BAI BAO KHOA HOC
XAY DV>^G PHirOfNG TRINH TlTOfNG QUAN T H V C NGHIEM XOI MON (AP DVNG CHO L i r u V1/C SUOI SA,P VA PHIENG HIENG
THUOC TINH SON LA) Dao T^n Quy*
Tdm tat: Su tdeh r&i ddt do tdc ddng cua mua phi^ thuge vdo nhieu thdng sd vd edng ed nhiiu thdng sd tham gia vdo qud trinh hinh thdnh van chuyin bun cat tren luu vyc. &ng v&i mdi logi ddt thi cd hi sd xdi mdn ddt, he sd xdi mon ranh, hi sd xdi mdn liin ranh khdc nhau vi chung cd cdc ddc trung vdt ly, hda hge khde nhau. Phuang phdp phdn tich dg nhgy de ehi ra thdng sd ndo co vai trd quan trgng, khdng quan trong trong qud trinh tinh todn xdi mdn ranh, xdi mdn lien ranh trin luu vyc.
Tir khda: He sd xdi mdn, dp ddc, tham phu, mat dd ranh.
i.MdDAu
Nhan td mua gay xdi mdn chu ySu thdng qua lugng mua vd cudng do mua. Lugng dat mat do xdi mdn ty If t h u ^ vdi lugng mua, cudng dd mua. DiSu ndy ddng nghia vdi mdt khu vue nghiSn ciiu nhdt dmh thi nhiing trdn mua nhd cd Iugng xdi mdn it hon nhiing ttdn mua ldn; cimg mpt lugng mua, ttdn mua ndo cd cudng dp mua ldn hon (thdi gian mua ngdn hon) thi lugng ddt xdi mdn se nhiSu hon. Nhung ttan mua cd cudng dp mua ldn se ldm cho Iugng nude mua khdng kip ngdm xudng dat, Iugng nude mua nay gan nhu chuySn todn bd thdnh ddng chdy mat ldm cho van toe ddng chay m$t tang ddng ke. Ddng chdy m|it cang ldn thi tao nSn xung lyc ldn va cudn trdi nhung hat ddt ttSn bS mat nhieu, V9.y lugng ddt bi xdi mdn Idn. (NguySn Trpng Hd, 1996).
Dja hinh dnh hudng dSn xdi mdn ddt chu yeu thdng qua dd ddc vd chiSu ddi sudn ddc. Dd ddc la nhan td quan ttpng anh hudng den xdi mdn vd ddng chdy mat. Dp ddc cang ldn thi xdi mdn mat cdng Idn vd ngugc lai. Cung mdt cdp dd ddc, nSu chiSu ddi sudn d6c cdng ldn thi nguy eo gay xdi mdn dat cang cao. Mpt sd kSt qud nghiSn ciiu da chi ra rang: Neu chiSu dai sudn ddc tang len hai ldn thi lugng dat xdi mdn cimg
Phdng Thanh tra, Tru&ng Dgi hge Thuy lgi.
tdng xdp xi hai ldn (ddi vdi ddt sdn xuat lam nghiep) vd tdng len gdn ba Idn ttSn ddt trdng ca phe. Trong diSu kifn nhift ddi thi dnh hudng ciia chidu ddi sudn d6c rd net hon so vdi (diSu kifn) cdc nude dn ddi (Pham Ngpc Diing, 1991;
Nguyen van Dung, Nguyen Dinh Ky, 2012).
2. P H A N T I C H © 0 N H ^ Y CUA CAC THONG SO M O HINH
Phucmg phdp phdn tich dd nhtxy cdc thdng sd P h a n t i c h d p n h ^ y Id s u n g h i S n c i i u m d i q u a n hf g i u a t h d n g t i n v d o v d r a c d a m d h i n h . Dp rih^y c d t h e t i n h t o d n b a n g n h i e u p h u o n g phap hay p h d n t i c h d i n h t i n h h o d c d i n h I u g n g . Cd thS k e dSn m p t sd e d n g t r i n h p h a n tich d p n h a y n h u ( h n a n R. L a n d H e l t o n J. C , 1 9 8 8 ; W e m e r M . G. F . , H u n t e r N . M . a n d B a t e s . P . D . , 1 9 8 8 ] .
DS p h d n t i c h d p n h a y c d c t h d n g sd t r o n g m d h i n h todn, n g u d i t a d u a r a k h a i n i f m v e c t o iing vdi m d i t h d n g sd (vi d u v e c t o x n h d n cdc gia tri t r o n g k h o a n g a -^ b , t a v i S t x [ a , b ] . Sd l u g n g cdc tti n h a n t d thuOc [a,b] n h i d u h a y it t d y t h u p c yeu cdu d p e h i n h x a c c u a p h u o n g p h d p .
Gid sit e d v e c t o x [ a , b ] , d i m g p h u o n g p h a p M o n t e - C a r l o dS ldy n g a u n h i e n c d c g i a trj n h d n t d x^ t h e o m d t h a m m | i t d d x a e sudt n h a t d i n h . i T n g v d i m o i g i a tri n h d n t d x'', n g u d i t a se n h d n d u g c m g t gid tti kSt q u a t i n h t o a n c u a m d h i n h , c d c g i a tri ciia c d e h a m e h i tiSu d u g c t i n h t o d n dS s o s d n h g i i i a kSt q u d t i n h t o d n v a
KHOA HQC K? THUAT THOY Uf\ VA Mdl TRllfllNG - S6 59 (12/2017)
gid trj quan tr5c. SSp xSp tiieo chieu giam ddn cde gid tri eiia hdm chi tieu, cdc gia tri x" dugc thay ddi theo. Cae gia tri phdn phdi xac sudt cua X dugc chia thanh hai phdn: Phdn thir nhdt la tdp hgp cdc gid tri "tdt" (A), phdn thii hai la tap hgp gid tri "khdng tdt" (B). Dp nhay ciia thdng sd dang xet dugc ddnh gid theo khodng each ldn nhdt d^cnc theo phuong diing cua hai dudng phdn phdi xdc sudt. Gia tri tinh toan ciia dmc.nc se SO sduh vdi gid tti tiSu chudn dmc.nc, khi gid tri tinh todn cua dmc.„c ldn hon gid tri tiSu chuan cua dmc.nc thi thdng sd x dang xet se dnh hudng nhieu den kSt qud tinh toan cua md hinh, nguge lai se khdng dnh hudng nhiSu. Gia tri tieu chudn dugc tinh theo cdng thiic 2-1 (Harvey G. and Jan T., 1988):
(2-1) trong dd p Id hf so phu thude vdo miic dp chinh xde de lay gia tri chi sd Iugng tinh toan
"tdt" hay "khdng tdt".
tic! Sd lugng cac ket qua tinh toan "tdt";
mc: Sd lugng cdc kSt qua tinh toan "khdng tdt".
Tren eo sd so sanh giiia kSt qua tinh toan cua md hinh vd gid tri quan ttae thye tS, cde gid tri thdng ke dugc gdn cho mdi thdng sd. Thdng qua cdc gia tri thdng kS dugc tinh todn dya vdo cdc ham tieu chudn nhu ham Nash. Vdi tap hgp cdc gid tri (gia tri ^ a di) ham tiSu chudn cua cdc thdng sd, chiing ta cd the phan tich dp nhay cua moi thdng sd ttong cimg mgt md hinh tinh todn.
KSt qua phan tich dp nhay cdc thdng sd Cd nhiSu thdng sd tham gia vao qua ttinh hinh thanh van chuySn bun cdt tten luu vuc vira va nhd ma da dugc md hinh hda thdng qua md hinh md phdng van chuySn biin cdt trSn luu vuc.
Phuong phap phdn tich dp nhay ed thS chi ra dugc thdng sd ndo cd vai trd quan trpng trong md hinh, thdng so nao khdng quan trpng. Tde gid phan tieh dp nhay to hgp eac thdng sd:
Cudng dp mua, hf sd xdi mdn bong tdeh lien ranh, dp ddc luu vuc, mat dp ranh, dp che phii ddt vd khd ndng xdi mdn cua ddt. Ket qua phan tich dp nhay cua cde thdng so thS hifn nhu trSn h i n h l .
^S:H::S£r;il.„h
, ^ ^ _ ^ ^ ^ , , . , - ^ - = = f - =
0 -io -20 6 20
^
40 BD fl
Hinh 1. Du&ng biiu diin ket qud khi thay ddi thdng sd md hinh
Qua phdn tich ket qud md phdng dp nhay cac thdng sd md hinh eho thay, eudng dp mua dnh hudng ldn nhdt dSn sir v ^ chuyen bim cat ttSn luu vuc. Cudng dp mua cang ldn thi miic van chuyen biin cdt tten luu vue eang cao. Tiep theo la thdng sd dp ddc luu vyc. NSu dp ddc luu vyc tang len 30% thi lugng biin cdt ttSn luu vuc tdng ISn khoang 19%. Nhu v|iy do ddc cdng ldn thi xdi mdn mat cang ldn vd ngugc lai. Df ddc cdng Idn thi ySu cdu ddi vdi cdu tnie thdm thuc vat rimg phdng hg edng eao. NSu dp ehe phu gidm xudng khodng 4% thi xdi mdn ddt se tang ISn khoang 42,2%. Vdy dp che phu cang nhiSu thi kha nang giii nude vd dat cang tdt.
3. PHAN TICH TU*ONG QUAN G l f A X 6 l MON LIEN RANH TREN LUtJ VUC V 6 l DQ DOC VA ClTdNG DQ
Lugng ddt bi xdi mdn liSn ranh ttSn luu vuc la ham sd cua cudng d^ mua va do ddc luu vyc.
Thir nghifm tinh toan vdi cdc cudng dp mua khdc nhau tren luu vuc PhiSng HiSng vd luu vyc Nam Sap cho ta ket qua tinh todn xdi mdn liSn ranh trSn luu vuc.
KHOA HOC K? THUAT THUY LQl VA Mdl TRIH^NG - S6 5 9 ( 1 2 / 2 0 1 7 )
rnuong uinn eo oan cno su oong tach iign rdnb cd dang tdng qudt nhu sau (Nearing, M.A., X.C. Zhang, W.P. MiLLer, L.D. Norton, L.T.West (1998)):
Ei=a.illo'' (3-1) ttong dd:
a, b: Hf sd ttong phuong trinh tuong quan i: Cudng dp mua (mm/h)
IQ: Dp ddc luu vue (%).
KSt qua phdn tich tuong quan giiia xdi mdn liSn ranh ttSn luu vuc vdi dp ddc va cudng dp mua dugc ehi ra ttong hinh 2.
,. » _ f - - , v i ' - " ^ • 9 50 100 1»)
• j , - '
200 250 30(
xac dinh dugc lugng ddt bi xdi mdn liSn ranh tten luu vuc dua vdo phuong trinh 3-2, tir dd dua ra cde gidi phap phdng chdng xdi mdn dS giam thilu lugng ddt bi mat di ttSn luu vyc.
4. P H A N TICK TU*0NG QUAN G I C A XOI M 6 N R A N H TREN LUU VV*C V<5fl DO D 6 C VA CU*6fNG DO M U A
Lugng bun cat xdi mdn ranh tten luu v\rc Id ham so eiia eudng dp mua va dp ddc luu vuc.
Thir nghifm tinh todn vdi cdc cudng dp mua khdc nhau trSn luu vuc PhiSng HiSng va luu vue Nam Sap eho ta ket qua tinh todn xdi mdn ranh tten luu vyc.
Phuong ttinh co bdn cho xdi mdn ranh cd dang tdng quat nhu sau (Hudson, N.W.(1986)):
£ , = c . / ' - / / (4-1) ttong dd:
c, d : Hf sd ttong phuong trinh tuong quan i: Cudng dp mua (mm/h)
lo: Df ddc luu vuc (%) Ef: T5' If bong tdeh rdnh (kg/m^ h).
KSt qua phan tich tuong quan gifia xdi mdn rdnh ttSn luu vuc vdi dp doc vd cudng dp mua dugc chi ra ttong hinh 3.
I 00- s eo-
I
Hinh 2. Tuang quan giica xdi mdn liin rdnh vol dg doc vd cuong do mua Tir ket qud tinh todn tdc gid xdy dyng dugc phuong trinh co bdn cho sy bong tdeh liSn rdnh tten luu vuc vira vd nhd thude tinh Son La dya ttSn sd lifu tinh todn nhu sau:
£,-=0,0002 •/•'•/„'-' (3-2) ttong do:
i: Cudng dg mua (mm/h) lo: Dp ddc luu vyc (%)
Ei: Ty If bong tdeh liSn ranh (kg/m^ h).
Nhu vay vdi ket qua tten, tren eo sd ban do dia hinh luu v\rc, xac dinh dugc dp ddc luu vuc tai cdc tieu luu v\rc, khi cd cudng dp mua, ta se
30-1 28- 24 22-
^ 20-
1 "
g 18 1 12 S 10 a 6 2
ry<
D«d5c(K)
800 1000 1200 1400 1600 1800
Hinh 3. Tuong quan giiea xdi mdn rdnh v&i dg ddc vd cu&ng dg mua
KHOA Hpc K? THUAT THOY LQI VA H O I TRUdNG • S6 59 (12/2017)
Tir ket qua tinh toan tac gia xay dvmg dupe 4-2, tit do dua ra cac giai phap chdng xoi mon phucmg trinh ca ban xoi mon ranh trSn lim vuc de giam thieu luong ddt mkt di tren luu vuc.
vira v4 nho thuoc tinh Son La d\ra tren s6 li$u 4. Kt.T LUAN
tinh to4n nhu sau: BM bao gi6i thieu vice xSy dung dugc phuong
£ , = 0 , 0 0 0 8 2 - i ^ - / , ' (4-2) trinh tuong quan giOa xoi mon lien ranh va xoi Tir ban dfl dja hinh Imi vuc, xac dinh dupe mon lanh vcri do dac va cuong do mua, dua tren do d6c luu vuc tai cac tiJu lim vuc, khi c6 qua trinh phSn tich dp nh^iy cua cac thong s6.
cuong dp mua, ta s5 xac djnh dugc lugng ddt bi Tren eg s6 66 cac nha qufci ly dua ra giai phap xdi mon ranh trSn lim virc dua v4o phuong trinh de han che sir xoi mon djt tren luu vuc.
TAI LlfiU THAM KHAO
Nguy6n Trong Ha., Xac dinh cdc yeu to gdy xoi mon vd khd nang du bdo xoi tnon tren ddt ddc.
Luan an Pho TiSn si KH-KT, Truong Dji hoc Thiiy lgi. m N^i, 1996.
Pham Nggc Dung., Nghien cm mot s6 bien phdp chdng xoi mon tren ddt do bazan trdng che vimg Tdy nguyen va xdc dinh gid trj cua cdc yiu id gdy xdi mdn ddt theo md hinh Wischmeier W. H and Smith D.D. LuSn an Pho tiSn si khoa hoc N6ng nghi$p. Ha Ngi, 1991.
Nguyen Van Dung, Nguyen Dinh Ky., Ddnh gid dinh lufmg xoi mdn ddt ddi niii vimg Thanh - Nghe - Tinh bdng phuong trinh mdt ddt phd dung vd he thdng thong tin dia ly. Tap chi cic khoa hge v6 trai dit, NXB Vi?n KH&CN Viet Nam, tap 34, s5 1, tr. 31 - 37, 2012.
Iman R. L and Helton J. C , An investigation of uncertainty and sensitivity analysis techniques for computer models. Risk Analysis, 8 (1), 71-90, 1988.
Wemer M. G. F., Hunter N. M. and Bates. P. D., Identifiability of distributed floodplain roughness values in flood extent estimation. Joumal of Hydrology, 314, 139-157,2005.
Harvey G. and Jan T., An Introduction to Computer Simulation Methods. Part 2, Applications to Physical Systems, 1988.
Hudson, N.W.(1986): Soil Conservation. London, Batsford.
Nearing, M.A., X.C. Zhang, W.P. MiLLer, L.D. Norton, L.T.West: Modeling Interrill Sediment Delivery. Soil Sci. Soc. Am.J. 62:438-444. 1998.
Abstract:
CONSTRUCTION THE CORRELATION EQUATION FOR EMPIRICAL OF EROSION (APPLY FOR SUOI SAP AND PHIENG HIENG BASIN IN SON LA PROVINCE)
Soil detachment by raindrop impact depetids on many parameters and there are also many parameters involving in the formation of sediment transport in the watershed. For each type of soil, there are specific coefficients of soil erosion, inter-rill and rill erosion because they have different physical and chemical properties. Sensitivity analysis method is used to show which parameters are most important, and vice versa in the process of calculating rill and interrill erosion in the watershed.
Keywords: Coefficient of erosion, slope, mats cover, groove density.
Ngay nhdn bai: 9/10/2017 Ngdy chdp nhdn ddng: 21/12/2017
KHOA HOC K» THUiT THliY L<(1 VA MOl TRltdNC - Sfi 5 9 (12/2017)
