India, July 10 -- The climate crisis is making India's water crisis harder to manage. Rainfall is becoming less reliable and more erratic, and is arriving in short, intense bursts that run off before the ground can absorb them, while aquifers that took millennia to fill are being depleted within decades. What, then, is India's water-resilience strategy for rural regions where nearly half of India's workforce lives and still depends on agriculture for their livelihood?

Part of the answer is in plain sight. Every city that consumes water also produces a steady, drought-proof stream of wastewater. Yet, across India, this resource is still largely treated as waste rather than a source of fresh water. Bengaluru offers a glimpse of what is pos...