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Rivers and the Environment Study Guide

by: Kerrian Johnson

Rivers and the Environment Study Guide EESC117001

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Kerrian Johnson

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All the notes for the midterm
Rivers and the Environment
Noah Synder
Study Guide
Rivers, Environment, Rivers and the Environment, environmental science
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This 40 page Study Guide was uploaded by Kerrian Johnson on Sunday January 17, 2016. The Study Guide belongs to EESC117001 at Boston College taught by Noah Synder in Fall 2015. Since its upload, it has received 57 views. For similar materials see Rivers and the Environment in Natural Sciences at Boston College.


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Date Created: 01/17/16
Rivers study guide Midterm format - chunk of multiple choice - short answer (word or couple words) - some more conceptual (few sentences or simple sketch) Hydrologic cycle  The circulation of the earths water between different reservoirs and states o Oceans o Lakes o Glaciers o Atmosphere o Biosphere o Ground water o Surface water  Solids  Liquids  Gasses  95.67% of earths water is in oceans  4.04 % fresh water o 2.6% in glaciers  1.46 * 10^9 km^3 how much water is on the planet  Evaporation o An endothermic reaction  Takes in heat from the air  and causes cooling  endothermic reaction  transpiration (or evapotranspiration) o endothermic reaction o evapiration of water transpired or released by plants  most of our available drinking water is underground  ideal gas law o PV=nRT  Percipitation occurs o As water vapor travels upwards in the atmosphere there is less pressure and it gets cooler so it becomes liquid again and falls o As it goes lower in the atmosphere it is under more pressure and heat  Orographic effect o An airmass is pushed up over a mountain range by wind  Convection o When you have heating from below the air mass becomes warmer and less dense  Generates a push up by the heating from underneath  Pushed to higher cooler elevation o The warm water rises and are replaced by colder water  Frontal wedging o When air masses meat the warm air mass override and goes over the cold front and becomes cooler o It is possible for cold air masses to override warm ones as well Climate change and rivers  Weather is the instantaneous conditions at any point  Climate is the average weather over a long period of time  Atmosphere o Nitrogen o Oxygen o Argon o Water o Carbon dioxide o Other greenhouse gasses  Cryosphere o Glacier o Snowpack o Ice sheet o Sea ice  Hydrosphere o Oceans o Rivers o Etc  Biosphere o Living organisms  Green house gasses o Reflect back long wavelength radiation from the surface  Greenhouse gas effect o Earths albedo is 31%  22% is from the clouds  9% is the earths surface o the remaining solar radiation incoming is absorbed  20% by earths atmosphere  49% the earths surface o the earth tries to balance the radiation by radiating that absorbed by the atmosphere and surface back into space o greenhouse gasses reflect most of that back as long wavelength (infrared radiation)  Carbon cycle o The movement of carbon between the oceans, biosphere, atmosphere and geosphere  Photosynthesis and respiration are the biggest fluxes  Sea air gas exchange is the second largest  Effects of carbon on the planet o Advance or retreat of glaciers shows changes in the climate  Must be colder and wetter for them to advance  The world is getting hotter and they are retreating in most places  Human effects on the carbon cycle o Humans change the balance of carbon by finding carbon stored in geological reservoirs and burning it into the atmosphere o Human activities release at least 7.1 Gt of carbon into the atmosphere each year  Burning fossil fuels 5.3  Land use/deforestation 1.7 o New plant growth and air/sea exchange removes 3.8 gt/yr o Net atmospheric increase of 3.3 Gt/yr  Keeling Curve o Atmospheric CO2 concentrations over time o Minimum around October  During October plants grow and therefore absorb more co2 o Maximum around may  During winter plants die and leaves fall  Microbes eat the plants and leaves releasing more carbon into the atmosphere  Yearly  Each year it fluctuates roughly 7 ppm  Isotopic work o Proves that carbon conditions have changed throughout geologic time  Ice albedo o Sea ice reflects 85% of radiation back into space  To compare the ocean only reflects 7%  Positive/negative feedback cycles o Positive feedback cycles (like with sea ice)  More sea ice leads to more cooling which leads to more sea ice  Less see ice leads to less cooling which leads to less sea ice  Loops enhance or amplify change o Negative feedback cycle (like with water vapor)  More water vapor leads to cooling which leads to less water vapor  Loops dampen or buffet changes  Climate computer models o Numerical representations of changes in climate over large periods of time o Climate models for global warming  Predict changes in global warming   Climate model predictions for global warming o The planet will get far warmer in the next 100 years o There will be wetter winters December through February o Pattern of changes in runoff  Decrease over dry regions  Increase over high latitude regions  Changes less reliable in low latitude regions o Increasing flood frequency since 1970 o It will rain more in general due to the water cycle  Individual storms will be more extreme Watersheds  Watershed o The area of land that contributes water to a river (not just the streams)  Divided by ridges  Can be defined upstream o The entire area that contributes flow to a body of water  Hillsides, hillslopes  Channels  Where the water concentrates and flows  The outlet of the watershed is where the water leaves o Channel  The term for the lower trough shaped parts where the water concentrates  Ephemeral o Rills, gullies, ravines  Appear only sometimes\  Perreneal o Brooks, creaks, streams, rivers  Year round  Desserts o Gulches, washes, arroyos o Hillslope  Unchanneled part of the watershed o The watershed is a fundamental unit of hydrology and geomorphology  Usually well defined  Transfer water, sediment, and biota to the outlet  Closed system “self-contained  Watershed geology basics o Rocks and minerals  All inorganic stuff on the earths surface  Some minerals are o Feldspar o Quartz o Biotite  Rocks are made of minerals  Igneous rocks o Crystallization of magma  Quartz  Feldspar  Sedimentary rocks o Deposition, burial, lithification  Metamorphic o Recrystalization of solid state materials o Chemical weathering  Decomposition of rocks by chemical reactions on the minerals surface  Chemical weathering can make soil o Physical weathering  Rivers do this  Mechanical or physical weathering of rocks o Sediments  Results of weathering  Broken up bits of rocks o Rivers have sediments Hillslope Hydrology: Groundwater  Water transfers between reservoirs o Percipitation  Water flows from the atmosphere to the watershed o Evapotranspiration  Water goes from the watershed to the atmosphere o Runoff or overland flow  Water goes from land surface to channels o Infiltration  Water goes from the land surface to the ground water  Soil o Saturation  Downward flow from the surface into soil or rock. o In the unsaturated zone water and air both occupy pore space o The saturated zone  Is below the groundwater table  Water fills all the pore spaces  Hillslope water budget o Inputs = outputs  Precipitation - evapotranspiration = runoff + infiltration  Flow pathways to channels o Horton Overland Flow (HOF) – If precipitation is greater than infiltration and Evapotranspiration Horton overland flow occurs. o Subsurface Storm Flow (SSSF) – this occurs when the precipitation rate is lower than the infiltration rate o Saturation Overland Flow (SOF) – This often occurs during long storms during the rainy season.  The line that divides the saturated zone from the unsaturated zone can rise and contribute to SOF  When the ground is so heavily saturated that the groundwater table returns to the surface as Return Flow and you have Direct Precipitation on Saturated areas you get Saturation Overland Flow  Return flow-> shallow groundwater flow that returns to the surface o Variable source areas  Parts of the landscape adjacent to channels get saturated during wet periods and or storms by sssf, contribute runoff directly to channels by return flow (RF) and direct precipitation on saturated areas (DPS)  Size of source area for runoff can change with the season o Groundwater flow  Slow and steady  Water flow in the subsurface (2 types) o Downward (vertical) flow in the unsaturated zone (interflow) o Flow parallel with the water table surface in the saturated zone.  Porosity & Permeability o Porosity  How much space there is between the pieces of rock in the ground o Permeability  How easily the water can move through those pores  Groundwater recharge and flow o Precipitation infiltrates the soil and percolates down to past the water table and flows into the river.  Groundwater Aquifers o Aquifer: a geological formation capable of storing and transmitting enough water to supply wells  Must be below the water table  Must have sufficient pore space to hold water  Must allow water flow (sufficient Permeability)  Must receive a sufficient amount of recharge (via infiltration and precipitation)  o Unconfined Aquifer  Idealized distribution of groundwater table beneath the land surface  Groundwater table mimics surface o Perched aquifer  In the unsaturated zone there is a low porosity and permeability layer so water piles up (not a part of the main groundwater table) o Confined aquifer  Water gets confined by overlying and underlying low permeability layers  This causes pressurization of the confined aquifer  **artesian well: water flows freely to the land surface because the piezeometric surface is above ground level.  Changes in the Groundwater Table o If you pump water faster than it is recharging you can get cone shaped depressions in the groundwater table  This slowly lowers the water table  Gaining/losing streams o Gaining  It is typical of wet climates that the water table intersects the water surface and the aquifer contributes flow to streams o Losing  Typical of dry climates  Water table below water surface  Streams contribute to aquifers. Stream Hydrology (discharge and floods)  Discharge (Q) o Streamflow  How much water is flowing through the river  The volumetric flow rate through a given stream cross section  Measured in meters cubed per second or feet cubed per second  Rational runoff equation o Used to estimate discharge o Q=CIA o Discharge is equal to C (rational runoff coefficient) I (rainfall intensity) and A (watershed drainage area)  Ways to measure Q o Cross section area (depth x width) * velocity o Guaging house  Measures water depth  It is a well that is hydrologically connected to a river  Rating curve o Empirical relationship between field measure flow depth and discharge  Floods o Variability in discharge is converted to risk by using rating curves o Rating curve: Empirical relationship between field measure stage and risk  Stage: level of water surface  This is applied in the creation of flood insurance maps o Magnitude: A flood of a given discharge (q) o Frequency: how often a given flood magnitude occurs o Recurrence interval (RI): Average years between a flood magnitude of a given size  Weibull equation: RI=(n+1)/rank  N is the number of years of record at the gauging station o Exceedence probability (P): the probability that an event of a given magnitude will occur in a given year  P=(1/RI)  Effects of urbanization o Urban hydrographs are more peaked and often have a greater volume than rural volume  More water and more impervious surface  Increase in annual peak flow tracking development Sediment transport  Is a function of o Available sediment supply and size o Amount of water flow o Rate of water flow o Turbulence of water flow  Laminar vs. Turbulent flow o Turbulent flow: chaotic disorganized flow  Sinuous motion  Rivers and streams are turbulent o Laminar flow: simple and if you were to follow a given particle in the flow it would move more or less in a straight line  Direct motion  Glaciers are laminar  Reynolds Number (Re) o (Velocity * depth * density)/(viscosity)  inertial forces/viscous forces  a nondimensional number o High Re = turbulent flow o Low Re = Laminar flow  Velocity profiles o In a river the fastest water flows at the top o The most viscous water is at the bed  Near the bed you get a laminar gentle flow\  Modes of sediment transport o Suspended load: particles that are traveling up in the flow suspended by the turbulent energy in the flow  Are supported by turbulent eddies and are barely deposited o Bed load  Courser particles that roll and hop along the river bed o They move in suspended load if their settling velocity is less than turbulent velocities of the water column.  Stokes Law o o Vs : settling velocity o g: gravitational acceleration o p: density of settling particle o : density of water o Dp: diameter of particle o : fluid viscosity  Sediment Transport terms o Saltation: the process by which bed load moves  It is the process of particles being sheared off the bed then falling back down to it and knocking other particles off the bed o Bedforms: particles form ripples on the bed  They migrate downstream (think of sand rivers) o Entrainment  Initial setting in motion of a particle o Transport  Particles in motion o Deposition  Particles settling to the bed  Sediment transport terms o Competence: maximum particle size that can be entrained by a given flow o Capacity: maximum quantity of sediment that can be transported by a given flow o Sediment load: total sediment transport rate of a give river  Suspended load + bed load o Sediment yield: Watershed load/drainage area   Bedload transport o Sets the competence of a river  The coarsest material in transport is the bedoad o Threshold process  Most of the time bedload is not moving and a large scale event (i.e. a flood) is needed to move the sediment o Set by the force of water moving over the bed  Force/unit area = stress  Hjulström diagram o o ^^ simplified hjulstöm diagram o x-axis is the sediment diameter o Y-axis is the velocity (cm/sec)  Logarithmic scale o Fall velocity  Bigger particles require faster water to move  An applocation of stokes law  Settling velocity  Above that line particles can be transported  Below that line particles will fall to the bottom o Consolidated sediment  Particles entrained by fluid above that line o Unconsolidated sediment  Below this line particles are not entrained  What happens when competence is exceded? o Causes massive deposition practically burying river valleys o Some sediment can not be transported and will have to erode in place River geomorphology  Imposed form rivers (bedrock rivers) o The bed and bank of the rivers are bedrock o Morphology: They have immobile beds and banks; their channels are armored by large boulders o Often located in mountains o Large rare events set morphology o Bedload transport rate are set by availability of sediment to transport  Self form rivers (alluvial) o Flow through sediment that are deposited by the river o Morphology: mobile bed and banks, channel bed composed of mobile sediment o Often located in lowland rivers o The morphology is set by common high flow events o The bedload transport rate is set by the rivers capacity and competence  Bankful Discharge (Q) o In rivers with floodplains the stage (elevation of the water surface) of the river rises rapidly with discharge until it spills out onto the floodplains o When it spills over consistently onto the floodplain it rises much less rapidly  The rollover in the discharge rating curve defines bankfull discharge o Importance of bankfull discharge  It is a channel forming event  More sediment moves at higher discharge  Discharge is more frequently small than large  Transport rate * time = total transport  Most transport is at intermedite q  Most effective discharge coincides with bankfull discharge o Geomorphic observation: for alluvial rivers, the discharge when flow spills over the banks onto the floodplain is also the “effective” discharge or flow that transports the most sediment o Hydrologic observation: Qb typically has a recurrence interval] of 1.5-2 years (meaning it has a 50-60% chance of happening in any given year)  Floodplain deposition o When water level in the river is at flood stage you get bankful discharge  The thickest and coarsest sediment is deposited at the channels edges  The thin fine sediment is deposited over the outer parts of the floodplain  This builds up natural levees  Channel Asymmetry and patterns o Downstream patterns  Pools: deep nonuniform parts  Riffles: usually shallow uniform parts o Cross Stream patterns  Point bars: sediment deposition in a meandering river across from a cut bank  Cut bank: bank opposite point bar that is often very steep as if cut straight down into the river o Bends (meanders)  Centrifugal acceleration pushes water to the outside of the bend  This drives erosion on the outside of the bend forming cut banks  Superelevation: water surface on the outside of the bend set up a circular current accross the channel  Bottom current toward the inside of the bend carries and deposits sediment on the point bar  The double current leads to a corckskrew effect of the water to the outside and the current to the inside of the bend  Drives meander migration  Large scale channel patterns in self formed rivers o Straight-sinuous: less common, can be sediment starved, usually big rivers with fine banks o Meandering: most common, typically sand bended rivers. Require active erosion, bedload transport, purturbations in thalweg path tend to gorw  Thalweg: main channel with deepest fastest part of river o Braided: multiple channels, high bedload transport, low bank stability with sparse vegetation and rapid variations in discharge. o Straight rivers: tend to be engineered, the rivers often work to make new bends in straight channels.  Meandering rivers o Very common especially in sand bedded systems  Characterized by pairing point bars and cut banks  Migrate toward the outside of the bends  Tend to form in relatively low sediment load  Form and evolve do to an asymmetric set up due to an energy balance going around the bend o Growth and cut off of meander bends  If one meander bend meets another the river cuts off and takes the more efficient path\  Braided rivers o Typically high gravel supply systems and energetic mountain river systems o They are very dynamic and have multiple channels\ o Very high flow during snow melt season o When the rivers come out of mountains and into flat lands you get a delta  The delta is essentially a braided system where the river deposits all its sediment in one spot  More general river information to know o How rivers vary down stream  Increase in discharge  Less exposed bedrock  Finer sediment  Decrease in channel slope o Tributaries add discharge  This increases capacity and thusly channel slope does not need to be as steep to carry the sediment load o Downstream “fining”  Sediment breaks into smaller pieces  Selective transport sorting  Again these factors mean that the channel slope does not need to be as steep to carry the sediment load o Graded stream  Stream with smooth concave longitudinal profile  Steep near the head of the river and nearly flat at the mouth  This is an indication that a river has achieved balance between erosion transport and deposition  Almost all rivers have this general longitudinal profile  The bedload and sediment are coarser near the head and finer near the mouth o Balance of driving and resisting forces  Resisting transport/erosion forces = transport forces  Sediment size and volume is equal to river slope and river discharge o Effects  When you decrease stream power or increase the resistance to transport you will have deposition because the resistance side is greater than the transport side  This happens because of an increase in sediment supply, change to drier climate, or dam construction  If you increase stream power (by increase in slope or discharge) or decrease the resistance to tansport ( reduce sediment size, supply, or volume) you will have a higher rate of erosion  This happens because of decrease in sediment supply because of dams, change to a wetter stormier climate, or increase in slope o Deltas: fanshaperd landforms developed where rivers spill into standing bodies of water, lose competence and capacity and deposit sediment  Most commonly associated with alluvial rivers  Fun fact: they also exist on mars o Alluvial fans: a delta that deposits in a flat valley not standing water  More commonly associated with imposed form bedrock channels o Terraces: floodplains abandoned due to changes in flood frequency and magnitude, sediment flux, and erosion rate.  Imposed form (bedrock channels) o Immobile bed and banks o Large, rare events set morphology  i.e. huge floos, landslides and volcanic eruptions o bedload transport rate set by availability of transportable sediment  limited by sediment supply not stream power o bedrock is often exposed and can be directly eroded by the river o Morphology dictated by factors external to the channel (as apposed to self formed channels) o They are found mainly in mountains, recently deglaciated landscapes, volcanic eruptions, and landslides  Many are both bedrock and alluvial in morphology  Bedrock and big sediment blocks cannot be transported by the river and must be slowly eroded in place  Bedrock Erosion Process o Sediment particles protect the bedrock from erosion, but when they are removed bedrock erosion results from saltation abrasion  The bedrock essentially gets sandblasted. o Plucking  Zones of weakness such as fractures in the bedrock get plucked at by particles of sediment in the water o Knick points  Headward erosion of waterfalls  Focus erosion of the head of the waterfall o This works the head upstream over time. Water Quality and Pollution  Types and sources of dissolved load in stream wayer o Sediment particles (bedload, suspended load) o Organic matter (suspended and dissolved) o Dissolved major ions (calcium sodium magnesium potassium)  Products of chemical weathering in rocks and minerals o Dissolved nutrients (nitrogen and Phosphorous) o Dissolved gasses (nitrogen & carbon dioxide)  More soluble in cold water o Dissolved trace metals o Other pollutants (chemicals)  Terms to know o Concentration: The measure of how much given substance there is mixed with another substance  Mass/volume o Salinity: The concentration of dissolved salts in water  Mostly sodium and cholire ions  Ocean water  96.5% water  3.5% salt o Ions: charged atoms or molecules  Total dissolved solids (TDS) o Definition: concentration of all dissolved ions and suspended matter less than 2 m in diameter o Commonly measured in fresh water systems o Units: mg of ions/liters of water o Sources of TDS  Rain  Ocean spray  Soil/dust  Pollution  Controls on stream water TDS  Bedrock geology of the drainage basin o Specific rocks and minerals produce specific water chemistry o Chemical weathering  Decomposition of rocks by chemical reaction on the mineral surface  Yields ions in solution  Dissolved major ions o Hydrologic cycle  Evaporation concentrates solutes in surface water  Climate sets water quantity and weathering rates  Groundwater flow carries chemical weathering products to streams  Ocean processes setting TDS levels o HCO3-, Ca2+, SiO2 precipitate in oceans  These form shells, and corals, and minerals o Na2+, Cl-, Mg2+, K+, SO4^2- precipitate less readily and get concentrated in water o Evaporation  Other controls on stream water chemistry  Biota through photosynthesis and respiration  Land use  Pollution: surface water, groundwater, atmosphere.  Water classifications o Fresh water: less than 1500 mg/l o Brackish water: between 1500 and 5000 mg/l o Saline water: more than 5000mg/l  Point source pollution o Watershed discharge from pipe or channel o EPA defines as: sewage treatment plants, industrial operation, active mines, oil fields, fuel and chemical storage tanks o “wet weather point sources”: combined sewage systems and construction sites  combined sewage systems: The water that flows into the sewer from the streets is the same sewer system that the waste water from your sink and toiled goes to as well. During rain storms you get lots of water coming into the storm drains and can overwhelm the sewage treatment system and you get combined sewage overflow  Non-point source pollution o Things such as city streets, cropland, animal feedlots, and suburban development. o Can not directly be pointed to as pollution sources o Pollutants picked up as it travels as runoff or groundwater  Agricultural fields and residential lawns: fertilizers, pesticides, herbicides  Urban runoff (that doesn’t enter the sewage system): oil, chemicals, bacteria  Roads: salt, oil, sediment  Abandoned mines  Pastures: livestock waste  Clean water act 1972 o Employs both regulatory and non regulatory tools  Reduce direct pollutant discharge into waterways (mainly point source pollution)  Finance municiple wastewater treatment facilities  Manage polluted runoff o Border Goals  Restore and maintain the chemical physical and biological integrity of the nations water  Can support the protection of fish shellfish and wildlife and recreation in water o It allows the EPA to set effluent standards on industry wide basis and water quality basis  Water quality standards are water body specific  (most to least regulated) drinking water, recreation, fishing and eating, aquatic life, agricultural water supply, industrial supply water. o People/companies who want to discharge pollution need to acquire a permit  This in turn covers point source pollution o Regulates nonpoint source pollution specifically and mostly from farming and forestry operations o Regulates the placement of dredge (fill material) in wetlands o Funds research o Hiw it goes about reaching its goals  First it monitors the quality of water  Then if impaired seta a total maximum daily load (TMDLs)  Or a watershed pollutant budget o It has reduced point source pollution and fecal bacteria and the demand for biological oxygen in rivers o Contaminents from nonpoint source have increased  Salts flushed into rivers from winter use of rock salts  Nitrate and fertilizers from agri-field runoff  Heavy metals from burning of fossil fuels and petroleum leaked from underground storage tanks  Pesticides from urban/agricultural sources  Salts from irrigation return flow  Reduced flows in rivers increased water temperatures, reduced dissolved oxygen, and concentrated other pollutants  Dissolved gasses in streams o Dissolved oxygen  Vital to aquatic life that use gills to breath  Fresh water fish require greater than 5mg/l  Water saturated in oxygen “tastes fresher”  DO is considered based on percentage saturation concentration (mg/l)  DO is highly dependent on water temp(colder holds more)  Eutrophication o A natural process that occurs in water bodies that leads to blooms of plant life which leads to depletion of dissolved oxygen in water bodies. o Process  1. Nutrients enter a waster body (e.g. fertilizer, sewage, etc)  2. Algae (phytoplankton motly) bloom or grow  3. Plants die and sink to the bottom  4. Bacteria consume the plants and dissolved oxygen through respiration  5. Water becomes hypoxic or anoxic -> fish die  hypoxic: low in DO  anoxic: no DO  Water related diseases o Two main types  No plumbing disease  Cholera  Fecal coliform diarrhea  Typhoid fever  Guinea worm  Hepatitis a  Polio  Giardia  Vector borne o These are most common in developing countries with wastewater management issues o 1/6 of the world population does not have access to clean water o 1/3 of the population has poor sanitation conditions that favor waterborne diseases  sewage treatment plants o primary treatment  main purpose: physical seperation of solids, greases, etc  removes 30-40% of pollutants  these are then dumped in landfills or elsewhere o secondary treatment  main purpose: reduce organic matter (BOD) by using bacteria  90% of organic matter is removed through this  produces sludge o Discharge or tertiary option  There are two options here  1. Discharge to surface or ground water  2. Send to tertiary treatment prior to discharge o the main purpose here is to reduce nitrogen and phosphorous by filtering with chemicals or soil o may also reduce heavy metals, human- made chemicals or microbes o still rare but use is increasing Water Use  Major water uses o Total water use is domestic + industry +agricultural use o 89% of our water used is surface water, 19% is ground water  Public supply 12%  Irrigation is 33%  Aquaculture is 3%  Thermoelectric power is 45%  Mining is 1%  Consumptive vs. nonconsumptive use o Consumptive use  Water lost to the atmosphere through evapotranspiration  Irrigaiton accounts for 80% of total water consumption o Nonconsumptive use  Water returned to surface or ground water systems (where we can conceivably retrieve it)  Most public use (wastewater treatment)  Most power plant cooling  Us and Global use (per capita and total) o 99% of the planets water is not readily accessible or useable o per capita water use in the US o improved water source: a source that is likely to provide safe drinking water  884 mill don’t have access to these o 2.5 billion are without improved santitation o Less developed countries use far less water for industrial use and far more for agriculture  Globally 70% of water is used for agriculture  Industrialized nations 30% agriculture 60% industry o Generally people around the world need 50liters per person per day for sanitation and drinking water  Not all water use is sustainable  Globally 15-35% of irrigation withdrawals are estimated to be unsustainable  Water stress o D+I+A/Q  D is domestic use  I is industrial use  A is irrigated agricultural use  Q is mean annual river discharge o D+I+A/Q =.2-.4 (20%-40% total water use)= medium-high stress  If it is greater than .4 or 40% it is severely high water limitations’  Population growth and climate change o The world population is growing rapidly  1.1% increase per year global average o may people depend on private water supplies  Virtual water and water footprint o The virtual water content of a product is the volume of fresh water used to produce the product measured at the place where the product was actually produced  The sum of water used in various steps in the production chain  Virtual refers to the fact that most of the water used in production is not actually contained in the product o 3 water footprints  green water footprint – water from precipitation that is stored in the rootzone of soil  this is consumptive water use  blue water use – water sourced from the surface and ground water  this is consumptive use  grey water – the amount of fresh water required to assimilate pollutants to meet specific water quality standards  considers point source pollution discharged to a fresh water source  this is nonconsumptive River Management  Goals of river management o Flood control o Navigation o Recreation o Power generation o Water supply  Methods of river management o Dams o Levees o Channel modifications o Diversions (aqueducts, pipes) o Land use (manage runoff) o Locks  Flood control o There are two strategies  Methods that slow flow down (and keep water in the watershed)  Land use practices decrease runoff  Channel and floodplain storage  Dams/reservoirs (temporary storage)  Methods that speed up flow (moves water through the channel faster)  Levees  Channel straightening, armoring, lining, deepening o Flood control through land use planning  Identifying flood prone areas (100 yr flood plain)  Set zoning requirements to limit damage  Don’t put residential buildings in the floodplain  Protect buildings using pumps and silt  Use floodplains for parks, athletic fields, community gardens, and forest buffers o Flood control dams are large structures that can contain huge amounts of water from behind them o In channel changes done to modify flood risk  Excavation of trapezoidal cross sections  Concrete lined channels  Straightening a meandering channel  Restraining a braided channel  Regrading a pool riffle sequence  Levees o Levees and channel modifications move more water faster  During low flow you have very little water between the levees and you get braided rivers and vegetation that grow and slow down flow o Channelized leveed river  Set back the levees a pretty good distance from the channel allowing natural floodplains  Levees would be smaller and less expensive  Flow constriction during floods associated with levees causes water to slow more quickly but deeper which causes flooding upstream as well as downstream o Channelizaiton  Where you take a river and excavate it and build a trapezoidal cross section  Minimizes erosion and deposition  You get a concrete channel that you can sloush water through easily  Deeper (floodwalls and levees) o Straightening rivers  Popular for a while to move water through quickly  Rivers don’t remain straight  Straightening the river decreases the distance between two points although the elevation drop remains constant this causes steepening of the river and erosion  This also causes deposition down stream  Effects of flood control projects o Channelization and levee projects for flood control  Pros:  Move water more quickly through channels (faster and deeper flow) o Good for protecting infrastructure  Works well at protecting infrastructure during high frequency low magnetude floods  Cons  Levels can fail catastrophically during big floods  The floodplain is often cut off from the channel o Habitat effects  Drying of floodplain and loss of nutrients to floodplain o Loss of temporary water storage on floodplain  Increased erosion and sediment transport o Faster flow o Rivers are self formed, often readjust back to their old shape  Faster transfer of floodpeaks downstream (increase flood hazard) o Navigation and recreation  Locking  In the western US there are a lot of dams that create lakes o Dams  Pros  Water storage for irrigation and public water supply  Flood control works well for moderate floods (Ri 2-25 years)  Cheap source of power  Clean source of power  Reliable source of power  Recreation opportunities  Improve river navigation  Cons  Can fail  Health effects o Can increase water borne disease  Displace people  Flood control is limited o Flood peaks reduction is less noticeable downstream o Reservoirs can fill (ri100)  Can reduce recreation opportunities downstream  Channel and floodplain become disconnected o Because of reduced peak q\  Adverse affects on biota o Restrict fish migration DAMS  Types of dams o Run-of-the-river: usually for power generation  You basically put a bump into your sloping river and create a flat reservoir  Slows down flow and leads to deposition  Keeps flowing through the reservoir  Qin always equals Qout  ∆ in storage = 0  examples: small dams, some water supply, hydropower, most dams in new england o Flood detention  Taller dam in bigger valleys  More storage capacity behind the dam in the reservoir  Most of the time the res will be partially full  Partially full in elevation but not in volume  Most of the time Qin=Qout  ∆=0  during floods you can raise the reservoir water level to the height of the dam and during the floods you can have a situation where Qin>Qout  ∆>0 o Multipurpose storage: water storage, power generation, flood control, and or recreation  Youll often have a reservoir where the water level goes up and down over the course of a day/season/floods  Can be huge to the point where they can store the annual flow of a river for two years  Water level in the reservoir can go up or down depending on demand for water or power  Qin is not equal to Qout  ∆ based on power generation over the course of a day  demand for power fluctuates throughout the day  big reservoirs can produce power according to demand  store water for supply, power generation  keep space for flood storage  requires forecasting of floods and droughts o seasonal effects (snowmelt)  ex  most big dams in the western US  advantages  lots of water storage for irrigation and public supply  works well for moderate floods  cons  variable daily discharge can alter habitat downstream  peak flood reduction less noticeable down stream from dams  reservoir fills up during big events  Multiple use dams,  Hydropower o Store water release base on demand o Daily flow fluctuations  Flood control o Fewer and low peaks, higher daily flow o Vary water level in reservoir  Water supply o Keep as much water available as possible o Save flood peaks for drought times  Recreation o Reservoir: boating want fixed water level o Downstream: cod water for fishing, minimize erosion of sand bar o Sufficient flow for boating  Environment o Maintain diverse habitat o Allow fish passage o Allow floodplain-channel cycling  Dam history o Biggest dam that supplies new york is the Croton dam 1906 o Mass winsor dam 1939 o Hoover dam 1938 o Gand coulee dam 1942  Floyd dominy USBR commissioner 1959-69 o Teton dam 1976 was a huge fail and end of the dam era  Power Generation o Originally we built small mill dams to mechanically power pelton wheels o Now we use dams to generate hydroelectric power  Dam with reservoir upstream  Outlet downstream  The water in the res is allowed to go through a tunnel where it speeds up due to gravity and turns a turbine  Converts spinning of the turbine in a generator to electricity  Discharge x Drop = Power  The drop is the difference between the top of the water surface in the res and the bottom of the dam  The Columbia river produces the most hydroelectric power  Hydropower is very cheap to produce  Downstream effects of dams o Change in hydrographs  Less total flow (water supply dams)  Fewer flood peaks (flood control and water supply dams)  Lower high flow (flood control and water supply dams) o Change in sediment load  Sediment trapping in reservoir; clear water downstream (most dams)  Flow Changes  transport changes (flood control and water supply dams  Can result in erosion and aggradation downstream o Change in temperature  Water is colder at the bottom of the reservoir and therefore colder water is released from the dam into the river o Change in habitat  Erosion and aggradation downstream  Loss of point bars  Examples of downstream effects for different types of dams o Rio grande River  Water supply dam (irrigation)  Downstream there is sometimes no water in the river  The tributaries still contribute sediment to the river  The bed of the river aggrades  Water would flow at a higher elevation and cause it to flood  Need to build levees to keep channel out of floodplain  Platte river NW  All the same as the rio grande effects  Vegetation growth in the channel o Snake river ID-Or  Sediment trapping behind dams, erosion of sand bars down stream from dams  Power generation dams  Little effect on flood peaks total flow  Daily flow fluctuations o Wetting and drying of banks can enhance erosion  Lots of sediment trapping o Erosion downstream due to sediment starved water o Bed armoring by boulders and bedrocks o Loss of habitat and recreation opportunities  Snake river dam blocks salmon from migrating up stream o Salmon bring ocean nutrients to the forest o Chatahoochie River & Buford dam: water, flood control, power and recreation  Flood peaks gone, total flow unchanged  Change in temperature downstream of dams  Downstream bank erosion  City of Atlanta: doesn’t want floods and wants plenty of cheap water and power  Power companies: fluctuate flow based on demand  Farmers downstream: want to minimize bank erosion and provide irrigation water  Fishermen: cold high oxygen water stocked, not much flow reservation  Boaters: want consistent water level in the res Case Studies  Boston’s water supply o Prior to 1795 the main water supplu was from springs and wells in boston commons  Local wells and springs were the water supply o After 1795 the water supply was Jamaica pond (the first public water supply) o 1845 first westward expansion: the Sudbury river tributary dammed to create lake cochituate, aqueduct to the brookline reservoir (this was the first dam in boston) o 1868 chestnut hill reservoir was built as storage for water from lake cochituate o 1878 sudbury ricer dammed further and diverted via the Sudbury aqueduct into the chestnut hill res o 1897: the wachussett reservoir construction began and the Nashua river was dammed. The chestnut hill res was the hub of the distribution system o 1926 onstruction on tunnels and dams to bring water form the swift river valley to boston o 1936 work began on the Windsor dam o 1939-46 quabbin reservoir was filled with water  watershed protection  85% forested or wetland  75% cant be built on  Water treatment  Disinfect water with ozone  Add fluoride  Adjust chemistry to reduce corrosion of lead and copper in inhome plumbing o Water demand  80 gal per person per day  we use about 60% of the water supply  Colorado river case study o The river is n the most arid part of the United states o Its watershed is in the four corners region and the mountain ranges and snow melt contribute to most of the water in the river o Hoover dam construction 1931-36  726 ft high  can hold 2x the annual flow o Colorado river compact 1922  Lower basin states must receive 9.3 km^3/yr of water form the upper basin states  Th eperdam mean annual flow at the grand canyon is 13.1 km^3/year  Not always enough water to go around o Lower Colorado river dams  Hoover dam, davis dam, parker dam, imperial dam, leguna dam o Glen canyon dam (built 1956-63)  Can hold about 2x the annual flow  Purposes of the dam  Generate power to pay for other Colorado river projects  Water supply for laower basin states  Flood control  Prolong the life of lake mead by trapping sediment  Recreation in lake powell o Effects of the Glen Canyon Dam on the Grand Canyon  Boulders and huge rocks from landslides and debris flows build up in the canyon  Temperature effects on fish  Reduction of ind-transport of sand up canyon  Erosion of archeological sites  Encroachment of invasive tamarisk trees on sandbars  Erosion of sandbars because of Fluctuating flows and sediment trapping  The bed downstream used to fluctuate 20 ft every year as sediment was deposited between floods but during floods it would erode out and be transferred down stream  After the dam it was constantly in the eroding stage because of sediment trapping and the bed was stripped down to minus 20 ft o Sand bars are very important  To restore them the experimental floods have been implemented to release sediment from being trapped behind the dams and restore the sediment load of the river that would then be deposited as sand bars down stream  Temporary success  1996 was the first experimental flood o during the flood sand suspension decreased and the grain size of the sediment on the bed increased because it winnowed away fine sediment o the grain size in suspension increased  temporary sand bar growth and quick erosion of those deposits o Western US water Crisis  California’s drought  California is currently in the fourth year of its severe drought  On april 1 2015 california department of water resources measured the statewide water content of the sierra snowpack at five percent the average april 1 level  The drought is not caused by global warming but is exacerbated by it  There is thought that they needa water market in the west and southwest o Many communities don’t have water meters and pay a flat rate for access rather than per gallon o Progressive rate structure proposed (pay more each successive gallon)  Recycled wastewater is crucial o Less than 10% of municipal wastewater in the US is intentionally reused o Irrigation is an excellent form of tertiary wastewater treatment o California has streamlined the permitting process for using recycled water  Allowing trading rights for farmers would be crucial o Simplest update of western water rights would be allowing farmers to trade water rights o Need careful government oversight  Another way to save water is to change our diets o Virtual water footprint of what we eat o Mississippi River  1700-1900s built levees and damned distributaries  the levees can raise the river stages and fail  levees push all the sediment too far down stream into the delta  spillways release discharge and lower the stage  the sea level has consistently risen since the 1920s  Because the sediment is channeled out there is a loss of wetland and the sea level rises  Atchafalaya River  Used to be the red river and the Mississippi river o 15 century the westward meander of the Mississippi river intercepted the red river and the red river became a tributary. The lower red river became a distributary called the Atchafalaya river o in 1831 shreve cut off the Tumbull’s bend Stream Restoration and Dam Removal  Stream restoration is the process of recovery of an ecosystem that has been degraded, damaged, or destroyed o The steps are first to determine the pre-disturbance reference condition and set goals, forecast effects, and monitor results  Goals and Actions o Aestetics/recreation/education: trash removal o Bank stabilization: re-vegetation, bank grading o Channel reconfiguration: alteration of channel plan form or longitudinal profile. Includes stream meander restoration and in channel structures that alter the flow of the streams o Dam removal/retrofit: removal of dams and weirs or modifications/retrofits in existing dams to reduce negative ecological effects o Fish passages: remove barriers such as dams, install fish ladders. Or place migration barriers at strategic locations along the stream to prevent undesireable species from


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