how to calculate river discharge

The discharge of a river is the volume of water which flows through it in a given time. The ADCP allows discharge measurements to be made in some flooding conditions that were not previously possible. Lag time -. This open channel flow calculator will help you determine the water flow rate of open channels for any typical cross-sectional area of water Flow Rate Calculator River Stream Flow Rate calculator uses Discharge in stream = ((Sewage Concentration*Sewage discharge)-(Mixing concentration*Sewage discharge))/(Mixing The instructor version includes the completed spreadsheet. These alternative energy resources are, Green Energy means not the color of energy. New discharge measurements plotted on an existing stage-discharge relation graph would show this, and the rating could be adjusted to allow the correct discharge to be estimated for the measured stage. The volume of the bath = 50 cm x 50 cm x 100 cm. In each subsection, the area is obtained by measuring the width and depth of the subsection, and the water velocity is determined using a current meter. To calculate stream discharge, we must first determine the velocity (or length of travel in unit time), average water depth, and stream width in their respective standard unit of measurement. Instead take measurements which will allow us to calculate discharge. The stage-discharge relation depends upon the shape, size, slope, and roughness of the channel at the streamgage and is different for every streamgage. The discharge measurementobtaining periodic measurements of discharge (the quantity of water passing a location along a stream) The PowerPoint includes links to information about measuring river discharge. Read on to learn more. If you have recorded the surface velocity, a good estimate of the average can be found by multiplying your surface . You can get an idea of what stream stage is by looking at a picture of a common staff gage, which is used to make a visual reading of stream stage. It is measured in meters cubed per second or cubic feet per second. Next, the depth of the river or stream needs to be determined for each of the verticals. The stage is then measured inside the stilling well using a float or a pressure, optic, or acoustic sensor. Use the formula q=va to calculate the discharge of a river, where "q" is the discharge, "v" is the velocity and "a" is the cross-sectional area of the river. This Surface Velocity is then converted into an Average Velocity. Generally, the unit of discharge is used to monitor the capacity or capacity of water in rivers and dams so that the volume can be controlled. Expand for more detail and links to related resources. The USGS operates over 8,200 continuous-record streamgages that provide streamflow information for a wide variety of uses including flood prediction, water management and allocation, engineering design, research, operation of locks and dams, and recreational safety and enjoyment. EnergyTransformation is nothing but simply converting onetype of energyinto another form. A section free from Weeds must be chosen to avoid the possibility of the Weeds at the bottom of the River to Interface with the Rod Float. Its like a teacher waved a magic wand and did the work for me. This tutorial is intended for introductory courses in water resource, hydrology, or aquatic ecology. Multiplying the cross-sectional area by the average velocity will give the river discharge. computational scheme with the pragmatic purpose of augmenting the efficiency of However, it is not practical for a streamgage to continuously measure discharge. The USGS has been measuring streamflow on thousands of rivers and streams for many decades and by reading this set of Web pages you can find out how the whole streamflow-measurement process works. Follow me to the Streamgaging Basics website! Then, the volume of the bathroom tub becomes: The volume of the bath = The volume of water in the bath. Water discharge is the flow rate of liquid in per unit time. It is not possible to measure river discharge directly in the field. The amount of time and rotation of the propeller is done with a stopwatch. Streamflow values are better indicators than gage height of conditions along the whole river. From this, it can be concluded that the discharge is influenced by the volume of the liquid and the time it takes for the substance to flow. For the question How and why does discharge change downstream at Glenderaterra Beck? you will need to measure those variables required for the calculation of Discharge Width, Depth and Velocity, but also may choose other variables that may help explain reasons for those changes. The discharge ( Q) can be calculated by the following formula: Q = V A where: Q is the Discharge in m3/s; V is the Average Flow Velocity in m/s; and A is the area in m2 of the Wetted Cross-section. If you like the post, share it with your friends and also on social sites. Download an image of your cross section and print the data calculations used to construct and analyse it. Secure .gov websites use HTTPS Actually I am trying to compare the discharge (m3/s) and precipitation (mm) of my basin with an area (A) of different years using the same unit (mm) in a graph. The gage is marked in 1/100th and 1/10th foot intervals. In this Spreadsheet Across the Curriculum Activity, students will learn to calculate river discharge from given field data in Excel. The device working on the principle of the Doppler effect is then guided across the water surface to obtain the measurements of velocity and depth across the stream or river channel. Volume flow rate, Q = A v Mass flow rate, M = Q Weight flow rate, W = Q Where: Q = discharge in m 3 /sec or ft 3 /sec <> River landforms can be recorded using annotated field sketches or annotated photographs. The shape of the channel is important because of the reduction in velocity due to friction along the channel margins. The velocity head rod (VHR) is a fast and inexpensive method of measuring velocity in a stream. In this method, the whole Width of the River is divided into an even number of equal Segments, so that there is an odd number of Depths taken at the end of each Segment. With the help of Single Float, the Surface Velocity, at any section of the River can be easily obtained. Figure 4. Discharge is usually expressed in cubic feet per second. {?"z-*-&so&9fM7})J^uVy*G~k"vpZ}+O{s?m/8v[l6z'[!G4[be'FtQV,-DKFE]sLmT5_@'TZa$XS1Lk3$%L&Sm/\"d>gTfX`VfB~$%;Fn*OkV ?.FR1$pH(i9'7 ku)#F6-p$Q0ye6L_BE|%3YKs~0^h(#8N)2\Jbr oYno.j=Xul>_@?D'Q3H%yxbi,K4N*=g#MVkeD`+J |pk/%;YI ^~~W 8c)7 pC=9b>m. The stream discharge will decrease following a decrease in velocity, width, and depth of the stream water. Converting stage information to streamflow information. numerical data analysis shows that the number of measurements can be Energy Conservation: 11 Proven Ways to a Better Energy Conservation, Geothermal Energy: 7 Things You Must Know About Earths Heat Energy, Tidal Power: A Brand New Alternative Energy Source for Electricity Generation, Hydroelectric Energy: 10 Things You must Know About hydroelectricity, Alternative Energy: A Detail Guide on Nuclear Power That You Must Read. The rating curve is a relation between stage (river level) and streamflow (discharge). Water Science School HOME Surface Water topics . Most USGS streamgages transmit stage data by satellite to USGS computers where the stage data are used to estimate streamflow using the developed stage-discharge relation (rating). The five categories included in the process are. In short: discharge = area X velocity Ensure the tape is not twisted pull the tape measure across the river and measure to the point where the water meets the bank directly opposite. Stream discharge can be calculated at a given point using the formula: D is the average depth of water flowing through a stream or river channel. A third mechanical current meter, also a variation of the Price AA current meter, is used for measuring water velocity beneath ice. An official website of the United States government. The formula is used if either the stream roughly has a shape of a square (or rectangle) at a given point, or average width and depth are used. The measured pressure is directly related to the height of water over the tube outlet in the stream. The U.S. Geological Survey (USGS) started its first streamgage in 1889 on the Rio Grande River in New Mexico to help determine if there was adequate water for irrigation purposes to encourage new development and western expansion. As the depth of water above the tube outlet increases, more pressure is required to push the gas bubbles through the tube. The stream discharge helps predict if streamflow is sufficient to provide people with enough drinking water, support agricultural irrigation, and meet industrial needs. How many cubic meters of water will flow through the hose in 60 seconds? to measure all parts of the river you will need to take a sample. - Definition & Process, Largest Revenue Sources for the Federal Government, What Do Archaeologists Study? Calculate how long it will take to fill the water reservoir. Streamflow values are better indicators than gage height of conditions along the whole river. Drainage Basin System & Examples | What Is a Drainage Divide? When filling water, whether in a bath or a fish pond, have you ever thought like, why does it take so long for the water to fill up even though you've been waiting a long time? Mahmud has taught science for over three years. - (Never Buy New Batteries Now) - Click here, A Textbook of Hydraulics, Fluid Mechanics, and Hydraulic Mechanics, Textbook of Fluid Mechanics and Hydraulic Machines, A Textbook of Fluid Mechanics and Hydraulic Machines, Current Meter: How to Measure Average Velocity of Flow by Current Meter. (L1d1+L2d2+L3d3). It consists of a Wooden Rod or a Metallic Rod Weighted at the bottom, so as to keep it Vertical or Inclined while traveling. Another is a Hallow Metallic Sphere which is heavier than Water is suspended from the former by a Wire or String, connecting the two Floats, in such that, the Lower Metallic Float is at Depth of 6/10 of the Total Depth of Flow, as the Average Velocity of Flow exists at a Depth of 6/10 to the Total Depth. A person measuring the average width of a stream. Below are other science topics associated with measuring streamflow. All other trademarks and copyrights are the property of their respective owners. Let us calculate the discharge of a stream having a width of 12 ft and an average depth of 8 ft at a point, while its water flows with a velocity of 10 {eq}ft/sec {/eq} under normal, natural conditions. Then, how many minutes does it take Mr. Tomo to fill the tub to the brim? The river-bottom tracking capability of the ADCP acoustic beams or a Global Positioning System (GPS) is used to track the progress of the ADCP across the channel and provide channel-width measurements. The total discharge is then computed by summing the discharge of each subsection. stream The hydrology, sediment transport, and hydraulics of flow were investigated for the Kankakee and Iroquois Rivers in Illinois and Indiana. The Velocity of Flow is then Calculated by Dividing the distance traveled by the Float by the time taken to travel that distance. However, merging small rivers, streams, or tributaries into a larger river would contribute to increased discharge. How to calculate the river discharge (Average velocity): The velocity of the water within a river channel varies according to depth and nearness to obstacles such as the bed, banks and boulders which generate friction and drag. Meanwhile, the flow velocity or V aN + b (a and b are the calibration values of the current meter). The average velocity of the water can be measured using an object in the float method or devices such as current meter, and acoustic doppler current profiler. This leads to several rotations of the wheel-cup or propeller corresponding with the velocity of the flowing water. To Measure, the Average Velocity of Flow following are three important Methods we can use. There are various ways of practically calculating the stream discharge by measuring the average velocity, width, and depth of the stream water. For example, assume a river is 4 metres deep and 5 metres wide in one area. So, To Measure the River Discharge, we require 01) Area of Flow 02) Average Velocity of Flow. Once this relationship is established, a simple water heigh measurement suffices to determine the discharge. Often during a large rainstorm you can hear an announcement on the radio like "Peachtree Creek is expected to crest later today at 14.5 feet." Enter Velocity (m/sec) to calculate discharge (m3), Enter slope length (m) and slope angle in degrees () to calculate Slope (S), Enter Slope and Manning's n value to calculate velocity (m/sec). The river discharge from a drainage basin depends on precipitation, evapotranspiration, andstoragefactors. The ADCP has proven to be beneficial to streamgaging in several ways. There will probably be some variation in channel depth across the cross profile, so it would not be representative to take a single measurement of depth. Want to learn more about how streamflow is measured? endobj A pressure Laminar vs. Turbulent Flow | Overview, Differences & Examples, Types of Wasting: Slump, Rockslide, Debris Flow & Earthflow, Climate Change Spatial vs Temporal Scales | Overview, Differences & Examples. How To Bring Any Dead Battery Back To Life Again? One common approach is with a stilling well in the river bankor attached to a bridge pier. So, the time it takes Mr. Tomo to fill the tub to the brim is 50 minutes. Calculate the amount of water used for activities. Alluvial Channels | Geography, Stream & Types. The discharge is normally calculated by multiplying the cross-sectional area of the river with the velocity of the water (m/s). It consists of two Floats connected by a Wire or String. Streamflow is reported as cubic feet per second (ft 3 /s). Each stream channel is different and, because the stage-discharge relation is a function of the streambed material and geometry, each rating curve will be unique to that site and a particular period of time. Try refreshing the page, or contact customer support. Still don't understand? If you have a dream to become a civil engineer or water resource engineer, then you must understand the formula for water discharge. To calculate discharge, multiply the area of water in a channel cross section by the average velocity of water in that cross section. The velocity of the water affects it; faster water means more passes per second so more discharge. Some of these systems can store data and automatically calculate discharge based on the velocity and depth readings being taken. Use this interval to measure at 9 equally spaced points across the channel. Besides this information, you are suggested to read something more from belowengineering books, So, Here you find the Best Engineering Resources for further details, To get the more details about the topic, I further recommended reading. The Velocity is Calculated by dividing the distance traveled by the Float by the time taken to travel that distance. 2 0 obj How to calculate river discharge using rainfall? The measured stage value is stored in an electronic data recorder on a regular interval, usually every 15 minutes. Now, the Area of Flow is the Sum of all Areas of Segments. 2. Discharge is the volume of water moving down a stream or river per unit of time, commonly expressed in cubic feet per second or gallons per day. The sound is transmitted into the water from a transducer to the bottom of the river and receives return signals throughout the entire depth. In order to find out discharge carrying capacity of each river cross-section manually, above method is used but the work becomes time consuming. Send your request to Len Vacher (vacher@usf.edu) by filling out and submitting the Instructor Module Request Form. On the other hand, if no water enters or leaves a stream, the discharge remains unchanged when compared near the source and down the stream. This is the total volume of water flowing through a river bed at any given point and is measured in meter/sec. So that the water source used can be optimized. The development of an accurate stage-discharge relation requires numerous discharge measurements at all ranges of stage and streamflow. Sediment Examples, Types & Features | What is Sediment? To obtain Average Velocity directly, a Double Float or Rod Float is used. Which river channel characteristics you chose to measure will depend on the question you investigate. The module is also intended to stimulate class discussion on environmental and human induced factors affecting these aquatic habitats and the importance of long-term monitoring. This method has several principles in measuring water discharge, including the following: Measuring the speed of water flow can also be done using the Flow Proble method by using a current meter. An alternative approach would be to base your sampling on areas where you might expect significant changes in river discharge By choosing sampling sites immediately downstream of confluences you may be able to identify the significant changes in discharge and consider the impact of stream order. However, the stream discharge remains the same if no water enters or leaves a stream when compared to the discharge near the source and further downstream. implements a numerical method to improve the efficiency of river discharge The USGS makes discharge measurements at most streamgages every 6 to 8 weeks, ensuring that the range of stage and flows at the streamgage are measured regularly. Students will be given the background information to understand how to calculate discharge in the equation form (Q=V x A) and then learn how to enter the equations needed to calculate river discharge in Excel. Graded Stream Overview & Function | What is a Graded Stream? Measuring channel width Using a tape measure, hold one end at the point where the water meets the bank one side of the channel. This is a faster, however more expensive, method in which the device can be mounted in a small watercraft with the acoustic beams directed into the water. This includes having students determining how to calculate the area of a non-uniform shape such as a stream or river cross-section. Dams, built across a stream or river, mainly act as the barriers that restrict or prevent the flow of water. Select the type of cross section required (drawn with rounded or . These are mainly useful in controlling floods, storing water, and generating electricity. How to effectively deal with bots on your site? Water Turbines: Why Water Turbines are developed? The gage height on August 30th, after the creek has fallen back down to base-flow conditions after a storm was 2 feet. In recent years, advances in technology have allowed the USGS to make discharge measurements by use of an Acoustic Doppler Current Profiler (ADCP). As you're enjoying yourself sitting on the peaceful bank of a local river, onequestion you may ask yourself is "How much water is flowing in this river?" Most of the stage and streamflow information produced by the USGS is available online in near real time through the National Water Information System (NWIS) Web. Creating the Rating Curve. Discharge = V x D x W If length is measured in feet and time in seconds, Discharge has units of feet3/sec or cubic feet per second (cfs). The rod can be made using a 3-6 ft long, two-inch wide, very thin, piece of wood. The withdrawal of water would cause a decrease in the water velocity, width, and depth resulting in a decreased discharge of a stream or river. The prefix Geo is a Greek word, meaning, Tidal power or tidalenergyis an alternative energy source ofhydropowerfrom which you can generate electricity. total discharge of the river or stream. x]mFn~b@= ~]4=#d,*?y]Ud7UlRbk4R[wun'~nO_>qn{:v=xy?$zf:d?:KER?7Y&+o_JR# _!y7o/CHf1L33B$YJ&M_Tt/33DT`wsVoo}{7B_"Won7S3!sT!E. V = R3 S2 (2) n. Where V = flow velocity (m/s), n = river bed roughness, R = hydraulic radius = A / P (m) and S = the river slope (m/m). However, on a small scale, it is certainly much more efficient to discharge water manually. So, the water flow required to fill the bathtub to the brim is 6.25 liters/minute. On the other hand, water withdrawals, splitting of a stream into two or more small streams, high evaporation rates in hot seasons, and other factors decrease the stream discharge. Use our River Cross Section Creator and Calculator to quickly and accurately create a river cross section and calculate the cross sectional area, wetted perimeter and hydraulic radius. Introduce the method for calculating discharge of flowing waters. Streamgaging involves obtaining a continuous record of stage, making periodic discharge measurements, establishing and maintaining a relation between the stage and discharge, and applying the stage-discharge relation to the stage record to obtain a continuous record of discharge. I feel like its a lifeline. Disclosure: Some Affiliate Links and Third Party Advertisement Links are used by this Site. Streamflow (also known as discharge) is the volume of water flowing past a given point in the stream in a given period of time. Learn how your comment data is processed. In shallow water, the Pygmy Price current meter can be used. One method of measuring water discharge that is commonly used is the Float Area. To ensure accuracy, turn the metre rule so that the narrow side of the ruler faces into the flow of the river. Stage-discharge relations are developed for streamgages by physically measuring the flow of the river with a mechanical current meter or ADCP at a wide range of stages; for each measurement of discharge there is a corresponding measurement of stage. Manning's n can be used to calculate river velocity. A hydrograph shows how a river responds to a period of rainfall. Share your experiences and modifications, Spreadsheets Across the Curriculum: The General Collection, Alignment of Learning Goals, Activities, and Assessments, Robustness (usability and dependability of all components), Completeness of the ActivitySheet web page. In India about 2200 Read More, In Mechanical Engineering one must have to study the turbine. The discharge of a stream is affected by various factors such as weather, seasons of the year, water withdrawals, construction of dams, and others. The module is a PowerPoint presentation with embedded spreadsheets. The velocity of stream water is generally measured with the help of a current meter, a device that consists of a horizontal wheel or a propeller. Hence For this, we have to count the time taken by the Float to Travel a known Distance. Sometimes, the current meter is attached to a height-calibrated rod for more accurate measurements. River discharge (Q) = A x V / A = A x K (Constant). Now let us calculate the stream discharge during the summer when the water flows at a velocity of 2 m/sec due to higher evaporation, and the cross-sectional area of the stream channel measures {eq}56 m^2 {/eq}.