Hydrology 4B Chapter 1 Introduction PDF

HYDROLOGY 4B Robert Elmer Horton CHAPTER 1: INTRODUCTION Father of Modern Hydrology As a pioneer in hydrology, Horton made What is Hydrology? imp...

HYDROLOGY 4B Robert Elmer Horton CHAPTER 1: INTRODUCTION Father of Modern Hydrology As a pioneer in hydrology, Horton made What is Hydrology? important discoveries in flood generation, Hydrology is the study of the distribution soil erosion, and the role of physical terrain and movement of water both on and below in runoff patterns. Horton overland flows the Earth's surface, as well as the impact of are named for his discoveries. The reason human activity on water availability and why he became the father of Modern conditions. Hydrology is because he analyzed and separated the water cycle into the History of Hydrology processes of infiltration, evaporation, It was along the Indus in Pakistan, interception, transpiration, overland flow, the Tigris and Euphrates in etc. Horton was the first to demarcate and Mesopotamia, the Hwang Ho in label these now-familiar stages of the China, and the Nile in Egypt that the cycle. first hydraulic engineers created canals, levees, dams, subsurface water conduits, and wells as early Hydrology as the study of Water as 5000-6000 years ago. Distribution Advances in the 18th century The distribution of water on Earth is included the Bernoulli piezometer uneven, with oceans holding about 97% of and Bernoulli's equation, by Daniel the planet’s water in the form of saline Bernoulli, the Pitot tube. water, while only around 3% is freshwater. The 19th century saw development Of that freshwater, the majority is locked in in groundwater hydrology, including glaciers and ice caps, while the remainder Darcy's law, the Dupuit-Thiem well exists in groundwater, lakes, rivers, and the formula, and Hagen-Poiseuille's atmosphere. Hydrology seeks to capillary flow equation. understand how this water is distributed Rational analyses began to replace geographically and temporally. empiricism in the 20th century, while governmental agencies Surface Water Distribution began their own hydrological Groundwater Distribution research programs. Of particular Glaciers & Polar Ice importance were Leroy Sherman's unit hydrograph, the infiltration Water Movement theory of Robert E. Horton, and Water moves continuously through the C.V. Theis' aquifer test/equation environment in a complex cycle known as describing well hydraulics. the hydrologic cycle. Hydrology Since the 1950s, hydrology has investigates the processes and pathways been approached with a more through which water moves across and theoretical basis than in the past, beneath the Earth’s surface and in the facilitated by advances in the atmosphere. This movement is driven by physical understanding of natural forces, including solar radiation, hydrological processes and by the gravity, and the Earth's rotation. advent of computers and especially geographic information systems Applications of Hydrology (GIS). The study of hydrology has several processes involved in the hydrologic cycle, practical applications that are crucial for the major processses are: managing water resources and mitigating environmental challenges. evaporation condensation Water Resource Management: Hydrology Precipitation helps in the sustainable management of water supplies for agriculture, industry, and Evaporation urban areas. By understanding water Evaporation is the change of state in a availability and movement, hydrologists substance from a liquid to a gas. can guide policies and practices that ensure long-term access to clean water. It can be easily visualized when our wet clothes dry in the sun. In this example, the Flood and Drought Prediction: Hydrologists liquid water is not actually vanishing — it use data on water movement and is evaporating into a gas, called water distribution to predict natural disasters vapor. such as floods and droughts. This is essential for developing early warning Condensation systems and planning infrastructure that can minimize the impact of such events. Condensation is the process whereby water vapor is changed into a liquid state. Environmental Protection: Hydrologists study how human activities, Condensation happens one of two ways: such as deforestation, urbanization, and Either the air is cooled to its dew point or it pollution, affect the natural water cycle. becomes so saturated with water vapor This knowledge is applied to develop that it cannot hold any more water. conservation strategies and restore Dew point is the temperature at which ecosystems affected by changes in water condensation happens. Air temperatures availability. can reach or fall below the dew point naturally, as they often do at night. That's Climate Change: why the ground, structures, and objects left Hydrology plays a vital role in outside are often coated with water understanding the impact of climate droplets in the morning. change on global water cycles, such as shifts in precipitation patterns, glacial Clouds are simply masses of water melting, and sea level rise. Hydrologists droplets in the atmosphere. Molecules in contribute to models that predict future water vapor are far apart from one another. water availability under different climate As more water vapor collects in clouds, scenarios. they can become saturated with water vapor. Saturated clouds cannot hold any HYDROLOGIC CYCLE more water vapor. The vapor condenses and becomes rain. According to the National Oceanic and Atmospheric Administration (NOAA), the hydrologic cycle involves the continuous circulation of water in the Earth - Atmosphere system. Of the many Precipitation Irrigation is an artificial watering of land necessary for vegetation that doesn't Precipitation is any liquid or frozen water acquire enough rainfall. It greatly affects that forms in the atmosphere and falls to the water cycle since these systems tap Earth. water from natural sources such as rivers and streams, which causes surface run-off Precipitation results when tiny and leaching. The presence of irrigation condensation particles, through collision systems also carries away the fertilizers and coalescence, grow too large for the and other pollutants used in farming to rising air to support, and thus fall to the these natural sources. Earth. Precipitation can be in the form of rain, hail, snow, or sleet. Precipitation is the Deforestation primary way we receive fresh water on Earth. Deforestation is the removal of a large number of trees over a wide area. Every HYDROLOGIC CYCLE IMPACT ON year, people cut and burn down billions of HUMANS trees to make room for agriculture, infrastructure, and urbanization and to Climate supply wood for construction, manufacturing, and fuel. The water cycle is intimately linked with energy exchanges among the atmosphere, A process called transpiration, occurs ocean, and land that determine the Earth's when trees and other plants suck water climate and cause much of natural climate from the ground through their roots, then variability. The impacts of climate change release that water from their leaves into the and variability on the quality of human life air. This process is a crucial part of how we occur primarily through changes in the get water. When people clear forests, this water cycle. water-storing effect vanishes along with the trees. The loss of transpiration has many Temperature Balance adverse impacts. Because forests are a primary source of rainfall, their destruction The water cycle is driven primarily by the causes severe droughts. energy from the sun. This solar energy drives the cycle by evaporating water from Urbanization the oceans, lakes, rivers, and even the soil. The process wherein water evaporates Urbanization involves the transformation of absorbs much of the energy from the sun natural landscapes into urban areas with thus balancing the temperature in most buildings, roads, and infrastructure. areas of the earth. Urban development dramatically alters the HUMAN IMPACTS ON HYDROLOGIC hydrological cycle by replacing permeable CYCLE surfaces (such as soil and vegetation) with impermeable surfaces (concrete, asphalt) Agricultural Activities Impermeable surfaces prevent infiltration, leading to reduced Agriculture is a major water user, especially groundwater recharge in dry and drought-prone areas that rely on Instead of infiltrating into the soil, irrigation to support agricultural production. rainfall quickly becomes surface  runoff, resulting in increased Terrestrial phase of the hydrologic flooding and diminished water cycle, on the other hand, describes water availability during dry periods movement in, over, and through the Earth. Surface Water Phase PHASES OF HYDROLOGIC CYCLE Runoff is the portion of precipitation that falls on areas ATMOSPHERIC PHASE where water is rapidly discharged Atmospheric phase of the from the area through stream hydrologic cycle describes water channels. Depending on the movement as gas (water vapor) and conditions, different types of runoff liquid/solid (rain and snow) in the are generated. atmosphere. ○ Infiltration Excess Runoff Precipitation Infiltration excess Precipitation is a process by runoff occurs when the which any liquid or frozen water that infiltration rate of the soil is forms in the atmosphere falls under less than the rainfall rate, gravity in the form of rain, snow, meaning, there is more hail, sleet, and fog. water than land can absorb. Condensation This type of runoff is Condensation is the more common in urban process by which water vapor is areas and generally occurs converted to liquid seen as clouds. during intense thunderstorms or on soils Evapotranspiration (Evaporation + with low infiltration rate, Transpiration) such as compacted soils Evapotranspiration is the and clays. sum of all processes by which water ○ Saturation Excess Runoff moves from the land surface to the Saturation excess atmosphere through evaporation runoff occurs when the soil and transpiration. profile becomes saturated with water and can store no Evaporation is the process more precipitation, by which water moves from the meaning, soil already holds surface to the atmosphere in the water as much as possible form of water vapor. thus it cannot further absorb more water. The process by which plants carry water from soil into Groundwater Phase leaves and then released to the ○ Infiltration atmosphere as water vapor is Infiltration is the called transpiration. process by which water infiltrates the soil. It is the TERRESTRIAL PHASE downward entry of water into the soil.  ○ Percolation Percolation is the process by which water enters the ground surface and travels through the soil to finally join the groundwater reserves. Percolation is responsible for recharging aquifers. Aquifer An aquifer is a body of porous rock or sediment saturated with groundwater. INTERRELATIONSHIPS OF PHASES OF THE HYDROLOGIC CYCLE The interrelationships of phases of the hydrologic Cycle are crucial in regulating the availability of water, supporting ecosystems, and influencing weather and climate. Disturbances in one phase, such as changes in evaporation rates caused by global warming, can have far-reaching consequences across the hydrologic cycle. Understanding these relationships aids in water resource management, flood mitigation, and drought prediction.