Hydrology and Environmental Studies | Geology Optional Notes for UPSC PDF Download

Geo-Hydrology and Hydrological Cycle

Geo-hydrological Investigation is a broad term referring to the study of the availability of water resources in specific areas. In India, this type of investigation encompasses various aspects, including:

• Assessing groundwater levels before and after the monsoon season
• Determining soil moisture content
• Evaluating the quality and quantity of water in various sources, such as rivers, lakes, groundwater, and reservoirs
• Analyzing the impact of urbanization on water demand
• Evaluating the influence of industrial and other economic activities on water demand
• Developing strategies for flood and drought control

Mapping plays a crucial role in geo-hydrological investigations, as it offers several benefits:

• Maps provide a clear and concise representation of complex water resource information, simplifying the investigation process.
• Topographic maps help identify flood- and drought-prone areas, allowing for better management and mitigation strategies. For instance, low elevation areas are more susceptible to flooding, while high elevations are more prone to drought.
• Mapping assists in strategic planning for projects such as river linking, by outlining routes and identifying potentially affected areas like national parks and wildlife sanctuaries.
• The use of maps aids in pollution mitigation and environmental conservation by providing visual data on water resources and their surrounding areas.

In summary, geo-hydrological investigation is a comprehensive study of water resource availability in specific regions. In India, this includes assessing groundwater levels, soil moisture, water quality and quantity, and the impact of human activities on water demand.

Hydrological Cycle Explained

• The hydrological cycle, also known as the water cycle, is a continuous process in which water is exchanged between the atmosphere, oceans, and continents through evaporation, transpiration, condensation, and precipitation. This cycle is essential for maintaining a constant amount of water vapor in the atmosphere, which in turn supports the Earth's climate and ecosystems.
• Evaporation is the process where water from bodies of water, such as oceans and lakes, is transformed into vapor and released into the atmosphere. Transpiration occurs when plants release water vapor through their leaves. Together, these processes are called evapotranspiration, which contributes to the moisture content in the atmosphere.
• In the next stage, this evaporated moisture condenses to form clouds. The process of condensation occurs when water vapor in the atmosphere cools down and turns back into liquid droplets, forming clouds. Following condensation, precipitation occurs when these water droplets, now in the form of rain, snow, or other forms, fall back to the Earth's surface.
• The hydrological cycle is a continuous process with no specific beginning or end, as water is constantly circulating within the Earth's system. This cycle plays a crucial role in shaping the Earth's climate and supporting life on our planet. Factors such as the sun's energy and air currents drive the hydrological cycle, enabling the various stages to occur and maintain balance within the Earth's water system.

Process of the Water Cycle

The water cycle is a continuous process that involves several stages, including evaporation and transpiration, condensation, precipitation, and runoff and infiltration.

1. Stage I: Evaporation and Transpiration: The first stage of the water cycle involves the sun's energy heating up bodies of water such as lakes, rivers, and oceans, causing the temperature of the water to rise. This increase in temperature leads to the evaporation of some water into the air. Rising air currents then carry the water vapor up into the atmosphere. Simultaneously, plants and trees lose water to the atmosphere through a process called transpiration, in which they release water vapor that also rises into the sky.
2. Stage II: Condensation: In the second stage, the water vapor that has risen into the atmosphere cools down due to the lower surrounding temperatures. As a result, the water vapor transforms back into a liquid through a process called condensation.
3. Stage III: Precipitation: During the third stage, wind movements cause the cloud particles to collide with each other. This causes the clouds to become heavy with water, eventually leading to the formation of rain-bearing clouds. The water then falls back onto the Earth's surface through a process known as precipitation, which can take the form of rain, hail, snow, or sleet, depending on temperature conditions.
4. Stage IV: Runoff and Infiltration: After precipitation, the water either runs off into oceans and rivers, flows along the ground surface, or is absorbed into the soil through a process called infiltration. Once the water has gone through these steps, it is ready to evaporate once more and repeat the earlier stages of the cycle.

By undergoing all these processes, the hydrological or water cycle continually replenishes the Earth's supply of fresh water.

Water Vapor in the Atmosphere

The atmosphere contains varying amounts of water vapor, ranging from zero to four percent by volume. On average, water vapor makes up approximately 2% of the atmospheric composition. A hygrometer is an instrument used to measure humidity, or the amount of water vapor present in the atmosphere.

• Significance of Atmospheric Moisture: Water vapor plays a critical role in regulating the Earth's temperature by absorbing both incoming and terrestrial radiation. This absorption process contributes to the heating of the Earth's surface. The amount of water vapor in the atmosphere also determines the energy available for the formation of storms and cyclones. Additionally, atmospheric moisture influences the rate at which the human body cools down in response to temperature fluctuations.
• Humidity: Humidity refers to the amount of water vapor present in the air or atmosphere. It is often expressed as relative humidity, which is a percentage of the maximum amount of water vapor that the air can hold at a specific temperature.

Conclusion

Geo-hydrological investigation is essential for understanding water resource availability and management in specific regions, such as India. The hydrological cycle, a continuous process involving evaporation and transpiration, condensation, precipitation, and runoff and infiltration, plays a crucial role in maintaining the Earth's climate and ecosystems. Water vapor in the atmosphere, which makes up approximately 2% of its composition, is significant in regulating temperature and influencing weather patterns. Overall, studying these processes and their impacts is vital for sustainable water resource management and environmental conservation.