Introduction to Hydrology

Hydrology can be classified into quantitative and qualitative processes. Quantitative analysis involves measurable data, such as rainfall in mm or stream flow in m³/s. Qualitative analysis explains water-related processes like water movement and the effects of urban development on streamflows.

About 69% of freshwater is found in glaciers and permanent frost, 30% is groundwater, and 0.9% includes soil moisture and swamp water. Only 0.3% of freshwater comes from lakes and rivers, highlighting the limited readily available sources for consumption.

Saltwater makes up 97.5% of Earth's water, while freshwater accounts for only 2.5%. Desalinating saltwater is possible but expensive due to advanced processes like reverse osmosis, which yields small volumes and has high maintenance costs. Thus, the world still heavily relies on natural freshwater sources.

The hydrological cycle begins with evaporation from heat and transpiration from vegetation. Water vapor rises, cools, condenses into liquid water, forming clouds and precipitation. When precipitation reaches the ground, it becomes runoff, flowing from higher to lower elevations into streams or lakes. Water also infiltrates the ground, becoming groundwater or interflow. This continuous process is essential for water distribution.

Hydrology is the study of water, its occurrence, circulation, and distribution on Earth and in the atmosphere. It is crucial for water-related decision-making and solving engineering problems such as water supply, floods, and droughts.