In the wake of the Cauvery verdict by the Supreme Court, bus services between Tamil Nadu and Karnataka have been curtailed as a precaution, media reports said.
Commuters in Tamil Nadu's Hosur said that the number of buses plying to Karnataka has been reduced, ANI reported.
Both states have kept police on standby in case of an unfavourable verdict.
Security has been tightened in Karnataka's Bengaluru.
Bengaluru police commissioner T Suneel Kumar said 15,000 police personnel and personnel of the Karnataka State Reserved Police and other forces would be deployed.
"Special attention will be given to the sensitive areas where riots had taken place in the past," the commissioner said.
The sharing of the waters of the Cauvery river has been a contentious issue between Tamil Nadu and Karnataka since the last 120 years.
A three-judge bench is set to deliver the judgement today.
A bench comprising Chief Justice Dipak Misra and Justices AM Khanwilkar and DY Chandrachud had on September 20 last year reserved the verdict on the appeals filed by Karnataka, Tamil Nadu and Kerala against the 2007 award of the Cauvery Water Dispute Tribunal on sharing of water.