Water Resources, Hydrologic Cycle, and Environmental Impact

Water and Life

Life depends on water. Life originated about 3,800 million years ago, and there is no life without water. The importance of water for life is significant because:

• It is the major component of living things.
• It is the principal biological solvent.
• It provides a suitable medium for many of the reactions that characterize life.
• It helps maintain our body temperature constant.

Water: A Limited Resource

A resource is any component of the natural environment whose use is of interest to people. Resources are classified based on their capacity for regeneration:

• Renewable Resources: These are part of a natural cycle that can regenerate after use. A renewable resource can be consumed permanently, provided consumption does not exceed its capacity for recovery.
• Non-Renewable Resources: These do not regenerate after use, meaning they are depleted as they are utilized.

The Hydrologic Cycle

Water is a renewable resource through the hydrologic cycle. The phases of the hydrological cycle include:

1. Evaporation: The sun heats the water in the oceans, and some of it evaporates, entering the atmosphere.
2. Condensation: Water vapor cools and forms clouds, which returns the water to the surface as rain or snow.
3. Surface Runoff: Water falls onto the surface, flowing in streams and rivers.
4. Infiltration: Water goes through the ground surface to form groundwater.
5. Evapotranspiration.
6. Groundwater Runoff.

Water Usage Classification

The many uses of water have been classified as:

• Primary Uses: Those that are deemed necessary.
• Secondary Uses: Those that are expendable.

Consumptive vs. Non-Consumptive Uses

Uses are also categorized by whether they involve consumption:

• Consumptive Uses: These involve the consumption of water, meaning the water is not immediately available for reuse (e.g., urban use, agriculture).
• Non-Consumptive Uses: These are uses in which no water is consumed, allowing it to be reused immediately (e.g., hydroelectric power generation).

Ecological Flow

Ecological flow (or environmental flow) is defined as the minimum water flow below which the survival of the flora and fauna of the aquatic ecosystem and its banks is endangered. The environmental flow is not strictly a water use but rather a use restriction, limiting the availability of water for human consumption. It is also called maintenance flow and varies from one river basin to another.

Impacts of Water Consumption

Environmental impact refers to the effects of human activities on the environment. High consumption of water affects both the quality and quantity of the remaining water resources.

Water Quality Degradation: Pollution

The environmental problem generated by waste is generally called pollution, which is defined as any undesirable change in the pattern of soil, water, or air that harmfully affects health or the environment. Various types of pollution sources are differentiated:

• Urban Sources: Such as food waste and chemicals.
• Industrial Sources: Industries generating waste like fatty oils and heavy metals.
• Agricultural Sources: Such as fertilizers and pesticides.