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EAS 345 HYDROLOGY Lab 6 Name__________________________________ Last First

GROUNDWATER

In Math Problems, show all work.

Introdution! In man" #$aes% #eo#$e obtain t&eir 'ater (rom t&e )round! *&e tota$ )round 'ater reser+oir onEart& is some ,-./061m3% '&i& (ar e2eeds t&e a#ait" o( a$$ t&e 'or$ds ri+ers and $a1es ombined! *&is)round 'ater is $ar)e$" on(ined to t&e sma$$ s#aes bet'een )rains o( soi$ or in t&e sma$$ ra1s in t&e ro1s!Near t&e sur(ae t&ese s#aes are on$" #art$" (i$$ed 'it& 'ater and #art$" (i$$ed 'it& air! *&is one is 1no'n ast&e +adose one or t&e one o( aeration! e$o' a $e+e$ 1no'n as t&e 'ater tab$e% a$$ t&e #ore s#aes are (i$$ed'it& 'ater!

orosit" is t&e #erenta)e o( t&e tota$ ro1 +o$ume t&at an be ou#ied b" 'ater! *&us i( a o$umn o( ro1 .meter &i)& &as a #orosit" o( P7!4 t&at means t&at i( a$$ t&e 'ater 'ere remo+ed it 'ou$d be a o$umn !4 m&i)&! Genera$$"% t&e #orosit" o( soi$s is about 8/94/: and dereases 'it& de#t& in t&e soi$ or eart&;A ro1 (i$$ed to its #orosit" is ui(er 'ater annot dri# o(( so t&e a+ai$ab$e 'ater is due to t&e om#ressibi$it" o( t&e ro1 and'ater $a"er% and is mu& $ess t&an t&e s#ei(i "ie$d! *&e re$e+ant >uantit" is t&en t&e Storati+it"% S% or t&e+o$ume o( 'ater e2trated (rom an a>ui(er #er unit area and unit $o'erin) o( t&e &ead or t&e 'ater tab$e! Sist"#ia$$" ./93and ./95(or a on(ined a>ui(er but e>ua$s s#ei(i "ie$d% S"(or an unon(ined a>ui(er!

=&en 'ater ($o's t&rou)& t&e )round% t&e soi$ or ro1 is #ermeab$e! ?ost soi$s -e2e#t (ine $a"s0 and somero1s su& as sandstone are #ermeab$e to some de)ree! @r"sta$$ine ro1s su& as )ranite are +irtua$$"im#ermeab$e un$ess ridd$ed 'it& ui(ers '&i$e im#ermeab$ero1s are a$$ed a>uitards!

ermeab$e soi$s and ro1s &a+e a &i)& &"drau$i onduti+it"% K! *&e &"drau$i onduti+it" o( di((erentro1s and soi$s is &i)&$" +ariab$e! In )enera$% t&e oarser t&e )rains and t&e $ar)er t&e ra1s in t&e ro1s t&e$ar)er t&e +a$ue o( K% '&i& an ran)e (rom ./9.or &i)&er in oarse )ra+e$ to $ess t&an ./9in (ine $a"s and)ranite!

?an" sedimentar" ro1s o(ten are $a"ered in su& a manner t&at a>ui(ers are on(ined bet'een im#ermeab$ero1 $a"ers! Su& $a"ers are 1no'n as on(ined a>ui(ers! Buite o(ten it is neessar" to dri$$ a 'e$$ t&rou)& anim#ermeab$e $a"er to rea& t&e a>ui(er! On oasion t&e #ressure or &ead in t&e a>ui(er is so $ar)e t&at its'ater 'i$$ rise and ($o' out on t&e sur(ae one t&e im#ermeab$e $a"er &as been #enetrated! *&is is 1no'n asan artesian 'e$$!

*&e basi $a' o( )round 'ater ($o' is Dar"s e>uation%

x

hK-=

A

q

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'&ere%

qis t&e dis&ar)e or ($o' rateAis t&e ross setiona$ areaKis t&e &"drau$i onduti+it"his t&e &ead or t&e &ei)&t o( t&e (ree 'ater tab$e!

Dar"s e>uation states t&at t&e rate o( 'ater ($o' is #ro#ortiona$ to t&e s$o#e o( t&e 'ater tab$e% and 'ater($o's (rom #oints '&ere t&e 'ater tab$e is &i)&er to '&ere it is $o'er! =ater 'i$$ )enera$$" ($o' do'ns$o#e%but in ases '&ere 'ater is on(ined it ma" atua$$" ($o' u#'ards!

*&e (orm o( Dar"s e>uation is identia$ to t&e (orm o( t&e $assia$ &eat ondution e>uation% and man" o(its so$utions &a+e been borro'ed diret$" (rom so$utions to &eat ondution #rob$ems!

*&e ($o' #er unit 'idt& in a on(ined a>ui(er o( t&i1ness% H is%

eause t&e #rodut% KH a##ears so o(ten% it is (re>uent$" ombined into a sin)$e term% TKH% or

transmissibility! -S#e$$in) t&is 'ord orret$" )i+es an e2tra 8/: on &"dro$o)" e2ams!0 T is t&e +o$ume

dis&ar)e #er unit 'idt& o( a>ui(er '&en t&e s$o#e o( t&e &ead% hCx7.!

*&e s#eed o( t&e mo+in) 'ater in t&e )round (or a )i+en dis&ar)e +aries in+erse$" 'it& t&e #orosit"! Sinet&e +o$ume o( )round 'ater dV'e>ua$s t&e +o$ume o( ro1 times t&e #orosit"% or% PdV'e &a+e a(ter di+idin)b" t&e time inter+a$% dt%

So$+in) (or t&e +e$oit"% v"ie$ds%

=&en 'ater is dra'n (rom t&e )round it de#resses t&e 'ater tab$e! *&e amount o( 'ater d 't&at an beobtained is t&e +o$ume o( ro1 or soi$% dVmu$ti#$ied b" t&e storati+it"% S! One a)ain% di+idin) b" t&e timeinter+a$ and notin) t&at no' dV7Abasedh% 'e )et%

eause bot& S. and P.% 'ater mo+es (aster t&rou)& t&e )round and t&e 'ater tab$e &an)es some'&at(aster t&an mi)&t be e2#eted!

x

hKH-=

L

q

q=PAv=dt

dVP

PA

q=v

SA

q-=

dt

dh

base

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EAS 345 HYDROLOGY Lab 6 Name__________________________________ Last First

GROUNDWATER

In Math Problems, show all work.

.! @a$u$ate t&e &"drau$i onduti+it"% K (or an unon(ined a>ui(er 'it& bottom at h 7 / '&ere t'o#ieometers 4/ meters a#art reord &eads -or 'ater tab$e &ei)&ts0% h.75/ m and h87 35 m! *&e dis&ar)e%qCL 7 /!/. m3s9.Cm is uni(orm and ($o's (rom h.to h8!

K7 _______

8! A on(ined a>ui(er 5/ m t&i1 'it& &"drau$i onduti+it"% K 7 ./93and &ead 'it& s$o#e hCx7 /!.

em#ties into a ri+er . 1m $on)! Find t&e ontribution o( )round 'ater ($o' into t&e ri+er!

qase7 ________ m3s9.

3! Find t&e tota$ and a+ai$ab$e +o$ume o( 'ater -to a 'e$$0 in an a>ui(er .// m t&i1 'it& an area o( . 1m 8i(#orosit"% P7 /!4 and s#ei(i "ie$d% Sy7 /!.5!

Vtot7 _______ m3 VA+ai$7 _______ m

3

4! @a$u$ate &o' $on) 'ater in t&e a>ui(er o( #rob$em 3 'ou$d $ast i( it is not re#$enis&ed and i( it is #um#edat t&e rate% q7 /!/. m3 s9.

dt7 __________ s

5! I( 8 m o( rain (a$$s but /!, m runs o(( on t&e sur(ae% a$u$ate t&e rise o( t&e 'ater tab$e i( t&e s#ei(i"ie$d% Sy7 /!8 and t&e soi$ 'as at (ie$d a#ait"!

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z7 ________ m

6! Find t&e rate o( &an)e o( &ei)&t o( t&e 'ater tab$e% hCt% in a retan)u$ar area 2 7 8// m $on) and " 7

.// m 'ide o( an unon(ined a>ui(er 'it& bottom at h7 / i( t&e 'ater tab$e &as a &ei)&t H7 35 m on t&e $e(tside and H7 8/ m on t&e ri)&t and t&e s$o#e o( t&e 'ater tab$e hCx7 9!85 on t&e $e(t and hCx7 9!./ on

t&e ri)&t! Assume t&e #orosit" is P7 /!85% s#ei(i "ie$d% S"7 /!.5 and &"drau$i onduti+it"% K7 ./94! *o

do t&is "ou must a$u$ate t&e dis&ar)e at t&e $e(t -in($o'0 and ri)&t -out($o'0 sides o( t&e a>ui(er% ta1e t&edi((erene to (ind t&e +o$ume aumu$ation rate and di+ide b" t&e sur(ae area o( t&e re)ion!

hCt7 ___________ m s9.

In t&is #rob$em% t&e 'idt&% yo( t&e re)ion is irre$e+ant! E2#$ain!

! Find t&e s#eed o( 'ater mo+in) t&rou)& an a>ui(er 'it& K7 ./95and #orosit"% P7 /!4 i( t&e s$o#e o( t&e

'ater tab$e% hCx7 .!

v7 _________ m s9.

,! Obser+ations s&o' t&at t&e tota$ $en)t& o( a$$ tributaries is re$ated to t&e 'aters&eds area b"%

'&ere t&e $en)t& is in 1m and t&e area in 1m8! I( t&e same unon(ined a>ui(er as in rob$em em#ties into a$$t&e tributaries in an area% A7 .// 1m8% (ind t&e tota$ $en)t& o( t&e tributaries% and t&e tota$ base ($o' t&at 'i$$resu$t! Assume t&e a>ui(er is H 7 35 m t&i1!

L7 ______

qase7 ________ m3s9.

A1.7=L!."#