
J. Jpn. Soc. Soil Phys.
?1
No. +*1, p. +1 ,0 ,**1



 !"#$ % &*ῌ**ῌ*ῌ *Analysis on Hydrological Aspects of Shallow Groundwaterin a Catchment with an Agricultural ToposequenceAn Implication for a Risk Assessment of Excess Nutrient
Discharge to Surrounding Water Body
Ippei IIYAMA*, Kenji MATSUMORI**, Hideshi FUJIWARA* and Yasuhiro NAKAJIMA** National Institute for Agro-Environmental Sciences, Kannondai -ῌ+ῌ-,
Tsukuba, Ibaraki, -*/ῌ20*., Japan** National Institute for Rural Engineering, Kannondai ,ῌ+ῌ0, Tsukuba, Ibaraki, -*/ῌ20*3, Japan
Abstract
In a series of agricultural land uses over a toposequence comprised of upland crop ﬁelds andlowland paddy ﬁelds, hydrological aspects are essential to an understanding of impacts ofagricultural managements on groundwater environment. The objective of this study was toevaluate amounts and ﬂow paths of shallow groundwater discharging from an agricultural
catchment using a physical model.
About 0+῍ of the shallow groundwater percolated into the deeper aquifer and exited thecatchment without passing through the paddy ﬁelds.

Only the rest of the shallow groundwater,which was within 1* m of the paddy ﬁelds, reached the paddy ﬁelds after +. years of travel.
These results indicated that in a convergent-shaped catchment a large part of leached nutrientsfrom upper crop ﬁelds can leave the catchment without being consumed in lowland paddy ﬁeld
area.
We deﬁned a risk of excess nutrient discharge from the catchment as a probability that 3/῍ ofthe recharged groundwater bypasses the paddy ﬁelds, assuming that the most inﬂuential parameter falls within an uncertainty range of two orders of magnitude around the value giving themodel’s deterministic solution. The evaluated risk came to ...2῍ even when the uncertainty
range would include 33῍ of the whole population of the parameter.
Key words : nitrate nitrogen, physical model, parameter uncertainty, shallow groundwater,
toposequence+    EFGHI@JKLM<N. /OP
:0QRSTU$V; AW=. /01XY-Z !"#$%&'[\]^@\]_`56aNb@c. GH()*+,-. /012345637489

I:defgRhijkNl. [6kNmnRo

:; <=. >?@AB'"#CD-.

pNlqer'$TUL:;* s tuvwx y-*/ῌ20*. z{|}~ -ῌ+ῌ** Ovwx y-*/ῌ20*3 z{|}~ ,ῌ+ῌ0 : 1 . ?qer. fg1. EF. k A ` +*1 µ ,**1

18 NO--N     

!

Hedin et al., +332 &' NO--N

"#$%

()

, 

 *+%,-. /0,+Cr  stuvwxv1 yD
1; 

z{ |E}@-,.+ ha

q2 +*~+* m12 Hill, +330 + 3$'4fW,

FG/HI8i 567, UJH

F K9JHTqH NO--N ()8'29:  Bohlker and Denver, +33/ ;LJHq M*^, ῌ+;

Devito et al., ,*** ; Hill et al., ,*** &%,/./ m 1C,;

;

/ C
FG/ +/.0

FKN -.+῍  +/.-῍

1C,; G/ ,*,/ m  O  '<=

!" >? # $@AB O-PQ$%,; G/ +2 m

%6 &'(6C, )*$%   ./ 12> D + (EF  G,H-,;F R 8^./  IJK0$% A1ῌLM +32. ;,,2N +33- 67; .

NO--N ()34 5OP 8.\ k8  ¡¢ q2-£yH

Q .6 +32- ; .6 +321 ; .6 +330 '^,; +¤ ¥¦§ ST i¨5U ©yH^ ª

OPQ .6ῌR. +33+ 67 S7$%T2 «of +1

:;<]^_ `ab# =cK0$%;++ ±-k-£X²^ ῌ,V

°^,W 
q

HI^

,;

d&"> + (EFA
-V Tq¬­ +*1

qCr®¯8i -£ ^,; ῌ+UV* ,W XYQZ8[$% .6+332; \9  TeG,Hῌ- ++ ±- k-£ . -£8Y k

Ufgh<] i?^ j@ kAlm

8°^,; ῌ, 

nop8B'^,AXYQ q2  :8`[^&'a^,;2 &% . -£8 ++ -£ ] S^^,; k
yHῌ+Fig. +

Cr_º\++ -£ ³%,k 8Z

FD

Te\

]



',´µ !"¶·¸o!¹ +331

Tq

*»¼

Location of the study site and the deﬁnition of the catchment.

q

@A : B C¸¹a bd>º)

A:T»¼

19

A 4 ,Bw @ C ) ῍- D-Cg, )EF)" .Cg )1)IJ)" K

LMLNO P

GH+ EF)=%2 

@IJ QC;<) Cg ) Gr ) "R0
L .Cg ) SL2?
)T" >@R0L>1

UVW)9 X8 .Cg )YZ[\P]+,2 S \+^_L

Z"` +-./ m +, a

b

c

d

>S Z )e1 8X+,2 fg+
 hi$j2k8@Xa

b

.Cg )

l

m9` +-./ m +no p@,- 
ῌ,
Fig. ,ab

(!<®

 qrst8
 bSoil types in the catchment.

 W+ W, W- 

W++ + ῍+ (!u W,

vw +* cm]vw 2./ cm, c

PVC x9@ Z_ W+ W, W-  W++

KLML+ 0.+ -.-+.3 ,.* m +, ' PVC xy@ _0z W+  W, +x/0 +./ m {+ |+W-  W++ +x/0 +.* m {+ |+ KL

ML}W~ 9d   
2 +33/  3 /0 +331  ++ {+ +*  +

q/0

o

,2!

"9 +330  ++ /0+331  / {+  q/0

9!b#  $9%&Xa b'ld()  9&8X N8L?*+, 9-X0  $ ./ ! " " 
 0. Q/"R0L
_0 10L)2 3
49&8 56

 0῍+ 97 892

( :T ῍. 9J 9 ¡..3 kPa {+ ¢£;9 ¡.3 kPa {+ 2 KLML

ῌ-

a b
() ()¯
±²³´µ +331 ¶·®

- °a bS W+ W, W-  W++

.

ª

.

!"#$%&' ()*+,
A ) B )-./012 3456 78

9:4;<= 78>? @ABC ,9&8X§¨

(H
(ῌ
(H῎
©
H¡BKs
(t
(x ῍
(x ῏



 ῍+   ῍-< ¤7¥9 ¦ .

<7¥9 Y

Fig. - Soil horizons observed in the catchment.

  

(ῌ(H῎
H¡BKs
¡pªr
(y ῍
(y ῏

SS+ x  y : a b«T¬ H :ῌ= «L¬ t : ­m «L¬ S : > ?" «L- L¡-¬

B : .Cg )m «L¬ K s : 56

 «L- L¡,yz ºN » +*1 ¼ Q,**1R20

῍ῌ+ yz9HI
Table +

Saturated hydraulic conductivity values for soil horizons in the study site
(after Matsumori et al. +331).

Type +
Soilkshorizon
(m/d)
Ahp
Bw
,Bw
-Cg+
-Cg,
.Cg

Type 1Soil
kshorizon(m/d)+43*¹+*+-4-1¹+**,410¹+**+42+¹+*34/*¹+*/-4/.¹+*+ῌῌ.
Fig. .

r :  L L-

Ap
A,
BCg
.Cg

-41,¹+**.4.+¹+**-4/.¹+*,-4/.¹+*+yz9HI

Type +*
Soilkshorizon
(m/d)
Ap
,A
-A
-Gr
.Cg

LMNOP

Type ++
Soilkshorizon(m/d)-41,¹+**,4,/¹+**-4,2¹+**.4*0¹+*,-4/.¹+*+

Ap
Cg+
Cg,
,Gm
,Gr
-Gr
.Cg

34/*¹+**,4/3¹+**+4*.¹+**
1412¹+*240.¹+*.
24,3¹+*.
-4/.¹+*+Q¶·/ +331R¸

Soil water characteristic curves for soil horizons in the study site
(after Matsumori et al. +331).

T+ p : .Cg  ῍/

{i Q¶·/ +331R¸, L- L, T++T   ῌ !"#$

%&' +, ()*+ +33/ , 3 -./ +331 , +, -0
123$ S, B, Ks, p, r ' 45678
$

g 9 hiI`j$ k` lm93`nL S c8$
B ' .Cg  o<F ,. , p qrs$

HIt u +-./ m
Ks ' xyz9;vw# $
{i Qj῍+R 9|Q῍- }~R +W =6X [wfg$

S ' 9:;9<=>?@ABCD8

95t S {iy 

EF@;9G$F F 9HI JKSS`' VW:hLMNOP Q῍.R ./7S$ TU BCDVῌyu]=mlI

W=6X YLZ 9I[\$P]L

$yz ¡¢ £¤:¥/m¦SlI

ZI^_ 9HI LMNOP S`a L§¨© I@ ª«/ Q+33*R

Zbc$ d BCDVW;9G$F:­®@v6 ¯°/ Q+322Ra eGaLZ=6XGL`f¦¬ y ±m²$ y³ ´./y µ

T : UV¹ºz{PQ »1¼VW

῏ῌ/

VWC{Rµ¶!BC45῎P῏
BC45 ῏  n BC·[d<¸Fig. /

Discretization of the catchment withthe boundary conditions (I) and (II). n
indicates a normal outward coordinate
deﬁned at any point on the catchment
boundary.







῏ῌ0

e0 S® !jk^#, ® !b¸

Fig. 0 Comparisons of changes in numericallyreproduced groundwater levels (thinlines) with measured ones (thick lines).

 

 -Cg   .Cg !"#$%

&'()*+', !-. -Cg /01 !'2 !3,uvwx9 !&,BC45 ῎ z{D 78 P ῏
8:78 &"\.[78  , ;&p  .Cg 45.-6-3,,

7 89:;<=>?@A Cloke

et al., ,**- ; de Vos et al., ,**, ; Batelaan et al., ,**-'!& Batelaan et al. ,**-  BC-.D<=>?@ p BC-

21

EF

, ῐ/ ῎ |45 ῏ BC[ < n !&+ \. * 45=,45 >0?@&, rI* 45Hῌ Vd 7,

O7,q=rst)PBC45 0vM !'2GH ',῍pIaHJBWC{DEF-.&, &+ Oe

῍ KL a  !"# r  * M3, +33/ $++ N ,/ %-. +330 $ + N +3 %O W+ PQ+33/ $ 2 N

A-. 3 Nle08Bjk& V&R '+ S'(OT7, S, B, Ks0)&6-3, W++ "G - 6e0
!HE]!63,u6G3+ 8B45!&,

UVW9' *.***+, XdayJ+Y !'2)*,VWv I "63,6

W+ Z+, -[\.]^" /Il8#J#!&+l& I_`^#a p bcd, !MK&+uvwx9

 !'2 ¡¢£¤r  e0)fghi01d6-3,

 ', L¥¦§6¨©MªN«O¬P­®!-. e02jkl<m>nmo¯#¨O# °L¥¦§6QI

pq=rst!& VWuvwxy!z{3|!&#±¦§6*.#,!I<4)T7,!²³+ J#T7,<m>nmop}545 . 6e0~'+78960M3,!-. W+ W, W- P W++ 'a#- e0-. -* cm G3

',



.ῌ ῎

°

῍

ῐ0  e02jk¯´M!*  +*1  9,**1?

22

ῌῌ1Fig. 1

ῌῌ2
Fig. 2+330 l ++ mq +331 l / m!1QS |XVQ 9a? > 9b? X W+W- N>

Simulated ﬂow paths of the shallow groundwater in the study site. (a) Horizontal section over the study site. (b) Vertical section along the line passing
through W+, W, and W-.

 W+  W,  .Cg  W-  W++  Cg

WXV 

Spring water discharge rate in the period from November +330 to May +331.
Circles denote the measured data while the thin line shows the predicted one.

  S  .Cg

 Cg 
#$%& '(

 W- !">ῌ1  1QRS!TUVWXV!"#Y- WXV Z[!\] ^_8 `ab('>cdTTU-1QRS ef! / m-ῌd)!*+ W- ,-./0

ghi!jPk +330 l ++ mno  +331 l - m

123405678 9:; /. <=!>ῌ2 9a??

poq . mno!rstui!vwxy z{W@;ABC DEFGHIJ( KL W- !
4MNOP%&)-Xu|X}  ~-1R40 W

!1340  !=789>ῌ

qJ : rs»¼^ Y12 ῌ,+"12%&   +332 6¹

Table ,

Time-averaged velocities of the shallow groundwater ﬂow at the four measurement wells. (a measured value wasfrom Matsumori et al. (+332)).
W+

W,

W-

P 
^

JKL

23

167

bG  6Y

YHIJKL

M

GLb{Qf Q P<jR Nc P<jR O
P8bkl ῏ ,ῐ/ iQWRR O
P86xSZT&UKVxQW?
1 5  X^ Y1?xf]&b
YHQfMean (m/d)
14+,+*. 34+1+*- ,41-+*,
S.D. (m/d),4*++*. ,4/-+*- +4+-+*,
C.V.
*4,2,
*4,10
*4.+Measured* (m/d) º/403+*º*  +332

,ῐ2 b  W+ W, W- \M EP8,  W+ W, W-  &
Z\ 6\? >R & R 
 " t8HIW]&B&gdf/, 

Z[-

 RC

0+ῌ 

'*Yi.P<

jRW &F Z ] F\2 a

ῐ,    
 3.+1+*- m ῌ d  W, /.01+*- 

/+  ()* 

&bHI?,,ῐ3 a
!"#$%& '+"    ,ῐ2 !"#<jR 

R = R

&\ ] dQ S

/ 0123   4 5 ῍

wQ¢.]xC   89& .CgS  *.+ c

Z , c -: bwQ¢ B st R£P

KL§

p 167 89 :; . <=>  \ ¡

$%& '()*  -. !"#$%&?@A B?_ZQW`b.[W B] -. 5 ῌ e ]^ S, Ks, p, r h? ,ῐ0 a & 0mῌd  +332 / W ]^

- o&x¤¥¦bw ,ῐ. .Cg¨ $bd? !3 b B st R O

P8bbwZ\]&6,ῐ3 b ¡

 .Cg 89

4 3  D?@A EC 

Ks  *.+ cZ +* c -: bd P<j5῍RCb Kse©fgyª =p 33  - F&D?@A <=>

! 89"# G%!3  ,ῐ.

H)IJ(KLMNO* * $% PQC  &?"R ST&U V'()W

X '*YZ 1* m +, -:.[ /0!

167

RC&x 

P<jRC>«\ Ks

RC+* c+,&e©6R6

R h¬b^ Y  GD Q¢ B

st P<jCb5 ῍ ­\?gy,ῐ3 c p W5 ῍

89 a  , ®¯b" +. 1+, \ 6\? ] ^ Y 23

wQ¢ 89 a

_4`5

89&? p be©W8Z °xTZ\ a

6ab .Cgf&gdf -; ῌ .Cg78cd?P*YZ

e9:Q- h Rie P<jR ῍ kl ῏ ZR ῎ = RBfmf+"  &]n ῌ  ++.*2 m-ῌd - o>

0+ῌ p qr?@ ῍  ,.+- m-ῌd +,ῌ ῎  ..32 m-ῌd ,1ῌ

a ij. cZ / c&= RC 

RC&x * k P<jRCbNc,ῐ3 d  
,

l4C r

st  r-23..- mmῌyrbwmWRC+" 

\ - h R  re©&&

xn?e©b B ,X i±\]f stZ ^ Y  
Au_4`5 6a ] ^ YW]&bBa 23CB xb

RKLe  ]e23
'*Y vw

Dybz&{

Qf ?! ^ Y| }E ~e F?DZ\ r¶ Cbb` o²³ ´µ -* 1" 1"m·+"   +*,/ mmῌyr*.1 cZ

 +.2 c -:\]&¸g ]fpqW-:&?

*.,/ cZ ,.* cHIº» \ R +*1 ¼ i,**1j

24

ῌ3

 - ° ±²³ iaj 4 ibj .Cg 9¤4´e icj ¢£¤´e
idj ³  Z<7 [¥I4  A, + !$%µ A³

Fig. 3

Sensitivities of the model outputs to the changes in such input parameters as(a) speciﬁc yield S, (b) saturated hydraulic conductivity Ks of .Cg horizon, (c)percolation coe$cient a in eq.(,) and (d) recharge r. Horizontal axis of graphs
show the ratios of the parameter values to those determined through reproducing the measured groundwater level changes.

   ῌ 

/-



   ῍



a !"#$%&



 


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polder. Journal of Hydrology, ,/1 : /3῎11.
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26

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forest riparian zone : Interactions between hy-

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