Hydrology: Study of Water and its Processes

Hydrology CEE 440 Lecturer Notes 1 • Hydrology is a multidisciplinary scientific field. • It studies water in the environment. • The scope includes the movement, distribution, and quality of water. • Hydrological cycle mechanisms are also studied. • It plays a crucial role in managing water resources, environmental impacts, and natural hazard mitigation. • Hydrology comes from Greek words "hydro" (water) and "logos" (study). • It deals with properties, distribution, and circulation of water. • Sub-disciplines include surface water hydrology, groundwater hydrology, and urban hydrology. • Surface water hydrology focuses on rivers, lakes, and streams. • Groundwater hydrology studies underground water systems. • Urban hydrology deals with water management in urban areas, considering runoff and drainage. • Essential in agriculture, ecology, urban planning, and disaster management. • Informed decisions on water allocation, flood control, and sustainable water management. • Crucial in assessing climate change impacts on water availability and quality. • Ancient civilizations recognized water's vital role. • Developed sophisticated irrigation systems. • Formalization as a scientific discipline began in the 18th and 19th centuries. • Pioneers like Leonardo da Vinci, Edme Mariotte, and Pierre-Simon Laplace made significant contributions. • Also known as the water cycle. • Describes the continuous movement of water between atmosphere, land, and oceans. • Includes processes like evaporation, condensation, precipitation, infiltration, runoff, and transpiration. • Solar energy drives the cycle. • Evaporation: Liquid to vapor form from oceans, lakes, and rivers. • Condensation: Water vapor cools and forms clouds. • Precipitation: Rain, snow, sleet, and hail fall to Earth's surface. • Infiltration: Water movement into soil surface, replenishing groundwater. • Runoff: Excess precipitation flows into streams and rivers. • Transpiration: Release of water vapor from plant leaves. • Solar radiation, atmospheric temperature, humidity, and wind patterns. • Topography and land cover. • Human activities like deforestation, urbanization, and agriculture. • Cornerstone of environmental science. • Provides insights into water's behavior and interactions. • Evolved from ancient agricultural practices to modern water resource management. • Continues to address contemporary water challenges and foster sustainable practices. • The hydrological cycle, also known as the water cycle, is a fundamental process governing the movement of water on Earth. • It involves various interconnected processes such as evaporation, condensation, precipitation, infiltration, runoff, and transpiration. • These processes redistribute water globally, maintaining Earth's water balance and sustaining life. • Key Processes of the Hydrological Cycle: 1. Evaporation: o Water transforms from liquid to vapor due to solar radiation. o Primarily occurs from oceans, lakes, and rivers. o Driven by heat energy absorbed from the sun. o Active in warm, sunny regions with abundant water bodies. 2. Condensation: o Warm, moist air rises and cools at higher altitudes. o Water vapor condenses into droplets or ice crystals, forming clouds. o Clouds are formed through this process of condensation. 3. Precipitation: o Cloud droplets combine to form larger droplets or ice crystals. o Heavy enough to fall under gravity. o Types include rain, snow, sleet, or hail. o Return water to the Earth's surface. 4. Infiltration: o Water percolates through the soil. o Replenishes groundwater reservoirs. o Influenced by soil type, vegetation cover, and land use. 5. Runoff: o Movement of excess water across the land surface. o Driven by gravity. o Flows into rivers, lakes, and oceans. o Influenced by terrain and land cover. 6. Transpiration: o Plants absorb water through roots and release it into the atmosphere. o Water vapor contributes to cloud formation and precipitation. o Completes the cycle. • Factors Influencing the Hydrological Cycle 1. Solar Radiation: o Primary energy source driving evaporation. o Determines regional temperature gradients and precipitation regimes. 2. Atmospheric Circulation Patterns: o Hadley, Ferrel, and Polar cells transport heat and moisture globally. o Influence precipitation patterns and climate zones. 3. Topography: o Orographic lifting modifies precipitation patterns. o Enhanced rainfall on windward slopes; rain shadows on leeward slopes. 4. Land Cover and Land Use Changes: o Deforestation, urbanization, and agriculture alter surface runoff and infiltration rates. o Impact evapotranspiration processes. 5. Human Activities: o Construction of reservoirs, dams, and irrigation systems. o Regulate water flow and distribution.