SB 4.18.11
samam ca kuru mam rajan
deva-vrstam yatha payah
apartav api bhadram te
upavarteta me vibho
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
My dear King, may I inform you that you have to make the entire surface of the globe level. This will help me, even when the rainy season has ceased. Rainfall comes by the mercy of King Indra. Rainfall will remain on the surface of the globe, always keeping the earth moistened, and thus it will be auspicious for all kinds of production.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
King Indra of the heavenly planets is in charge of throwing thunderbolts and giving rainfall. Generally thunderbolts are thrown on the tops of hills in order to break them to pieces. As these pieces are spread asunder in due course of time, the surface of the globe gradually becomes fit for agriculture. Level land is especially conducive to the production of grain. Thus the planet earth requested Maharaja Prthu to level the surface of the earth, breaking up the high land and mountains.