The answer to the question is: The mourning of Odisha is associated with the Mahanadi river.

In Odisha, the Mahanadi river is considered to be of great cultural and religious significance. The river is not only an important source of water and irrigation for the state, but it is also associated with several religious and cultural traditions.

The term “mourning of Odisha” refers to a ritual performed by the people of Odisha during the month of Kartik, which is considered to be a sacred month in the Hindu calendar. During this time, people offer prayers and perform rituals in honor of their ancestors and deceased loved ones.

The Mahanadi river is an important part of this ritual, as people take a dip in the river and offer prayers to their ancestors. The river is also considered to be a symbol of life and fertility, and its waters are believed to have healing properties.

In conclusion, the mourning of Odisha is associated with the Mahanadi river, which holds great cultural and religious significance in the state of Odisha.