Mentor’s comment:

•  The question is straight forward.
•  In the intro, define what you understand by water stress.
•  In the body explain how water stress in India experience regional variation with some area experiencing more stress than the other like Vidarbha, Shimla, and Chennai with each experiencing the water stress. Also explain the reasons for the water stress like low groundwater levels, the salinity of water, lack of canal network, etc.
• Conclude by stressing the need to address the problem of water shock.

Answer:

Water stress is a condition where the demand for water exceeds the available amount during a certain period or when poor quality of available water restricts its use. Thus water stress occurs when deterioration of freshwater takes place in terms of quality and quantity.

Why does water stress differ regionally in India?

• Geographical variation: Geographically some areas are bound to be affected due to water shortage. These areas may be in rain shadow regions leading to depleted water tables. Ex: Vidarbha and Marathwada are water-stressed regions due to their location on the leeward side of western ghats.
• Agricultural patterns: Some agricultural regions over-utilize water leading to shortages. Such regions differ in terms of water stress when compared to regions that grow water-efficient crops. Ex: Sugarcane belt in UP is water-stressed due to the water drawing ability of the crop.
• Population density: The water availability for usage depends on the number of people depending on it. In areas where there is a high population per area such as urban areas, water stress is a common phenomenon. Ex: The Indus plains experience more water stress in comparison to coastal plains due to higher population density.
• Water management practices: Some parts of the country are very well ahead regarding water management techniques. The techniques may be modern technology-based such as water recycling or traditional ones like bawris. This ensures results in differences in water stress. Ex: Farmers in arid Rajasthan plains are likely to suffer less compared to their counterparts in Vidarbha due to their better water management techniques.

How water stress varies across regions in India

• The Himalayas: the main source of water for the Himalayan states are the freshwater springs fed by numerous rivers originating in the mountains. Global warming-related melting of glaciers has changed the water availability in these streams. Urbanization and the resultant pollution, lack of traditional water harvesting methods in these once upon a time water-ample regions is turning them into water-stressed regions.
• North Indian Plains: Population pressure, untreated sewage, overexploitation of water for agriculture and industries is polluting the rivers of these regions, thus making drinking water unavailable for many. 
• South India: Erratic rainfall, pollution of rivers due to heavy development activities, inadequate agricultural practices, over-dependence on groundwater, and lack of conservation efforts are resulting in an acute shortage of drinking water in many regions. Example: the recent water crisis in Chennai.
• Northeast: Despite being a region of high rainfall, received from both orthographic and monsoon winds, NE is facing a water crisis due to anthropogenic reasons such as mining, pollution and lack of water conservation strategies.
• Western India: Arid and semi-arid climate of Rajasthan and Gujarat due to scanty rainfall create the conditions of water scarcity. In regions of Maharashtra, the reason for the water crisis was incorrect cropping patterns.
• The Coastal plains: Rising sea level and overexploitation of groundwater are leading to the ingress of saline water in the aquifers leading to water stress.

Way forward

Water scarcity needs immediate attention. Long term solutions are better suited to handle the problems. Modification in water distribution techniques is the key. Steps that can be taken to reduce water stress are:

• Sustainable water management: Improving water infrastructure must be a priority, as water conservation and efficiency are key components of sustainable water management.
• Restoring and reviving traditional water harvesting structures such as wetlands, lakes, Johads(earthen check dams), etc.
• Reclaimed water: Rainwater harvesting and recycled wastewater also allow to reduce scarcity and ease pressures on groundwater and other natural water bodies. 
• Pollution control & better sewage treatment: Without proper sanitation, the water becomes full of diseases and unsafe to drink. That is why addressing pollution, measuring and monitoring water quality is essential. 
• Awareness & Education: Education is critical to solving the water crisis. In fact, in order to cope with future water scarcity, it is necessary to radically reform all forms of consumption

The reasons for water scarcity and the extent to which they are felt differ from region to region. However, it is clear that an acute shortage of drinking water is felt in both- regions with heavy rainfall and rainfall deficit regions. This calls for urgent actions in a decentralized manner to handle the water crisis all over the country.