has been supplying for the last 22 years and not to disrupt it till the issue is finally decided by the courts," Mr Kejriwal said in the letter.
The Haryana government on Wednesday told the Supreme Court that it would maintain status quo on the supply of Yamuna river water to Delhi till May 21.
The top court asked the Delhi government and the Delhi Jal Board (DJB) to request Haryana for the maintenance of status quo on water supply and directed Haryana to take an independent decision on the matter.
He requested L-G Baijal to talk to the prime minister seeking his intervention in the matter if there is no response from Haryana.
Yesterday, too, Mr Kejriwal had written to his Haryana counterpart Manohar Lal Khattar and Delhi L-G over the issue.
In his letter to PM Modi, the chief minister said disruption in water supply from Haryana could affect Chandrawal water treatment plan, which supplies water to NDMC area where Rashtrapati Bhavan, parliament, embassies and major establishments like railway stations and hospitals are located.
"In addition to affecting the public at large, any disruption in water supply would affect all these establishments also. The Delhi government has already filed an application before Upper Yamuna River Board. However, final adjudication by the board could take some time," Mr Kejriwal said.