大量(dà liàng) - a large amount of, a great deal of; massive in Mandarin

大量 (dà liàng) sits in front of a noun and marks the quantity as large. It is written and formal in flavour: reports, news, business writing. 大量的水, 大量时间, 大量资金.

In everyday speech people say 很多 instead. 我喝了很多水 is what you actually hear; 我喝了大量的水 sounds like a medical note. Use 大量 when the scale itself is the point, or when the register is formal.

Two things to watch. It modifies nouns, not verbs, so it cannot mean "a lot" after a verb: for that you want 很多 or a resultative phrase. And 的 after it is optional before most nouns, so both 大量时间 and 大量的时间 are correct.