Solution:
(i) Classification of situations
- **(a)** Region with high annual rainfall: **Not suffering from water scarcity**
- **(b)** Region having high annual rainfall and large population: **Suffering from water scarcity** (due to high demand)
- **(c)** Region having high annual rainfall but water is highly polluted: **Suffering from water scarcity** (pollution affects usability)
- **(d)** Region having low rainfall and low population: **Not suffering from water scarcity** (low demand)

(ii) Statement not in favour of multi-purpose river projects
- **(c)** Multi-purpose projects lead to large scale displacements and loss of livelihood. (This is a disadvantage, not an argument in favour.)

(iii) Correcting false statements
- **(a)** Multiplying urban centres with large and dense populations and urban lifestyles have **not** helped in proper utilisation of water resources.
- **(b)** Regulating and damming of rivers **does** affect the river’s natural flow and its sediment flow.
- **(c)** Today in Rajasthan, the practice of rooftop rainwater harvesting has gained popularity **despite low water availability** due to the Indira Gandhi Canal.

Solution:
(i) Water becomes a renewable resource through the natural hydrological cycle, where evaporation, condensation, and precipitation continuously recycle water, replenishing sources like rivers, lakes, and aquifers.

(ii) Water scarcity refers to the insufficient availability of freshwater, caused by factors like over-extraction, pollution, climate change, and population growth, leading to competition for limited resources.

(iii) Advantages of multi-purpose river projects include irrigation, flood control, and hydroelectric power. Disadvantages involve ecological disruption, displacement of communities, and high financial costs, potentially harming local economies and environments.

Solution:
(i) In semi-arid regions of Rajasthan, rainwater harvesting involves constructing structures like johads, which are small earthen dams that capture runoff water. These are built in low-lying areas to recharge groundwater. Villagers also create rooftop harvesting systems, directing rainwater into storage tanks. The technique reduces surface runoff and minimizes soil erosion, enhancing water availability during dry periods.

(ii) Modern adaptations of traditional rainwater harvesting include using advanced materials like reinforced concrete for storage tanks, incorporating filtration systems for cleaner water, and employing smart sensors for monitoring water levels. Additionally, community awareness programs promote sustainable practices and encourage the use of technology, such as apps for tracking rainfall and water usage. These adaptations help maximize efficiency, ensuring that harvested rainwater effectively meets the needs of growing populations.