The document discusses unit hydrographs and their applications in flood prediction. A unit hydrograph models the runoff response of a watershed to one inch of excess rainfall over a given duration. It can be used to predict the runoff hydrograph from a storm of any size by applying the principles of superposition and proportionality. The key steps in developing a unit hydrograph involve analyzing rainfall and runoff data from a storm event to separate baseflow, calculating the volume of excess runoff, and adjusting the hydrograph to represent the response to one inch of rainfall.
This document provides information about hyetographs and hydrographs. It defines a hyetograph as a graphical representation of rainfall intensity over time, showing total rainfall. A hydrograph shows variations in river discharge over time at a measurement point. It describes the components of hydrographs, including the rising and falling limbs and peak. It also discusses runoff classifications, the unit hydrograph concept for analyzing surface runoff, and key hydrograph terminology like time to peak, time of concentration, and lag time.
This document discusses hydrographs and unit hydrographs. It defines a hydrograph as a graph showing the rate of flow versus time past a specific point in a river. It notes that hydrographs are commonly used in sewerage design. It then describes the components of a hydrograph including the rising limb, recession limb, peak discharge, lag time, and time to peak. Finally, it discusses unit hydrographs, defining a unit hydrograph as the runoff resulting from 1 unit of rainfall excess. It provides examples of deriving unit hydrographs from observed hydrographs and flood hydrographs.
There are three main equations that describe the shape of an infiltration capacity rate curve: Horton's equation, Phillips equation, and Holtan's equation. The infiltration capacity rate generally decreases over time from an initial maximum rate to a minimum steady rate. The infiltration index and W-index provide a constant infiltration rate for calculating runoff. The W-index is more accurate than the infiltration index because it excludes depression and interception losses. Both indices are commonly used to estimate flood magnitudes from critical storms.
- A hydrograph shows the rate of water flow over time at a specific point along a river or channel. It is used in sewer system design.
- The main components of a hydrograph are the rising limb, peak discharge, recession limb, lag time, time to peak, and discharge rate.
- A unit hydrograph represents the runoff from 1 unit of effective rainfall over a given watershed's duration. It allows prediction of runoff from different rainfall amounts. Synthetic unit hydrographs use watershed characteristics to model ungauged areas.
This document discusses floods and methods for estimating peak flood discharge. It begins by defining a flood and design flood. It then describes various methods for estimating peak flood discharge, including using physical indicators, empirical formulas, unit hydrographs, the rational method, and flood frequency studies. As an example of applying the rational method, it calculates the peak discharge for a culvert project in Alberta, Canada with a 50-year return period. It also provides an example of using Gumbel's extreme value distribution to estimate flood discharges with 100-year and 150-year return periods based on annual maximum flood data from 1951-1977.
Flood has a great role in the socioeconomic status of the community living in the sourrounding of the river. How to analyze and manage the flood water is a real issue facing throughout the world specially in the developing countries. Unit Hydrograph play a vital role in predicting and analyzing the watershed water.
1. Distribution of Runoff
2. Hydrograph Analysis
a) Hydrograph & Unit Hydrograph
b) S - Hydrograph & Synthetic Unit Hydrograph
3. Computation of Design Discharge
a) Rational Formulae
b) SCS Curve Number Method
4. Flood Frequency Analysis
5. Flood Routing
This document discusses principles of groundwater flow. It defines Darcy's law, which governs groundwater movement, and presents the governing equations for confined and unconfined aquifers. It also discusses flow nets, which can be used to graphically analyze groundwater flow, and the Dupuit equation, which approximates unconfined flow between two bodies of water. The document provides an example problem applying the Dupuit equation to calculate groundwater discharge to two rivers separated by 1,000 meters.
This document provides information about hyetographs and hydrographs. It defines a hyetograph as a graphical representation of rainfall intensity over time, showing total rainfall. A hydrograph shows variations in river discharge over time at a measurement point. It describes the components of hydrographs, including the rising and falling limbs and peak. It also discusses runoff classifications, the unit hydrograph concept for analyzing surface runoff, and key hydrograph terminology like time to peak, time of concentration, and lag time.
This document discusses hydrographs and unit hydrographs. It defines a hydrograph as a graph showing the rate of flow versus time past a specific point in a river. It notes that hydrographs are commonly used in sewerage design. It then describes the components of a hydrograph including the rising limb, recession limb, peak discharge, lag time, and time to peak. Finally, it discusses unit hydrographs, defining a unit hydrograph as the runoff resulting from 1 unit of rainfall excess. It provides examples of deriving unit hydrographs from observed hydrographs and flood hydrographs.
There are three main equations that describe the shape of an infiltration capacity rate curve: Horton's equation, Phillips equation, and Holtan's equation. The infiltration capacity rate generally decreases over time from an initial maximum rate to a minimum steady rate. The infiltration index and W-index provide a constant infiltration rate for calculating runoff. The W-index is more accurate than the infiltration index because it excludes depression and interception losses. Both indices are commonly used to estimate flood magnitudes from critical storms.
- A hydrograph shows the rate of water flow over time at a specific point along a river or channel. It is used in sewer system design.
- The main components of a hydrograph are the rising limb, peak discharge, recession limb, lag time, time to peak, and discharge rate.
- A unit hydrograph represents the runoff from 1 unit of effective rainfall over a given watershed's duration. It allows prediction of runoff from different rainfall amounts. Synthetic unit hydrographs use watershed characteristics to model ungauged areas.
This document discusses floods and methods for estimating peak flood discharge. It begins by defining a flood and design flood. It then describes various methods for estimating peak flood discharge, including using physical indicators, empirical formulas, unit hydrographs, the rational method, and flood frequency studies. As an example of applying the rational method, it calculates the peak discharge for a culvert project in Alberta, Canada with a 50-year return period. It also provides an example of using Gumbel's extreme value distribution to estimate flood discharges with 100-year and 150-year return periods based on annual maximum flood data from 1951-1977.
Flood has a great role in the socioeconomic status of the community living in the sourrounding of the river. How to analyze and manage the flood water is a real issue facing throughout the world specially in the developing countries. Unit Hydrograph play a vital role in predicting and analyzing the watershed water.
1. Distribution of Runoff
2. Hydrograph Analysis
a) Hydrograph & Unit Hydrograph
b) S - Hydrograph & Synthetic Unit Hydrograph
3. Computation of Design Discharge
a) Rational Formulae
b) SCS Curve Number Method
4. Flood Frequency Analysis
5. Flood Routing
This document discusses principles of groundwater flow. It defines Darcy's law, which governs groundwater movement, and presents the governing equations for confined and unconfined aquifers. It also discusses flow nets, which can be used to graphically analyze groundwater flow, and the Dupuit equation, which approximates unconfined flow between two bodies of water. The document provides an example problem applying the Dupuit equation to calculate groundwater discharge to two rivers separated by 1,000 meters.
This document describes Snyder's synthetic unit hydrograph method. Snyder's method allows computation of key hydrograph characteristics using watershed properties. These include:
1. Lag time, which is related to watershed time of concentration based on length and slope.
2. Hydrograph duration, which is typically 1/5.5 of the lag time.
3. Peak discharge, which is related to watershed area, storage coefficient, and time parameters.
4. Other hydrograph properties like width can also be estimated using the peak discharge and empirical coefficients. The synthetic hydrograph provides an estimate of watershed runoff for both gauged and ungauged locations.
This document describes how to derive a required time (T) unit hydrograph from a given time (D) unit hydrograph when T is not a multiple of D using the S-curve method. It explains that an S-curve hydrograph is generated by continuous, uniform effective rainfall and rises continuously in the shape of an S until equilibrium is reached. The ordinates of the S-curve can be calculated using the equation S(t) = U(t) + S(t-D), where S(t) is the ordinate of the S-curve at time t, U(t) is the ordinate of the given unit hydrograph at time t, and S(t-D) is the
Non equilibrium equation for unsteady radial flowAbhishek Gupta
This document discusses unsteady radial flow in aquifers and methods for analyzing pumping test data. It describes equations for confined, unconfined, and leaky aquifers. The Theis and Cooper-Jacob methods are presented for analyzing confined aquifer data using type curves. For unconfined aquifers, Neuman's equation and the Penman method are described. The Hantush-Jacob solution and Walton graphical method are provided for analyzing pumping tests in leaky aquifers.
This document discusses stream gauging techniques used to measure stream discharge. It begins by explaining that stream flow represents the runoff phase of the hydrologic cycle and is the most important data for hydrologic studies. It then describes various methods for measuring stream stage including staff gauges, suspended wire gauges, automatic stage recorders, and bubble gauges. Common techniques for directly measuring stream discharge are also summarized, such as area-velocity methods using current meters and floats, as well as moving boat methods. Site selection criteria and types of stage data collected are also briefly outlined.
1) A pumping test was conducted where a well was pumped at 2500 m3/day and drawdowns were measured in an observation well 60 m away at various times.
2) The transmissivity and storativity of the confined aquifer were estimated using the Theis and Cooper-Jacob methods in AquiferTest software by analyzing the linear relationship between the logarithm of time and drawdown.
3) The accuracy of the aquifer parameter estimates depends on maintaining a constant pumping rate and measuring drawdowns at appropriate time intervals in multiple observation wells.
This document provides an introduction to hydrology. It discusses the hydrologic cycle and its components like evaporation, transpiration, infiltration, etc. It also discusses different types of precipitation like rain, snow, drizzle and methods of precipitation classification. Measurement of rainfall using rain gauges and estimation of rainfall for areas between gauges using methods like arithmetic mean, Thiessen polygon and isohyetal maps are described. Optimum density of rain gauges for different terrains is also mentioned.
This document discusses practical applications of hydrology. It begins by defining hydrology as the science of water on Earth, including its occurrence, movement, distribution, and circulation. Hydrology can be scientific or applied/engineering. Engineering hydrology deals with water resource estimation, precipitation/runoff processes, and flood/drought problems. Some key practical applications of hydrology include water supply and treatment, irrigation, drainage, hydropower, flood control, and pollution control. Hydrology and hydraulics intersect in areas like water supply, power generation, dams/reservoirs, flood protection, and wastewater management. Engineering uses of surface water hydrology include modeling average and extreme events for applications like infrastructure design, water supply
The document discusses engineering hydrology, which uses hydrologic principles to solve problems related to water resource management and development. It defines engineering hydrology as studying the hydrologic cycle and its components like precipitation, evaporation, infiltration and runoff. Engineering hydrologists work on projects for water control, utilization and management by estimating maximum floods, droughts, water supply and more using statistical and modeling techniques. The key aspects of hydrology discussed are data collection, analysis and prediction.
This document discusses techniques for measuring stream flow. There are two main categories of measurement: direct determination using area-velocity methods, dilution techniques, electromagnetic and ultrasonic methods; and indirect determination using hydraulic structures like weirs, flumes and gates or slope-area methods. Velocity is an important aspect measured using current meters, which are the most commonly used instruments. Current meters consist of rotating cups or propellers connected to mechanisms that count revolutions to determine flow velocity. Floating objects can also be used to estimate surface velocities. Accurate stream flow measurement is important for hydrologic studies.
Introduction to Hydrology, Stream GaugingAmol Inamdar
Introduction to Hydrology, Types of Rain gauges, Factors affecting evaporation and infiltration, Stream gauging, Mass curve, Hyetograph, DAD Curve, Horton's Method, Infiltrometers, fi-index, W-index, Methods of measurement of Discharge of Stream, Area-Velocity Method, Moving Boat Method, Salt concentration method, ADCP, Current meter, River staging
Diversion headworks are structures constructed across rivers to raise water levels and divert water into canals. They have several purposes, including increasing the commanded area, regulating water supply to canals, and controlling silt entry. There are two types - temporary and permanent. Key components include weirs/barrages, under sluices, divide walls, fish ladders, and head regulators. The optimal location depends on the river's characteristics, balancing factors like water availability, construction costs, and proximity to agricultural land.
Well hydraulics analyzes the drawdown of groundwater levels due to pumping from wells over time and distance. It is important to understand well hydraulics to design effective pumping strategies that can meet water demand by withdrawing adequate amounts of groundwater from aquifers. Basic assumptions are made about steady versus unsteady flow, and models examine steady radial flow of groundwater to wells pumping from both confined and unconfined aquifers.
This document provides information on reservoirs for water storage. It defines a reservoir as an artificial lake created by a dam to store excess water. Reservoirs can be used for multiple purposes like flood control, irrigation, water supply, power generation, fisheries and navigation. The key aspects discussed include reservoir types (storage, flood control, distribution), site selection factors, necessary investigations like surveys and yield/capacity calculations. Sedimentation in reservoirs over time is also explained, along with various control measures like afforestation, check dams and contour bunds.
Stream flow representing the runoff phase of the hydrologic cycle is the most important basic data for hydrologic studies. Runoff is generated by rainstorms. Its occurrence and quantity are dependent on the characteristics of the rainfall event, i.e. intensity, duration and distribution. This module highlights about runoff components of the hydrological cycle.
Hydrology and water resources engineering.vivek gami
This document provides an overview of hydrology topics including evaporation, evapotranspiration, and infiltration. It defines these processes and lists key factors that influence each one. Evaporation is the process where water is converted to vapor and returns to the atmosphere. Evapotranspiration is the combination of evaporation and plant transpiration. Infiltration is the downward flow of water into soil from the land surface. The document discusses methods of measuring these hydrologic processes and factors like temperature, soil type, and rainfall intensity that impact infiltration rates.
Precipitation occurs when atmospheric moisture condenses and falls to the earth's surface. The main forms of precipitation are rain, snow, hail, drizzle and dew. Precipitation is measured using rain gauges and satellite imagery. There are various types of precipitation depending on what causes the air to lift and cool, such as convection, orographic lifting, and cyclonic storms. Data from rain gauges needs to be quality controlled to ensure accuracy by checking for consistency using methods like double mass curves and adjusting records when inconsistencies are found.
The document discusses unit hydrographs, which are used to model the response of a watershed's streamflow to rainfall. It covers topics such as:
- Defining a unit hydrograph and explaining its use in predicting streamflow from rainfall amounts.
- Describing the assumptions and terminology used in unit hydrograph models, such as uniform rainfall distribution and the components of a hydrograph.
- Explaining how to create a unit hydrograph from streamflow data or synthetically, and how to apply it to calculate a direct runoff hydrograph from rainfall inputs.
A study confined to the lower tapi basin in Gujarat, India to find out the primary causes for 2006 floods in Surat city. The study involves collection of topographical data from the local geological survey organization, rainfall data from meteorological department of india and the application of HEC-HMS software from US Army corps of engineers to identify the primary cause of the runoff.
This document describes Snyder's synthetic unit hydrograph method. Snyder's method allows computation of key hydrograph characteristics using watershed properties. These include:
1. Lag time, which is related to watershed time of concentration based on length and slope.
2. Hydrograph duration, which is typically 1/5.5 of the lag time.
3. Peak discharge, which is related to watershed area, storage coefficient, and time parameters.
4. Other hydrograph properties like width can also be estimated using the peak discharge and empirical coefficients. The synthetic hydrograph provides an estimate of watershed runoff for both gauged and ungauged locations.
This document describes how to derive a required time (T) unit hydrograph from a given time (D) unit hydrograph when T is not a multiple of D using the S-curve method. It explains that an S-curve hydrograph is generated by continuous, uniform effective rainfall and rises continuously in the shape of an S until equilibrium is reached. The ordinates of the S-curve can be calculated using the equation S(t) = U(t) + S(t-D), where S(t) is the ordinate of the S-curve at time t, U(t) is the ordinate of the given unit hydrograph at time t, and S(t-D) is the
Non equilibrium equation for unsteady radial flowAbhishek Gupta
This document discusses unsteady radial flow in aquifers and methods for analyzing pumping test data. It describes equations for confined, unconfined, and leaky aquifers. The Theis and Cooper-Jacob methods are presented for analyzing confined aquifer data using type curves. For unconfined aquifers, Neuman's equation and the Penman method are described. The Hantush-Jacob solution and Walton graphical method are provided for analyzing pumping tests in leaky aquifers.
This document discusses stream gauging techniques used to measure stream discharge. It begins by explaining that stream flow represents the runoff phase of the hydrologic cycle and is the most important data for hydrologic studies. It then describes various methods for measuring stream stage including staff gauges, suspended wire gauges, automatic stage recorders, and bubble gauges. Common techniques for directly measuring stream discharge are also summarized, such as area-velocity methods using current meters and floats, as well as moving boat methods. Site selection criteria and types of stage data collected are also briefly outlined.
1) A pumping test was conducted where a well was pumped at 2500 m3/day and drawdowns were measured in an observation well 60 m away at various times.
2) The transmissivity and storativity of the confined aquifer were estimated using the Theis and Cooper-Jacob methods in AquiferTest software by analyzing the linear relationship between the logarithm of time and drawdown.
3) The accuracy of the aquifer parameter estimates depends on maintaining a constant pumping rate and measuring drawdowns at appropriate time intervals in multiple observation wells.
This document provides an introduction to hydrology. It discusses the hydrologic cycle and its components like evaporation, transpiration, infiltration, etc. It also discusses different types of precipitation like rain, snow, drizzle and methods of precipitation classification. Measurement of rainfall using rain gauges and estimation of rainfall for areas between gauges using methods like arithmetic mean, Thiessen polygon and isohyetal maps are described. Optimum density of rain gauges for different terrains is also mentioned.
This document discusses practical applications of hydrology. It begins by defining hydrology as the science of water on Earth, including its occurrence, movement, distribution, and circulation. Hydrology can be scientific or applied/engineering. Engineering hydrology deals with water resource estimation, precipitation/runoff processes, and flood/drought problems. Some key practical applications of hydrology include water supply and treatment, irrigation, drainage, hydropower, flood control, and pollution control. Hydrology and hydraulics intersect in areas like water supply, power generation, dams/reservoirs, flood protection, and wastewater management. Engineering uses of surface water hydrology include modeling average and extreme events for applications like infrastructure design, water supply
The document discusses engineering hydrology, which uses hydrologic principles to solve problems related to water resource management and development. It defines engineering hydrology as studying the hydrologic cycle and its components like precipitation, evaporation, infiltration and runoff. Engineering hydrologists work on projects for water control, utilization and management by estimating maximum floods, droughts, water supply and more using statistical and modeling techniques. The key aspects of hydrology discussed are data collection, analysis and prediction.
This document discusses techniques for measuring stream flow. There are two main categories of measurement: direct determination using area-velocity methods, dilution techniques, electromagnetic and ultrasonic methods; and indirect determination using hydraulic structures like weirs, flumes and gates or slope-area methods. Velocity is an important aspect measured using current meters, which are the most commonly used instruments. Current meters consist of rotating cups or propellers connected to mechanisms that count revolutions to determine flow velocity. Floating objects can also be used to estimate surface velocities. Accurate stream flow measurement is important for hydrologic studies.
Introduction to Hydrology, Stream GaugingAmol Inamdar
Introduction to Hydrology, Types of Rain gauges, Factors affecting evaporation and infiltration, Stream gauging, Mass curve, Hyetograph, DAD Curve, Horton's Method, Infiltrometers, fi-index, W-index, Methods of measurement of Discharge of Stream, Area-Velocity Method, Moving Boat Method, Salt concentration method, ADCP, Current meter, River staging
Diversion headworks are structures constructed across rivers to raise water levels and divert water into canals. They have several purposes, including increasing the commanded area, regulating water supply to canals, and controlling silt entry. There are two types - temporary and permanent. Key components include weirs/barrages, under sluices, divide walls, fish ladders, and head regulators. The optimal location depends on the river's characteristics, balancing factors like water availability, construction costs, and proximity to agricultural land.
Well hydraulics analyzes the drawdown of groundwater levels due to pumping from wells over time and distance. It is important to understand well hydraulics to design effective pumping strategies that can meet water demand by withdrawing adequate amounts of groundwater from aquifers. Basic assumptions are made about steady versus unsteady flow, and models examine steady radial flow of groundwater to wells pumping from both confined and unconfined aquifers.
This document provides information on reservoirs for water storage. It defines a reservoir as an artificial lake created by a dam to store excess water. Reservoirs can be used for multiple purposes like flood control, irrigation, water supply, power generation, fisheries and navigation. The key aspects discussed include reservoir types (storage, flood control, distribution), site selection factors, necessary investigations like surveys and yield/capacity calculations. Sedimentation in reservoirs over time is also explained, along with various control measures like afforestation, check dams and contour bunds.
Stream flow representing the runoff phase of the hydrologic cycle is the most important basic data for hydrologic studies. Runoff is generated by rainstorms. Its occurrence and quantity are dependent on the characteristics of the rainfall event, i.e. intensity, duration and distribution. This module highlights about runoff components of the hydrological cycle.
Hydrology and water resources engineering.vivek gami
This document provides an overview of hydrology topics including evaporation, evapotranspiration, and infiltration. It defines these processes and lists key factors that influence each one. Evaporation is the process where water is converted to vapor and returns to the atmosphere. Evapotranspiration is the combination of evaporation and plant transpiration. Infiltration is the downward flow of water into soil from the land surface. The document discusses methods of measuring these hydrologic processes and factors like temperature, soil type, and rainfall intensity that impact infiltration rates.
Precipitation occurs when atmospheric moisture condenses and falls to the earth's surface. The main forms of precipitation are rain, snow, hail, drizzle and dew. Precipitation is measured using rain gauges and satellite imagery. There are various types of precipitation depending on what causes the air to lift and cool, such as convection, orographic lifting, and cyclonic storms. Data from rain gauges needs to be quality controlled to ensure accuracy by checking for consistency using methods like double mass curves and adjusting records when inconsistencies are found.
The document discusses unit hydrographs, which are used to model the response of a watershed's streamflow to rainfall. It covers topics such as:
- Defining a unit hydrograph and explaining its use in predicting streamflow from rainfall amounts.
- Describing the assumptions and terminology used in unit hydrograph models, such as uniform rainfall distribution and the components of a hydrograph.
- Explaining how to create a unit hydrograph from streamflow data or synthetically, and how to apply it to calculate a direct runoff hydrograph from rainfall inputs.
A study confined to the lower tapi basin in Gujarat, India to find out the primary causes for 2006 floods in Surat city. The study involves collection of topographical data from the local geological survey organization, rainfall data from meteorological department of india and the application of HEC-HMS software from US Army corps of engineers to identify the primary cause of the runoff.
Gw02 role of dwlr data in groundwater resource estimationhydrologyproject0
This document discusses the role of data from Deep Well Logging Recorders (DWLRs) in estimating groundwater resources. DWLRs provide high-frequency water level data that can help understand recharge processes and parameters. Their data allows identifying accurate peaks and troughs in the water table to define optimal periods for water balance studies estimating specific yield and rainfall recharge. DWLR hydrographs also aid in determining rainfall amounts needed to initiate recharge, lag times between rainfall and recharge, effective rainfall events, and periods of evapotranspiration loss - all improving the accuracy of water balance assessments and groundwater resource estimation.
This document contains 43 questions related to hydrology and water resources engineering. The questions cover topics like the hydrologic cycle, precipitation, rainfall measurement, runoff analysis, unit hydrographs, flood frequency analysis and flood routing. Most of the questions ask students to explain hydrologic concepts, factors affecting runoff and infiltration, methods to derive unit hydrographs and questions related to flood estimation. A few questions ask students to perform hydrologic calculations related to rainfall measurement, runoff estimation and unit hydrograph development.
This document discusses methods for estimating the maximum discharge in small catchment areas of less than 50 square kilometers. It focuses on the rational method, which estimates peak discharge as the product of rainfall intensity, catchment area, and a runoff coefficient. The key parameters in the rational method - runoff coefficient, catchment area, and time of concentration - are defined. Typical values of runoff coefficients for different land uses are provided. Methods for calculating the time of concentration using empirical equations are also described. The document emphasizes that the storm duration used in the rational method should be equal to the time of concentration for the catchment area.
This document provides guidance on how to compile discharge data, including:
1. Aggregating data to longer time intervals through arithmetic averaging or summation.
2. Calculating volumes in cubic meters and runoff depth in millimeters from discharge data and catchment area.
3. Extracting maximum and minimum values over various time periods like days, months, or years for analyses.
Hydrologic data generally consist of a sequence of observations of some phase of the hydrologic cycle made at a particular site. The data may be a record of the discharge of a stream at a particular place, or it may be a record of the amount of rainfall caught in a particular rain gage.
Although for most hydrologic purposes a long record is preferred to a short one, the user should recognize that the longer the record the greater the chance that there has been a change in the physical conditions of the basin or in the methods of data collection. If these are appreciable, the composite record would represent only a nonexistent condition and not one that existed either before or after the change. Such a record is inconsistent.
This document discusses hydrographs and the factors that influence them. It defines a hydrograph as a graphical representation of discharge over time at a particular point in a river. It also defines components of the hydrograph like the rising and falling limbs. Additionally, it discusses how watershed characteristics such as area, slope, rock type, soil, land use and precipitation patterns can impact the shape of the hydrograph. Specifically, steeper slopes and impermeable surfaces can produce a steeper rising limb while permeable soils and rocks or forested land can result in a more gradual rising limb.
The document provides an outline for a presentation on the SWAT (Soil and Water Assessment Tool) hydrological model. It begins with an introduction to hydrological modeling and the development and utilities of the SWAT model. It describes the data requirements, model framework, and step-by-step procedure to run the model. A case study applying the SWAT model to the Simly Dam watershed in Pakistan is summarized. The limitations and future developments of the SWAT model are briefly discussed, followed by references.
Precipitation analysis - Methods and solved examplesantoshichekka
This document discusses quantitative analysis of precipitation including depth-area analysis, depth-duration analysis, intensity-duration analysis, and intensity-duration-frequency analysis. It provides definitions and formulas for key terms like rainfall event, rainfall depth, duration, intensity, and frequency. Examples are given to demonstrate how to derive equations relating intensity and duration from rainfall data and construct intensity-duration-frequency curves.
This document provides guidance on how to correct and complete discharge data records. It discusses several methods for estimating missing or incorrect discharge values, including interpolation during short gaps or recessions, regression analysis using data from neighboring stations, flow routing to ensure water balance, and rainfall-runoff simulation with a calibrated hydrologic model. The Muskingum method for flow routing between stations is presented as an example. The key is to select the most appropriate technique depending on the type, duration and location of the missing data, while ensuring continuity and physical realism in the corrected or completed record.
This document discusses key concepts in hydrology including hyetographs, hydrographs, unit hydrographs, and instantaneous unit hydrographs. It defines each term and concept and provides examples to illustrate them. Specifically, it defines a hyetograph as a plot of rainfall intensity over time, a hydrograph as a plot of discharge over time, and unit and instantaneous unit hydrographs as tools used to model watershed response to rainfall of different durations. Limitations and uses of unit hydrographs are also summarized.
This document discusses hydrologic design storms and methods for developing design precipitation hyetographs. It defines key hydrologic concepts like return period, depth-duration-frequency curves, and SCS design storm methods. The SCS method involves selecting a standard SCS rainfall distribution type curve based on location and scaling it using the design storm depth to develop a hyetograph for the given duration and return period. The document provides an example of applying the SCS method to develop a 25-year, 24-hour hyetograph for Harris County, Texas.
This presentation summarizes key concepts related to hydrographs including:
1) A hydrograph shows the variation of discharge over time at a particular point in a river. It has three main components: the rising limb, peak, and recession curve.
2) Factors like area, slope, land use, and precipitation affect hydrograph shape.
3) A unit hydrograph represents the response of a watershed to 1 cm of direct runoff from rainfall of a given duration, and is used to estimate flood discharge from future rainfall.
4) Methods like superposition and S-curves are used to derive unit hydrographs from storm hydrographs and to estimate hydrographs for different rainfall scenarios.
Revision of the Rainfall Intensity Duration Frequency Curves for the City of ...theijes
This work involves the revision of the Rainfall Intensity Duration Frequency (IDF) Curves for the city of Kumasi. Annual Maximum Rainfall depths of various durations over twenty-two years were obtained from the Ghana Meteorological Services. The data set was then subjected to frequency analysis to determine the distribution of which best characterize the data set. The annual maximum series were found to be drawn from the Gumbel distribution whose parameters were computed by fitting the statistics to the data. The Chi-square test and the Kolmogorov-Smirnov test prove the appropriateness of the fitting. Since the data available was only 22 years, IDF values for return periods higher than 22 years were obtained using frequency factors. The IDF estimates resulting from this work have been compared with the existing IDF curves prepared by J.B Danquah. The results show that for shorter durations (12 min and 24 min), the new IDF Curves give higher intensities for the same return period; the percentage increase ranges between 2% and 25%, whiles for longer durations (42min, 1 hr, 2hr, 3hr, 6hr, 12hr and 24 hr), the new IDF Curves give lower intensities for the same return period with the percentage decrease ranging between 3% and 49% when compared with the existing J.B Danquah IDF Curves. This might be as a result of low precipitation trends for shorter durations and high precipitation trends for longer durations in 1970s and before. These therefore call for the revision and updating of the existing IDF Curves for all the major cities and towns in Ghana to take into account the effect of climate change
Module 2 ch-1 heytograph and hydrology analysisAnkit Patel
This document discusses hyetographs, hydrographs, runoff, and unit hydrographs. It contains the following key points:
1. A hyetograph is a graphical representation of rainfall intensity over time, showing the relationship between rainfall amount and time. A hydrograph shows stream discharge over time.
2. Runoff is the portion of rainfall that flows into streams and rivers. It is affected by rainfall characteristics and basin properties like soil, vegetation and topography.
3. A unit hydrograph represents the runoff from 1 cm of effective rainfall uniformly distributed over a basin and duration. It can be used to estimate flood hydrographs from storm rainfall amounts and distributions.
Unit Hydrograph (UH) is the most famous and generally utilized technique for analysing and deriving flood hydrograph resulting from a known storm in a basin area. For ungauged catchments, unit hydrograph are derived using either regional unit hydrograph approach. Central Water Commission (CWC) derived the regional unit hydrograph relationships for different sub-zones of India relating to the various unit hydrograph parameters with some prominent physiographic characteristics. In this study, the lately developed UH model is applied located between Latitude 15º54′2′′ N to 16º16′19′′ N Latitude and 76º48′40′′ E to77º4′21′′ E Longitude. The study area covers an area of 466.02 km2, having maximum length of 36.5 km. The maximum and minimum elevation of the basin is 569 m and 341 m above MSL, respectively. The Peak discharge of unit hydrograph obtained is 171.58m3/s. The final cumulative discharge is 1669.05 m3/s.
IRJET- A Review of Synthetic Hydrograph Methods for Design StormIRJET Journal
This document reviews various synthetic unit hydrograph methods for modeling runoff from design storms in ungauged or data-limited watersheds. It groups the methods into four categories: traditional empirical methods, conceptual methods, probabilistic methods, and geomorphological methods. The document then describes several traditional methods in detail, including the Snyder, Mitchell, Commons, SCS, and Taylor-Schwarz methods. It discusses how these methods relate key watershed characteristics like area, channel length, and slope to unit hydrograph parameters like peak discharge and time to peak. Finally, it introduces some conceptual hydrologic models that have been adapted as synthetic unit hydrograph methods.
This document discusses the sewer network distribution for a particular area. It includes tables showing wastewater generation from households and infiltration in the pipe network based on sub-area population and characteristics. The total wastewater generation calculated is 1744.59 m3/day based on contributions from household usage of 1683.73 m3/day and infiltration of 60.6749 m3/day into the pipe network from surrounding areas. Diagrams of the pipe network and a selected loop are referenced to aid in the analysis and discussion.
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2. Coverage
Flood pictorial views
Hydrograph - Review
Unit Hydrograph
Unit Hydrograph. Why ?
Assumptions For UH
Terminology for UH
Creating Unit Hydrograph
Applications of Unit H
27. Why
Construct & Analyse
Hydrographs ?
To find out discharge patterns of
a particular drainage basin
Help predict flooding events,
therefore influence implementation
of flood prevention measures
29. Hydrograph
Graphical representation of time
(hours) versus discharge (cfs or
acms) at a particular point on
stream or channel
the watershed area
which drains
31. -------------------------YES
?Then we will be able to
1. Manage the Storm water.
2. Identify the Flood Plans on downstream side.
3. To place the Hydraulic structures at safe level.
4. Efficient Urban Storm water management plan.
5. Design the Different types of Hydraulic structures.
6. Minimize the effects of Floods.
33. Unit Hydrograph
A conceptual direct runoff
hydrograph resulting from a
rainfall excess of unit depth and
constant intensity for a particular
watershed is called a unit
hydrograph
34. The unit
calculate
hydrograph method is employed to
the direct runoff hydrograph at the
watershed outlet given the rainfall excess
produced by a storm event.
This method is categorized as a lumped model
in which the hydrologic characteristics of the
entire watershed are combined and typified by
one or more parameters, simple mathematical
expressions, or graphs.
35. The Unit hydrograph is a useful tool in the process of
predicting the impact of precipitation on stream flow.
The Unit depth is 1cm in the SI unit system and 1inch
in the U.S. system.
It is usually abbreviate as a Uhc.
The subscript “c” indicate the Duration of the rainfall
excess.
36. For instance, the direct runoff hydrograph
produced by a rainfall excess that has a
duration of 3 hr and constant intensity of 1/3
in./hr is denoted by UH3 and depth of the
rainfall excess is (1/3 in./hr)(3 hr) = 1 in
37. We can develop a unit hydrograph for a gaged
watershed by analyzing the simultaneous
rainfall and runoff records.
Unfortunately, most small, urban/rural
watersheds are ungaged. However, there are
several
available
ungaged
synthetic unit hydrograph methods
to develop a unit hydrograph for
watersheds e.g. Espey Ten-Minute
Unit Hydrograph.
38. UNIT HYDROGRAPH—WHY ?
Simplifying our task / work / procedures.
Gives us a base line for a specified watershed.
Standardize the hydrograph for different watersheds.
Gives us information that how the flow of a stream will
be affected over time by the addition of one unit of
runoff.
39. The role of Unit Hydrograph theory in the flood prediction
process is to provide an estimate of stream flow given
and amount precipitation.
Once we know how much rainfall or snowmelt has
occurred, or is likely to occur, and we have an idea of
how much of this will turn into runoff, we still need to
know how the flow of a stream will be affected over time
by that runoff. The unit hydrograph provide us with a way
to estimate this, and is an integral part of many
hydrological modeling systems.
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41. ASSUMPTIONS
The primary assumption of unit hydrograph theory is
that the rainfall has uniform distribution, both in space-
with minimal variations across the basin-and in time; in
other words, the rainfall rate did not vary much during
the event.
In reality, precipitation events are rarely uniform in
space and time. Often, one portion of the basin
experiences higher intensity precipitation than another
portion.
42. The base duration of direct runoff hydrograph due to an effective
rainfall of unit duration is constant.
The ordinates of DRH are directly proportional to the total amount
of DR of each hydrograph (principles of linearity, superposition,
and proportionality)
For a given basin, the runoff hydrograph due to a given period of
rainfall reflects all the combined physical characteristics of basin
(time-invariant)
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45. BASIN-AVERAGED RAINFALL
In typical non-snow situations, we begin the hydrologic process with
rainfall. In particular, we start with a basin-averaged rainfall. This simply
tells us how much rain fell, or is forecast to fall, on a given basin and
typically takes the form of a rainfall depth per time. In unit hydrograph
theory, we assume that this rainfall has fallen uniformly across the
basin
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47. BASIN-AVERAGED EXCESS
RAINFALL
From averaged rainfall, we need to know how much of the basin-
averaged rainfall will become runoff. In unit hydrograph theory, runoff is
often referred to as “excess precipitation” or “excess rainfall.” Rainfall
runoff models will typically provide an estimate of what becomes
excess rainfall.
So, for example, if 25% of our 4.00 cm basin-averaged rainfall
becomes excess rainfall, then we have a basin averaged excess
rainfall of 1.00 cm
48. The unit hydrograph represents the excess
prCecoipnitteantiotsn or quick – response runoff
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Direct Runoff
49. TERMINOLOGY - UH
Duration
Rising Limb
Recession Limb (falling
limb)
Peak Flow
Time to Peak (rise time)
Time of Concentration
Recession Curve
Base flow Separation line
Base flow
Quick Response Run off
Point of inflection
51. CREATING U.HYDROGRAPH
From Stream flow Data
Synthetically
Espey Ten-Minute Unit Hydrograph
Snyder
SCS Unit Hydrograph
Time-Area Unit Hydrograph(Clark, 1945)
Gamma Function Unit Hydrograph
“Fitted” Distributions
Geomorphologic
My Concern
52. STEPS FOCRonDteEnRtsIVING THE UNIT HYDROGRAPH
flow hydrograph at a given stream gauge location
along with the following information:
• The Basin Area
• The Basin-averaged rainfall depth
• The duration over which the excess precipitation
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A unit hydrograph can be derived from a total stream
occurred.
53.
54. When deriving a unit hydrograph it is important to
start with an archived hydrograph in which the
quick-response runoff portion is from one single
storm event. In addition, that storm should have
produced its excess precipitation with nearly
uniform coverage in space and time over the basin
Select Appropriate Precipitation EventStep-1
56. The total volume of water from the quick-response runoff needs
to be calculated. This is done by summing the areas under the
QRR Hydrograph for each time step, in this case, hourly.
Calculate Quick – Response VolumeStep-3
58. Determine Excess PPT Depth from BasinStep-4
For example, assume we have a basin area of 100 square km,
which is 100,000,000 sq.m and calculated volume of quick-
response to be 2,000,000 cum-then the depth will be
59. Adjust the Quick-Response Hydrograph
Step-5
The excess ppt depth probably won`t be exactly one unit as unit
hydrograph requires. So, we have to adjust the QRR
hydrograph to show what the response from one unit would be.
60. Adjust the Quick-Response HydrographStep-5
Once we multiply each point on the hydrograph by our
adjustment factor of 0.5, our resulting unit hydrograph is for
exactly 1 cm of excess precipitation
61. Determine Duration of UHStep-6
The duration of a unit hydrograph refers to a continuous
time period during which one unit of excess ppt occurred.
If it took 6 hours for the one unit of excess to occur, we
have a 6-hr unit hydrograph. Remember, the unit
hydrograph duration does not refer to the duration of the
stream flow response.
62. The difficult part of determining the duration of a unit
hydrograph is estimating which portion of the entire
precipitation event actually contributes to excess ppt.
Recall that the water that infiltrates & percolates into
deeper storage and base flow is not part of excess ppt.
We can estimate this portion of the ppt. by applying a
constant loss function to the rainfall.
Recall that we have already calculated the depth of the
excess ppt to be 2.0 cm. Now, we need to know how
long it took for that excess to occur.
63. So we move this loss function line such that the
amount of ppt. above the line is equal to the depth
of excess ppt. that we already calculated for the
basin.
Below that line the ppt. goes to long-term storage.
Above the line is the excess ppt.
64.
65.
66. Now we have an excess precipitation bar graph of 6-hr.
Notice that the amounts from hour to hour on this
graph are not truly uniform. This is typical.
For purposes of calculating a unit hydrograph duration,
however, we assume that all excess ppt occurred
uniformly in time.
67. Final Unit Hydrograph
At the end of these steps, we have a 6-hr unit hydrograph.
It show the stream flow response to 6 hrs of excess ppt
that produced one unit of depth.
69. The UH method is based on the assumption of a linear
relationship between the rainfall excess and the DR
rates. More specifically, the method assumes that
The base time of the DRH resulting from a rainfall
excess of a given duration is constant regardless of
the amount of the rainfall excess, and
The ordinates of a DRH resulting from a rainfall
excess of a given duration are directly proportional
to the total amount of rainfall excess
70. In other words, the base of the DRH resulting from a
rainfall excess of, say, 1.5 in. produced over af 2-hr
duration is the same as that of the 2-hr UH. Also the
ordinate of this DRH are 1.5 times the ordinates of the
UH2 at respective times. We can simply state that
DRH = cUH2
DRH = 1.5 UH2
General Form
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73. Example:
•Two storm each of 6-hr duration and having rainfall excess values of
3.0cm and 2.0 cm respectively occur successively. The 2-cm ER rain
follows the 3-cm rain. The 6-hr UH for the catchment is the same as
given in previous example. Calculate the resulting DRH.
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77. Unit Hydrograph of Different Durations
Under condition where lack of adequate data in
developement of unit hydrograph
D-hour unit hydrograph is used to develop unit
hydrographs of differing durations nD
Two method available:
1. Method of superposition
2. The S-Curve
78. If a D-h unit hydrograph is available, and its desired to
develop unit hydrograph of nD, its is easily
accomplished by superposing n unit hydrographs with
each graph separated from the previous on by D-h.
Method of Superpositions
79. D = 2-Hr Unit Hydrograph
Adjusted Net Rainfall
one inch over basin
Qp
81. Example
Given the ordinates of a 4-hr unit hydrograph as
below derive the ordinates of a 12-hr unit
hydrograph for the same catchment
Time (hr) 0 4 8 12 16 20 24 28 32 36 40 44
Ordinates of
4-hr UH
0 20 80 130 150 130 90 52 27 15 5 0
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83.
84. S-Curve
Also known as S-hydrograph
Hydrograph produced by continous effective
rainfall at a constant rate for infinite period.
Curve obtained by summation of an infinite series
of D-h UH spaced D-h apart.
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87. S-Curves
• Convert 2 hr UH to 3-hr
• Lag each 2-hr UH
by Duration D
• Add to produce S-curve
S-curve
88. Example
Solve previous example with S-curve method:
Given the ordinates of a 4-hr unit hydrograph as below
derive the ordinates of a 12-hr unit hydrograph for the
same catchment
Time (hr) 0 4 8 12 16 20 24 28 32 36 40 44
Ordinates of
4-hr UH
0 20 80 130 150 130 90 52 27 15 5 0