streamphysical

Physical Characteristics of Streams: 

Physical Characteristics of Streams What is a stream? water -- usually freshwater moving in a channel Close up look of streams stream

What makes a stream channel?: 

What makes a stream channel? The stream itself. Start water moving and it will form a channel. So, where does the water come from? Yellowstone Steve

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Aristotle -- thought water vapor condensed in the soil Middle ages -- thought water came from the ocean Palissy, 16th century More springs in the mountains Water not salty Pierre Parroult, 1674 Seine River in France Rain 6X stream flow Stream water comes from rain Where does the rest of the water go?

Hydrologic Cycle: 

Hydrologic Cycle 10-20% of precipitation Pine forest > hardwood forest

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Surface runoff stomata

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Evapotranspiration (ET) Interception Transpiration Evaporation

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Runoff Surface Subsurface

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P = ET + RO Precipitation Evapotranspiration Runoff

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Oceans Land Global Hydrologic Cycle

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Oceans Land Global Hydrologic Cycle

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Oceans Land Global Hydrologic Cycle P=23 ET=16 RO=7 7/23 = 30% On average, 30% of precipitation ends up as runoff

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On average, 30% of precipitation ends up as runoff Highly variable! Endorheic basin (no outlet) ET = 100%, no runoff Parking lot ET = small, RO  100% Humbolt River, NV Carson Sinks Parking lot

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Deleware R., NJ Sudbury R., MA Neches R., TX Red R., ND Percent of precipitation 0 20 40 60 80 100 Evapotranspiration Runoff ET RO Runoff varies spatially

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Runoff also varies seasonally

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J F M A M J J A S O N D Discharge (L/s) 0 10 20 30 40 50 60 70 80 Mean daily discharge Coweeta WS 32, 1991

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Runoff can even vary daily

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So, the short answer is that streamflow is the excess of precipitation over evapotranspiration RO = P - ET So, now we have water in the stream, flowing downhill Escher

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Water flowing downhill

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Total Energy = Potential Energy (Z) + Kinetic Energy (V) TE1 = PE1 + KE1 TE2 = PE2 + KE2 TE1 = TE2 (First Law of Thermodynamics) PE2 < PE1 Moving downhill

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TE1 = PE1 + KE1 TE2 = PE2 + KE2 TE1 = TE2 First Law of Thermodynamics PE2 < PE1 Moving downhill So, KE2 > KE1??? Does velocity increase downstream? We have to include heat. When a stream does WORK, KE and PE are converted to heat. Little Stony Mississippi

Streams do 3 kinds of work: 

Streams do 3 kinds of work Transportation -- carrying material (“load”) Erosion -- creating load Deposition -- when a stream can’t do work; it doesn’t have enough energy to carry its load

Transportation: 

Transportation I. Dissolved load Chemicals in solution -- solutes No work required Doesn’t “settle out” II. Solid load Particles Settle out if no motion > 0.45 µm (by definition)

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I. Dissolved load May cause color, but water stays clear II. Solid load Causes water to be turbid, that is, to lack clarity blackwater river New River, Wolf Creek

Solid load: 

Solid load 1. Floating load -- less dense than water New River

Solid Load: 

Solid Load It takes work to keep the suspended load in suspension. This work is the result of turbulence, the chaotic movements of water molecules. 2. Suspended load particles in the water column

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There must be turbulence in order to have turbidity.

Solid Load: 

Solid Load 3. Bed Load Moves along the stream bed, at least occasionally in contact with the bottom Little Stony

CompetenceThe largest particle a stream can carry at a certain flow: 

Competence The largest particle a stream can carry at a certain flow Little Stony 2

Solid Load1. Floating2. Suspended3. Bed: 

Solid Load 1. Floating 2. Suspended 3. Bed In practice, difficult to separate

ErosionBrings material into the stream: 

Erosion Brings material into the stream 1. Corrosion -- chemical weathering creates dissolved load St. Elena Canyon

Erosion: 

Erosion 2. Corrasion -- Mechanical wearing away of particles

The larger the particle, the greater the force needed to move it ????: 

The larger the particle, the greater the force needed to move it ???? Cohesion of small particles

Factors affecting erosion: 

Factors affecting erosion Climate Rainfall Vegetation Erosion Soil Geology Rock type, topography

How does rain affect erosion?: 

How does rain affect erosion? Rain Erosion ???? HWC 2 Sediment vs Q

How does precipitation affect erosion?: 

How does precipitation affect erosion? Annual Precipitation (cm) Erosion Forests Grasslands Desert 50 100 150

Factors affecting erosion: 

Factors affecting erosion Climate Rainfall Vegetation Erosion Soil Geology Rock type, topography

What happens when a stream loses velocity?: 

What happens when a stream loses velocity? Less velocity Less turbulence Less ability to carry suspended load Deposition

How can a stream lose velocity?: 

How can a stream lose velocity? 1. Decrease in gradient stream comes out on a plain alluvial fan RMP fan, Lawn Lake Desert fans

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2. Stream enters standing water Delta deltas 3. Stream enters lower gradient river deltas Lake Peppin Waterton River Ain and Rhone

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4. Stream goes around a bend Point bar 5. A flood -- stream goes out onto floodplain Point bars flood floodplain

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Erosion, transportation, and deposition These are the processes that shape the stream channel.

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Easy way: Since this is a 1 millimolar (0.001 molar) solution of Ca3PO4, it is also 1 mM P, which is 31 mgP/L.   Or: Molecular weight of Ca3PO4 is 215 g, and 31 g of this is phosphorus. So Ca3PO4 is 14.4% phosphorus. Multiply 0.144*215 mg/L to get 31 mgP/L. In order to make a 0.001 molar solution of Ca3PO4, I would add 215 mg of this chemical to 1 liter of distilled water. What would be the phosphorus concentration in this solution? Note, this could be a trick question as Ca3PO4 is essentially insoluble. In actuality, you would end up with a liter of distilled water with 215 mg of white powder on the bottom. But just for funzies, let’s pretend that this much stuff easily dissolves in water.

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Your boss has asked you to analyze a bunch of water samples for SRP (soluble reactive phosphorus = PO4-P. These samples were all taken from undisturbed small streams, so you know the SRP levels will be low. The first thing you need to do is make a standard solution, and you decide that 100 µgP/L would be a good stock solution to start with. Explain how you would make this solution using NaH2PO4 and standard laboratory equipment -- a balance that weighs to the nearest mg and volumetric flasks ranging from 10 mL to 1 L.

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Molecular weight of NaH2PO4 is 120. 100 g P * (120 g NaH2PO4 / 31 g P) = 387 g NaH2PO4 But our balance only weighs to nearest mg. So weigh out 100 times this much (38.7 mg), add it to 1 L of distilled water, and dilute it 100:1 (add 10 ml of the solution to a 1 L flask and fill the flask to 1 L).

Morphology and other physical characteristics of streams: 

Morphology and other physical characteristics of streams I. Gradient -- the slope of a stream Stream profiles 3

This ideal concave shape = graded stream: 

This ideal concave shape = graded stream Ideally, streams reach grade due to a balance between erosion and deposition. erosion deposition

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Elevation Distance Convex profiles and waterfalls can occur where there are changes in rock type. L. Tenn 2 waterfalls 2 Elevation Distance

II. Channel Pattern: 

II. Channel Pattern Straight Meandering Braided straight, Florida meandering 3 braided 3

III. Drainage network: 

III. Drainage network Horton 1940’s Strahler 1950’s Stream Order Actually reach order

Drainage patternsDepends on rock type: 

Drainage patterns Depends on rock type Dendritic – flat rock strata Rectangular – faulted rock Trellised – folded strata Patterns James River

IV. Stream size: 

IV. Stream size Stream order Different map scales Different areas of the country Streams of similar order may have different “size”

Streams in U.S.: 

Streams in U.S.

Width: 

Width Compare the New River at McCoy Falls with Narrows Width is a good descriptor of a site but not of a stream in general. Depth Same problem New River

4. Length: 

4. Length Length (mi) of the ten “largest” rivers of the world 1 Amazon 3,900 2 Congo 2,900 3 Yangtze 3,600 4 Mississippi 3,890 5 Yenisei 2,800 6 Lena 2,660 7 Paraná 1,500 8 Ob 3,200 9 Amur 2,900 10 Nile 4,160

5. Watershed area: 

5. Watershed area watershed 2 Watershed – the area drained by a stream

6. DischargeThe amount of water flowing down the river: 

6. Discharge The amount of water flowing down the river Ten “largest” rivers of the world

DischargeNormally measured in L/s or m3/s : 

Discharge Normally measured in L/s or m3/s Measuring discharge Flow continuity equation Q=WDV Q=discharge W=width D=depth V=velocity velocity

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Measuring discharge b. Weir or flume Weirs and flumes 5

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Measuring discharge c. Stage recorder Stage recorder 2

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Discharge is not constant Hydrograph – a graph of discharge vs. time Storm hydrograph base flow storm flow rising limb falling limb = recession curve Annual hydrograph Utah North Carolina hydrographs 3

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J F M A M J J A S O N D Discharge (L/s) 0 10 20 30 40 50 60 70 80 Mean daily discharge Coweeta WS 32, 1991

IV. Stream Size1. Order2. Width3. Depth4. Length5. Watershed area6. Discharge: 

IV. Stream Size 1. Order 2. Width 3. Depth 4. Length 5. Watershed area 6. Discharge

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Velocity (Physical characteristics of streams) Easy to make point measurements rubber duckie current meter Spatial variability cross section depth velocity profiles

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Velocity varies width depth

Manning EquationAn empirical equation that shows what factors affect velocity: 

Manning Equation An empirical equation that shows what factors affect velocity V = velocity R= hydraulic radius R=A/P S=slope (gradient) n=Manning roughness coefficient

Hydraulic Radius (R): 

Hydraulic Radius (R) R=A/P A=cross sectional area (width * depth) P=wetted perimeter If PW:

So, for most streams velocity is a function of depth, gradient, and roughness: 

So, for most streams velocity is a function of depth, gradient, and roughness

Manning roughness coefficients: 

Manning roughness coefficients

VI. Type of flow: 

VI. Type of flow Turbulent chaotic movement eddies Laminar Smooth, straight channel Very low velocity All water molecules going in the same direction Parallel streamlines

Reynolds Number, NR: 

Reynolds Number, NR =density of water V=velocity R=hydraulic radius (=depth) =viscosity NR small (< 300) – laminar flow NR large (>2000) – turbulent flow In between -- transitional

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Reynolds Number, NR Typical stream:  = 1.0 g/mL V = 20 cm/s R = 50 cm = 0.0114 N·s/m2 NR = 87,600 Typical streams are turbulent

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Unusual stream:  = 1.0 g/mL V = 2 cm/s R = 5 cm = 0.0114 N·s/m2 NR = 876 Still above the 300 for laminar flow. To get NR down to 300 we would need to reduce V to 0.68 cm/s. With a Manning n of 0.05 and keeping depth at 5 cm, the slope would have to be 0.6 cm/km!