What does the Brahma Vaivarta Purana say about the end of Kali Yuga?

Kalauḥ pañcasahasre ca gate varṣe ca mokṣaṇam।
Yuṣmākaṁ saritāṁ bhūyo madgṛhe cāgamiṣyatha॥

- Brahma Vaivartha Purana (Page 202, Verse 89, Prakriti Khand, Chapter 6)

Mother Lakshmi, Saraswati, and Ganga had to descend on earth due to a mutual curse. Regarding their salvation, the Lord tells them that after five thousand years of Kaliyug, they will attain salvation, and after being freed from the form of a river, they will come back to me in Vaikuntha.

Kaleḥ pañcasahasrāṇi varṣāṇi tiṣṭha bhūtale।
Pāpāni pāpino yāni tubhyaṁ dāsyanti snānata॥

Manmantropāsak sparśād bhasmībhūtāni tatkṣaṇāt।
Bhaviṣyanti darśanāc ca snānād eva hi Jāhnavi॥

- Verse 50, Krishna Janma Khand, Chapter 129

Shri Krishna said- O Ganga, you will stay on earth for five thousand years in Kaliyug. All the sins of the devotees will be destroyed by bathing in your water, chanting mantras, and seeing you.

Madbhaktāśūnya pṛthvī kaligrasta bhaviṣyati।
Etasminnantare tatra kṛṣṇādehavinirgataḥ॥

Verse 60, Krishna Janma Khand, Chapter 129

The effects of Kali will affect the earth, which is devoid of my devotees. Saying this, Shri Krishna left the earth.