Hydrology Chapter 1 PDF

CHAPTER 1A: HYDROLOGY AND HYDROLOGIC CYCLE A. a.a.r., long term precipitation, space average over the basin using isohyets and several other methods LEARNING OUTCOMES...

CHAPTER 1A: HYDROLOGY AND HYDROLOGIC CYCLE A. a.a.r., long term precipitation, space average over the basin using isohyets and several other methods LEARNING OUTCOMES (Rainbird, 1968) B. Depth-area-duration (DAD) curves for critical storms 1. Hydrology vs. Hydraulics (station equipped with self-recording raingauges). 2. Scope of Hydrology 3. Sample Hydrologic Data HYDROLOGIC CYCLE 4. Hydrologic Cycle 5. Watershed/Drainage Basin 6. Watershed Delineation 7. Philippine Watersheds HYDROLOGY VS. HYDRAULICS HYDROLOGY science, which deals with the occurrence, distribution and disposal of water on the planet earth; it is the science which deals with the various phases of the hydrologic cycle. Keywords: natural processes HYDRAULICS branch of engineering that applies fluid mechanics principles to problems dealing with the collection, storage, control, transport, regulation, measurement, and use of water. Keywords: man-made processes SCOPE OF HYDROLOGY 1. Maximum probable flood that may occur at a given site and its frequency; this is required for the safe design of drains and culverts, dams and reservoirs, channels and other flood control structures. 2. Water yield from a basin—its occurrence, quantity and frequency, etc; this is necessary for the design of dams, municipal water supply, water power, river navigation, etc. 3. Ground water development for which a knowledge of HYDROLOGIC CYCLE- is the water transfer cycle, which the hydrogeology of the area, i.e., of the formation soil, occurs continuously in nature. recharge facilities like streams and reservoirs, rainfall pattern, climate, cropping pattern, etc. are required. IMPORTANT PHASES 4. Maximum intensity of storm and its frequency for the design of a drainage project in the area. 1. Evaporation 2. Evapo-transpiration or Transpiration HYDROLOGIC DATA 3. Condensation 4. Precipitation 1. Climatological data 5. Runoff 2. Hydrometeorological data like temperature, wind 6. Infiltration velocity, humidity, etc. 7. Groundwater Flow 3. Precipitation records 4. Stream-flow records WATERSHED/DRAINAGE BASIN 5. Seasonal fluctuation of ground water table or piezometric heads For every stream, a well-defined area of land intercepts the 6. Evaporation data rainfall and transports it to the stream. The area of land is called 7. Cropping pattern, crops and their consumptive use the catchment area, watershed, or drainage basin. These three 8. Water quality data of surface streams and ground water terms generally are used interchangeably. 9. Geomorphologic studies of the basin, like area, shape and slope of the basin, mean and median elevation, mean temperature (as well as highest and lowest temperature recorded) and other physiographic characteristics of the basin; stream density and drainage density; tanks and reservoirs 10. Hydrometeorological characteristics of basin: WATERSHED/DRAINAGE BASIN Swale: bent contour lines that point uphill Ridge: bent contour lines that point downhill Saddle: transition between two ridges and two swales. WATERSHED DELINEATION STEPS 1. Identify peak points or those with the highest elevations (usually closed shapes on a contour map 2. Following the rules on the next slide, connect each peak. 3. Locate the draining point. 4. Find the watershed area using squares. Trace the watershed on a graphing paper then count all the squares located within the watershed boundaries. RULES PHILIPPINE WATERSHEDS 1. Draw the divide perpendicular to contour lines (when the contour lines represent a slope). 2. Draw the divide along a ridge and across a saddle. 3. Never draw the divide along or across a swale. 4. Draw the divide between and parallel to two contour lines of the same elevation. 5. When in doubt about your line, test it by imagining a drop of rain landing near the line; then trace the runoff path taken by the drop. If the drop flows toward the point of analysis, it landed inside the basin. (When water runs downhill, it travels perpendicular to the contour lines.)  It flows towards Manila Bay during the wet season and reverses to Laguna de Bay during the dry season. Brackish water resulting from the mix of fresh and saltwater is favorable to fishermen and aquaculture operators who grow bangus and other brackish water species in the lake. [Project e-SMART, 2020] The La Mesa Reservoir releases 10 times more water than it receives from its own catchment area. The La Mesa Watershed is the last rainforest of its last rainforest of its size in NCR, as majority of the metro has an urban land PASIG RIVER IS THE ONLY DRAINAGE OUTLET OF cover. LAGUNA BAY All other streams within the Laguna de Bay watershed are draining into the lake. Pasig River is the only stream through which Laguna de Bay drains to Manila Bay. The 25-km long stream (inclusive of Napindan Channel) serves as the main conveyance channel not only of water but also of contaminants and other materials from the drainage basin to Manila Bay, and between the two water bodies. The Manila Subbasin which is around 346 sq.km is part of the Pasig-Marikina-Laguna de Bay Basin. It connects the whole basin to Manila Bay through the Pasig River. PASIG RIVER IS CONNECTED TO MARIKINA RIVER, Which has the largest drainage area in the Pasig-Marikina- Laguna de Bay Basin. Pasig River is situated at the downstream end of Marikina River, which has the largest drainage area (around 534.8 sq. km) in the whole Pasig-Marikina-Laguna de Bay complex. The Marikina River Basin receives an average annual rainfall of approximately 2,750mm. PASIG RIVER CHANGES FLOW DIRECTION DEPENDING ON THE TIME OF THE YEAR THE PASIG-MARIKINA-LAGUNA DE BAY BASIN IS MOSTLY COMPOSED OF THE PROVICES OF LAGUNA, RIZAL, AND METRO MANILA.s About 55% of the Pasig-Marikina- Laguna de Bay Basin is within Laguna. Rizal and NCR also constitute a significant part of the basin forming around 23% and 11% of it respectively. Other areas also found within the basin lie in the provinces of Batangas, Cavite, Quezon, and Bulacan. The Pasig-Marikina-Laguna de Bay basin is the 2nd largest major subbasin within the Manila Bay Watershed Area. LAGUNA DE BAY To mitigate flooding downstream, which includes a portion of the highly urbanized Metro Manila, flood waters are diverted to Laguna de Bay through the Rosario Weir (flood gate) and the Manggahan Floodway (diversion channel). In addition, to regulate the storage of flood waters in Laguna de Bay, the Napindan Hydraulic Control Structure (NHCS) was constructed to control the exchanges between Pasig River and PHILIPPINE WATESHEDS Napindan Channel. Learn more about these hydraulic structures Watch the following videos about the different subbasin and and the flood control system in the next slides. watersheds within and near Metro Manila. Via Facebook page of Project e-SMART: https://fb.watch/3sMRi8idz_/ La Mesa Watershed: https://www.youtube.com/watch?v=PqqihHnVdmk CHAPTER 1B: CLIMATE CHANGE WEATHER refers to atmospheric conditions that occur locally over short periods of time—from minutes to hours or days. Familiar examples include rain, snow, clouds, winds, floods or thunderstorms CLIMATE refers to the long-term regional or even global average of temperature, humidity and rainfall patterns over seasons, years or decades. OZONE DEPLETION OZONE LAYER CAVITE RIVER BASIN thin part of the Earth's atmosphere that absorbs almost The Cavite River Basin has the longest coastline along Manila all of the sun's harmful ultraviolet light. Bay. Along its coast is also a unique feature called the Cavite Part of the stratosphere Spit. The basin has long and narrow subbasins and its river Made of ozone which is a system has a radial drainage pattern. molecule with three oxygen atoms  also as a result of certain chemical reactions (e.g., manufacture of cement). removed from the atmosphere (or "sequestered") when it is absorbed by plants as part of the biological carbon cycle. METHANE (CH4): From the production and transport of coal, natural gas, and oil. from livestock and other agricultural practices and by the decay of organic waste in municipal solid waste landfills. NITROUS OXIDE (N2O): From agricultural and industrial activities, combustion OZONE DEPLETION of fossil fuels and solid waste, as well as during treatment of wastewater. Thinning of ozone layer due to chlorofluorocarbons (CFCs) FLOURINATED GASES: which are everywhere, mostly in refrigerants and plastic Hydrofluorocarbons, perfluorocarbons, sulfur products since they are hexafluoride, and nitrogen trifluoride inexpensive, they don't catch because they are potent greenhouse gases, they are fire easily, and they don't sometimes referred to as High Global Warming usually poison living things Potential gases ("High GWP gases"). EL NINO PHENOMENON Caused by the warming of sea surface temperature in the Pacific and can affect air and sea currents. Results in reduced rainfall that led to dry spells, droughts and stronger typhoons. lasts for more or less 18 months in the Philippines trade winds weaken. Warm water is pushed back east, toward the west coast of the Americas. Term means “Little Boy,” or “Christ Child” in Spanish GREENHOUSE GASES Gases that trap heat in the atmosphere CARBON DIOXIDE (CO2 ): From burning fossil fuels (coal, natural gas, and oil), solid waste, trees and other biological materials, and LA NINA PHENOMENON characterized by unusually cold ocean temperature in the Equatorial Pacific which causes increased numbers of tropical storms in the Pacific Ocean. brings plenty of rain, with accompanying hazards Term means “Little Girl” GLOBAL EFFECT OF CLIMATE CHANGE EL NINO VS. LA NINA GLOBAL WARMING long-term heating of Earth’s climate system observed since the preindustrial period (between 1850 and 1900) due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth’s atmosphere.  measured as the average increase in Earth’s global It also encompasses making the most of any potential surface temperature. beneficial opportunities associated with climate change (for example, longer growing seasons or increased yields in some regions) GLOBAL WARMING VS CLIMATE CHANGE HOLISTIC APPROACHES: Climate Change refers to both human- and naturally produced 1. Global cooperation warming and the effects it has on our planet. It is the long-term 2. Enhanced government climate and environmental change in the average weather patterns that have come to policies define Earth’s local, regional and global climates. 3. Changed energy sources, from non-renewables to renewables (not abrupt but gradual shift) EFFECTS OF CLIMATE CHANGE 1. Global Warming 2. Lengthened Frost- free and Growing season 3. Changes in precipitation patterns 4. Extreme cyclone events HOW CAN YOU LESSEN THE AFFECTS OF CLIMATE 5. Extreme drought and CHANGE: heat waves 1. Speak up. “Climate change is real” 6. Iceberg melting 2. Power your home with renewable energy 7. Rise in sea level 3. Invest in energy-efficient appliances MITIGATION OF ON EFFECT OF CLIMATE CGANFE 4. Reduce water waste 5. Reduce waste MITIGATION 6. Buy better bulbs 7. Pull the plugs (in short lessen energy consumption) reducing climate change through reducing the flow of 8. Drive fuel-efficient vehicles heat-trapping greenhouse gases into the atmosphere, 9. Shrink your carbon imprints and profiles either by reducing sources of these gases (for example, the burning of fossil fuels for electricity, heat or transport) or enhancing the “sinks” that accumulate and store these gases (such as the oceans, forests and soil). Goal: to avoid significant human interference with the climate system, and “stabilize greenhouse gas levels in a timeframe sufficient to allow ecosystems to adapt naturally to climate change, ensure that food production is not threatened and to enable economic development to proceed in a sustainable manner” ADAPTATION adapting to life in a changing climate – involves adjusting to actual or expected future climate. Goal: to reduce our vulnerability to the harmful effects of climate change (like sea-level encroachment, more intense extreme weather events or food insecurity).  Common value = 1,374 W/m2 CHAPTER 1C: WEATHER BASICS (METEOROLOGY) EARTH-SUN RELATIONSHIP SOLAR RADIATION electromagnetic radiation emitted by the sun SOLAR CONSTANT rate at which solar radiation reaches the upper limits of earth atmosphere on a surface normal to the incident radiation and at earth’s mean distance from the sun  when the sun is nearest from the earth (occurs about January 3) SOLSTICE when the sun’s apparent path is displaced farthest north (Tropic of Cancer) or south (Tropic of Capricorn) from the earth’s equator. Solar radiation = “short” wavelengths (range 0.1 to 4.0 μm) Terrestrial radiation = “long” wavelengths (4.0 to 50 μm) ALBEDO Percent of the incoming solar radiation that is reflected from a EQUINOX surface. when the sun passes directly over the equator or when the sun’s apparent path and plane of the earth’s equator coincide. In Northern Hemisphere Vernal Equinox: on or about March 21 Autumnal Equinox: on or about September 22 Seasons: occur because the tilt of the Earth’s axis keeps a constant as the Earth revolves around the Sun. a) Summer in Northern Hemisphere b) Winter in Southern Hemisphere SUN-EARTH GEOMETRY affects the solar radiation received at any location and time ATMOSPHERIC PARAMETERS PRESSURE GENERAL RULE: Weather becomes stormy when air pressure falls and becomes fair when air pressure rises APHELION when the sun is farthest from the earth (occurs about July 4). PERIHELION  Idealized global circulation BAROMETER: Instrument used to measure pressure TEMPERATURE amount of heat energy possessed by an object degree of hotness or coldness of an object LOCAL ATMOSPHERIC CIRCULATION Units °C (Celsius) - Metric/SI °F (Fahrenheit) - English K (Kelvin) HUMIDITY amount of water vapor in the air. Relative humidity: measures the amount of water in the air in relation to the maximum amount of water vapor (moisture). The higher the temperature, the more water vapor the air can hold. SEA AND LAND BREEZES  TROPICAL heated air ascends at the equator, CELL proceeds toward the poles at upper levels, loses heat and descends toward the ground at latitude 30 °. Near the ground, it branches, one branch moving toward the equator and the other toward the pole. MIDDLE driven frictionally by the other two; its CELL surface air flows toward the pole, producing prevailing westerly air flow in the mid- latitudes POLAR CELL air rises at 60° and flows toward the poles at upper levels, then cools and flows back to 60° near the earth's surface ATMOSPHERIC PARAMETERS (AIR CIRCULATION) GLOBAL-SCALE AIR CIRCULATION Due to: Latitudinal difference in solar HADLEY CIRCULATION heating of the earth’s surface Air would rise near the equator and travel in the upper Inclination of the earth’s axis atmosphere toward the poles, then cool, descend into the lower of rotation atmosphere, and return toward the equator. Mechanics of the atmosphere fluid flow Coriolis effect CORIOLIS EFFECT produces the changes in wind direction and velocity towards the equator CLIMATIC CONTROLS The rotation of the earth from west to east changes the 1. Topography and location circulation pattern. As a ring of air about the earth's axis 2. Trade winds moves toward the poles, its radius decreases. In order 3. Fronts to maintain angular momentum, the velocity of air 4. Intertropical convergence zone (ITCZ) increases with respect to the land surface, thus 5. Monsoon winds producing a westerly air flow. The converse is true for 6. Tropical cyclones a ring of air moving toward the equator—it forms an 7. Easterly waves easterly air flow GENERAL ATMOSPHERIC CIRCULATION  Northern Hemisphere and a clockwise direction in the Southern Hemisphere. COMPOSITION OF TOTAL RAINFALL IN THE PHILIPPINES SOURCE OF RAIN % DISTRIBUTION TROPICAL CYCLONE 47 ITCZ, EASTERLY WAVES 39 SOUTHWEST MONSOON 7 NORTHEAST MONSOON 7 ITCZ a belt of low pressure which circles the Earth generally near the equator where the trade winds of the Northern and Southern Hemispheres come together. It is characterized by convective activity which generates often vigorous thunderstorms over large areas. CYCLONE general term for a weather system in which winds rotate inwardly to an area of low atmospheric pressure. For large weather systems, the circulation pattern is in a counterclockwise direction in the  “HABAGAT” OR SOUTHWEST MONSOON Summer Monsoon Hot and Moist wind from TROPICAL CYCLONE VS. HURRICANE VS. TYPHOONS Indian Ocean which may difference on where the storm originates in the world. strengthen tropical cyclone North Atlantic Ocean, central North Pacific Ocean, Brings rain over the and eastern North Pacific Ocean = “Hurricane” western seaboard Northwest Pacific Ocean = “Typhoon” May to September South Pacific and Indian Ocean = “Tropical Cyclone“ “AMIHAN” OR NORTHEAST MONSOON Winter monsoon Dry and cold wind from Siberia which may weaken tropical cyclones Brings rain over the eastern seaboard October to March EASTERLY WAVES a westward-moving, wavelike disturbance of low atmospheric pressure embedded in tropical easterly winds. affects the country from April to May FRONT transition zone between two different air masses at the Earth's surface. Each air mass has unique temperature and humidity characteristics. Often there is turbulence at a front, which is the borderline where two different air masses come together. The turbulence can cause clouds and storms. Types: 1. Cold Front 2. Warm Front 3. Occluded Front 4. Stationary Front