Water Resources Exam 2

surface water hydrology

the study of the moving water found in rivers, open channels, lakes, reservoirs, and runoff flowing across the open land surface

stream

a body of water that flows down slope along a defined natural passageway or channel

• river > creek > brook > rill

river

a stream with a larger volume of water and a well-defined channel

• <0.01% of Earth’s water

drainage basin

an area drained by a stream system

divides

topographic highs (ridges or hills) that separate drainage basins

watershed

(river basin, drainage basin, or catchment)

fundamental hydrologic unit of land area that contributes surface water to a stream

• as small as a parcel of ground that drains into a pond or as large as the Amazon basin

Amazon river basin

largest in the world

• 82% of Brazil’s geographic area

• covers 2,722,000 square miles

• extends from Guiana Shield/Highlands on north, Central Brazilian Plateau in the south, Andes in the west, and flows eastward emptying in the Atlantic Ocean

• water from 15,000 tributaries and sub-tributaries

Mississippi river watershed

largest river basin in North America, 3rd largest in the world

• extends from Appalachian to Rocky Mountains, and from southern Canada to the Gulf of Mexico

• annual runoff: <5 cm/yr in western part to >60 cm/yr in humid eastern part

• one of the world’s most productive farming regions in the world - 58% of basin is cropland

• river has a depth of 4 inches (10cm); reaches half a mile wide (800m) and 200ft deep (61miles) at New Orleans

Zaire Congo basin

second largest watershed in the world

topographic map

invaluable tool for geographers, planners, engineers, hikers, etc.

• invented by USGS (1879)

• called quad sheets

• info on: slope, elevation, distance, and physical features

• land surface presented at various scales of measurement (ex: 1:24,000)

index contour

a thicker line on a topographic map generally every 5th contour line

topographic linear ridges and valleys

contour lines repeat on opposite sides of

delineating a watershed

marking the ridge or drainage divide on a topographic map that marks the boundary of the basin

• locate lowest point = watershed outlet

• follow elevation until a ridge/highpoint is identified

Nile river

• White Nile - Great Lakes region of central Africa; distant source in southern Rwanda; flows north through Tanzania, Lake Victoria, Uganda, and southern Sudan

• Blue Nile - Lake Tana, Ethiopia; into Sudan from southeast; meets white nile near Khartoum, Sudan

• Northern section - flows through desert; Sudan to Egypt (most cities along the water)

• ends in a large delta emptying into the Mediterranean Sea

Amazon river

the most voluminous river on Earth

• 11x the volume of the Mississippi and drains an area equivalent in size to the US

• daily freshwater discharge into the Atlantic enough to supply NYC for 9 years

• force of current from water volume causes current to flow 125 miles out to the ocean before mixing with Atlantic salt water

• in high-water season, river mouth may be 300 miles wide and up to 500 billion cubic feet per day flow into Atlantic

• early sailors could drink freshwater out of the ocean before sighting South America

• carries tons of suspended sediment (muddy appearance); 106×10^5 ft3/day swept into ocean; Majaro island at the mouth of the Amazon is the world’s largest river island (size of Switzerland)

Zaire Congo River

Africa’s most powerful river and the second most voluminous river in the world

• 1.5 million ft3/s at its mouth

• 5th longest river in the world, draining a basin of 1.5 million square miles

• gradually widens and picks up speed until entering final channel “Gates of Hell,” a 75-mile long canyon of impassable rapids

• crosses equator twice with relatively stable flows since a part is always in a rain zone

stream’s main processes

• erosion

• transportation

• deposition

parameters determined after defining/delineating a watershed

• size, max and min elevation, shape, slope, and drainage patterns

• aspect - direction of exposure of sloping lands

• orientation - general direction of main portion of a river as it moves down a watershed

overland flow

runoff water moving along the land surface toward a river or stream during and after a storm event

interflow

occurs when precipitation percolates just below the land surface and moves at a slower rate

suspended sediment load

small particles suspended in water

dissolved sediment load

carrying ions in solution due to the chemical properties of water

bed sediment load

large particles that roll, slide, or hop along the bottom

• coarsest particles rolling and sliding on bottom

saltation

transportation of larger sediments through a series of leaps or bounces along the bottom of a river channel

• bouncing and rolling of grains downstream along bed

sediment yield

the total amount of sediments carried from a watershed by a river

stream competence

the largest sized particle a stream can transport

• one criterion in determining a stream’s ability to carry a load

stream capacity

the total amount of sediment a stream can carry at any time

• one criterion in determining a stream’s ability to carry a load

stream discharge

the volume of water passing by a point at a given time = stream cross section X flow velocity

• Q = (A)(V)

• cubic feet per second (ft3/s=cfs, or m3/s)

• increase causes stream channel to widen and deepen to handle additional water

river discharge

the amount of water carried in a river at any one time = (volume/time)

discharge

the amount of water in a river, pipe, or any conduit that passes a given point during a given period

current meter

device used to measure the velocity of moving water

stream gauging station

measures the two most fundamental items of hydrologic information about a river: stage and flow for some period

hydrograph

a graph of a stream’s discharge over time; charts flood runoff

• stream flow increases from surface runoff shown by a steep rising limb reaching a peak flow

• from peak, discharge decreases slowly as infiltrate rain flows underground and feeds the stream

river components

a main channel and all tributaries that flow into it

• sources are headwaters

tributaries

small streams that combine to form larger streams and ultimately the river

confluence

the point where the tributary joins the main river channel

upstream

a location toward the headwaters of a river

downstream

a location toward the confluence of a river

first order stream

springs or boggy seeps of groundwater

• the beginnings of a stream

second order stream

when two first order streams meet

• picks up additional first order streams but remains called this

third order stream

when two second order streams meet

• can pick up more 2nd order streams

first through third order streams

85% of stream miles in the US are made of _______________

river thalweg

the imaginary line that connects the deepest points of a river channel

river bank storage

temporary storage of water in the banks of a river

hyporheic zone

area directly beneath a river

• surface zone receiving at least 10% of water by input from the stream (>10% channel water)

geomorphology

the study of forces that shape the surface of the Earth

river morphology

moving water can greatly impact morphology of a region

• a young river has a V shape valley

• lower slope increases valley width = U shape

• wider in the end when slope becomes less steep

braided stream

water splits apart and rejoins through 2+ channels separated by sediment bars

• formed in areas with high fluctuations in water flow combined with high sediment loads

• banks easily eroded, adding to sediment supply

meandering stream

streams with channels that form bends and curves

• common in gently sloping areas (lower energy) with fine-grained sediments

• velocity profiles not uniform due to friction on bottom and sides of channel (create cutbanks on outer banks and point bars on inner banks)

• floodplain created by a stream’s constant shifting of channel over time

laminar river flow

straight or gently curved parallel streamlines

• depends on velocity, channel geometry, viscosity, friction, and roughness

turbulent river flow

complex, with mixing and crossing, often forming eddies and swirls (common in fast flowing rivers)

• depends on velocity, channel geometry, viscosity, friction, and roughness

ephemeral stream

river located in dry climates that are not fed by any continuous water source and flow only after storm events

• North Africa (Wadies) and southwestern US and Northern Mexico (Arroyos)

• deadly surprise of caravans and campers

intermittent flow stream

has flowing water during certain times of the year, when groundwater feeds the stream

• may not have flowing water during dry periods; runoff is a supplemental source

perennial stream

has flowing water year-round

• water above streambed for most of the year

• groundwater is the primary source

influent river

losing river; when river channel is located above groundwater system → often discharge some water through percolation

effluent river

gaining river; when the river receives groundwater through baseflow and increase discharge

river gradient

the slope or fall of a river

• measured in terms of ft/mi or m/km

• generally decreases as it continues downstream, reducing velocity

• variation affects stream velocity and material transport

• = change in height/change in length

• ex: Little Conemaugh river (PA) avg slope 53 ft/mi, 10 m/km; Ohio river (OH) >6 in/mi, 9.5 cm/km; red river (ND) 5 in/mi, 7.9 cm/km

rating curve

performed to continuously monitor the discharge of a stream based on the stage heights

• stage vs discharge are performed and plotted on graph paper to produce the rating curve

weir

small dam with a spillway opening of a specified shape to measure discharge of a small stream

• most common 90 degree V-notch or rectangular cutout

• elevation of backwater above crest (H) is measured - dam impounds small amount of water that should free fall over the crest or lowest point of the spillway

discharge weir formula

rectangular weir: Q=3.33(L-0.2H)H^(3.2)

90 degree V notch weir: Q=2.5H^(5/3)

Q = discharge (ft3/s)

L = length of weir crest (ft)

H = head of backwater above the weird crest (ft)

cirque lake

lake created behind the debris left by a melting glacier

• common in rocky mountains

pluvial lake

lake formed during a period of increased precipitation

• dry climates

oligotrophic lake

a young lake with little or no organic material on its bottom

• see a secchi disc greater than 16 ft

mesotrophic lake

a middle aged lake with adequate organic material to support a wide variety of aquatic species

• see a secchi disc 6.5-16 ft

eutrophic lake

an old lake that has excessive organic material which inhibits or prevents the growth of aquatic species

• see a secchi disc less than 6.5 ft

littoral ecological lake zone

area of a lake near its shore which provides adequate sunlight to promote shallow-rooted plant growth

limnetic ecological lake zone

area of a lake toward open water where sunlight cannot penetrate to the lake bottom

profundal ecological lake zone

area at a lake bottom where rooted plans cannot grow due to a lack of sunlight

thermal cycles in lakes

stratification zones in temperature created by changes in water temperature

• warm air in the spring and summer heats the surface of a lake causing the water to become less dense

epilimnion thermal layer

a surface layer of warm water in a lake (less dense → float)

hypolimnion thermal layer

a cooler layer beneath the epilimnion

thermocline thermal layer

layer of water with a rapid change of temperature in the vertical direction

lake turnover

natural process of the hypolimnion replacing the epilimnion

• occurs more frequently with climate with hot and cold seasons

• essential to lake ecology

• summer: little water movement between hypolimnion and epilimnion

• fall: surface water temp drops, cooler water at surface settles and replaces now warmer water at the bottom

seiche

differences in water elevations in a lake as a result of wind or sudden changes in atmospheric pressure

• ex: Jan 1942, lake Erie 13ft high at shore of Buffalo NY than Toledo OH

• ex: June 1954, 10ft high wall of water along Chicago waterfront killed 8 people

transportation and deposition

movement and settling of materials (sediment) in moving water

sediment

unconsolidated particles created by weathering and erosion of rock, chemical precipitation from solution in water, or secretions of organisms

• transported by wind, water, or glaciers

sedimentation

settling of sediments from water as velocity decreases

natural levee

elevated landforms that parallel some rivers, deposited by sediments of previous floods

floodplain

flat, low-lying lands adjacent to a river and subject to periodic flooding

yazoo stream

tributary stream that flows parallel to a main river

• a natural levee separates the two river systems

hjulstrom curve

graph showing the relationship between the velocity of a river and the particle sizes that may be transported, deposited, or eroded

sorting

process whereby geologic material of various sizes is moved by water and deposited into different areas based on size and weight

fluvial material (alluvial deposit)

sediments deposited by flowing rivers

alluvial fan

landform created by the deposition of sediments from a river, and generally found near the mouth of the canyon

delta

landform created by the deposition of sediments at the mouth of a river

overland (sheet) flow

surface water runoff that is moving within a watershed toward a river

• 1889 rational formula

• Q=CIA

rational formula

mathematical formula used to determine overland flow; proposed in 1889, continues to be used today

• used to design storm drains, culverts, and other structures to control RO in Urban Areas

• Q = CIA

• Q = peak rate of runoff in cfs

• K = runoff coefficient

• I = intensity of rainfall in in/hr

• A = watershed area in acres

stage

water level in a river or lake above a set reference point

staff gauge

metal ruler used to determine the stage of a river or lake

gauge height

elevation of a water surface on a staff gauge

storage

computed by measuring first the depth and area of the lake

• measured in million or billion cubic feet in eastern US

• measured in acre-ft in most western states

• = Qi + Gi - E - Q0

• Qi = surface water inflow

• Gi = GW infiltration

• E = evaporation

• Q0 = surface water outflow

depth

measured by using a sounding equipment or a rod or cables

area

measured by developing topographic elevation contour (GIS)

stage capacity curve

graphic representation of reservoir storage volumes at various water depths

flood events

occur when P and RO exceed the capacity of a river channel to carry the intense discharge

flood frequency

predicting floods is a function of determining the probability of high precipitation

• recurrence interval of various flood flows (100yr flood Q(100))

• Q(100) = 1 in 100 yr flood = probability of 0.01 or 1%; P=1/T

• P = flood probability

• T = recurrence interval

• used for flood plain management, flood insurance regulations, and engineering designs of dam spillways, road culverts, bridge abutments

probable maximum precipitation (PMP)

greatest amount of precipitation that is reasonably expected from a single storm event at a given location

• has: location, duration of storm, area of coverage

• uses for it: dams; undesirable to have a design with known probability of failure

• expressed in %

estimating PMP

use meteorological methods and historical records to determine the greatest amount of precipitation which is theoretically possible within a region

• historical data: point precipitation measured at rain gauges throughout the region being studied, or a region with similar meteorological and topographical characteristics

• rainfall data: maximized through moisture maximization and other methods; max possible atmospheric moisture for a region applied to rainfall data from a historic storm - increases rainfall depths, bringing closer to potential maximum