Measuring Temporal Changes in Flooding Depths in a Rice Paddy Field Using Time Domain Reflectometry

Transcription

1 J. Jpn. Soc. Soil hys. No. +*3, p. /10/,**2 DR * * * Mesuring emporl Chnges in Flooding Depths in Rice ddy Field Using ime Domin Reflectometry omotsugu Y AZAKI*, Yuki S HOJI* nd Kosuke N OBORIO* * School of Agriculture, Meiji Univeristy, +++ Higshimit, m-ku, Kwski, Kngw,+. 2/1+, Jpn Abstrct Mesurement of temporl chnges in hydrologicl condition such s flooding depth is needed to understnd green-house gs exchnge between pddy rice fields nd the tmosphere. We introduced simple method to monitor the flooding depth using time domin reflectometry (DR). he results of lbortory experiments indicted tht depths mesured with DR greed well with those observed when the depth ws estimted ssuming tht the second reflection of DR pulse occurs not t the end of the rod, but t the surfce with lrge depths. he lbortory experiments reveled tht DR provided precise enough depths so tht field experiments were conducted. Wter levels mesured with,*-cm long DR probe greed well with those mesured with pressure-type guge with root men squre error (RMSE) of *,2. cm. he levels mesured by DR, however, might be # ected by rindrop depositions. Key words : DR method, electromgnetic wve, rice pddy field, flooding depth, continuous mesurement + Ndler et l.,**- ime domin reflectometry DR +32* ng et l. opp et l. DR,**+ DR homsen et l.,*** +,. m DR Noborio,**+ Jones et l.,**,,**- DR Hou et l.,,*** *,+. 2/ :DR

2 58 +*3,**2 + Fig. + DR An exmple of DR wveform. m c + *- tl ns DR + ct, + + +, L e DR L ct,, L e DR L homsen et l.,*** DR Cmpbell CDR CR,-X Schp et l.,,**- - DR, - e W opp et l., +32* L, e L L, +, e e +, + DR, e e +*. e e e e West, +320 ; epin et l., +33/ e ct, L e totl totl ir, w. mns 12./. +../13 +*,/ /, 2 - +* W,/, 2 +* W,/. + +, +,

3 : DR 59 Fig.,, DR Lbortory experimentl design for mesuring depth with the DR technique. L L L L -,. mm - DR CV L -., mm,* mm - L - L /*, L L LLir L DR, DR DR Mojid et l.,**,,* +* cm+/ cm,* cm DR +/ cm,+ cm +, cm Cmpbell DR DR+**, *-. cm +* cm L L L L L L, ir + *. + cm DR+** L L, DR RS,-, C CDR L L L L / L L - L,**1 1, DOY +2-2,3 DOY,.+,** DOY +02 : +

4 60 +*3,**2 Fig. - - DR he dimension of DR -depth meter instlled in rice pddy field. DR 1/ mm -- cm - : DR DOY,*0 +0 /* / cm 0mm - WL cm DR L DR WLL L WL ref ref SDMx/* Cmpbell L WL CR,- X, Cmpbell DR+** DOY,*0 +0 /* L DR DR cm L L L KADEC- * cm MIZU, DR.* mm, +** cm, DR./ cm RMSE DR / cm 0mm DR, ref..+ DR No. -.-, +* +/,* cm DR L CR,- X, Cmpbell /. b L ref

5 : DR b 2 DR L +*. cm Fig.. he reltionship between mnully-observed nd DR-mesured depths for di# erent lengths of DR rods. DR-mesured depths L were clculted () with Eq. ( 0) nd (b) with Eq. ( 2 ). Dshed lines show the depths of + cm. +../,*.* L L,**/ L + : + +*. cm L L root men squre error RMSE */+. cm */-.., DR cm *-*. cm L WL RMSE +* cm +/ cm,* cm DR WL / *+3. cm *1-. cm +-0. cm,*. cm WL WL RMSE WL +*. cm L DR WL WL +*.,*. cm WL WL L DR. b L L DR DR L + Mojid,,**, L + L L + WL +*.,*. cm,* cm L,., WL WL DR L +,. L *-. cm + / WL +*. cm WL WL GHz DR / WL +*. cm WL

6 62 +*3,**2 WL WL +*. cm WL DOY,*0 DR DOY DR + cm +02 DR DR.- 0 DR WL,*. cm +*. cm WL +*. cm WL DR DR 1 b DR / DR WL-WL WL WL,*. cm WL WL * cm WL */. cm + : + WL WL RMSE *,2. cm +*. cm,*. cm DR WL Fig. / he reltionship between levels 2 mesured with DR, WL, nd those + mmh / b mesured with pressure-type guge, WL, in rice pddy field. Dt DR c for WL **. cm were not shown. A DOY+3. +, -* solid line shows + : + line. Dshed +/ ** DR lines show the levels of + cm nd */. cm, cm. +,,- ref 0 DR,**1 DOY +*. cm,*. cm Fig. 0 emporl chnges in levels mesured with pressure-type guge nd DR. he horizontl xis shows the dy of yer (DOY) in,**1. Dshed lines show the levels of + cm nd, cm.

7 : DR 63 Fig. 1 1 b DR emporl chnges in () hourly precipittion nd (b) the di# erences of levels mesured between DR nd pressure-type guge. 2 DR b DR c DR Fig. 2 An exmple of the DR- guge noise observed on riny dy. () Hourly precipittion (mm), (b) temporl chnges in levels mesured every five minutes with pressure-type nd DR guges, nd (c) the di# erences of depths mesured between pressure-type nd DR guges.

8 64 +*3,**2 -* */. mm DR DR 2 WL DR DOY,+0 DOY,,3 / DR DR, DR DR L L Cmpbell DR+** DR / DR DR L L L + DR A : +2,*2*,+ B +312*+2- DR WL Jones, S.B., Writh, J.M. nd Or, D. (,**,) : ime WL WL domin reflectometry mesurement principles p,*. cm WL WL,.* cm WL +/-. nd pplictions. Hydrologicl rocesses, +0 : +.+ DR Hou, A.X., Chen, G.X., Wng, Z.., vn Cleemput, O. nd tric, W.H. Jr. (,***) : Methne nd nitrous oxide emissions from rice field in reltion to soil redox nd microbiologicl processes. Soil DR Science Society of Americ Journl, 0. :,+2* *./ cm,+20. DR RMSE *.,2 Mojid, M., oride, N. nd Cho, H. (,**,) : he e# ect of cm DR heterogeneous soil- distribution on the DR mesurement of soil- content.

9 : DR 65 3* : Ndler, A., Rvehb, E., Yermiyhub, U. nd Green, S. Schp, M.G., Robinson, D.A., Friedmn, S.. nd Lzr, A. (,**-) : Mesurement nd modeling of R. (,**-) : Evlution of DR use to monitor the DR signl propgtion through lyered di content in stem of lemon trees nd soil nd electric medi. Soil Science Society of Americ their response to stress. Soil Science Soci- Journl, 01 : ,+. ety of Americ Journl, 01 : ng, L., o, X. nd Choy, C.-l. (,**+) : ossibility of Noborio, K. (,**+) : Mesurement of soil con- using coxil cble s distributed strin tent nd electricl conductivity by time domin sensor by time domin reflectometry. Smrt Mreflectometry : review. Computers nd Elec- terils nd Structures, +* :,,+,,2. tronics in Agriculture, -+ :,+-,-1. homsen, A., Hnsen, B. nd Schelde, K. (,***) : Ap-,**- : DR 3- : /10/.,**/ : pliction of DR to level mesurement. Journl of Hydrology,,-0 :,/,,/2. opp, G.C., Dvis, J.L. nd Annn, A.. ( +32* ) : Elec-,* GHz-DR.. : 31 +*+. tromgnetic determintion of soil content : Mesurements in coxil trnsmission lines. Wter epin, S., Livingston, N. J. nd Hook, W. R. ( +33/ ) : Resources Reserch, +0 : /1. /2,. emprture-dependent mesurement error in West, R.C. (ed.). ( +320) : Hndbook of chemistry nd time domin reflectmetry determintion of soil physics. pp.e/+ E /-. 01th ed. CRC ress. Boc. Soil Science Society of Americ Journl, Rton, FL. /3 : time domin reflectometry DR DR DR,* cm DR DR root men squre error RMSE *,2. cm :,**1 +*,. :,**2. -*