Water Resources Final Exam Material

True or False: The loss of energy caused by the resistance of flow due to the friction created by the pipe waslls is known as the major losses.

True

ordinary flow in ordinary open channels.

Turbulent Flow

The pressure loss that occurs in a flow through pipes is proportional to:

length of pipe, coefficient of friction, and density of the fluid

A _____ shape watershed generates, for the same rainfall, a lower outlet flow, as the concentration time is higher.

long

The loss of energy caused by the resistance of flow due to the friction created by the pipe walls is known as the _____

major losses

Orographic Precipitation

mechanical lifting

Energy losses in pipe flow due to pipe accessories such as elbows, contractions, or valves, are known as the ______

minor losses

Larger watersheds could contain many smaller watersheds... It all depends on the ________ point.

outflow

assumes that if rainfall were applied at constant rate for a long enough period of time, then runoff would eventually be linearly related to rainfall, as follow: Q = k c I A

rational method

is the portion of rainfall, snowmelt, and/or irrigation water that runs over the soil surface toward the stream rather than infiltrating into the soil

runoff

Factors affecting the flow in an open channel are:

slope, cross section, silting and couring

Mention at least three watershed characteristics the influence the watershed's hydrologic response

soil type, size, land use

Drainage basins characteristics that influence the watershed's hydrologic response are:

soil type, size, shape, land use, position

_________ is the part of rainfall, which first enters into the soil and moves laterally without joining the water-table to the streams, rivers, or oceans

sub-surface runoff

Fr < 1

subcritical flow (slow flowing water)

crest is across the width of channel

suppressed weir

Convective Precipitation

thermodynamic lifting

N-S orientation

time of melting of snow

_____ _____ = Kinetic Energy + Potential Energy + Pressure Energy

total energy

True or False: The depth upstream of a hydraulic jump is always supercritical

true

A _____ is an area of land that drains all the streams and rainfall to a common outlet such as the outflow of a reservoir, mouth of a bay, or any point along a stream channel.

watershed

The ______ consists of surface water--lakes, streams, reservoirs, and wetlands--and all the underlying ground water.

watershed

is important in hydrologic computations; the length is defined as the distance measured along the main channel from the watershed outlet to the basin divide, along the principal flow path.

watershed length

Three types of hydraulic jumps (based on Froude's number) are:

weak, oscillating, steady, strong

a barrier across of an open channel that alters the flow characteristics of the water and usually results in a change in the height of the water level.

weir

Primary characteristics of a rainfall event:

- Total quantity (expressed as rainfall depth) - Duration -Intensity - Aerial distribution

Time between peak precipitation and peak runoff.

Lag Time- TL

very slow and shallow flowing water in very smooth open channels.

Laminar Flow (Re < 500)

True or False: Lag time is the time between peak precipitation and peak runoff.

True

Hydraulic Structures can generally be grouped into three (3) categories:

- Flow measuring structures - Regulation structures - Discharge structures

three advantages of weirs.

- If the bed level of the canal is higher than the water level, constructing a weir will raise the water level upstream of the weir - Adjustable plates can be added to the weir to raise the water level to a desired level. - Potentially the greatest advantage of a weir is that it is relatively low in cost.

Weirs can be used to:

- Measure the discharge rate in an open channel. - In water management, to control the discharge rate from reservoirs and detention basins (preventing flooding) - To raise the level of water upstream or regulate its flow. - To make a body of water more navigable

WHAT IS OPEN CHANNEL FLOW?

- Natural and/or artificial conveyances of water in settings that are open to the atmospheric pressure. - Referred as free-surface flow or gravity flow

Mention two assumptions that are made while using the unit hydrograph.

- Rainfall is uniformly distributed over the area within the duration of the event. - The time duration of the hydrograph of direct run-off due to an effective rainfall of unit duration is constant

Drainage basins characteristics that influence the watershed's hydrologic response.

- Size - Land Use and Soil type - Position and orientation - Shape - Slope - Elevation - Drainage - Network

three disadvantages of weirs.

- Weirs normally increase the water oxygen levels which can have a detrimental effect on the ecological life in the water body. - While the surface water around the weir seems relatively calm to the eye, it is extremely dangerous for boaters, swimmers, etcetera. - The hydraulic jump created by the weir can be extremely dangerous to a person, it can potentially drag a person down and submerge them indefinitel

Give a detailed description of the concept of compound weirs.

A compound weir is what it sounds like. It is a weir with multiple stages and cuts. For example, V-notch, rectangular, and Cipoletti have all been used for various purposes. A compound weir normally has two stages, a rectangular notch with a 90-degree V-notch cut into the center of the crest. A compound weir is normally used where flow rates are expected to have a vary to a large degree. While it is useful in this situation, it does have its drawbacks. When the discharge becomes greater than the capacity of the v-notch, water will begin to overflow in irregular intervals causing irregularities in the discharge curve. In order to minimize this impact, normally the fix has been to change the size and angle of the V-notch to minimize the change of discharge measurements

Mention and describe five types of hydraulic jumps based on Freud's number.

A hydraulic jump is created when high-velocity flow comes in contact with lower velocity flow. There are different types of hydraulic jumps that might be described by Froude's number. Froude's Number is a dimensionless parameter that measures the inertia force of the fluid element divided by gravitational force (Froude 2004). Undular jump is the weakest form of hydraulic jump. Physically, the water at the surface is only rotating slightly with a gentle wave with basically no energy loss and has a Froude's number of 1-1.7. A weak jump has a Froude's number between 1.7-2.5. Small rolls of water form at the surface but quickly disappear after the hydraulic jump with little energy loss. An Oscillating jump has a Froude's number of 2.5-4.5. There are visible large waves at irregular periods. The waves do not dissipate and are carried until they come in contact with an embankment. A steady jump has a Freud's number of between 4.5-9. There is a clear separate hydraulic jump and energy losses range from forty to seventy percent. A strong jump is the strongest of the hydraulic jumps. It's Freud's number exceeds 9 and has greater energy losses with the surface of the water very rough for long distances downstream

To understand the concept of the "unit hydrograph": Give a definition for Unit Hydrograph

A unit hydrograph is a direct runoff hydrograph with a runoff volume of 1 unit.

Give a definition and establish the difference between "watershed" and "USGS HUCs (Hydrologic units)".

A watershed is an area of land that drains all the streams and rainfall to a common outlet such as the outflow of a reservoir, mouth of a bay, or any point along a stream channel. USGS HUCs are drainage areas that drain into a multiple level hierarchal drainage system. The system is defined by its boundaries which are hydrographic and topographic criteria. Those criteria delineate an area of land that is upstream from the outflow point. Hydrologic units can accept surface water directly from upstream drainage areas, as well as indirect surface areas such as remnant, non-contributing, and diversions that form drainage areas with single or multiple outflow points. They are only similar to classic watersheds when their boundaries include all sources contributing surface water to a single outflow point.

Define and establish the difference between a dam, a weir, and a barrage?

All three structures, dam, weir, and barrage are hydraulic structures intended to raise the water level on the upstream side to be used for certain purposes. A dam is a tall impenetrable structure that is constructed across the width of a river to create a deep storage reservoir. It is designed to keep the water level below a certain level and does not overflow the dam through the use of gates or spillways at some certain level (Civil Vedant, 2021). A weir is constructed of a variety or mixture of materials such as wood, concrete, metal, or even rocks and boulders depending on its age. It can have a variety of purposes, from controlling water flow, measuring discharge, preventing flooding, or assisting to make the river more navigable . While the river is more navigable, there is no means of transportation over the weir. Weirs are low cost but to minimize costs there is little control of the flow that exits through the weir . However, a barrage has a high cost, strong control of the water flow, and a means of transportation can be established over the barrage . Barrages are constructed of concrete with several large gates that can be opened or closed to control the amount of water that escapes. This purpose helps lower or raise the upstream water elevation to the desired level even in high water conditions

Geographic position

Climatology

aused by the natural rising of warmer lighter air at colder, denser surroundings.

Convective Precipitation

Fr = 1

Critical Flow

Depends on soils characteristics, land cover and antecedent moisture conditions.

Curve Number

When two air masses, because of contrasting densities and temperatures, clash with each other, precipitation and condensation, occur in the surface of contact. The surface of contact is called a 'Front' or 'Frontal Surface,' and the precipitation is called frontal precipitation.Source: https

Cyclonic Precipitation

True or False: Lag time is the time required for a rainfall excess falling at the most hydraulically remote part of the watershed to reach the outlet

False

is the amount of time that a given magnitude flood may occur in a given period.

Frequency

Mention and describe the classification of open-channel flows, using time and space as a criterion.

If you describe open-channel flows with time, then it is classified into steady and unsteady flows. If the flow at a given point is constant with respect to time, then the flow is considered to be steady. While on the other hand, if the flow at a given point is not constant with respect to time, then the flow is considered to be unsteady. If you describe open-channel flows using space as a criterion, the flow is described as uniform if the flow remains constant along the channel. Adversely, a nonuniform flow varies along the channel either gradually or rapidly.

What are the friction losses in a straight pipe? Explain.

In a straight pipe, the friction losses are related to the length of the pipe section, the velocity of the fluid, and the diameter of the pipe. As the fluid moves through the pipe, contact with the inner surface of the pipe causes friction between the fluid and the pipe. In short, the larger the length of the pipe the greater the frictional losses will be. The velocity that the fluid is moving at also plays a part in how much energy is lost in the form of friction. As the velocity increases, the drag forces also increase. The drag forces within the pipe are directly proportional to the friction. So, if the drag forces within the pipe increase, then so will the friction losses in that pipe. The diameter of the pipe is also a factor that affects the frictional losses. Pipes with a larger diameter have more surface area contact between the fluid and the pipe surface leading to more friction. Likewise, a pipe with a smaller diameter will have less contact with the fluid meaning there will be less friction and smaller losses of energy.

List at least five meteorological factors and at least five physical factors affecting runoff. - Meteorological factors - Physical Factors

MF: types of precipitation rainfall intensity rainfall amount distribution of rainfall direction of storm movement (Runoff n.d) PF: land use soil type vegetation Slope drainage area basin shape (Runoff n.d)

Velocity distribution in open channels mainly depends upon different factors. Mention three factors and explain how they affect the velocity distribution on an open channel.

Open channels do not have uniform flow, meaning that the velocity changes depending on depth. Multiple factors influence the velocity profile within an open channel. Such as the roughness, alignment, and slope of the channel. The roughness of a channel affects the ease and ability of the water to flow. For example, for man-made channels made of concrete or clay-lined walls, there is not much resistance for the water to flow and which allows for the water to flow faster. Oppositely, natural channels do not have a uniform shape and are not free of obstructions. Vegetation, boulders, and channel bed materials restrict the flow of the water and decrease the flow velocity in the channel. The alignment of the channel is another important factor that affects the velocity profile. Straight channels have no change in velocity while meandering channels will have varying velocities at bends due to the centrifugal action of the flow. Lastly, the slope of the channel will also affect the velocity profile. At steeper slopes, the velocity profile will increase due to the sharper change in-depth in regard to the distance from the banks. Less steep slopes have more of a normal gradient and the velocity profile will decrease compared to that of steeper slopes

caused by moist air masses. Which strikes some natural topographic barriers like mountains, causing, rise up, condensation, and precipitation.

Orographic Precipitation

What natural process would affect pipe roughness?

Pipe roughness can vary by several factors. Pipe roughness is not solely dependent on the pipe material, but it is a major component. For new pipes, roughness depends on the pipe material and the production process. As pipes get older, pipe roughness will increase due to the buildup of deposits from the fluid being transported through the pipe or corrosion/deterioration of the pipe caused by the operation.

How the pipes' diameter affects the pressure loss, why?

Pipes with smaller diameter have a smaller surface area for there to be pressure loss due to friction. For there to be a lot of pressure loss due to friction, there will need to be a lot of surface area inside the pipe for there to be friction loss. Thus, pipes with smaller diameters will have less pressure loss due to friction than pipes with larger diameters

has a high variability in time and space

Precipitation

represents a major input in hydrologic budget.

Rainfall

dominates the stream flow rate for a watershed

Rainstorm

Measure Discharge and Change Water Elevations

Rectangular weir

is the remaining water after accounting for losses due to hydrologic abstractions.

Runoff

Fr > 1

Supercritical flow (fast flowing water)

In the following example, consider two watersheds (A and B) with the following characteristics: - Watersheds A and B are the same size and shape. - Watersheds A and B receive the same uniformly distributed rainfall. - Watersheds A and B have almost the same basin characteristics. They only differ in the storage areas (e.g. lakes, ponds, puddles) present in each watershed. Consider the following hydrograph, which watershed would you say has more storage areas? Why? (picture is from lab 1 question 2)

The relationship between Capacity (Q) and time (t) represented in the graph shows that Watershed A has a greater capacity with respect to time than Watershed B. The elongated shape of graph A means that there is a higher concentration time and a lower outlet flow, meaning that there is a larger storage area in Watershed A.

Knowing how much water is available in a system for design purposes and water management decisions is important. Describe in detail each variable in the water-budget equation. The water budget equation is, I - O = ds/dt.

The variable, I, is the inflow of water to a particular area. This variable is the summation of all water that will or can enter the system such as precipitation, inflow from drainage, subsurface flow, etcetera. O is the variable describing the outflow. This variable is the summation of all the losses of water to that system. For example, the surface drainage of water, infiltration into the ground, evaporation, transpiration, etcetera. All the variables you must account for will equal ds/dt. Ds/dt is the change in storage with respect to time. It is very important, when designing or making decisions, that you account for the total storage of an area's water budget and account for every factor when determining its storage capacity.

What effect would rougher pipe materials (concrete, clay, etc.) have on velocity profile?

The velocity profile in a pipe depends largely on two different types of flow, laminar flow, and turbulent flow. In laminar flow, the particles move in parallel layers and do not mix with each other. This creates a nonuniform velocity profile. The fluid's velocity profile is greatest in the center of the pipe and is smallest along the boundary layer between the pipe and the fluid due to frictional losses between the two. In turbulent flow, the fluid flayers do flow parallel to each other. Instead, the fluids move unpredictably in three dimensions swirling and losing energy between each layer. This makes the velocity profile for turbulent flow nearly constant over a wide range of the cross-sectional area of the pipe. If you were to increase the roughness of the pipe by changing the material the pipe was constructed out of, for example, concrete or clay, then the velocity profile would be diminished. As was said earlier, the velocity profile in laminar flow is nonuniform, with a smaller velocity along the edge of the pipes with the greatest velocity being in the center of the pipe. Increasing the pipe roughness coefficient by changing pipe material would cause the flow at the edge of the pipes to decrease even more and in turn would make the max velocity in the center of the pipe smaller as well. In turbulent flow, increasing the roughness coefficient would have similar effects on the velocity profile as it does with laminar flow. The sporadic behavior of fluid particles in turbulent flow would react greater with the roughness of the new pipe material and increase the drag within the pipe making the velocity profile throughout the cross-sectional area smaller.

There are three major types of runoffs: surface flow, subsurface flow, and base flow. Describe each of them.

There are three different major types of runoff flow as mentioned above. Surface flow is the runoff that enters a stream or channel immediately after precipitation falls. Surface flow is the result when all losses are satisfied, and the precipitation rate is greater than that of the infiltration rate. Subsurface flow is the runoff that enters the soil and moves laterally without joining the water table and joins some type of body water such as streams, lakes, etcetera. Base flow is the delayed flow which after falling onto the ground infiltrates into the soil down to the water table

Rainfall abstractions process must be accounted for in estimating the surface runoff resulting from a given rainfall event. Mention and describe three rainfall abstraction processes.

Three rainfall abstractions are interception, infiltration, and evapotranspiration. Interception refers to the rainfall that does not become surface flow or subsurface flow and instead is intercepted by vegetation canopy, forest floor, urban features, etcetera (Fleming, 2021). Infiltration refers to the part of the runoff that enters the soil but remains in the shallow soil layer and does not make it to groundwater aquifers (Infiltration 2019). Evapotranspiration is the water lost to the atmosphere from the ground surface, evaporation from the capillary fringe layer of the groundwater table, and the transpiration from the roots of plants that tap the capillary fringe. The transpiration aspect of evapotranspiration also refers to the evaporation of water from plant leaves

Time required for rain falling at the most hydraulically remote part of the watershed to reach the outlet.

Time of Concentration-TC

Measure Discharge and Change Water Elevations with Large Head

Trapezoidal

Measure discharge

Triangular

A broad-crested weir has the lowest risk of sediment deposition upstream

True

Knowing how much water is available in a system for design purposes and water management decisions is important. Describe the uncertainty in water-budget calculations variables.

While you can use this equation to gain a general idea of what that area's water budget is, you must still account for errors that may occur from either the inflow or outflow. For example, when calculating your inflow, adding up precipitation is usually completed by taking the average amount of rainfall over a period of time. The longer that period of time is the smaller the error you should account for when determining the precipitation and vice versa. When calculating a component of outflow, withdrawals due to evaporation, absorption through the ground, and transpiration have the least amount of information to get an accurate estimate from historical data. Each variable in the water budget equation must account for possible errors when finding the total water budget for that area.

Which of the following statements are true? a) all watersheds are exactly the same size b) the speed the water moves in a watershed varies depending on various factors like the soil type and land use c) the speed the water moves in a watershed is always the same d) if you are 10 miles away from a river, you are not in a watershed

b) the speed the water moves in a watershed varies depending on various factors like the soil type and land use

Watershed = _______ = Drainage Area

basin

has notch cut into it, adding to the head loss

contracted weir

The most common discharge structures are:

culverts and spillways

what is a watershed? a) the shape of the land determined by elevation b) a natural stream of water of considerable volume c) an area delimited by the land use d) an area of land that drains all the streams and rainfall to a common point e) both, c and d

d) an area of land that drains all the streams and rainfall to a common point

Exposition to air flow

depends on latitude and position

Hydraulic jumps are used to....

dissipate the energy of water

The area of watershed is also known as the ______ area and it is the most important watershed characteristic for hydrologic analysis.

drainage

Reflects volume of water generated from rainfall. The volume of water available for runoff may be assumed as product of rainfall depth and the drainage area.

drainage area

Ridges and hills that separate two watersheds are called the _____ ______.

drainage divide

Surface runoff in a watershed that empties into the Mississippi River has become polluted by sewage and fertilizers. Which of the following environments might become polluted as a result? a) aquatic environment downstream of the watershed b) land environments along the banks of the river c) Aquatic environment upstream of the watershed d) and c only e) a and b only

e) a and b only

Hydraulic jump is used to dissipate or destroy the ________ of water where it is not needed otherwise it may cause damage to hydraulic structures.

energy

Amount of heat

evapotranspiration losses

A watershed having a ____-shape presents a lower concentration time, and it generates higher flow.

fan

Cyclonic Precipitation • Cold Front • Warm Front • Stationary Front

frontal lifting

Wind ward side of mountain receives higher intensity

higher runoff volume

The shape of a watershed influences the shape of its characteristic _______

hydrograph

The flow types are determined by relative magnitudes of the governing forces of motion

inertia, viscosity, and gravity forces

Three processes that are considered hydrologic abstraction are:

infiltration, interception, evapotranspiration

Mention three energy components to consider when evaluating pipe flow:

kinetic energy, gravitational energy, and energy due to pressure