Groundwater flow Groundwater flow

M odu le 4 – ( L1 2 - L1 8 ) : “ W a t e r sh e d M ode lin g”

  

St a n da r d m ode lin g a ppr oa ch e s a n d cla ssifica t ion s, syst e m con ce pt St a n da r d m ode lin g a ppr oa ch e s a n d cla ssifica t ion s, syst e m con ce pt

for w a t e r sh e d m ode lin g, ove r a ll de scr ipt ion of diffe r e n t h ydr ologic

pr oce sse s, m ode lin g of r a in fa ll, r u n off pr oce ss, su bsu r fa ce flow s a n d gr ou n dw a t e r flow g

  Su bsu r fa ce & Gr ou n dw a t e r Su bsu r fa ce & Gr ou n dw a t e r 1 8 1 8

L1 8 L1 8 – Su bsu r fa ce & Gr ou n dw a t e r Flow s Fl

  

Topics Cove r e d Topics Cove r e d

    Subsurface flow , I nfilt rat ion, Aquifers Subsurface flow , I nfilt rat ion, Aquifers Groundw at er flow, Groundw at er flow Groundw at er flow, Groundw at er flow Groundw at er flow Groundw at er flow Groundw at er flow Groundw at er flow m odeling, Num erical m odeling, Groundw at er m odeling, Num erical m odeling, Groundw at er qualit y qualit y li li

    Subsurface flow, I nfilt rat ion, Aquifer, Subsurface flow, I nfilt rat ion, Aquifer, q q Keywords: Keywords: y y Groundw at er flow , Groundw at er flow m odeling, Num erical Groundw at er flow , Groundw at er flow m odeling, Num erical m odeling, Groundw at er qualit y. m odeling, Groundw at er qualit y.

  Re ch a r ge _{Pu m pin g} D isch a r ge w e ll _{Un con fine d}

  Su bsu r fa ce Flow _{a qu ife r a qu ife r I m pe r viou s la ye r} Subsurface wat er – all wat er • _{Con fin e d}

  beneat h t he Eart h’s surface _{I m pe r viou s la ye r I m pe r viou s la ye r a qu ife r}

• Recharged by infilt rat ion eit her R h d b i filt t i it h _{Con fin e d} direct ly on t he land surface or in _{a qu ife r} t he beds of st ream s, lakes & oceans. _{Un sa t ur a t e d soil Un sa t ur a t e d soil}
• Discharged t hrough - evaporat ion,
_Soil t ranspirat ion, from springs, seeps on land _{a ir pa r t icle} surface or beds of surface wat er bodies, surface or beds of surface wat er bodies, pum ping wells, gravit y drains et c. W a t e r<
• Subsurface environm ent –som e _{Sa t u r a t e d soil} arrangem ent of porous m at erials – wat er arrangem ent of porous m at erials wat er _Soil m oves wit hin t he pores of t hese m at erials. _{pa r t icle}
• Most t errest rial hydrologic act ivit ies t akes y g
_{W a t e r} place wit hin root zone.

  Evapot ranspirat ion Rainfall Unsat urat ed

Su bsu r fa ce W a t e r

  zone  - divided int o 3 part s

  S il t Soil wat er Recharge _{Capillary fringe} Wat er Table

   Drainable wat er – t hat readily

  drains from soil under t he influence of gravit y – w at er

  Fully Sat urat ed Zone

  occupying pores larger t han

• Groundwat er capillary size.

   Plant available wat er – volum e of

  wat er released from soil bet ween a soil wat er pressure head of p about - 1/ 3 bar ( field capacit y) and about - 15 bars ( wilt ing point )

• – w at er det ained in st orage by capillary forces. ll f

   Unavailable wat er – hygroscopic

  wat er – w at er held t ight ly in film s around individual soil part icles.

I n filt r a t ion

  I nfilt rat ion: process by which wat er on t he ground surface ent ers t he soil .

    I nfilt rat ion capacit y I nfilt rat ion capacit y of soil det erm ines – am ount &amp; of soil det erm ines – am ount &amp;

  t im e dist ribut ion of rainfall excess for runoff from a st orm .

   I m port ant for est im at ion f of surface runoff, subsurface f f ff b f flow &amp; st orage of wat er wit hin wat ershed.

   Cont rolling fact ors: Cont rolling fact ors: Soil t ype ( size of part icles, degree Soil t ype ( size of part icles, degree

  of aggregat ion bet ween part icles, arrangem ent of

  part icles) ; veget at ive cover; surface crust ing; season of t he year; ant ecedent m oist ure; rainfall hyet ograph; of t he year; ant ecedent m oist ure; rainfall hyet ograph; subsurface m oist ure condit ions et c. _{Soil zone}

  Recharge Wat er t able

  Un sa t u r a t e d &amp; Sa t u r a t e d Flow s _{Un sa t ur a t e d soil Un sa t ur a t e d soil} 

  Unsat urat ed soils: wat er m oves

  prim arily in sm all pores &amp; t hrough _{a ir pa r t icle Soil} film s locat ed around and bet ween film s locat ed around and bet ween solid part icles. As wat er cont ent _{W a t e r} decreases, cross sect ional area of _{Sa t u r a t e d soil} t he film s decreases &amp; flow pat hs t he film s decreases &amp; flow pat hs becom e m ore lim it ed. Result is a _{Soil pa r t icle} hydraulic conduct ivit y funct ion t hat decreases rapidly wit h wat er decreases rapidly wit h wat er _{W a t e r} cont ent .

   Sat urat ed soils: Soil pores are

  considered full wit h wat er ( m ay not

  unsat urat ed flow

  be com plet ely full due t o air

  Wat er t able

  e ent rapm ent ) ; Hydraulic conduct ivit y ap e ) ; yd au c co duc y _{Surface wat er Surface wat er}

Un sa t u r a t e d & Sa t u r a t e d Flow s.

   Soil Wat er Movem ent : response t o a gradient

   Wet soil t o Dry Soil - low soil m oist ure t ension t o high SMT; high soil wat er pot ent ial t o low soil pot ent ial SMT; high soil wat er pot ent ial t o low soil pot ent ial

   Sat urat ed condit ions: w at er m oving m ainly in t he m acropores, all of t he pores are filled.

   Unsat urat ed condit ions: U t t d dit i m acropores full of air m icropores f ll f i i filled wit h wat er &amp; air - m oist ure t ension gradient creat es unsat urat ed flow.

   Sat urat ed flow S t t d fl ( gravit at ional flow ) occurs under sat urat ed ( it t i l fl ) d t t d condit ions w hen t he force of gravit y is great er t han forces holding w at er in t he soil. Capillary flow occurs in unsat urat ed soil ( also called unsat urat ed flow ) .

   Measuring Soil Moist ure: Gravim et ric m et hod, _{Unsat urat ed} Tensiom et er, Elect rical resist ance m et hod Tensiom et er, Elect rical resist ance m et hod _{Surface wat er Surface wat er}

  Wat er t able

Gr ou n dw a t e r

   

  I nfilt rat ed wat er I nfilt rat ed wat er – som e replenishes soil m oist ure deficiency som e replenishes soil m oist ure deficiency

• – if soil is not sat urat ed

  

  When sat urat ed – shallow groundwat er syst em

  

  Wat er t hen percolat es down unt il it reaches t he sat urat ed zone – called Aquifer or deep groundwat er syst em

   

  Upper wat er surface of sat urat ed zone – groundwat er – is Upper wat er surface of sat urat ed zone groundwat er is called wat er t able .

  Hydrologic processes  not sat urat ed –

  Soil above wat er t able –

  vadose or unsat urat ed zone Precipitation

   Groundw at er – im port ant source of

  Overland Evaporation

  fresh wat er part of hydrologic cycle fresh wat er–part of hydrologic cycle

  Land Hydrology 

  Const it ut es m ore t han 80 t im es am ount of fresh wat er in rivers &amp;

  Groundw ater Groundw ater

  lakes com bined. lakes com bined

  River

Gr ou n dw a t e r - Aqu ife r s

   Aquifer- form at ion t hat cont ains sufficient sat urat ed

  perm eable m at erial t o yield significant quant it y of wat er t o wells/ springs e.g. Sand. wat er t o wells/ springs e.g. Sand.

   Aquiclude: sat urat ed but relat ively im perm eable m at erial – does not yield appreciable quant it ies of w at er; e g Clay wat er; e.g. Clay.

   Aquifuge: relat ively im perm eable form at ion – neit her cont ain nor t ransm it wat er; e.g.: granit e . _{Re ch a r ge}

   Aquit ard: sat urat ed but poorly _{D ischa r ge} ; e.g.: sandy clay.

  perm eable st rat um _{Pu m pin g}

   Aquifers: Confined or unconfined Aquifers: Confined or unconfined _{w e ll aquifer Unconfined a qu ife r Con fin e d la ye r} I m pe r viou s pe ou s Aquifer Charact erist ics 

  Porosit y ( n) : Porosit y ( n) : Those port ions of soil, not occupied by solids; Those port ions of soil, not occupied by solids; Rat io of volum e of pores or int erst ices t o t ot al volum e.

   Percolat ion – rat e at w hich w at er m oves dow nw ard t hrough soil; soil; Perm eabilit y Perm eabilit y – an expression of m ovem ent of w at er in an expression of m ovem ent of w at er in any direct ion.

   Specific yield ( S ) : rat io of volum e of w at er t hat , aft er y sat urat ion can be drained by gravit y sat urat ion, can be drained by gravit y.

   St orage coefficient ( S- st orat ivit y) : volum e of w at er t hat an aquifer releases from or t akes int o st orage per unit surface area of aquifer per unit change in head norm al t o t hat area of aquifer per unit change in head norm al t o t hat surface.

   Hydraulic conduct ivit y ( K) : const ant t hat serves as a

m easure of t he perm eabilit y of t he porous m edium m easure of t he perm eabilit y of t he porous m edium .

   Transm issivit y ( T) : Rat e at which wat er is t ransm it t ed t hough a unit w idt h of aquifer under unit hydraulic gradient ; T = Kb; b is sat urat ed t hickness of aquifer. T Kb; b is sat urat ed t hickness of aquifer Groundwat er Flow

 Darcy defined how wat er m oves t hrough

  Darcy’s Law:

  a sat urat ed porous m edium wit h analogy of a cylinder fit t ed wit h inflow and out flow pipes fit t ed wit h inflow and out flow pipes He showed t hat He showed t hat

  .

  velocit y was a funct ion of difference in head ‘h’ over a finit e dist ance ‘l’

  

  Darcy’s law: Velocit y of flow: v = - K ( dh/ dl) Where v is Darcy velocit y or specific discharge; K is hydraulic conduct ivit y; dh/ dl is hydraulic gradient ; hydraulic conduct ivit y; dh/ dl is hydraulic gradient ; ‘- ’ sign – flow wat er in t he direct ion of decreasing head; act ual velocit y = v/ n.

   Darcy’s law valid: D ’ l lid w hen Re ( Reynolds num ber - &gt; I nert ia h R ( R ld b &gt; I t i

  force/ viscous force) &lt; 1

  

  Hydraulic conduct ivit y K: found by pum ping t est s, t racer y y y p p g , t est s, form ulas, laborat ory m et hods et c.

  Groundw at er Flow in Porous Media 

  Porous m edia – het erogeneous &amp; anisot ropic 

  Geologic form at ion as aquifers: Alluvial deposit s,

  lim est one, volcanic rock, sandst one, igneous &amp; lim est one volcanic rock sandst one igneous &amp; m et am orphic rocks – accordingly porous m edia charact erist ics changes.

  

  Hydraulic conduct ivit y varies from one locat ion t o anot her d l d f l h ( het erogeneous) and varies wit h respect t o direct ion.

   Accordingly groundwat er m ovem ent varies. Accordingly groundwat er m ovem ent varies. 

  Groundwat er flow analysis – very com plex due t o com plexit y of aquifer m edia and various ot her param et er.

  

  Com plex C l hydrogeological syst em s h d l i l

  

  Field invest igat ions - Lim it at ions

    I m port ance of I m port ance of groundwat er flow m odeling groundwat er flow m odeling . Groundwat er Qualit y Problem s  Groundwat er Pollut ion- a m aj or problem in m any count ries. 

  I ndiscrim inat e disposal of indust rial w ast es, ext ensive use of chem icals in agricult ure ( fert ilizers &amp; pest icides) and a f h i l i i lt ( f t ili &amp; t i id ) d host of ot her hum an int ervent ions have been causing pollut ion.

  

  Effluent s in w at er bodies aft er affect ing soils, ext ends t o t he groundwat er syst em t hrough downward gravit at ional m ovem ent , lat eral dispersion &amp; advect ive m igrat ion. m ovem ent , lat eral dispersion &amp; advect ive m igrat ion.

  

  Fract ures, Fissures, Joint s et c., provide addit ional preferred pat hways for fast m igrat ion of pollut ant s

  

  Wit h increase in indust rializat ion &amp; increasing use &amp; reliance on groundwat er, it is im perat ive t o assess t he w at er qualit y &amp; st udy t he m ovem ent of cont am inant s in an aquifer y q syst em t o predict t he m igrat ion.

  

Gr ou n dw a t e r Con t a m in a t ion Sou r ce s

 

  Nat ural cont am inat ion Nat ural cont am inat ion

  Groundwat er pollut ion 

  Agricult ural cont am inat ion

  Landfill 

  I ndust rial cont am inat ion

  Seepage Farm pollut ion 

  U d Underground st orage t anks d t t k

  Runoff Percolat ion

  

  Land applicat ion and

  Well Sept ic t ank m ining i i Pollut ant m ovem ent

  

  Sept ic t anks

  Unconfined aquifer 

  Wast e disposal inj ect ion wells

  _{Plum e m ovem ent} landfill Cont am inant plum e

  Groundwat er Cont am inat ion Mechanism Mechanism 

  Ch a n ge s in ch e m ica l con ce n t r a t ion occu r s in gr ou n dw a t e r syst e m by fou r dist in ct pr oce sse s gr ou n dw a t e r syst e m by fou r dist in ct pr oce sse s

  1. Advect ive t ransport Dissolved chem icals are m oving wit h t he groundwat er flow.

  2. Hydrodynam ic dispersion

  2 Hydrodynam ic dispersion

  Mechanical , hydraulic, m olecular and ionic diffusion

  3. Fluid sources

  Wat er of one com posit ion is int roduced in t o and m ixed Wat er of one com posit ion is int roduced in t o and m ixed wit h wat er of different com posit ion.

  4. React ions

  S Som e am ount of a part icular dissolved chem ical species f i l di l d h i l i m ay be added or rem oved from groundwat er as a result of chem ical, biological and physical react ions in t he wat er or bet ween t he wat er and t he solid aquifer m at erials.

Work Elem ent s for Groundwat er I nvest igat ions

• – Well invent ory and select ion of observat ion w ells Preparat ion of groundw at er level m ap – Preparat ion of groundw at er level m ap
• – Geophysical invest igat ions t o decipher t he subsurface layers and t heir charact erist ics subsurface layers and t heir charact erist ics
• – I dent ificat ion of hydrogeological feat ures of int erest w hich are likely t o cont rol groundw at er flow &amp; t ransport .
• – Underst anding of aquifer geom et ry D t il d d i di l t lit l i – Det ailed and periodical wat er qualit y analysis
• – Periodical m onit oring of w at er levels in observat ion w ells w ells

  

Groundw at er – Mat hem at ical Model



  A Model is a represent at ion of a syst em - only effect ive w ay t o t est effect s of only effect ive w ay t o t est effect s of groundw at er m anagem ent st rat egies groundw at er m anagem ent st rat egies d d

   Mat hem at ical m odel: sim ulat es ground- wat er flow

  and/ or solut e fat e and t ransport indirect ly by m eans / p y y of a set of governing equat ions t hought t o represent t he physical processes t hat occur in t he syst em .

   Governing Equat ion G i E i

  

  ( Darcy’s law + wat er balance equat ion) wit h head ( h) as t he dependent variable

   Boundary Condit ions

   I nit ial condit ions ( for t ransient problem s) Derivat ion of Groundwat er Flow Equat ion Q x y

  R y

q q

  z x y y

  1. Consider flux ( q) t hrough REV

  2. OUT – I N = - Storage

  3 Com bine wit h: q = - K K gr a d h K gr a d h

  3. Com bine wit h: q = - K Derivat ion of Groundwat er Flow Equat ion La w of M a ss Ba la n ce + D a r cy s La w Gove r n in g Equ a t ion for Gr ou n dw a t e r Flow

La w of M a ss Ba la n ce + D a r cy’s La w =

• - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

  div q = - S s

  ( h t) ( Law of Mass Balance) q = -

  K grad h ( D a r cy’s La w ) div ( K grad h) = S s

  ( h t) ( S s

  = S /  z)

Gr ou n d W a t e r Flow M ode lin g

  General 3D equat ion h h h h h h h h

                x y z s

  K K K S R ( )  ( )  ( )  

x x y y z z t

         h h h

       x y

  T T S R ( )  ( )  

  2D confined: x x y y t

       h h h

       x y s

  K K S R ( ( ) )  ( ( ) )  

  2D unconfined: f d x x y y t

            St orage coefficient ( S) is eit her st orat ivit y or specific yield.

  S = S b &amp; T = K b; R is recharge or pum ping ( - ,+ ) .

  C’ is t he sorbed concent rat ion Velocit y com put at ions ( Darcy’s law ) h K v x x

  i j 

  n is t he porosit y dim ensionless,

  

  x

  i

  , x

  j

  are t he Cart esian co ordinat es, ( L) ,

  V

  C is t he concent rat ion of solut e in source or sinks fluid ( ML ) ,

  i

  is t he seepage velocit y ( L T

  )

  

  W( x,y,z,t ) is t he volum e of flux per unit volum e ( T

  ) C’ i h b d i

  

  

  i i 

  CV x x C D x i i i ij i

  C C n W t z y x

  Ground Wat er Transport Modeling Th e a dve ct ive - dispe r sive solu t e t r a n spor t e qu a t ion in gr ou n dw a t e r ca n be w r it t e n a s

  3 , 2 , , 1 ,

) , , , (

  ) ( '

    

 

     

     

     j i t

• 1
• 3

  )

  

  D

  i j

  is t he hydrodynam ic dispersion coefficient t ensor ( L

  2 T

  ) ,

  

  C is t he concent rat ion of solut e in source or sinks fluid ( ML

• 1
• 1

      h K v y y

      e x x

  V / n v  e y y n v

  V /  x x x

   y y y

   e x x e y y

  I nit ial &amp; Boundary condit ions

Types of Solut ions of Mat hem at ical Models

• Analyt ical Solut ions : h= f( x,y,z,t )

  A l t i l S l t i h f( t ) y

  ( exam ple: Theis equat ion)

• Num erical Solut ions

  Finit e difference m et hod ( FDM) Finit e elem ent m et hod ( FEM) , FVM, BEM et c.

• Analyt ic Elem ent Met hods ( AEM)

  y ( )

Gr ou n d W a t e r Flow M ode lin g

  A pow erful t ool for furt hering our underst anding of hydrogeological

  Aquifer m edia syst em s &amp; groundw at er flow syst em s &amp; groundw at er flow

  I m port ance of ground wat er flow m odeling

  Const ruct accurat e represent at ions of hydrogeological Const ruct accurat e represent at ions of hydrogeological syst em s Underst and int errelat ionships bet ween elem ent s of syst em s Efficient ly develop a sound m at hem at ical represent at ion Make reasonable assum pt ions and sim plificat ions Underst and t he lim it at ions of t he m at hem at ical Underst and t he lim it at ions of t he m at hem at ical represent at ion Underst and lim it at ions of t he int erpret at ion of t he result s

Gr ou n d W a t e r Flow M ode lin g Pr e dict in g h e a ds ( and flows) a n d Pr e dict in g h e a ds ( and flows) a n d Appr ox im a t in g pa r a m e t e r s

  h(x,y,z,t)?

  Solut ions t o t he flow equat ions

  Most ground wat er flow m odels are Most ground wat er flow m odels are solut ions of som e form of t he x ground wat er flow equat ion

  Part ial different ial equat ion q needs t o be solved t o calculat e

  K head as a funct ion of posit ion and t im e, i.e., h= f( x,y,z,t ) d i i h f( ) x h o h(x)

  “ e.g., unidirect ional, st eady- st at e x x flow wit hin a confined aquifer q

  Darcy’s Law Integrated x Finit e Difference Met hod 

  Cont inuous variat ion of t he funct ion concerned by a set C i i i f h f i d b of values at point s on a grid of int ersect ing lines.

   The gradient of t he funct ion are t hen represent ed by e g ad e o e u c o a e e ep ese ed by differences in t he values at neighboring point s and a finit e difference version of t he equat ion is form ed.

   

  At point s in t he int erior of t he grid, t his equat ion is used At point s in t he int erior of t he grid t his equat ion is used t o form a set of sim ult aneous equat ions giving t he value of t he funct ion at a point in t erm s of values at nearby point s. i t

   At t he edges of t he grid, t he value of t he funct ion is fixed, or a special form of finit e difference equat ion is , p q used t o give t he required gradient of t he funct ion.

  FD M for Gr ou n dw a t e r Flow Eqn . q _{2 2}  h  h S  h R x , y , t

    ₂    ₂ 

  Eg. Ex plicit sch e m e : Consider a  x  y T  t T groundw at er flow equat ion for g q _{2 2 n}

   h h S h R x , y , t     hom ogeneous isot ropic aquifer

    ₂    ₂   x y T t T

     

  Using t he finit e difference schem e, 

   _{I , J} for a node I ,J &amp; for a specific t im e n for a node I ,J &amp; for a specific t im e n

   Using forw ard discret izat ion in t im e and cent ral difference discret izat ion _{Tim e in t e r va l} in space in space

   t  t

• – FTCS in spat ial and t em poral dom ain
• – choosing const ant m esh int ervals choosing const ant m esh int ervals

  x x and y n n n n n n n  1 n n

       h 2 h h h 2 h h h h R S

    I  1 , , J I , , J I  1 , , J I , , J 

  1 I , , J I , , J 

  1 I , , J I , , J I , , J  

       

  2

  2 Finit e Elem ent Met hod 

  The region of int erest is divided in a m uch m ore flexible way flexible way

   The nodes at which t he value of t he funct ion is found have t o lie on a grid syst em or on a flexible m esh

  

  The boundary condit ions are handled in a m ore h b d d h dl d convenient m anner.

   Direct approach, variat ional principle or weight ed Direct approach, variat ional principle or weight ed residual m et hod is used t o approxim at e t he governing different ial equat ion

Ca se st u dy: I D A Pa t a n ch e r u

  I ndust rial Developm ent Areas of Pat ancheru near Hyderabad in A.P , part of t he st ream cat chm ent s of Naka vagu, a t ribut ary of Manj ira River. of Naka vagu a t ribut ary of Manj ira River The area is in Medak dist rict covering about 500 sq km spread over in t hree m andals Pat ancheru, Jinnaram and Sangareddy; More t han 600 indust ries in t his area dealing w it h p pharm aceut icals, paint s and pigm ent s, m et al , p p g , t reat m ent &amp; st eel rolling, cot t on &amp; synt het ic yarn &amp; _{Nakkavagu Watershed Medak District , A.P. N} engineering goods w ere est ablished since 1977 _{14000 12000 Ismailkhanpet Ismailkhanpet Arutla Chidrupa 2000 2000 4000 4000 m m m} As part of cont am inant t ransport st udy a flow As part of cont am inant t ransport st udy, a flow _{10000 av N ak k ag u} m odel using an FDM package Visual MODFLOW is ₈₀₀₀ developed _{4000 6000 6000 INDEX INDEX Stream Road Ganapathigudem Mutangi Pocharam Bachuguda}

Ca se st u dy: I D A Pa t a n ch e r u

   The gr oundwat er rechar ge varies from 100- 110 m m yr ־¹ for an annual rainfall of 800m m .

   Perm eabilit y values as high as 50- 80 m / day were found in t he alluvium around Arut la village alluvium around Arut la village ₂

  

Transm issivit y is found t o vary from 140 m / day in granit es t o

₂ 1300 m / day in alluvium .

   Observed sit e dat a show s t hat t he t op w eat hered aquifer is having Ob d it d t h t h t t h t t h d if i h i 10- 15 m t hick is underlain by fract ured layer.

  

The sim ulat ed m odel dom ain of Pat ancheru I DA and it ’s environ

consist s of 55 rows and 65 colum ns ( sm all rect angles, consist s of 55 rows and 65 colum ns ( sm all rect angles 2 5 0 m x 2 5 0 2 5 0 m x 2 5 0 m ) and t wo layers covering an area of 16000 m x 13500 m .

  

Ca se st u dy: I D A Pa t a n ch e r u



  Top layer consist s of 10- 25 m t hick alluvium along Nakka vagu or weat hered zone in granit es and is underlain by 10- 20 m fract ured zone.

   

  Vert ical sect ion sim ulat ed in m odel is Vert ical sect ion sim ulat ed in m odel is having t he t ot al t hickness of 45 m .

  

  Wat er t able in t he area has an elevat ion difference of 75 m w it h l t i diff f 75 it h sout hern boundary near Beram guda having a wat er t able of 570 m ( am sl) and lowest wat er t able elevat ion of 495 m elevat ion fixed as a const ant head @ Manj ira river confluence. @ j

Ca se st u dy: I D A Pa t a n ch e r u

   By using t he visual MODFLOW soft ware ( Guiger and Franz, ( g 1996) t he aquifer m odel sim ulat ion is carried out .

   Model is calibrat ed bet w een observed dat a &amp; sim ulat ed result s. Wat er t able configurat ion of Novem ber 2003 was adopt ed for t his purpose.

  Com put ed &amp; observed w at er level for t he st eady st at e condit ion is shown in Fig.

   Good agreem ent is observed bet w een com put ed &amp; observed

  . w at er levels

Ca se st u dy: I D A Pa t a n ch e r u

    Using MT3D: Values for dispersivit ies ( Using MT3D: Values for dispersivit ies ( ) are assum ed as ) are assum ed as 100m , 1m , 0.01- based on field observat ion.

   A const ant TDS concent rat ion at different nodes of Nakka vagu was assigned varying from 4500 m g/ L at CETP g g y g g

Pat ancheru t o 1500 m g/ L dow n st ream near I sm ailkhanpet .

   Dow nst ream concent rat ion of t he order of 1500 m g/ L is observed all along Nakka vagu right up t o confluence w it h Manj ira river Manj ira river – based on 2003 m easurem ent s based on 2003 m easurem ent s.

   The t im e st ep used in t his m odel is one day. 

  Cont am inant predict ion is done for t he year 2007 1500 mg/L 1800 mg/L 1800 mg/L 2000 mg/L 4500 mg/L 500 g/

Re fe r e n ce s Re fe r e n ce s

  J.V.S Murt hy ( 1991) , Wat ershed Managem ent , New Age int ernat ional • J V S Murt hy ( 1991) Wat ershed Managem ent New Age int ernat ional • Publicat ions 

  

Anderson, M. P. and Woessner, W. W. ( 1992) . Applied Groundwat er

Modeling- Sim ulat ion of Flow and Advect ive Transport g p , Academ ic Press, , , San Diego, CA, U. S. A.

   Bear, J. ( 1972) . Dynam ics of Fluid in Porous Media, Am erican Elsevier Publishing Com pany, New York.

   Bear, J. and Verruij t , A. ( 1979) . Modeling Groundwat er Flow and Pollut ion, Kluwer Academ ic Publishers Group, Auckland, New Zealand.

   Eldho, T. I . ( 2001) . Groundwat er cont am inat ion, t he challenge of pollut ion cont rol and prot ect ion, Journal of I ndian w at er Works ll t i t l d t t i

  J l f I di t W k Associat ion, Vol. 3 3 ( 0 2 ) , pp. 171- 180.

  

Freeze, R. A. and Cherry, J. A. ( 1979) . Groundw at er, Prent ice Hall,

Engle Wood Cliffs Engle Wood Cliffs.

   Todd, D.K. ( 2001) . Groundwat er Hydrology, John Wiley and Sons Pvt .Lt d- Singapore.

    Wang, F. H. and Anderson, P. M. ( 1995) . I nt roduct ion t o Groundwat er Wang, F. H. and Anderson, P. M. ( 1995) . I nt roduct ion t o Groundwat er Modeling.

Tu t or ia ls - Qu e st ion !.?

   How groundw at er condit ion can be im proved in a w at ershed.? in a w at ershed ? .

    Discuss t he im port ance of groundw at er in Discuss t he im port ance of groundw at er in wat ershed m anagem ent plans. wat ershed m anagem ent plans wat ershed m anagem ent plans. wat ershed m anagem ent plans

    Discuss groundwat er resources Discuss groundwat er resources im provem ent by rainwat er harvest ing &amp; im provem ent by rainwat er harvest ing &amp; i i t b t b i i t t h h t i t i &amp; &amp; art ificial recharge. art ificial recharge.

  Prof. T I Eldho, Department of Civil Engineering, IIT Bombay

Se lf Eva lu a t ion - Qu e st ion s!. Q

   Why groundw at er is very im port ant in wat ershed m anagem ent ?. wat ershed m anagem ent ?

   Describe different t ypes of soil w at er. 

  Different iat e bet w een unsat urat ed flow s and Different iat e bet w een unsat urat ed flow s and sat urat ed flow s.

   

What are t he im port ant w ork elem ent s in What are t he im port ant w ork elem ent s in

groundw at er invest igat ions?.

    Discuss groundw at er qualit y issues. Discuss groundw at er qualit y issues.

  Prof. T I Eldho, Department of Civil Engineering, IIT Bombay P f T I Eldh D t t f Ci il E i i

  IIT B b

Assign m e n t - Qu e st ion s?. g Q

   Explain how t o assess groundw at er pot ent ial?. pot ent ial?

   Describe different t ypes of aquifers &amp; classify aquifers according t o charact erist ics. classify aquifers according t o charact erist ics

   Discuss fundam ent al law s governing groundwat er in a wat ershed. groundwat er in a wat ershed.

   How t o m odel groundw at er flow ?. 

  Explain m aj or m odeling t echniques for groundw at er flow ?.

Un solve d Pr oble m !. Un solve d Pr oble m !

   

  St udy t he groundwat er pot ent ial of your wat ershed St udy t he groundwat er pot ent ial of your wat ershed area. area.

     

  Collect dat a relat ed t o aquifer, soil, land use/ land Collect dat a relat ed t o aquifer, soil, land use/ land Collect dat a relat ed t o aquifer soil land use/ land Collect dat a relat ed t o aquifer soil land use/ land cover et c. cover et c.

   

  Obt ain hydrogeological m aps &amp; t op sheet s of t he Obt ain hydrogeological m aps &amp; t op sheet s of t he w at ershed. w at ershed. h d h d

   

  Assess t he groundwat er pot ent ial based on available Assess t he groundwat er pot ent ial based on available dat a. dat a. dat a. dat a.

   

  Get t he dat a relat ed t o num ber of wells in t he Get t he dat a relat ed t o num ber of wells in t he wat ershed and st udy t he head variat ions wit hin t he wat ershed and st udy t he head variat ions wit hin t he wells. wells wells. wells

   

  Discuss how you can im prove t he groundwat er Discuss how you can im prove t he groundwat er availabilit y in t he area. availabilit y in t he area.

  Dr. T. I. Eldho Dr. T. I. Eldho Professor, Professor, Department of Civil Engineering, Department of Civil Engineering, p p g g g g Indian Institute of Technology Bombay, Indian Institute of Technology Bombay, Mumbai, India, 400 076. Mumbai, India, 400 076. Email: Email: Email: Email: eldho@iitb.ac.in eldho@iitb.ac.in eldho@iitb.ac.in eldho@iitb.ac.in