Topic-1-Hydrologic-Cycle.pdf

HYDROLOGY TOPIC 1: HYDROLOGIC CYCLE Prepared by Sir O  Water, which is found everywhere on the earth, is one of the most basic and commonly occurring substances. It is the only substance on earth that exists naturally...

HYDROLOGY TOPIC 1: HYDROLOGIC CYCLE Prepared by Sir O  Water, which is found everywhere on the earth, is one of the most basic and commonly occurring substances. It is the only substance on earth that exists naturally in the three basic forms of matter, i.e., liquid, solid, and gas WATER  Means the science of water Science that deals with the occurrence, circulation and distribution of water of the earth and earth’s atmosphere HYDROLOGY  Deals with estimation of water resources, the study of processes such as precipitation, runoff, evapotranspiration and their interaction Study of problems such as floods, droughts, and strategies to combat them. HYDROLOGY  HYDROLOGIC CYCLE The water cycle describes how water is exchanged (cycled) through Earth's land, ocean, and atmosphere. The water cycle consists of three major processes: evaporation, condensation, and precipitation.  HYDROLOGIC CYCLE The water cycle describes how water is exchanged (cycled) through Earth's land, ocean, and atmosphere. The water cycle consists of three major processes: evaporation, condensation, and precipitation.  HYDROLOGIC CYCLE The water cycle describes how water is exchanged (cycled) through Earth's land, ocean, and atmosphere. The water cycle consists of three major processes: evaporation, condensation, and precipitation.  1. Water Redistribution IMPORTANCE OF 2. Sustaining Ecosystems THE 3. Agriculture and Food Production HYDROLOGIC 4. Human Water Needs 5. Temperature Regulation CYCLE IN 6. Weather and Climate EARTH'S WATER 7. Erosion and Sediment Transport BALANCE 8. Groundwater Recharge 9. Sea Level Regulation  Human activities affecting the hydrologic cycle 1. Deforestation - increased runoff, soil erosion, and reduced groundwater recharge, disrupting the natural flow of water 2. Urbanization- water quickly runs off surfaces and can cause flooding and erosion 3. Agriculture - Over-irrigation can lead to waterlogging, salinization of soils, and increased evaporation. Runoff from agricultural fields can carry pollutants like fertilizers and pesticides into water bodies 4. Dams and Reservoirs- The construction of dams and reservoirs can regulate the flow of rivers, impacting downstream ecosystems and altering sediment transport 5. Water Withdrawal- Excessive extraction of water from aquifers (groundwater) for drinking, irrigation, and industrial purposes can deplete aquifer storage and lead to land subsidence 6. Climate Change- climate change can alter precipitation patterns, temperature, and snowmelt timing, affecting the hydrologic cycle 7. Pollution- Pollutants can disrupt aquatic food chains, harm aquatic life, and degrade water resources 8. Land Use Changes- Conversion of natural landscapes to agriculture or urban areas can alter the natural flow of water 9. Mining- Mining activities can alter the hydrologic cycle by disrupting the natural drainage patterns, releasing pollutants into water bodies, and depleting groundwater resources. 10. Hydrological Engineering-Human-engineered activities like channelization, flood control structures, and levees can alter the course of rivers and alter natural flow patterns  PRECIPITATION general term for all forms of moisture emanating from the clouds and falling to the ground from the time of its formation in the atmosphere until it reaches the ground Drizzle Rain Snow Hail consists of drops under greater than 0.02 precipitation in the is precipitation in 0.02in diameter inches, drops greater form of ice the form of ice balls than 0.25 in diameter crystals resulting over 0.2 in tends to break up from deposition diameter 10  MEASUREMENT OF PRECIPITATION All form of precipitation are measured on the basis of the vertical depth of water that would accumulate on a level surface if the precipitation remained where it fell. Standard Tipping Weighing Precipitation gage bucket type gage  EVAPORATION Is the process by which the precipitation reaching the earth’s surface is returned to the atmosphere as water vapor. Primary source of heat at earth’s surface is Solar radiation 1. Water losses from open water bodies 2. Crops and vegetation 13  MEASUREMENT OF EVAPORATION The most common method of measuring evaporation is the evaporation pan or tank 14  TRANSPIRATION is the process by which water is absorbed by plants from the soil, travels through the plant's tissues, and eventually evaporates into the atmosphere from the plant's leaves, stems, and other aerial parts. Transpiration rates can vary depending on factors such as environmental conditions (temperature, humidity, wind speed), plant species, and the physiological state of the plant. It is an essential process for maintaining plant health and facilitating the movement of water and nutrients within the plant and its environment. 15  INFILTRATION is the process by which water from precipitation, such as rain or snowmelt, enters and soaks into the ground rather than running off the surface. It is a crucial component of the water cycle and plays a significant role in recharging groundwater, sustaining soil moisture, and supporting various ecosystems. 1. Groundwater Recharge 2. Soil Moisture 3. Flood Prevention 4. Water Quality 5. Erosion Control 16  RUN OFF Runoff refers to the movement of water, usually from precipitation, across the land surface and into rivers, streams, lakes, and other water bodies. It occurs when the amount of water that falls on the land exceeds the soil's capacity to absorb it, causing the excess water to flow over the surface and eventually accumulate in natural or man-made watercourses. Aspects of runoff include: 1. Surface Flow 2. Erosion and Sediment Transport 3. Urbanization Impact 4. Floods 17  water balance refers to the accounting of all the water inputs, outputs, and storage changes within a specific area or system over a defined period of time. It is a fundamental concept used to understand and quantify the movement of water through various components of the hydrological cycle within a particular region 𝑄𝑖𝑛 − 𝑄𝑜𝑢𝑡 +𝑃 − 𝐸 + 𝐺𝑖𝑛 −𝐺𝑜𝑢𝑡 = ∆𝑆𝑡𝑜𝑟𝑎𝑔𝑒 WATER BALANCE Clear lake has a surface area of 708,000 m2. For the month of March, the lake had an inflow of 1.5m3/s and an outflow of 1.25m3/s. A storage change of +708,000m3 was recorded. If the total length of rainfall recorded at the local rain gauge was 225mm for the month, estimate the evaporation loss from the lake in m3 and in mm. Assuming seepage to be negligible. SEATWORK A lake had a water surface elevation of 103.2m above datum at the beginning of the month. In that month the lake received an average inflow of 6m3/s. Further, in that month, the lake received a rainfall of 145mm and evaporation was estimated as 6.10 cm. Calculate the water surface elevation at the end of the month. The average lake surface area is 5000 ha. Assume that there is no contribution to or from the groundwater storage.