Option 1 -> Directly mentioned in the passage as challenges hindering widespread adoption.
Option 2 -> The passage discusses water crisis and scarcity, not surplus availability—this contradicts the context.
Option 3 -> The passage describes rainwater harvesting as "simple" and "relatively easy to implement even on a small scale"—not technology-dependent.
Option 4 -> Mandatory regulations are presented as positive measures that have "significantly improved water availability," not as challenges.
Hence, Option 1: lack of awareness and poorly designed systems -> The passage explicitly states "challenges such as lack of awareness, poor maintenance and improper design of harvesting systems hinder its widespread adoption" -> correct