
J. Jpn. Soc. Soil Phys.

No. +*3, p. /10/ ,**2

TDR 



4 5µ*ῌ¶m6·*ῌ23¸¹*
Measuring Temporal Changes in Flooding Depths in a Rice Paddy Field
Using Time Domain Reﬂectometry
Tomotsugu YAZAKI*, Yuki SHOJI* and Kosuke NOBORIO** School of Agriculture, Meiji Univeristy, +ῐ+ῐ+ Higashimita,
Tama-ku, Kawasaki, Kanagawa ,+.ῐ2/1+, Japan
Abstract
Measurement of temporal changes in hydrological condition such as a ﬂooding depth is needed
to understand green-house gas exchange between paddy rice ﬁelds and the atmosphere. We
introduced a simple method to monitor the ﬂooding depth using time domain reﬂectometry(TDR). The results of laboratory experiments indicated that water depths measured with TDR
agreed well with those observed when the water depth was estimated assuming that the second
reﬂection of TDR pulse occurs not at the end of the rod, but at the water surface with large water
depths.

The laboratory experiments revealed that TDR provided precise enough water depths sothat ﬁeld experiments were conducted.

Water levels measured with a ,*-cm long TDR probe

agreed well with those measured with a pressure-type water gauge with a root mean square error(RMSE) of *.,2 cm.

The water levels measured by TDR, however, might be a#ected by raindrop

depositions.
Key words : TDR method, electromagnetic wave, rice paddy ﬁeld, ﬂooding depth, continuous
measurement

KLM8N"O+C PQ Nadler et al. D,**-E+ !" #Time domain reﬂectometry DTDRE
Topp et al. R TDR

 +32* .

$#%& '()*+,-./0!1C Tang et al.

6!1  STD,**+E UVWUX.YZ)[\ ]!" UVW".^!"_  `a!b*+cd.c+eTfW6*+YZ)[\gh)i

.jT1C TDR#pJUVW qr*+#"k ῌ lm cd.no$s!1C t1uvwx%R&O,- ῍ yz{[)|}R~

Thomsen et al. D,***E "j49)[ FG'(.6 )ῌvw - jO,!" (HI !1C J 9:;- ῎ *+R,6+,- ῏ 23 4!"5*+,-6 78 +., m 9:;.

9)[6 -. -.)R6+,

9:;<= >?*+1@#A)B) .!1C-j6+C TDR


-.)

 pJ#/ 0*+19)[%j.O"

.c+-R tT"O+C #)¡¢¡6  pJ£

Noborio D,**+E Jones et al. D,**,E 23 D,**-E j(-¤¥¦§/ROC  .¨+,NJ©ª «¬8N1OC

#/  ¥­® I~¯

TDRST1_°±²*    ,+.ῐ2/1+   
 : TDR      j.³´*+ DHou et al., ,***EC ¥­®

+ῐ+ῐ+ 

58

+*3  ,**2

῍ῌ+

TDR 

Fig. +An example of TDR waveform.

 !"#$%&'()*+,

-





m c  ./0 ,1 *.- m ns+&2345  - 6 78t  .4 L &9:3#3;<=&>?@A,B3CD4EF? F

GH ns ,5 TDR , I,JKLM, NGOP&234Q,5

4RS

.4&93T U, V WXY<&!Z NGB4[ῐ+ #\Z@ ctῌ, &7]<L^_<8 [ῐ+ +"`@Z a##b@ cKdef

WgXh7f8ijX [ῐ+  , k$ 3O

8Y%E&'GlmnhXopBqrs(tuvF( La 3

@Zp TDR &!ZE&wB4x,,5La ctῌ, & ῌ y#-.@ lmnhXoT /?@ZdzX{K&!Z@ TDR , -&B,|}

e

>!3B

q~&+3M4,|, 0B#16?@)* + e 

ῌLa῎,
῍L῏

῍

#3

D,5 F Thomsen et al. ,*** ,

2 , &w34&

5O67e<&>!3, vF(

0,5@ )* +&B3M,-&3T# 8O7^ &B3 TDR e<4)**} Campbell  PCTDR  CR ,- X %7

@Z| e<)* + ¡y#^ 4>*OZ¢&45 2:;, ?@£p+ Schaap et al., ,**-B! - ¤y TDR e<&>?@-

P&B ¥¦8#"`@ZV y ῌ῎ῌ ῑ ῏ῌ ῐ῎῍ ῑ ῏῍ ῎,῍῏῎etotalB<)§ a B#bt¨=>A?#©Z@rª@, «¬3,ῌ ῎
TDR , )*+O9#῎MM, etotal 9­®)* + L+ L, ¯°+῏, #±@Ze+e, ¯

° +  , )* +,5 2 , + &0+40A²)*, &@e+ &0)* ++³B|ZM&C! e<&´.

eair +.* e, &)* + ewater )* ewater )* +F+¯+&µ3

¶ Tw ·¸¹e<&´.)* + e ῌ ct ῎,e῍,L῏¡yF+£pM4,|Weast, +320 ; Pepin et al., +33/ῌ Topp et al., +32*  L 

ewater

12./.+../13+*-TW,/+.+3
+*/TW,/,,.2+*2TW,/-῏

89OPF : TDR 27%$%& QR'

῏ῌ,
Fig. ,!"# TDR $%&'()*+Laboratory experimental design for measuring water depth with the TDR technique.

ST, UVW4"7 S Lair-L+, %-ῌ ῎ ῍ ῐ ῑW4"7 S Lwater-L, X6YZ%& 5X

 -., mm

75 ῌ )5 ῍ )@T,
La 
L


4# - )῎

῍La ῌL/L
air
῎L


῏
ῐ





TDR [P\4#+ PCV ]^_ -., mm ,* mm  -  ,

-`a6723bcd, 5^_HefghWij4#+ k 

567+ ῎ ) Lwater l"mX75,
Lwater-59

 /* .
῏

noP\pq, ri5noP\p Wuv4#+
89, wx!2 TDR

7+5{}, *ῒ,23~r`z6#+ ,

 '4#, UV5W4# :'Ss#%5&4#+'X7+ Mojid et al. ,**, ,  y` yX7, ~r %)`*S675, p

A  E g ,  r6¡¢£0¤Ts7{5¦4"7+89§, { 152,`%-5675©4

E

g

#+ 4#` ῎ ), ῐ )«z¬¤Ts7+ 
La
L


ῐ

῍La῏
῎Lῐ



!, V( ,*0!4#+ 234# +* cm, +/ cm, ,* cmTDR +4, Ksts [P\, ,- +/ cm1,+ cm, &S +, cm./ PpoP,-k, ~rz4[P\¥xcd4,
Campbell ¨]TDR ( TDR+** 5*ῒ,23

Wu4#+ K4, %& *.- cm @T +* cm

3ª

*.+ cm ­l4®S¯6`T%&5 TDR +**°$

7 L a ῌ L 5K

5z

%'4#+ * ῒ ,TDR 5D± RS,-,C'4#+ 6N, LaῌL
ῑ



89, ῏ )5 ῑ )2:;4# Lwater

&4#+< %N", TDR %:5$)%23

'²oP\pWu4,

ABCDEFGHI PCTDR ", LaῌL 

ST, ῐ )%& Lwater mX75,
Lwater-y%

:"%&`'z7{5!"|#4723 TDR 4#5z, % %W4#

567+



,

KstsWu4, j4, Hefg]v³´4, Ksts %& / J'4, K LMK %&N 7 LaῌL
54#+
< ,**1
T 2 = ,3

1=,

 > ? DOY +2- @DOY,.+ 4#+ ,**1

0 = +1

DOY+02 : µ@T( + ¶ , ·5¸¹6º456 7 +*3 8 ,**2

60

ῌFig. -TDR 



The dimension of a TDR water-depth meter installed in a rice paddy ﬁeld.

  TDR 

1/ mm !

= -- cm >?@ABCD?EF%GHI)J

9%2:(;<()%K LM=N
M=?./OP6NQ/)R῏- : S TDR  ./   L N

T 2:UL+,X

YZM=[/\]^A_ C`Q

) abSc dXe [/L M=fg0VW2:(;[Ngh(ij 45k:() [l a>@C mna ./ dXe [/ XeKCoNYZ[/\] pfgq!r K DOY,*0  +0 s /*)u; / cm v9%w

 WL cm K d z TDR 0 Lwater

0 mm xQI) R῏- y) a>@{K4N|g} +,~X 

Ky)K I *(;/a () a TDR  B SDMx/* Campbell #$ (;"CR,-X, Campbell #$ %&'() TDR+***(2:() Q/st

fgS\u;()
῎

WLLwaterLwaterrefWLref)( Lwater, ref

WLref K Q/st aa%K0

2:() DOY,*0  +0 s /*

  Lwater012) a\]() TDR ; TDR 

3 cm %Q/ Lwater  ῌ %./ 

 LaῌL 2:() Ys  KADEC-

K 

MIZU, F#$  TDR 

().* mm, != +** cm,

 ¡%K TDR ¢£K ¤¥vl ./ cm ( 2:() a

I/ £§¨¢£ RMSE

()>@$2C 
L¦* cm 0LlI/3

2CJ TDR r)u; / cm v9%w

Ypfgq!

%©()

0 mm xQI; TDR . C CNYZ[/\]()

.+ y)  ª  45 W T«¬-% c­®y.¯ No. -.-T, °Lwater+,! +* +/ ,* cm -./0123

±$²³$ %db´b2:() abgK

%2:(;ῌ " CR,-X, Campbell #$ µu; /¶·db´bR῏. av

 TDR  TDR

῍ \u;()0 L water b ©. 1¸U;<=>? : TDR @75+ AB  CDῌ.


 

Fig. .

E 
 +.* cm !"#a 0  b 2 

FGH I ῌ  +../$,*.*%

YZ8(/08

 8 0+PQ῍  [ Lwater

\T



+ : + h7iM +.* cm 9j

D7 ῍ 

[ L water

rsrtuv,- root

mean square error RMSE

wx *./+ cm *./-*.-* cm  y



RMSE

s8 ῌ 7TU TO9

. RMSE 8XM῍ !῏UT Lwater !#+O7#+
\T 

Lwater8(/U/ 

8X0+75K(/0 4῎.῎b

8X0+ Lwater 8

!j

8XUPQ Lwater 8m

n op!qN#0+M3123+7(/U/TDR

bcd_ 4῎+

¢g ef Mojid, ,**,

8]^_`aZ#£g ef ¨© Lwater    ª«#+ s8X0 ¬7i­U/ mn῍±ῑ8 +
TDR

I+¥¦ L water¶[ Lwater

LaῌL 8 + K 

TDR,-.(/0+O0+PQ ]^_`aZbcd_ ef
op!qN Lwater 8!'()*#+

,-.(/0+123+TDR 



A7zN+ {ΐ

e

.,



g

j7kl#+mn

[



e WLP e [ e WLT!4῎/ 7"#e8 ,.* cm 9j / WLTWLP P~[TDR {ΐ e
TDR

e

4῎ /

e WLP 8 +.* cm 9: /e WLT/ῐ 7j[ y
WLT 8 WLP !j

567 WLP 8 +.* cm 9: /7 WLT  WLP

8(/0

;< }῏[TU+ TDRKa? ῌ123+ ;<}῏[TU+ TDR a?



! w !.7a>?>b][ w¡ῐ L a !

#+8 8 7¤[TUU¥¦]^_^_`aZbcd_

ef!

`aZbcd_ ef8 ,ef7 T[
y6O8I+ w ®¯ °e(/0

123+ y WLP 8 +.* ῎ ,.* cm

/7,., 7i­0 ῎ ²+

WLT 8 WLP !j³´7µzK+., 7i­/ &

8XM· Lwater8mn op!qN#0} ῏ [ ++M3123+*.- cm !jTU 37;<
GHz ¸

 La

8RSTU+ VW3 ,**/ O 567 8X

WLP 8 +.*῎,.* cm

iM8

8 ,* cm

῔J7K LMNῌ  [ Lwater+* cm +/ cm ,* cm 7|[Twx *.+3 cm *.1- cm +.-0 cm  ῍ !}6§ TDR  Lwater

The relationship between manually-observed and TDR-measured water depths for di#erent
lengths of TDR rods. TDR-measured water depths Lwater were calculated (a) with Eq. (0) and (b)with Eq. (2). Dashed lines show the water depths of + cm.

 Lwater   cm

61

ῒ8X0+8y 4῎/ M3 WLP 8 +.* cm 9: /

WLT

62

89:;< = +*3 > ,**2 WLP #('?@%ABC A# WLP

D?E

 +.* cm N# IJKOP/0

R ST UVC & WLref # DOY,*0 ?

QK FGH?IJKBL?M TDR WXYZ[\]^%G?@TR% AAN#_?IJKMab RUVC cde # FG. DOY

TDR WXYfZIJK\]g + cm PTH`]

+02 ? IJK TDR fZhiP?@C\

VC WXYfZ\]^%N@% TDR )j%R)klm?

+

U

Cn?# IJK# /0?oTRIJK
pqῌM)r]s+A)tu?vN WXYfZ89JK\]w[?^%G?@C\D?FG+CAxy `C.- 

zῌ0 # TDR -./0 `C WLP  ,.* cm pN# {|}~ +.* cm .#m?/0+.* cm N WLT m?/0

 WLP 

# 

? \D? K TDR WXYfZ\]^%G?`TQ TDR

G)?+CA N@T

QU

VC
zῌ1 # a  b  TDR ῌ/

TDR   WLT  
WLP   * cm  !"#$
%  &'# + : + (')*+ ,'# +.* cm  ,.* cm )*+Fig. / The relationship between water levels
measured with TDR, WLT, and thosemeasured with a pressure-type water
gauge, WLP, in a rice paddy ﬁeld. Datafor WLP*.* cm were not shown. A
solid line shows a + : + line. Dashedlines show the water levels of + cm and
, cm.

ῌ0

 TDR ,'#  +.* cm  ,.* cm )*+

?\TR WLP-WLT -./0`C WLP  ,.* cm pN?vC WLP 
WLT # {| *./ cm  `T  S 
WLT  WLP ?+C RMSE # *.,2 cm
TDR

 WLT`T # 6? ¡C¢£¤¥¦  zῌ 2 #6Ha §¨ mm h+  / [©ª TDR b c «-./0)*+ DOY+3.  +, . -* [¬+/ . ** [¬?R TDR *./ cm p }.m?7­p®

g @v ¯°S+

?\C# ¢£¤(g +, .©H ,--./0 12# ,**1 34567 DOY )*+Fig. 0 Temporal changes in water levels measured with a pressure-type water gauge and TDR. The
horizontal axis shows the day of year (DOY) in ,**1. Dashed lines show the water levels of +cm and , cm.

&'() : TDR *+,-./

ῌῌ1 a  b 

 TDR 

63

Fig. 1 Temporal changes in (a) hourly precipitation and (b) the di#erences of water levels measured
between TDR and a pressure-type water gauge.

ῌῌ2  TDR  !" a #$ b  $ c  TDR % 

 TDR Fig. 2 An example of the TDR-water gauge noise observed on a rainy day. (a) Hourly precipitation(mm), (b) temporal changes in water levels measured every ﬁve minutes with pressure-type and
TDR water gauges, and (c) the di#erences of water depths measured between pressure-type and
TDR water gauges.

   +*3 . ,**2

64 -* /01%  2&3&"3: 3!"% 3 *./ mm  2;

45&"67"8# 9% 
<=: TDR ##>$?

@3#1%" A BCDE 

F

J? ( K@3E ) 7;

6  7"7;   TDR  LF&"K

; * ῌ 2 M  N +, O - ::  PQRBCDGH %&FSH./WLTTDR TUV01 3 45W"#XY!" DOY ,+0  DOY ,,3

WH@34?BC

DL! 8#7;  BCDGH

7" 

2Z

A: BCD %& [3\-./7]H 2   : F / J#
5J^

88 TDR TUV01

%&'I

 BCDGH %&6_37 TDR +'ISH8#* #XY!"  

$Z`&45F18&" 37 01FaE&"

FbcRdef&"K: BCD9g"67"

A :;*ῌ,#XY HY i=J^F5,&"./7"

WH,h* TUV<>*F>*j?@A BCAkFM9 lm 701##AkN+nDo#XY!"

TDR: pTQq kEFG

&"8#:7;  &rsH;  88: N

tu ILvLwxyJK6#HJL7"

+

$ LaῌL Z`&4

zY Campbell M

;~FJK&"K O; eN

BCAk

Do TDR

5F+N&8#* TDR 

TDR+**

{|}

 701W;  P45FZ`&6* Q7"8#S% 

TU+  bcRdef6# "8#

 3R ./ , -  

$%"/ῌ ῍ ῐ ῏ ῎ΐ: TDR FK F\Vῒ P WX#hj (K, YZF18

<=F[A"7 - \]^_` abc  :;( lm TDR  d Lwater :W-ef KF6   \]^g

eVdx{eh 9g"#<=eRQ ij: ef k K&"# (K d#W,Nl  8H

$Fm  noppg<= qrN

¡sW- >$FtK  2   F\V

Lwater : dp*#*:(P+ du%#*:(PW-p*, ;  &"7 - ¢vw W- £x y¤F¥;  d7"z{p*j d(P

Lwater 

8 <= N|: ¦ 4}~§¨©<=yª «<= A ¬Z. : +2,*2*,+ Z­ <

&"'( )* + +, - TDR

*"8#® %   TUV#6= B ¬Z. +312*+2-°FN2&



d

¯

F®&"8#*;    

 TDR   WLT #>$  WLp
 ,.* cm ± ,F18 

lm WLP #*: WLT # WLP :²`N l  ,.* cm ±O #*: WLT :/p %  2
 iNh  ³% Do& A (

K

q´

῔

 !"#$%"

K: TDR yFjS;  iῑJones, S.B., Wraith, J.M. and Or, D. (,**,) : Timedomain reﬂectometry measurement principles
and applications. Hydrological Processes, +0 : +.+ῌ+/-.
Hou, A.X., Chen, G.X., Wang, Z.P., van Cleemput, O.

TUV«|iand Patric, W.H. Jr. (,***) : Methane and nitrousNhW- "WH&"µ*oxide emissions from a rice ﬁeld in relation to

7"8#?; soil redox and microbiological processes. Soil

TDR #>$ F6_ lm¶:·¸*./ cm¯;7;  P   &" TDR   P>$

Science Society of America Journal, 0. : ,+2*ῌ
,+20.

RMSE : *.,2

Mojid, M., Toride, N. and Cho, H. (,**,) : The e#ect of

cm 7- W,Nl  TDR  $:@heterogeneous soil-water distribution on the

34BCD"8#7- 3701 

TDR measurement of soil-water content.  : TDR 

! 3* : ++ῌ+3.

65

Schaap, M.G., Robinson, D.A., Friedman, S.P. andNadler, A., Ravehb, E., Yermiyahub, U. and Green, S.

Lazar, A. (,**-) : Measurement and modeling ofR. (,**-) : Evaluation of TDR use to monitor

the TDR signal propagation through layered di-water content in stem of lemon trees and soil andelectric media. Soil Science Society of America

their response to water stress. Soil Science Society of America Journal, 01 : .-1ῌ..2.

Journal, 01 : +++-ῌ++,+.
Tang, L., Tao, X. and Choy, C.-l. (,**+) : Possibility ofNoborio, K. (,**+) : Measurement of soil water con-using a coaxial cable as a distributed strain

tent and electrical conductivity by time domain

sensor by time domain reﬂectometry. Smart Ma-

reﬂectometry : a review. Computers and Electronics in Agriculture, -+ : ,+-ῌ,-1.

"#$% ,**- : &' TDR () *+,-ῌ.
-/0

terials and Structures, +* : ,,+ῌ,,2.
Thomsen, A., Hansen, B. and Schelde, K. (,***) : Ap-*+ ! 3- : /1ῌ0/.

plication of TDR to water level measurement.
Journal of Hydrology, ,-0 : ,/,ῌ,/2.

"#$% ῌ 12345 ῌ 6789 ῌ 8:; ,**/ :Topp, G.C., Davis, J.L. and Annan, A.P. (+32*) : Elec-,*GHz-TDR <=>?@ABCDEFG H

tromagnetic determination of soil water content :IJK .. : 31ῌ+*+.

Measurements in coaxial transmission lines. Water

Pepin, S., Livingston, N. J. and Hook, W. R. (+33/) :Resources Research, +0 : /1.ῌ/2,.

Temparature-dependent measurement error in

Weast, R.C. (ed.). (+320) : Handbook of chemistry andtime domain reﬂectmetry determination of soil

physics. pp.E/+ῌE/-. 01th ed. CRC Press. Boca

water. Soil Science Society of America Journal,

Raton, FL.

/3 : -2ῌ.-.

῍ῌLMNOPQRS>TUV WXYZ[\X] ^_V time
domain reﬂectometry TDR >)]` abc>Ud>efgA Mh&ijO

klmlXnopq TDR rns_gAV Ytu]vu&v:wg
TDR >)]xyY_uzvY{|kxA }~jO Yx !YkxA ,* cm q TDR nop>?@A TDR ccV c
v root mean square error RMSE *.,2 cm _:wgA : ,**1  +*  ,.  : ,**2  .  -* 