When the water dries up in a sub-basin, it can have severe consequences for both the environment and the communities that rely on it. Here is a short explanation of what typically happens in such a situation:

1. Environmental Impact:
   • Ecosystem Disruption: The loss of water can disrupt the delicate balance of the local ecosystem. Aquatic habitats may disappear, leading to the decline or extinction of fish and other aquatic species.
   • Vegetation and Wildlife: Reduced water availability can lead to the withering of vegetation along the riverbanks and in wetlands, affecting the wildlife that depends on them.
   • Water Quality: As water levels drop, the remaining water can become more concentrated with pollutants and contaminants, further degrading water quality.
2. Economic Impact:
   • Agriculture: Agriculture heavily relies on water for irrigation. The drying up of a sub-basin can lead to crop failures and economic losses for farmers.
   • Industry: Many industries depend on water for their processes. Water scarcity can lead to production slowdowns or even shutdowns, causing job losses and economic hardships.
   • Energy Production: Hydroelectric power generation can be severely affected by reduced water levels, leading to energy shortages.
3. Social Impact:
   • Drinking Water Shortages: Communities that rely on the sub-basin for their drinking water supply may face shortages, which can pose health risks and necessitate emergency measures.
   • Migration: In extreme cases, prolonged water scarcity can force people to leave their homes in search of water and better living conditions, resulting in population displacement.
4. Conflict and Tensions:
   • Competition for Resources: Water scarcity can lead to conflicts and tensions between different user groups, such as agriculture, industry, and municipalities, all vying for the limited available water.
   • Legal Battles: Legal disputes over water rights and access to dwindling water resources can escalate.
5. Long-Term Consequences:
   • Ecosystem Recovery: Even if water returns to the sub-basin in the future, it can take years, or even decades, for ecosystems to recover and for communities to rebuild.

In essence, when the water dries up in a sub-basin, it can trigger a cascade of ecological, economic, and social challenges that require careful management, cooperation, and sustainable water resource practices to mitigate and address effectively.