Sentence:  The system, which involves an enormous network of fuel-burning chambers installed high up on the Tibetan mountains, could increase rainfall in the region by up to 10 billion cubic metres a year ... One of the biggest challenges the <WSD>rainmakers</WSD> faced was finding a way to keep the chambers operating in one of the world's most remote and hostile environments. 
Meaning of the word marked with <WSD> tags:  A person who seeks to induce rainfall through scientific methods, such as cloud seeding.