Engineering Hydrology Lecture Notes PDF

Engineering Hydrology (CEI 541) Lecture (1) Introduction Hydrological Cycle component By: Dr. Samia Abou El-Fetouh  Date LECTURE TOPIC...

Engineering Hydrology (CEI 541) Lecture (1) Introduction Hydrological Cycle component By: Dr. Samia Abou El-Fetouh  Date LECTURE TOPIC Lecturer 15/10/2024 1 Introduction to Hydrological Cycle Dr. Samia Abou El Fetouh 22/10/2024 Hydrometeorology (Temperature, Humidity, Wind, Solar Radiation), 2 Dr. Samia Abou El Fetouh The Effect of Climate Change on Water cycle 29/10/2024 Water losses from water cycle 3 (Interception, Evaporation, Infiltration, and transpiration) Dr. Samia Abou El Fetouh 5/11/2024 Precipitation & Catchment characteristics, time of concentration Dr. Samia Abou El Fetouh 4 12/11/2024 Hydrograph components, base flow separation & Stream flow Measurements Dr. Samia Abou El Fetouh 5 19/11/2024 Dr. Mahmoud Salah Runoff computations (Rational Method) &SCS Method 6 26/11/2024 Runoff computations (Unit Hydrograph) 7 Dr. Mahmoud Salah 3/12/2024 Dr. Mahmoud Salah Statistical Analysis for max. rainfall & Introduction to Models used in rainfall data 8 analysis and rainfall- Runoff Simulation 10/12/2024 Introduction to flood routing, and Reservoir Routing 9 Dr. Haitham 17/12/2024 Flood Hazards, risk assessment - Methods of Flash Flood Control and Mitigation 10 Dr. Haitham 24/12/2024 Dr. Haitham Sediment Transport by Flash Floods: Volume Estimation and Control - Sediment loss 11 through Wadis (USLE)  What is Hydrology? ◦ It is a science of water. ◦ It is the science that deals with the occurrence, circulation and distribution of water of the earth and earth’s atmosphere. ◦ A good understanding of the hydrologic processes is important for the assessment of the water resources, their management and conservation on global and regional scales. Engineering hydrology  In general sense engineering hydrology deals with ◦ Estimation of water resources ◦ The study of processes such as precipitation, evapotranspiration, runoff and their interaction ◦ The study of problems such as floods and droughts and strategies to combat them Flash Floods - Egypt Hydrologic Cycle The movement of water from the sea through the air to the land and back to the sea Hydrologic Cycle Components Evaporation from water bodies Water vapour moves upwards Cloud formation Condensation Precipitation Interception Transpiration Infiltration Runoff–streamflow Deep percolation Ground water flow Expressions ◦ Evaporation – process by which liquid water passes directly to the vapor phase ◦ Transpiration - process by which liquid water passes from liquid to vapor through plant metabolism ◦ Sublimation - process by which water passes directly from the solid phase to the vapor phase ◦ Condensation - The transported water vapour eventually condenses, forming tiny droplets in clouds. Expressions ◦Transport – The movement of water through the atmosphere, specifically from over the oceans to over land, is called transport. ◦Precipitation-The primary mechanism for transporting water from the atmosphere to the surface of the earth is precipitation. ◦Groundwater - Groundwater is water that infiltrates the soil flows downward until it encounters impermeable rock and then travels laterally. ◦Run-off - Most of the water which returns to land flows downhill as run-off.  Water budget or Water Balance The water volume in the globe is considered to be constant but changes from a phase to another and this relation is known as the water budget which states that the change in the storage within a certain domain is equal to the summation of the inflow, outflow, underground flow, evaporation and precipitation.  Inputs - Outputs ± accumulation = 0 The water budget equation for any domain (area or place) can be written in its simplest form as follows; S = P + I ± U - O -E Where, I is the Inflow to the domain, E is the Evaporation, O is the Outflow from the domain, U is the Underground flow from or into the domain, P is the Precipitation, and S is the Storage change Watershed delineated on a topographic map Watershed water balance P P − R − G − E − T = S E+T Q S G  Example 1 In a given year, a catchment with an area of 2500 km2 received 130 cm of precipitation. The average flow rate measured in the river draining the catchment was 30 m3/s. 1-How much runoff reached the river for the year (in m3)? 2-Estimate the amount of lost due to the combined effects of evapotranspiration and infiltration to groundwater (in m3)? 3-How much precipitation is converted into river runoff (in percentage)? (130/100)x2500x10^6 = 3.25x10^9 m3  Example 2 For a certain month (30 days) in a reservoir, the head (H) at the beginning of the month was 80 m. During the month, the average Inflow was 1600 m3/day while the average release was 2500 m3/day. The volume of precipitation equaled the sum of the volumes of evaporation and seepage together during the month. If the Storage-Head relation of the reservoir is given by: S =0.01H^0.36 Where S and H are reservoir storage (m3) and reservoir water head (m). Calculate the head in the reservoir at the end of the month. Example 3 A lake has a surface area of 7.0 x 105 m2. During a given month, the mean inflow to the lake was 2.5m3/s. The increase in stored lake volume was observed to be 6.5 x 105 m3. Precipitation during the same month was 250 mm and evaporation was 420 mm. Calculate the outflow from the lake for the same month.  Soil and Water Assessment Tool (SWAT) ▪The SWAT (Soil and Water Assessment Tool) is a river basin, or watershed, scale model developed by Dr. Jeff Arnold (1998) for USDA Agricultural Research Service (ARS). ▪The model is the modification of the SWRRB model for application to large basins (Arnold et al., 1990). ▪The model was used with success in several basins worldwide, primarily in United States and innmany European countries, like the Motueka basin (2075 km²) in New Zelande (Cao et al., 2003), the Alban Hills basin (1000 km²) in Central Italia (Benedini et al., 2003), the Celone Creek basin (24072 km²) in Italia (Papagello et al., 2003), and others. ▪The SWAT simulation tool was developed to simulate the effect of alternative management decisions on water, sediment, and chemical yields with reasonable accuracy for ungaged basins. This is the most complete and used model ▪SWAT is a comprehensive model that requires a diversity of information in order to run. This information, organized into database, is related to hydrology, weather, sedimentation, soil temperature, crop growth, nutrients, pesticides, ground water and lateral flow, and agricultural management. The hydrological cycle simulated by SWAT model is based on the water balance equation Where: SWt , SW0 are, respectively, final and initial soil water content (mm/d) t is the time (day) Rday is the precipitation (mm/d) Qsurf is the runoff (mm/d) Ea is the evapotranspiration (mm/d) Wperc is the percolation (mm/d) Qgw is the return flow (mm/d) The hydrological cycle process of the SWAT model SWAT operates on a daily time step and requires the use of, if available, daily rainfall data and maximum and minimum air temperature. If not, they are generated by the model. The precipitation simulation model developed by Nicks (1974) is a first order Markov chain model. Solar radiation, wind speed and relative humidity are always simulated. The SWAT model simulates surface runoff by using the SCS curve number technique (USDA-SCS, 1972).  ENGINEERING HYDROLOGY Lecture 1: Hydrometeorology Name : Michael Mefreh Khalaf ID: 2401528 Under Supervision: Dr. Samia Aboul Fetouh  Introduction to Hydrometeorology Hydrometeorology: is the study of the transfer of water and energy between the land surface and the lower atmosphere. It focuses on how meteorological factors such as temperature, humidity, wind, and solar radiation affect the distribution and movement of water in the hydrological cycle. Importance in Hydrology: Hydrometeorology is crucial for understanding precipitation patterns, evaporation rates, and extreme weather events like storms and droughts, which are key in water management, flood control, and predicting water availability in reservoirs and rivers. These factors directly influence water supply, flood risks, and drought management. Components of Hydrometeorology Temperature: Influences evaporation, precipitation patterns, and snowmelt. It controls how quickly water evaporates from surfaces like lakes and oceans.Humidity: The amount of water vapor in the air affects cloud formation, precipitation, and condensation rates. Wind: Drives the movement of moisture and weather systems across regions. It can transport moist air masses to areas that need water, or dry air to arid zones. Solar Radiation: The primary energy source driving the water cycle, affecting evaporation and heating of land and water surfaces. These components interact to influence the water cycle, directly impacting hydrological processes like runoff, infiltration, and groundwater recharge. Water Cycle Review The water cycle or hydrological cycle describes the continuous movement of water on, above, and below the surface of the Earth. Understanding these processes helps hydrologists predict water availability, flooding, and the impact of weather patterns on water resources. Temperature and Its Role in Hydrology Temperature affects the rate of evaporation—warmer temperatures increase evaporation from oceans, rivers, and lakes. Temperature influences the energy balance of the earth’s surface, which affects how much water evaporates and the amount of moisture the atmosphere can hold, impacting precipitation and water availability. Example: During heatwaves, increased temperatures can cause drought by increasing evaporation and reducing water supplies.  Temperature Terminologies Mean Daily Temperature: The average of the daily high and low temperatures. Mean Monthly Temperature: The average temperature across all days of the month. Mean Annual Temperature: The average of the monthly means over a year. Lapse Rate: The rate at which temperature decreases with an increase in altitude (typically 6.5°C per 1000m). It’s important for understanding how temperature changes in mountainous regions affect snowmelt and precipitation patterns. Importance: These metrics help hydrologists model weather patterns and predict water flows, particularly in mountainous regions where temperature gradients influence snow and ice melting rates, a key factor in seasonal river flows.  Temperature's Role in Evaporation Evaporation: The process where water changes from a liquid to a vapor. Temperature is the main factor controlling evaporation rates— higher temperatures increase the energy available for evaporation. In Hydrological Modeling, evaporation is a key factor in estimating water loss from lakes, rivers, and reservoirs. Temperature's Role in Snowmelt Snowmelt is a critical source of water for rivers and groundwater recharge. Changes in temperature can affect the timing and volume of snowmelt. Example: Melting snow from the Himalayas feeds major rivers like the Ganges, sustaining water supply for millions. Impact of Humidity on Water Cycle Absolute Humidity: The total amount of water vapor in the air, measured in grams per cubic meter. Relative Humidity (RH): The percentage of moisture the air can hold at a given temperature compared to the maximum amount it could hold (saturation). Dew Point: The temperature at which air becomes saturated, and condensation begins, leading to cloud formation and precipitation. Importance: High humidity increases the likelihood of precipitation, while low humidity leads to more evaporation. Relative humidity is crucial in hydrology for understanding local and regional rainfall patterns, as well as drought and flood conditions Impact of Humidity on Water Cycle Saturated Vapor Pressure (es): The maximum pressure exerted by water vapor in the air at a specific temperature. Formula: 𝑒𝑠=611×exp(17.27𝑇/(237.3+𝑇)) where T is the temperature in °C. Importance in Hydrology: Knowing the saturated vapor pressure helps determine whether the atmosphere is capable of holding more moisture, which influences cloud formation and precipitation. This is key for forecasting rain events and understanding drought conditions. Humidity's Role in Transpiration Transpiration: The process by which plants release water vapor into the air through their leaves. Effect of Humidity: Higher humidity reduces the rate of transpiration since the air is already saturated with moisture, while lower humidity increases transpiration. Importance: Transpiration, along with evaporation, forms evapotranspiration, which is a major pathway for water to leave ecosystems and affects the overall water balance, especially in agricultural regions.  Wind Speed and Direction Wind Speed: Measured with an anemometer, indicates how fast air is moving, typically in meters per second (m/s) or kilometers per hour (km/h). 1 Knot = 1.852 km/h and 1 mph = 1.61 km/h Wind Direction: Measured with a wind vane, it tells where the wind is coming from. Wind affects how moisture-laden air masses move, pushing clouds to new areas and influencing rainfall distribution.  Wind and Its Relation to Hydrology Wind redistributes moisture across regions, affecting precipitation patterns. Strong winds can drive storms or, conversely, dry out areas by pushing moist air away, impacting water availability and local weather systems. Wind can lead to more precipitation in coastal areas (due to moist air being pushed inland) and contribute to the formation of extreme weather events like hurricanes, which bring intense rainfall and affect water levels in rivers and lakes. Measurement of Solar Radiation Solar radiation is measured in Watts per square meter (W/m²). Radiometers measure the intensity of solar radiation. Solar Radiation and Drought: Prolonged high levels of solar radiation increase evaporation and decrease water levels in rivers and lakes. This can lead to drought conditions, especially if precipitation is low. Solar Radiation and Its Role in Hydrology Solar radiation is the primary energy source that drives the hydrological cycle by powering evaporation and heating the Earth’s surface. Solar energy affects temperature and, therefore, evaporation rates. It also influences the melt of snow and ice, contributing to seasonal water flows in rivers. Importance: Understanding solar radiation patterns is essential for modeling evaporation and predicting water availability, particularly in regions dependent on snowmelt or experiencing extreme sunlight (e.g., deserts). Conclusion Importance of Hydrometeorology in Water Resource Management Hydrometeorology provides valuable insights into the atmospheric processes that govern the availability and movement of water on Earth Water Resource Management: Hydrometeorology plays a critical role in designing systems for water storage, flood control, irrigation, and drought mitigation. The Effects of Climate Change on the Water Cycle Ahmed Muhammed Ibrahim Abduljabbar ASU  Introduction Climate change is primarily caused by increased greenhouse gas (GHG) emissions from human activities :[(CO₂): 76% (CH₄): 16% (N₂O): 6% - Fluorinated Gases: 2%)] IPCC (2021).  The hydrological cycle Water Cycle is affected by the Climate change  Warmer Temperatures and Evaporation How warmer temperatures intensify the cycle.  Effects of Climate change on Water Cycle Impact on Precipitation Patterns Glacier Melt and Sea-Level Rise Groundwater and Climate Change Storm Intensification  Impact on Precipitation Patterns Warmer temperatures increase evaporation rates, intensifying the water cycle These changes will result in more variable rainfall, with wet regions becoming wetter and dry regions becoming drier. IPCC2021  Case Study The World Weather Attribution study suggests that climate change significantly increased extreme rainfall in Pakistan by 50-75%.  Glacier Melt and Sea-Level Rise glacier melt contributed approximately 27 ± 22 millimeters to global sea levels between 1961 and 2016. As glaciers in mountainous regions shrink, the seasonal water supply to rivers will diminish, affecting agriculture, hydroelectric power generation, and ecosystems  Case Study: Andean Glaciers Glaciers in the Andes are retreating rapidly due to climate change, with some regions losing 30-50% of their glacial mass since 1990. This has serious consequences for water, energy, and food security in the region. Ice caps melt on the Nevado Pastoruri mountain in the Peruvian Andes [Angela Ponce/Reuters]  Groundwater and Climate Change Increased climate variability, including more frequent droughts, reduces groundwater recharge rates.  Groundwater Depletion Taylor, R.G., et al., 2013  Adaptation Strategies The Flood-Managed Aquifer Recharge (Flood-MAR) strategy in California is used to capture floodwater and recharge groundwater aquifers, helping to reduce groundwater extraction during droughts providing benefits such as drought preparedness, flood risk reduction, and ecosystem improvements  Storm Intensification Storms, particularly tropical cyclones, are becoming more intense due to rising sea surface temperatures Emanuel (2013) shows that the frequency of intense tropical cyclones is likely to increase in the 21st century  Case Study: New Orleans Hurricane Katrina August 28-29 , 2005 catastrophic flooding in New Orleans, caused by Hurricane Katrina 1,800 deaths and $100 billion in damages  Uncertainty in Climate Change Projections There are considerable uncertainties in climate change projections due to the variability of climate models, emission scenarios, and socio-economic factors Reducing uncertainisites  Conclusion Climate change has profound and far-reaching impacts on the global water cycle. Altered precipitation patterns, glacier melt, sea-level rise, and increased storm intensity are reshaping water availability. These changes contribute to heightened risks of floods and droughts worldwide. Groundwater resources, essential for many regions, are under threat due to altered recharge rates from climate variability. Adaptation strategies, such as sustainable water management practices, are critical to building resilience. Integrated approaches like Flood-Managed Aquifer Recharge offer innovative solutions to mitigate extreme weather impacts and enhance water security. Continued research and technological advancements are essential to safeguard water resources in the face of climate uncertainties Water losses from water cycle (Interception, Evaporation) Prepared By: Shehab Eldin Emad Engineering Hydrology (CEI 541)  Hydrological Cycle Losses in hydrological cycle 1. Interception Interception in the hydrological cycle refers to the process by which precipitation is captured and stored by vegetation (like leaves, branches, and stems) before it reaches the ground. This can include rainwater being held on the surface of leaves or branches, where it may evaporate back into the atmosphere rather than falling to the soil. Interception plays a crucial role in regulating water movement, influencing local hydrology, and affecting soil moisture levels. Factors affecting the amount of intercepted water Types of vegetation Weather Conditions Rainfall intensity Methods estimating the amount of intercepted water Field measurements Models and Equations (Gash and Rutter models) Remote sensing Advantages of inception Water Regulation Reduce flood risks Reduce soil erosion Enhance soil moisture Water quality improvement 2. Evaporation the process by which water is converted from liquid form to vapor and enters the atmosphere. This occurs when water from various sources such as )rivers, lakes, oceans, and soil( absorbs heat energy from the sun, causing it to change into water vapor. Factors Influencing Evaporation Temperature Wind speed Humidity Surface area Methods estimating the amount of intercepted water Water Balance Equation Field Measurement Empirical Evaporation Equations (Mayer’s Equation)  Methods estimating the amount of intercepted water 1. Water Balance Method ΔS=P−E−Q−D Where: ΔS= Change in storage (in the soil or water bodies) over a specified period P = Precipitation (input of water) E = Evaporation (and transpiration, if included, often referred to as ET) Q = Surface runoff (outflow of water) D = Deep percolation (outflow of water beyond the root zone)  Methods estimating the amount of intercepted water 1. Water Balance Method (Example:1) You are studying a small watershed and want to estimate the evaporation over a 30-day period. You have collected the following data: Precipitation (P)= 150 mm Change in soil moisture (ΔS): +30 mm (indicating an increase in soil moisture) Surface runoff (Q): 20 mm Deep percolation (D): 10 mm E= P-Q-F- ΔS E=150-30-20-10 = 90mm/30day = 3mm/day  Methods estimating the amount of intercepted water 2. Field Measurement (Evaporation Pan)  Methods estimating the amount of intercepted water 2. Field Measurement (Evaporation Pan) E=Kp×Ep E: Actual evaporation from the specific surface (like soil or a natural water body), typically measured in mm/day Kp: Pan coefficient. This is a dimensionless factor that accounts for the difference between evaporation measured in a pan (like a Class A evaporation pan) and the actual evaporation from the surrounding environment. The value of Kp​ generally ranges from 0.6 to 0.8 Ep​: Reference evaporation, which is the evaporation rate measured from the evaporation pan, also expressed in mm/day.  Methods estimating the amount of intercepted water 2. Field Measurement (Evaporation Pan) (Example:2)  Methods estimating the amount of intercepted water 2. Field Measurement (Evaporation Pan) (Example:2)  Methods estimating the amount of intercepted water 2. Field Measurement (Evaporation Pan) (Example:2)  Methods estimating the amount of intercepted water 3. Empirical Evaporation Equations (Mayer’s Equation) EL = Km (ew – ea) (1 + u9/16) EL = Lake evaporation in mm/day ew = Saturated vapour pressure at the water surface temperature ea = Actual vapour pressure of over lying air at specified height u9 = Monthly mean wind velocity (km/hr) at about 9m above the ground Km = Coefficient, 0.36 for large deep waters and 0.5 for small shallow waters  Methods estimating the amount of intercepted water 3. Empirical Evaporation Equations (Mayer’s Equation) (Example:3) A lake with a surface area of 250 hectares had the following average values : Water Temperature = 20° Relative humidity = 40% Wind velocity at 9m above ground = 21.9Km/hr ew = 17.54mmHg Km = 0.5 (calculate the monthly evaporated volume )  Methods estimating the amount of intercepted water 3. Empirical Evaporation Equations (Mayer’s Equation) (Example:3) Solution : EL=Km (ew-ea) (1+u9/16) EL = 0.5*(17.54-0.4*17.54) (1+21.9/16) =12.46 mm/day For month = (12.46/1000)*250*10000*30 = 934827.2 m3 Water losses from water cycle Infiltration And Transpiration Ahmed Saqr Water Cycle Transpiration: the process where water evaporates into the atmosphere through plants ❖ Involving root uptake of soil moisture and the loss of water vapor through plant stomata during photosynthesis Infiltration: portion of the water that falls as rain and snow infiltrates into the subsurface soil and rock ❖ A portion of this water may also penetrate deeper, contributing to the recharge of groundwater aquifers. 2 CEI 541 Engineering Hydrology 1/2/2025 Transpiration Many factors effecting in transpiration process ❖ Relative humidity – Relative humidity (RH) is the amount of water vapor in the air compared to the amount of water vapor that air could hold at a given temperature. Any reduction in water in the atmosphere creates a gradient for water to move from the leaf to the atmosphere. The lower the RH, the less moist the atmosphere and thus, the greater the driving force for transpiration. When RH is high, the atmosphere contains more moisture, reducing the driving force for transpiration. ❖ Temperature – Temperature greatly influences the magnitude of the driving force for water movement out of a plant. In warmer air will increase the driving force for transpiration and cooler air will decrease the driving force for transpiration. ❖ Soil water – The source of water for transpiration out of the plant comes from the soil. Plants with adequate soil moisture will normally transpire at high rates. ❖ Light – Stomata are triggered to open in the light so that carbon dioxide is available for the light-dependent process of photosynthesis. Stomata are closed in the dark in most plants. 3 CEI 541 Engineering Hydrology 1/2/2025 Transpiration Many factors effecting in transpiration process ❖ Air movement - when air movement increases it will Removes water vapour from leaf surfaces; more water diffuses from the leaf ❖ Surface Area of the Leaves - A leaf having more surface area will show more transpiration rate than the leaf with a lesser surface area. 4 CEI 541 Engineering Hydrology 1/2/2025 Transpiration Measuring the rate of transpiration ▪ The uptake of water can be measured using a Potometer in Under normal circumstances, the rate of water uptake gives a measure of the rate of transpiration. ▪ In this experiment assumes that water uptake and water loss by transpiration are equal ▪ In reality will be a very small difference between the volume of water taken up and the volume of water lost in transpiration, as some water is used in photosynthesis; this means that potometers provide an indirect measure of transpiration rate 5 CEI 541 Engineering Hydrology 1/2/2025 Transpiration Measuring the rate of transpiration ▪ The movement of the bubble is monitored and the distance traveled by the bubble is recorded over time. 𝑫𝒊𝒔𝒕𝒂𝒏𝒄𝒆 𝒎𝒐𝒗𝒆𝒅 𝒃𝒚 𝒂𝒊𝒓 𝒃𝒖𝒃𝒃𝒍𝒆 The Rate Of Transpiration = 𝑻𝒊𝒎𝒆 6 CEI 541 Engineering Hydrology 1/2/2025 Transpiration Measuring the rate of transpiration ▪ Different factors affect transpiration and therefore water uptake. They can be investigated using a potometer 7 CEI 541 Engineering Hydrology 1/2/2025 Infiltration Infiltration refers to the ability of the soil to allow water to move into and through the soil profile. Infiltration allows the soil to temporarily store water Factors Affecting Infiltration - Residence Time How much time that water remains on the surface depends on the slope, the roughness of the soil surface - Soil condition The infiltration rate is generally highest when the soil is dry. As the soil becomes wet - Vegetation A high percentage of plant cover and large amounts of root biomass generally increase the infiltration rate. Different plant species have different effects on infiltration 8 CEI 541 Engineering Hydrology 1/2/2025 Infiltration Factors Affecting Infiltration - Soil Properties - Texture - Soil layers - Soil density - Minerals in the soil - Organic matter and soil biota - Water-repellent layer - Pores and channels - Clay mineralogy 9 CEI 541 Engineering Hydrology 1/2/2025 Infiltration INFILTRATION RATE is the velocity or speed at which water enters into the soil. It is usually measured by the depth (in mm) of the water layer that can enter the soil in one hour. An infiltration rate of 15 mm/hour means that a water layer of 15 mm on the soil surface, will take one hour to infiltrate. According to fao.org 10 CEI 541 Engineering Hydrology 1/2/2025 Infiltration Infiltration Measurements - Field test (infiltrometer) The infiltrometer consist of two cylinders of 25 cm height and 2 mm thickness The inner diameter is 30 cm and the outer cylinder is 60 cm The inside cylinder is used to measure the rate of infiltration The outer cylinder is used to prevent ponding water in the buffer area around the inner cylinder 11 CEI 541 Engineering Hydrology 1/2/2025 Infiltration 12 CEI 541 Engineering Hydrology 1/2/2025 Infiltration Infiltration Measurements - Equation (Horton) Horton observed the above facts and concluded that infiltration begins at some rate fo and exponentially decreases until it reaches a constant fc. He proposed the following infiltration equation fp = fc + (f0− fc) e−kt 13 CEI 541 Engineering Hydrology 1/2/2025 Infiltration Infiltration Measurements - Equation (Horton) Example The initial rate of infiltration of a watershed is estimated as 2.1 mm/hr, the final capacity is 0.2 mm/hr, and the time constant, k, is 0.4 hr-1. Use Horton’s Equation to find: -The infiltration capacity at t = 2 hr and t = 6 hr t=19 hr t=25; Answer fp = fc + (f0− fc) e−kt fp = 0.2 + (2.1− 0.2) e−0.4∗t AT t=2hr AT t=6hr AT t=19hr AT t=25hr fp = 0.2 + (2.1− 0.2) e−0.4∗2 fp = 0.2 + (2.1− 0.2) e−0.4∗2 fp = 0.2 + (2.1− 0.2) e−0.4∗2 fp = 0.2 + (2.1− 0.2) e−0.4∗2 fp = 1.05 mm/hr fp = 0.37 mm/hr fp = 0.2mm/hr fp = 0.2mm/hr 14 CEI 541 Engineering Hydrology 1/2/2025 Precipitation Yara Farghali ID: 2401758 Supervised by : Dr. Samia Aboul Fetouh Engineering Hydrology (CEI 541)  Table of Contents 01 02 Measuring Introduction Precipitation 03 04 Spatial Calculating Representation Average Rainfall Depth  01 Introduction Precipitation It is any kind of liquid or solid water that falls to the ground from the atmosphere. Precipitation can take many different forms as rain, snow, hail, or sleet As part of the water cycle, water on the surface of the Earth evaporates up from the ground into the atmosphere above. Then, that water cools and condenses into different types of clouds in the atmosphere. Finally, when those water droplets get so large that the atmosphere can no longer support their weight, they fall from the ground in the form that we know as precipitation Types of Precipitation 1. Liquid Precipitation 2. Frozen Precipitation Types of Storms  02 Measuring Precipitation  Measuring Precipitation Weather Satellite Standard Rain Gauge Weather Radar Automatic Rain Gauge  Measuring Precipitation ❑ Standard Rain Gauge: A simple cylindrical container that collects and measures rainfall. It’s usually placed in an open area and is manually read to determine the amount of precipitation over a certain period. ❑ Automated Rain Gauge: An electronic rain gauge that automatically records rainfall amounts. It uses sensors to detect and measure precipitation, transmitting data remotely for continuous monitoring without manual intervention.  Measuring Precipitation ❑ Tipping Bucket Rainfall Gauge: Consists of a small bucket that tips when it fills to a certain level. Each tip is counted electronically, giving an accurate measure of rainfall over time. It’s useful for automated and continuous recording of precipitation intensity.  Measuring Precipitation ❑ Weather Radar: Uses radio waves to detect precipitation in the atmosphere. Radar systems send out pulses that bounce off raindrops, snow, or hail, allowing meteorologists to map rainfall intensity and location in real-time over large areas.  Measuring Precipitation ❑ Weather Satellites: Orbiting satellites equipped with sensors that detect cloud cover, moisture content, and precipitation from space. They provide broad-scale data useful for tracking weather systems and monitoring precipitation over vast regions, including oceans and remote areas. Ideal Location for a Rain Gauge Station I. Place the rain gauge on flat, even ground; avoid sloped areas, or inclined surfaces. II. Select a location in an open area, free from nearby obstructions. III. Keep the site protected from strong and continuous winds to maintain accuracy. IV. Choose an easily accessible site to facilitate maintenance and data collection. V. Make sure the rain gauge is installed perfectly vertical to ensure precise readings. VI. Use self-recording rain gauges in each basin to automate data logging. VII. Have an observer visit the site regularly to check that the gauge is in proper working condition for accurate measurements. Recommendations on rain gauge Density Estimating Missing Data When there is over a 10% difference in normal annual precipitation between index stations and the station with missing data, use the Normal-Ratio Method. This method adjusts precipitation data at each index station, weighting it by the ratio of their normal precipitation to that of the missing-data station. Note: This method helps improve accuracy when there are significant differences in climate or terrain between stations.  Adequacy of Rain Gauge Stations Objective: Determine the optimal number of rain gauge stations (NNN) to estimate mean rainfall with an acceptable error. Adequacy of Rain Gauge Stations Note: A higher ​ indicates greater variability, which may require more rain gauge stations.  Double-Mass Analysis The consistency of a rainfall record is tested with double-mass analysis. This method compares the cumulative annual (or alternatively, seasonal) values of station X with those of a reference station. The reference station is usually the mean of several neighboring stations.  03 Spatial Representation  Spatial Representation An isohyetal map is a type of contour map used in meteorology and hydrology to display the distribution of precipitation across a region. In this map, isohyets (lines) connect points that have received equal amounts of rainfall or precipitation over a specified period. The purpose of an isohyetal map is to visualize variations in rainfall patterns, which is useful for understanding water resources, watershed management, and flood forecasting.  Temporal Representation Rainfall hyetograph – plot of rainfall depth or intensity as a function of time Cumulative rainfall hyetograph or rainfall mass curve – plot of summation of rainfall increments as a function of time  04 Calculating Average Rainfall Depth Calculating Average Rainfall Depth 1 2 Arithmetic Mean Thiessen polygon Method method 3 4 Isohyetal Method Inverse Distance Weighting  Arithmetic Mean Method This is the simplest method, where the average rainfall depth is calculated by taking the arithmetic mean of rainfall values recorded at different stations in the area. It works best when stations are uniformly distributed, but it may be less accurate in areas with significant rainfall variability.  Thiessen Polygon Method In this method, the area is divided into polygons around each rain gauge, with each polygon representing the area closest to its station. The rainfall for each station is weighted by the area of its corresponding polygon. This method accounts for station distribution and is more accurate than the arithmetic mean in unevenly spaced networks.  Isohyetal Method This method uses an isohyetal map, where lines (isohyets) connect points with equal rainfall amounts. The area between each pair of isohyets is calculated, and the average rainfall is weighted by the area between each pair. It’s particularly accurate in regions with high variability in rainfall distribution, as it provides a more detailed spatial representation.  Inverse Distance Weighting (IDW) IDW calculates rainfall at unsampled locations by assigning weights to each rain gauge based on its distance to the point of interest (closer stations have more influence). This approach can be extended across an entire region to estimate average rainfall, weighting each station based on its proximity to other points. It’s useful when nearby stations are more likely to have similar rainfall patterns, but it may be sensitive to outliers if there are few stations.  Comparsion Summary Arithmetic Mean is straightforward but less precise. Thiessen Polygon improves accuracy in areas with irregular station distribution. Isohyetal Method provides the most accurate results in complex rainfall regions. IDW is flexible and uses spatial influence, but it can be sensitive to the placement and number of stations. Rainfall maps in GIS Research Papers (Case Studies) 3 papers  1. ESTIMATION OF MEAN AREAL RAINFALL AND MISSING DATA BY USING GIS IN NINEVEH, NORTHERN IRAQ Objective: To estimate the mean areal rainfall in Nineveh Governorate (35152 km²) using three methods: Arithmetic Mean, Thiessen Polygon, and Isohyet. Data & Period: Rainfall data from eight stations (Mosul, Sinjar, Zummar, Talafar, Hatra, Ba'ashiqah, Tal Abtah, Rabia) covering 2000 to 2019 were analyzed using ArcGIS 10.5. Missing Data: The Normal Ratio method was used to fill gaps due to station distribution inconsistencies; USGS data supplemented missing values for 2014-2016. Data Validation: Consistency of rainfall records was verified using the double-mass curve technique, with a significant correlation (0.61 to 0.9) found between measured and estimated values.  1. ESTIMATION OF MEAN AREAL RAINFALL AND MISSING DATA BY USING GIS IN NINEVEH, NORTHERN IRAQ Results: Mean rainfall was calculated as 298.94 mm (Arithmetic Mean), 230.12 mm (Thiessen Polygon), and 260.10 mm (Isohyet). Isohyet method was deemed most accurate due to its adaptability to the inhomogeneous distribution of rainfall stations and topographical influences. Findings: Northern areas received more rainfall due to higher elevation, making the Isohyet method particularly suitable for this region 1. ESTIMATION OF MEAN AREAL RAINFALL AND MISSING DATA BY USING GIS IN NINEVEH, NORTHERN IRAQ  2. Global Precipitation for the Year 2023 and How It Relates to Longer Term Variations and Trends. https://doi.org/10.3390/atmos15050535 This article looks at global rainfall patterns in 2023, comparing them to long-term trends (from 1983 to 2023) to understand how this year's rainfall fits into broader climate patterns. The authors used data from the Global Precipitation Climatology Project (GPCP) to analyze the rainfall distribution globally and regionally. Global precipitation has remained fairly consistent over time, with changes mainly driven by El Niño and La Niña events. In 2023, there was a small increase in global rainfall. Climate models that used real sea surface temperatures (SSTs) predicted rainfall patterns that were similar to observed data, while models that didn’t use SSTs showed only a general agreement. The Inter-Tropical Convergence Zone (ITCZ) near the equator experienced the highest rainfall ever recorded in 2023, with increasing rain rates over the past decades, likely due to global warming.  2. Global Precipitation for the Year 2023 and How It Relates to Longer Term Variations and Trends. El Niño is characterized by warmer ocean temperatures and generally causes drier conditions in some regions and wetter conditions in others, contributing to global climate disruptions. La Niña is marked by cooler ocean temperatures and often causes opposite effects to El Niño, such as increased rainfall in some regions and droughts in others. 3.Quantitative Estimation of Rainfall from Remote Sensing Data Using Machine Learning Regression Models (2023) https://doi.org/10.3390/ Objective: Estimate rainfall in northern Algeria using machine learning models with satellite remote sensing data. Data Used: Satellite data (MSG) paired with rain gauge readings (day/night) for model training and validation. Models Applied: 1- K-Nearest Neighbors Regression (KNNR): Predicts rainfall by averaging values from the closest data points. 2- Support Vector Regression (SVR): Finds the best-fitting line while balancing prediction accuracy and simplicity. 3- Random Forest Regression (RFR): Combines multiple decision trees to improve accuracy and manage complex data. Model Combination (Com-RSK) Optimization Strategy: A weighted average of KNNR, SVR, and RFR outputs was used to improve predictions. Results: Lower Errors: MAE, MBE, and RMSE values improved significantly compared to individual models, High Accuracy: A correlation coefficient of 94%, outperforming separate models and classification-based methods. 3.Quantitative Estimation of Rainfall from Remote Sensing Data Using Machine Learning Regression Models (2023) https://doi.org/10.3390/ Comparison with Other Methods: Com-RSK showed superior performance over ECST, MMultic, CS-RADT, and satellite products (CMORPH, CHIRPS). Key Findings: Best Model: SVR performed best individually with the lowest error rates and highest correlation. Combined Model Performance: Com-RSK provided the most accurate and reliable rainfall estimates across different time scales (daily, monthly, seasonal). Broader Implications: Methodology adaptable to similar climates, with potential to update for varied climate regions.  Any Questions… Thank YOU !  Watershed characteristics & Time of concentration Prepared by: Ahmed Fawzy 1 CEI 541 Engineering hydrology  Definition of watershed An area of land that channels rainfall, snowmelt, and runoff into a common body of water Divider Outfall 2 CEI 541 Engineering hydrology 3  1. Basin area/size 2. Basin slope 3. Basin shape 4. Land Use 5. Quantitative characteristics 6. Time of concentration 4 CEI 541 Engineering hydrology  1. Basin area/size 2. Basin slope 3. Basin shape 4. Land Use 5. Quantitative characteristics 6. Time of concentration It reflects the volume of water that can be generated from rainfall Small Watersheds A < 250 km2 Medium Watersheds 250 km2 < A < 2500 km2 Large Watersheds 2500 km2 < A 5 CEI 541 Engineering hydrology  1. Basin area/size 2. Basin slope 𝐿 ∗ 𝐶. 𝐼. 3. Basin shape 𝐿𝑎𝑛𝑑 𝑆𝑙𝑜𝑝𝑒 = 𝐴 4. Land Use Where: L is total length of contours 5. Quantitative characteristics C.I. is contour interval A is basin area 6. Time of concentration Flat Basin Steep Basin 6 CEI 541 Engineering hydrology  1. Basin area/size 2. Basin slope 3. Basin shape Can be defined by 3 watershed parameters 4. Land Use 5. Quantitative characteristics 6. Time of concentration Form Factor Circularity ratio Basin Shape Compactness coefficient 7 CEI 541 Engineering hydrology  1. Basin area/size 2. Basin slope 3. Basin shape 4. Land Use 5. Quantitative characteristics 6. Time of concentration a. Form factor 𝑊𝑏 𝐴 = = 2 𝐿𝑏 𝐿𝑏 b. Circularity ratio 𝐴 4𝜋𝐴 = = 2 𝐴0 𝑃 8 CEI 541 Engineering hydrology  1. Basin area/size 2. Basin slope 3. Basin shape 4. Land Use 5. Quantitative characteristics 6. Time of concentration c. Compactness coeff. 𝑃𝑒𝑟𝑖𝑚𝑒𝑡𝑒𝑟 𝑃𝑏 𝐶𝐶 = = 𝑐𝑖𝑟𝑐𝑢𝑚𝑓𝑒𝑟𝑒𝑛𝑐𝑒 2 𝜋𝐴 Pb = perimeter of basin 9 CEI 541 Engineering hydrology  1. Basin area/size 2. Basin slope 3. Basin shape 4. Land Use 5. Quantitative characteristics 6. Time of concentration Agricultural – Urban – Desert Mountainous – Forest – Mixed 10 CEI 541 Engineering hydrology  1. Basin area/size 2. Basin slope 3. Basin shape 4. Land Use 5. Quantitative characteristics 6. Time of concentration A- Stream frequency 𝑁𝑠 𝐹𝑠 = 𝐴 Where: Ns is number of streams B- Drainage density 𝐿𝑠 𝐷𝑑 = 𝐴 Ls is length of streams 11 CEI 541 Engineering hydrology  Time of concentration 12  CEI 541 Engineering hydrology Definition Time required for water to travel from the most hydraulically remote point in the basin to the basin outlet. 13  CEI 541 Engineering hydrology Definition Source: NEH Ch15 Pg15-4 14  CEI 541 Engineering hydrology Equations to estimate Tc 1- Kirpich equation (1940) 𝑇𝑐 = 0.01944 ∗ 𝐿0.77 ∗ 𝑆 −0.385 Where: Tc is time of concentration (min) L is max flow length (m) S is watershed LFP slope (m/m) Note: This equation was developed for rural catchments 15  CEI 541 Engineering hydrology Equations to estimate Tc 1- Kirpich equation (1940) 16  CEI 541 Engineering hydrology Equations to estimate Tc 2- Horton’s equation 𝐿 𝑇𝑐 = 3.6 ∗ 𝑉 Where: Tc is time of concentration (hr) L is max flow length (Km) V is mean velocity (m/s) Source: NEH Ch15 Pg15-8 17  CEI 541 Engineering hydrology Equations to estimate Tc 3- Kerby’s equation (1970) 𝑛 ∗ 𝐿 0.467 𝑇𝑐 = 0.828 ∗ ( ) 𝑠 Where: Tc is time of concentration (hr) L is flow length (ft) n is manning coefficient s is dimensionless flow slope Note: This equation was developed for small catchments (Flow length < 350 ft) 18  CEI 541 Engineering hydrology Equations to estimate Tc 4- Lag method by NRCS(1970) 𝑙0.8 ∗ (𝑆 + 1)0.7 𝑇𝑐 = 1140 ∗ 𝑌 0.5 Where: Tc is time of concentration (Hr) l is flow length (ft) S is max potential retention (in) Y is land slope (%) 1000 𝐿 ∗ 𝐶. 𝐼. 𝑝𝑜𝑡𝑒𝑛. 𝑟𝑒𝑡𝑒𝑛. 𝑆 = − 10 𝐿𝑎𝑛𝑑 𝑆𝑙𝑜𝑝𝑒(𝑌) = 𝐶𝑁 𝐴 19  CEI 541 Engineering hydrology Equations to estimate Tc https://doi.org/10.3390/su15031987 20 Thank Any Q? you 21  Hydrograph components & Base flow separation By: Eng. Ahmed Emad El-Din 2401536 CEI 541 Engineering  Hydrograph definition A hydrograph is a graph showing the rate of flow (discharge) versus time past a specific point in a river, channel, or conduit carrying flow. The rate of flow is typically expressed in units of cubic meters per second (m³/s) or cubic feet per second (cfs). CEI 541 Engineering  Types of hydrograph Natural hydrograph Direct runoff hydrograph Unit hydrograph CEI 541 Engineering  Hydrograph Components The Approach segment starts with rain fall beginning and ends at peak rain fall CEI 541 Engineering  Hydrograph Components The peak rainfall is the time of highest rainfall (W) CEI 541 Engineering  Hydrograph Components The peak discharge occurs when the outlet of the basin reaches its highest flow. CEI 541 Engineering  Hydrograph Components Lag time Time between peak rain fall and peak discharge Time between the center of mass of the effective rainfall hyetograph and the center of mass of the direct runoff hydrograph. CEI 541 Engineering  Hydrograph Components The rising limb begins when flow of the basin starts to rise and reach the basin outlet. CEI 541 Engineering  Hydrograph Components The falling limb shows that water is still reaching the outlet but in decreasing amounts. CEI 541 Engineering  Hydrograph Components The Crest segment (X to Y) the area represents peak flow at the catchment outlet. CEI 541 Engineering  Hydrograph Components Time of Concentration , Tc Time required for water to travel from the most hydraulically remote point in the basin to the basin outlet. The drainage characteristics of length and slope, together with the hydraulic characteristics of the flow paths, determine the time of concentration. Time to Peak, Tp Time from the beginning of the rising limb to the occurrence of the peak discharge For more details CEI 541 Engineering  Factors affecting a Hydrograph Weather & Climate(Precipitation) CEI 541 Engineering  Factors affecting a Hydrograph The Drainage Basin ( Area& Slope) CEI 541 Engineering  Factors affecting a Hydrograph Soil & Rock Type CEI 541 Engineering  Factors affecting a Hydrograph Human Activity CEI 541 Engineering  Base flow separation Base flow This is the portion of the hydrograph that remains relatively steady over time, reflecting groundwater contributions Base flow separation It is the deduction of base-flow from total storm hydrograph to get surface flow hydrograph CEI 541 Engineering  Base flow separation methods Straight line method Assume Base flow constant regardless of discharge CEI 541 Engineering  Base flow separation methods Constant slope method Assumes flow from aquifers began prior to start N: Time in days of current storm, arbitrarily sets to inflection A: Basin area (km^2) point. This method assumes that the base flow recession follows a linear decline with a constant slope after the direct runoff has ended. CEI 541 Engineering  Base flow separation methods Fixed base method Assume base flow decreases while stream flow N: Time in days increases. A: Basin area (km^2) CEI 541 Engineering  Base flow separation methods Advantages of these methods Simplicity No complex calculation Can be applied to daily, monthly, or even longer time series data. Useful when no detailed data on catchment characteristics or groundwater storage is available. CEI 541 Engineering  Example CEI 541 Engineering CEI 541 Engineering  Faculty of Engineering Ain Shams University Irrigation and Hydraulics Department Academic Year: Fall 2024 Engineering Hydrology CEI541 Stream Flow Measurements Prepared by : Aya Tullah Tarek  Definition Stream flow measurement refers to the process of quantifying the volume of water flowing through a river or stream over time. 2 CEI 541 Engineering Hydrology 11/16/2024 Methods of Measuring Stream Flow Direct Measurement: Direct methods involve real-time physical measurements of stream flow at a specific location. Indirect Measurement: Indirect methods estimate stream flow without direct measurements, often utilizing models and empirical data. 3 CEI 541 Engineering Hydrology 11/16/2024 Direct Measurement Velocity-Area Method: Measure flow velocity and cross-sectional area. Use a flow meter to assess velocity. Q=A×V Where: A is the cross-sectional area V is the average velocity. 4 CEI 541 Engineering Hydrology 11/16/2024 Direct Measurement Float Method A floating object is released, and the time it takes to travel a known distance is measured. Calculate average velocity and multiply by the cross- sectional area to estimate flow rate. 5 CEI 541 Engineering Hydrology 11/16/2024 Direct Measurement Weirs and Flumes: Structures that control flow and allow for measurement based on height. 6 CEI 541 Engineering Hydrology 11/16/2024  Indirect Methods Stage-Discharge Relationship Uses a stage gauge to measure water level and correlates it with discharge through a pre-established curve. Q=C×(H−H0)^n Where: Q = Discharge H = Stage (water surface elevation, in meters) H00 = Reference stage or gauge height at zero flow (in meters) C = Empirical coefficient (depends on the river channel characteristics) n = Empirical exponent (depends on the river channel characteristics) 7 CEI 541 Engineering Hydrology 11/16/2024 Indirect Methods Hydraulic Modeling Simulates flow conditions based on channel shape, slope, and roughness. 8 CEI 541 Engineering Hydrology 11/16/2024 Indirect Methods Remote Sensing Analyzes satellite or aerial imagery to assess flow characteristics and estimate stream flow indirectly. 9 CEI 541 Engineering Hydrology 11/16/2024  Equipment Used in Stream Flow Measurement Flow Meter: Electromagnetic, acoustic, and mechanical devices for measuring velocity. Stage Sensors: Pressure transducers and ultrasonic sensors for water level measurement. Data Loggers: For continuous data collection. Remote Sensing Tools: Satellite imagery and LiDAR for large-scale assessments. 10 CEI 541 Engineering Hydrology 11/16/2024  Solved Examples Example 1: A stream has a width of 10 meters and an average depth of 1.5 meters. The velocity of the stream is measured at several points, and the average velocity is found to be 2.5 m/s. Calculate the streamflow (discharge) using the velocity-area method. Calculate the Cross-Sectional Area (A): A=width × average depth A=10×1.5=15 m2 Calculate the Discharge (Q): Q=A×V Q=15×2.5=37.5 m3/s 11 CEI 541 Engineering Hydrology 11/16/2024  Solved Examples Example 2: A stream is divided into 3 sections for measurement. The width of each section is 3 m. Depth and velocity are measured at each section as follows: 12 CEI 541 Engineering Hydrology 11/16/2024  Solved Examples Example 2 Solution: Calculate the Area for Each Section: Section 1: A1= width× depth=3×1.2=3.6 m2 Section 2: A2=3×1.5=4.5 m2 Section 3: A3=3×1.1=3.3 m2 Calculate the Discharge for Each Section: Section 1: Q1=A1×V1=3.6×1.8=6.48 m3/s Section 2: Q2=4.5×2.0=9.0 m3/s Section 3: Q3=3.3×1.6=5.28 m3/s Calculate the Total Discharge: Q total=Q1+Q2+Q3=6.48+9.0+5.28=20.76 m3/s 13 CEI 541 Engineering Hydrology 11/16/2024  Solved Examples Example 3: A rectangular weir is installed in a stream. The width of the weir is 2 m, and the height of the water above the weir crest (H) is measured to be 0.50m. The discharge coefficient Cd for the weir is 0.60 Calculate the stream flow. Q=Cd×b×2g×H3/2 Solution: Q=0.6×2×2×9.81×(0.5)3/2 Q=1.2×19.62×0.3536 Q=1.2×4.429×0.3536=1.88m3/sec 14 CEI 541 Engineering Hydrology 11/16/2024  Case Study Low Flow Measurement in a Small Channel Using Teledyne RDI’s StreamPro ADCP with a Customer-Made Traveler System 15 CEI 541 Engineering Hydrology 11/16/2024 Acoustic Doppler Current Profiler (ADCP) a device designed to measure water velocity profiles using acoustic pulses. It is specifically geared towards shallow and small streams, where traditional flow measurement methods might be challenging. How It Works: The ADCP uses the Doppler effect to measure the velocity of particles suspended in the water column. By emitting sound waves and analyzing the reflected signals, it can calculate the velocity at various depths, providing a detailed profile of streamflow. Objective: The primary objective of this study was to evaluate the effectiveness of ADCP technology for measuring streamflow under various flow conditions, including low, medium, and high flows, to enhance the accuracy of hydrological data collection for flood prediction models. Study Case Work the traveler system was used in a low-velocity channel measuring about 2.6 meters in width and 0.3 meters in depth. By using the traveler system, precise flow measurements with a low coefficient of variation (about 2%) were achieved, compared to typical variations of ±10% in previous measurements. Advantages of This Method: High Accuracy in Low Flow Conditions: Acoustic Doppler technology is effective at capturing slow-moving water velocities that traditional methods struggle with. Non-Intrusive Measurement: The ADCP does not require physical contact with the streambed, minimizing disturbance and sediment resuspension. Real-Time Data: Immediate feedback allows for on-site verification of data quality.