Urban Nature: When it Rains it Drains Students construct a model watershed.  Through this lesson, students add pollu7on and rain to the watershed to model the fate of watershed contaminants. 

Credits Jennifer Davis Jim Neiss Vanessa Sorrell Gaby Geyer

Companion Video www.youtube.com/imakechange/ Select Video: Urban Nature

Funded by the National Oceanic and Atmospheric Administration's Bay Watershed Education and Training Program (B-WET)

Grade9‐129cCaliforniaGeology

CAStateScienceStandard

Students construct a model watershed.  Through this lesson, students add pollu7on and rain to the watershed to model the fate of watershed contaminants. 

UrbanNature:WhenitRainsitDrains

BACKGROUNDWhenwaterfallsontothesurfaceoftheEarth,itwillseepintothegroundand/orrunoffoverthesurface.ThenatureofthegroundandtheintensityandduraHonoftheraingovernhowmuchwaterthegroundwillabsorbandhowmuchwillrunoff.Withthicksandysoilsandlongdryperiodsbetweenrainfalls,forexample,mostoftheearlyrainwillseepintotheground.Oncethesoilissaturated(longduraHonrainfall),oriftherainisfallingfasterthanthegroundcanabsorbit(highintensityrainfall),waterwillbegintorunoff.Onhardrockygroundnotmuchrainwillbeabsorbed.Rather,mostwillflowdownhill,overthesurface,especiallyduringhighintensityrainfall.

Gravityandtopographygovernwhererunoffwillcollectandflow.Waterflowsdownhillandfollowsthepathofleastresistancetowardsomebaselevel(anotherlargerriver,lake,orocean).Aslongasthereisagradient(slope)tothesurface,waterwillconHnuetoflowdownhill.Waterthatisabsorbedintothegroundisstoredasgroundwaterreservoirs.Likesurfacewater,groundwateralsoflowsdownhilltowardsstreams,lakes,andtheoceanbutatamuchslowerrate.ItisimportanttounderstandthisconnecHvityofwaterespeciallyinareaswherepollutantscangetintothegroundwater,rivers,andlakesthataretobeusedforresidenHalpurposes.

KeyTerms

Watershed DischargeWaterbasin DendriHcDrainagebasin TributaryDrainagedivide RiversourceUrbanizaHon RidgesUrban RiverouUlowConfluence PolluHonLandslide

OBJECTIVESStudentswillbeableto:

o  explainthemajorpathsofthewateronearth’ssurfacesandunderstandthefactorsthatcontributetothosepaths.

o  demonstratetheirunderstandingofawatershedbyidenHfyingthedefiningfeaturesofawatershedsuchasridgesandvalleysandpredicHngtheflowpathofwater.

o  explainhowpollutantscontaminatewatersources.

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OVERVIEW

1.  StudentswillwatchtheSF‐ROCKSUrbanNaturevideoandanswertheaccompanyingquesHons.

2.  StudentswillparHcipateinWhenitRainsitDrainsacHvityandhavethestudentsansweranyquesHonsyouchoosefromtheassessment.

1.  MakeenoughcopiesofthevideoquesHonsforeachstudent.

2.  Fill the mist spray bottle with water.

3.  Cut heavy duty wrapping paper into 3ft x 3ft pieces for each student or group.

SET‐UP

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MATERIALSo  Video:goto

www.youtube.com/user/imakechange/Select“Urban Nature” 

o  heavydutywrappingpaperapproximately3ax3apiece

o  1blackpermanentmarkingpen

o  1blueand1redwatersolublemarkingpens(OverheadProjectorPens)

o  1mistspraybobles

o  smallbeakerofsand,smallbeakerofclay(opHonal)

o  tracingpaper,oneperstudent(opHonal)

o  sponges/papertowels(forcleanup)

PROCEDURE

1.Crumplea3'x3'sheetofheavydutywrappingpaper,andallowittoslightlyunfoldsothatyouhavearough,irregularsurface,approximaHngahillylandscape.Youcanmakeslightadjustmentssothattheterrainlookshillyormountainous.TheideaistobeabletoidenHfylandscapeelementsthatapproximatevalleysandridges.

2.Todeterminewherewaterwouldflowifitrainedonyourwatershedmodel,idenHfypotenHalstreamsbydrawingbluelines(solublepen)alongvalleypaths.Todeterminewatershedboundaries,idenHfythehighestridgesthatseparateadjacentstreamsflowingawayfromoneanotherbydrawingblacklinesalongtheiredges.

3.Withyourblackmarker,drawspotsofresidenHallocaHons.Withthesolubleredmarkerpens,drawspotsofpolluHon‐‐represenHnggastanksorsepHcsystems,ferHlizersorpesHcides‐‐onthesidesofhillsadjacenttorivers.Placesmallamountsofsandandclaysinflaberareasadjacenttothestreamsaswell(opHonal).

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4.SpraytheenHrecrumpledpaperwatershedwiththefinemistandnotethepabernofriverflow(inblue),contaminantflow(inred),andanysandand/ormudslidesthatresult.Becarefultosprayfromadistancesothattheforceofthespayedwaterdoesnotflabenyourlandscape!Thewatershouldlandonthepaper,begintosoakin,andthenbegintocollectandrunoffoncethepaperisslightlysaturated.Oncethepaperissaturated,itwillbegintoflabenonitsown.Itisbestnottooverdothe“rainfall”duraHonandmakeobservaHonsquickly.

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Assessment1.Whatisawatershed,andhowcanwedefineitsboundaries?2.Tributariesarethesmallerstreamsthatflowintothemajor(trunk)streams.Countthenumberoftributariesjoiningeachofthelargerstreams,andnotethatnumber.Howmanytributariesarethere?Howmanymajortrunkstreamsarethere?HowcanyoudifferenHatebetweenatributaryandamajortrunkstream?Whicharelonger?Canyoutellwhicharesteeper?3.Whichoftheriverswouldhavethegreatestflow(calledDischarge),andwhatcontributestothatdischarge?4.Ifyoudidnotputarrowsonyourwatershed,couldyoutellwhichdirecHonthestreamsandriversareflowing?How?5.Whatdoestheriversystemofyourwatershedlooklike,andcanyousuggestanameforthispabern?Inyourownwords,howwouldyoudefineawatershedordrainagebasin?7.Whataffectstheflowofpollutantsaboveandbelowtheground,andcanyoupredictthepathspollutantswilltakeevenifyoucan'tseethem?8.Whenandwheredolandslidesoccur?

TAKEACTION!

Use compost and other natural fertilizers on your lawns and in your gardens to prevent phosphates in the watershed.

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LookingverHcallydownoverthelandscapeyoujustcreated,withthebluemarkerandonaseparatepieceofpaper,drawamapviewoftheriversystem,includingallthetributaries.Onthismapdrawtheoutlineoftheridgesinblack.Witharrows,showthedirecHonofflowofthestreamsandrivers.

Thelongestrivers,withthelargestwatersheds,asdefinedbytheblacklinesalongtheridges,willtendtohavethelargestdischarges.Thiscanbeaffectedbythenatureofsoilorrock.Thicksoilswouldabsorbmorewateranddecreaserunofftotheriver,reducingriverdischarge,andsteeperslopesdrainmoreeffecHvelythangentleslopes.VegetaHonwouldalsoaffectrunoff,thoughyoucan'ttellthatfromourmodel.)

QuesHon:Howwouldyoudefineawatershed?Theword"drainagebasin"meansthesameaswatershed.WriteashortdescripHonofwhatawatershedis.Numberthedifferentwatershedsonyourmapinorderofsize.Howdothesizesofthewatershedscomparetothesizesoftheriverstheycontain?

QuesHon:Lookingattheworldmap,idenHfy3ofthelargestriversonEarth(thosethathavethelargestdischarges).Withtracingpaper,outlinethewatershedareaforeach,anddrawthemajorriversystemswithinthatwatershed.HowdidyoumakethisdeterminaHon?OnthemapofSanFranciscocanyououtlinethedrainagebasin(watershedarea)thatincludesyourschool?Whatmakesthatdifficult?(IdenHfyingwatershedsinSFwillbecompletedduringanotherlesson)

QuesHon:Fromyourreading,idenHfyanareathathasexperiencedamajorflood.Whereisit?Whydofloodsseemtoperiodicallyoccurinthesameareas?Whatmakestheseplacesmorevulnerable?Whatfactorsotherthanrainfallcancontributetoflooding?(StudentsmightidenHfyareaswithhighrainfallrates,largewatersheds,regionsthatmighthavebeenurbanizedormodifiedbyhumanacHvitylikelumbering‐thoughthisisaliblesophisHcated.TheymightidenHfydamorleveebreaks,orotherhuman‐inducedfactors.ThiscouldleadtoaninteresHngdiscussionofthesefactors).

Extension

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As you watch Urban Nature, answer the following ques7ons.  

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Name UrbanNature

1.  WhereisHeron’sHeadPark?

2.  WhatwasHeron’sHeadParkbeforeandwhocleaneditup?

3.  WhatarethestudentstesHngfor?

4.  Whatdidtheyusethecolorimeterfor?

5.  Whatweretheirresults?Explainwhetherthisisgoodornot.