The khadin rain water harvesting technique was originally developed in the 15th century by the Paliwal Brahmins in Jaisalmer district of western Rajasthan. ... The khadin system is based on the principle of harvesting rainwater on farmland and subsequent use of this water-saturated land for crop production.

Introduction:
Water harvesting is a traditional practice in India that involves collecting and storing rainwater for future use. Different regions in India have developed various methods of water harvesting based on their specific geographical and climatic conditions. One such method is the Khadin water harvesting technique.

Explanation:
The Khadin water harvesting method is primarily used in the state of Rajasthan, making option 'B' the correct answer. Let's explore this method in detail:

1. What is Khadin?
Khadin is a traditional water harvesting system that consists of a small earthen embankment built across a gentle slope. It is designed to capture and store rainwater during the monsoon season.

2. How does it work?
The Khadin system involves constructing a long earthen embankment perpendicular to the slope of the land. The embankment acts as a barrier, preventing the rainwater from flowing away and allowing it to collect in a storage pond or reservoir behind it. The embankment is built with a gentle slope on the upstream side and a steeper slope on the downstream side.

3. Key features of Khadin:
- The embankment is constructed using locally available materials, such as soil, stones, and rocks.
- The embankment is typically between 1 to 3 meters high and 10 to 15 meters wide.
- Vegetation is planted on the embankment to prevent erosion and improve water percolation.
- The storage pond behind the embankment can store a significant amount of rainwater for agricultural and domestic purposes.

4. Advantages of Khadin:
- The Khadin system helps recharge groundwater by allowing rainwater to percolate into the soil.
- It provides a reliable source of water for irrigation, especially during dry seasons.
- The stored water can be used for livestock and household needs, reducing dependence on external water sources.
- The embankment also acts as a windbreak and prevents soil erosion.

Conclusion:
The Khadin water harvesting technique is a sustainable and efficient method used in Rajasthan, India, to capture and store rainwater. It helps in addressing the water scarcity issues in the region and enables agricultural activities to thrive even in arid conditions.