ESHLDY30 Lecture 1 Introduction to Hydrology PDF

LECTURE 1: INTRODUCTION TO HYDROLOGY HYDROLOGY the branch of physical geography focused on studying water. HYDRO = WATER LOGY = THE STUDY OF NO WATER = NO LIFE HYDROLOGY the branch of physical geography focused on studying water. Existence Distribution Movement of water EXISTENCE OF WATER 1...

LECTURE 1: INTRODUCTION TO HYDROLOGY HYDROLOGY the branch of physical geography focused on studying water. HYDRO = WATER LOGY = THE STUDY OF NO WATER = NO LIFE HYDROLOGY the branch of physical geography focused on studying water. Existence Distribution Movement of water EXISTENCE OF WATER 1. Formation: Water likely existed on Earth from its early formation, around 4.5 billion years ago, primarily through two mechanisms: Outgassing from Volcanic Activity: When the Earth was still forming, volcanic eruptions released gases, including water vapor, from the planet’s interior. As the earth cooled, this water vapor condensed into liquid water, forming oceans. EXISTENCE OF WATER Water likely existed on Earth from its early formation, around 4.5 billion years ago, primarily through two mechanisms: Delivery by Comets and Asteroids: Some scientists believe that water could also have been delivered by icy comets or water-rich asteroids that collided with Earth during its early history, contributing additional water. EXISTENCE OF WATER These processes combined with Earth’s position in the “habitable zone” of the Sun, allowed liquid water to exist and persist essential for life as we know it. EXISTENCE OF WATER 2. States: Water exists in three states—solid (ice), liquid (water), and gas (vapor)—thanks to Earth's moderate temperatures and atmospheric pressure. 3. Reservoirs: Water is stored in oceans, glaciers, rivers, lakes, groundwater, and the atmosphere. DISTRIBUTION OF WATER Oceans: About 97.5% of Earth's water is saltwater in oceans, making it unsuitable for direct human use. Freshwater: Only 2.5% is freshwater, and most of this (about 68.7%) is locked in glaciers and ice caps. Groundwater accounts for 30.1%, while rivers and lakes make up only about 1.2%. Atmospheric Water: A small fraction exists as water vapor, but it plays a critical role in weather and climate systems.  SOURCES OF WATER ATMOSPHERIC WATER precipitation SURFACE WATER lakes, rivers, seas, oceans SUBSURFACE WATER groundwater EARTH’S ATMOSPHERE METEOROLOGY the science of the atmosphere, weather, and climate. METEOROS = THINGS IN THE SKY LOGY = THE STUDY OF  EARTH’S ATMOSPHERE an envelope of gases surrounding the earth and bound to it permanently by gravitational force composed of clean dry air, water vapor and impurities COMPOSITION OF THE EARTH’S ATMOSPHERE Constant Components: Proportions remain the same over time and location Variable Components: Amounts vary over time and location WATER VAPOR Water vapor is water in its gas form. It is created when water from oceans, rivers, or other sources evaporates (turns from liquid to gas) or when ice sublimates (turns directly from solid to gas). WATER VAPOR Water vapor changes phase easily because critical pressure and atmosphere are above atmospheric ranges 0-4% by volume agent or medium of heat transfer in the atmosphere polar regions have lesser distribution compared to the equatorial regions  >120km altitude: The final layer stretches into space and houses satellites. 90-120km altitude: This is the hottest layer because it absorbs the sun's radiation. Auroras occur in this layer. 50-90km altitude: The coldest layer which protects us from meteors because they burn up in this layer. 10-50km altitude: The ozone is found in this layer protecting us from UV rays. 0-10km altitude: The layer in which we live and weather occurs. MOVEMENT OF WATER HYDROLOGIC CYCLE deals with the storage, movement/transport and transformation of water in earth MOVEMENT OF WATER HYDROLOGIC CYCLE Water moves continuously through the hydrological cycle, driven by solar energy and gravity: HYDROLOGIC CYCLE movement of water through the cycle is erratic both in time and over area Drought Torrential rains El Niño/La Niña episodes HYDROLOGIC CYCLE El Niño: A climate phenomenon where sea surface temperatures in the central and eastern Pacific Ocean become unusually warm. Effects: Alters global weather patterns, often causing drought in some regions (e.g., Southeast Asia, Australia) and heavy rainfall/flooding in others (e.g., South America). Cause: Weakening or reversal of trade winds that usually push warm water westward in the Pacific. HYDROLOGIC CYCLE La Niña: The opposite of El Niño, where sea surface temperatures in the central and eastern Pacific Ocean are unusually cool. Effects: Generally brings more rainfall to places like Southeast Asia and Australia and can cause drier conditions in parts of South America and the U.S. Cause: Strengthening of trade winds that intensify the upwelling of cold water in the Pacific. HYDROLOGIC CYCLE Water is stored in: Atmosphere - water vapor Soil - soil moisture Surface waters - seas, oceans, streams, lakes, wetlands Plants and animals Groundwater HYDROLOGIC CYCLE There are 7 major processes in hydrologic cycle: EVAPORATION - water transports from free water surfaces or land surfaces to the atmosphere (liquid to gas). TRANSPIRATION - water transports from plants and animals to the atmosphere. CONDENSATION - water is converted from gas to liquid. PRECIPITATION - water transports from the atmosphere to land and/or water surfaces. RUNOFF - water flows on land surface or subsurface. INFLITRATION - water enters soil surface. GROUNDWATER FLOW - water flows beneath soil surface and stored in rock formations. HYDROLOGIC CYCLE Water is transformed: LIQUID TO GAS - evaporation and transpiration. GAS TO LIQUID - rainfall. GAS TO SOLID - solid forms of precipitation. SOLID TO LIQUID - snowmelt.