Think of them as giant water buckets, collecting and storing water. With the pace of almost two big dams (more than 15m high) constructed every day, they're the celebrities of the water world.

Pros:

• 'Flood-Drought Bouncers': Dams control both floods and droughts.
• 'Power Plants': They generate hydroelectric power.
• 'Irrigation Improvers': They provide water for farming.
• 'Water Highways': They improve navigation.
• 'Holiday Spots': They're hotspots for recreation and tourism.

Cons:

• 'Water Wasters': They lose water through evaporation.
• 'Salinization Source': They cause salt accumulation.
• 'People Displacers': They require people to relocate.
• 'Time Capsule Drowners': They submerge archaeological sites.
• 'Quake Makers': They add seismic stress.
• 'Erosion Enablers' and 'Silt Settlers': They cause channel erosion downstream and silt buildup upstream.
• 'Fertility Faders': They reduce fertility downstream due to sediment decline.

Real World Example: The Three Gorges Dam in China, while generating massive hydroelectric power and preventing floods, led to significant population displacement and archaeological site submersion.

Imagine it like a water delivery system. From an area with plenty of water to areas running dry.

Real World Example: China's South–North Water Diversion Project is like a long water highway, spanning 2,400 km, redirecting 44.8 billion cubic meters of water from the wetter south to the dry north. The project cost a whopping £48 billion and required 350,000 people to move.

They're like superheroes that convert salty seawater into fresh, potable water for us to drink or to irrigate crops.

Real World Example: The Sorek Desalination Plant in Israel is a marvel of technology, supplying large amounts of freshwater from the salty Mediterranean Sea.

Here, we're setting up nets to catch rain and direct it to the soil where it can be used by crops, stored for later, or allowed to seep into the ground to recharge groundwater.

Real World Example: In India, rainwater harvesting has been practiced for centuries, with innovative methods like the "step wells" in Rajasthan or the "Ahar Pynes" system in Bihar.