Chuong1(Dtai 5 Ngay)Hong-thai Binh

Xy dng cng ngh d bo dng chy 5 ngy n cc h cha ln trn h thng sng v sng L

Bo co tng kt ti cp B 2008 Xy dng cng ngh d bo dng chy 5 ngy n cc h cha ln trn h thng sng v sng L TS. Nguyn Vit Thi CHNG I C IM A L T NHIN, QUY LUT HNH THNH DNG CHY V PHN CHIA LU VC B PHN 1.1. LU VC SNG N P HO BNH 1.1.1. iu kin a l v mng li sng Sng , phn thuc lnh th Trung Quc c tn gi l sng L Tin, bt ngun t vng ni cao thuc tnh Vn Nam (Trung Quc). Tng din tch ton lu vc sng l 52.900 km2, trong din tch phn Vit Nam l 26.800 km2 - khong 50,7 %, sng di 1.010 km, trn lnh th Vit Nam khong 570 km. Lu vc sng hp, thuc a phn khu Ty Bc rng trung bnh 80 km, ko di theo hng ty bc - ng nam. Phn ln a hnh sng l i ni [12], c ti gn 80 % din tch cao trn 500 m, cao trung bnh lu vc l 1.130 m (Bng 1.1). ng phn thy pha ng ca lu vc l dy ni Hong Lin Sn, Pu Lung vi nh cao t 2.500 3.000 m. Pha Ty c dy ni cao Phu en inh (1.886 m), Phu Hui Long (2.178 m), Phu Ta Ma (1.801 m), Phu Tung (1.480 m) v Phu Sang (1.518 m). Pha bc c dy ni cao Pu Si Lung (3.076 m) v Ng i Sn (3.048 m). Pha ng nam l vng ni thp Ba V (1.287 m), Vin Nam (1.029 m) v i Thi (1.198 m). a hnh lu vc c dng ni v cao nguyn, chia ct mnh theo chiu thng ng. Cc dy ni, cao nguyn v thung lng xp song song theo hng ty bc - ng nam. Bng 1.1: Phn b cao theo din tch lu vc sng phn Vit Nam cao (m) Trn 3.000 3.000 2.500 2.500 2.000 2.000 1.500 1.500 1.000 1.000 - 500 Di 500Trung tm D bo KTTV T, TS. Nguyn Vit Thi

Din tch (km2) 0,1 0,4 3 8,2 27,4 39,8 21,1

Ghi ch Ti liu tham kho [12]

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Phn ln lng sng cao hn mt bin t 100 500 m, bi t t v lm thc ghnh. Thng lu sng k t ngun ti Park Ma, dng sng chy theo hng ty bc - ng nam. Lng sng rng trung bnh 40 60 m vo ma cn. T bin gii Vit Trung ti Lai Chu khong 125 km c dc bnh qun 160 cm/km. Trung lu sng t Park Ma ti sui Rt, dc y sng gim cn 38 40 cm/km, lng sng rng trung bnh 90 100 m. H lu, t sui Rt n ca sng (Trung H) lng sng m rng khong 200 m v ma cn, dc cn 42 cm/km. T sui Rt, sng chuyn hng ty ng cho ti Ha Bnh. Trn lnh th Vit Nam, sng c 10 ph lu cp 1 (Bng 1.2), trong c 4 sng nhnh chnh vi din tch lu vc trn 2.000 km2: Nm P, Nm Na, Nm Mc, Nm Mu; hai ph lu nh hn l Nm Sp v Nm B. Mng li sng sui trn sng phn b khng u: vng vi ma t nh lu vc Nm Sp mt sng sui di 0,5 km/km 2; vng ni cao ma nhiu nh thng lu sng Nm Mu mng li sng dy khong 1,67 km/km2; cc vng cn li khong 0,5 - 1,5 km/km2 Bng 1.2: Cc sng nhnh cp 1 chnh ca sng trn a phn Vit Nam TT 1 2 3 4 5 6 7 8 9 10 Sng Nm M Nm Bum Nm P Nm Na (a) Nm Mc Nm Na (b) Nm Mui Nm Mu Nm B (Pn) Nm Sp Din tch (km2) Ton b/Vit Nam 918 653 2.280 6.860/2.190 2.930/1.810 770 712 3.400 1.410 1.110 di (km) Ton b/Vit Nam 63 36 103 235/86 165/86 51 50 165 82 83

Trong iu kin a hnh mi c nng cao sau vn ng Himalaya, sng ngi trong lu vc sng c c im ca mt mng li sng tr, biu hin chia ct mnh, thung lng su hp hnh ch V, dc ln. Mng li

Trung tm D bo KTTV T, TS. Nguyn Vit Thi

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sng sui dy, t sng ln. Hng ca dng sng ln trng vi hng kin to a cht ca khu Ty Bc Bc B. Do s khc nhau v a hnh, lng ma, nham thch v lp ph thc vt nn mt sng sui trong lu vc sng khng ng nht m phn ho phc tp. Vng ni phn xut, cao ln, ma nhiu, mt sng sui rt dy ln hn 1,5 - 1,78 km/km2, phn b b tri sng , pha ty Hong Lin Sn - Phu Lung. Vng ni thp, ma t hn vng trn, t ch yu l sa dip thch, kh hu kh nng, mt sng sui thuc loi tha n tng i dy (0,5 - 1,5 km/km2) phn b cc vng T Phnh, Xin Chi, b phi sng trn lu vc sng Nm P v Nm Mc. Vng cao nguyn vi ma t, mt sng sui t tha n tng i dy (0,5 -1 km/km2). Vng thng lu sng Nm B mt sng sui tha nht, di 0,5 km/km2. y l vng ma t v nhiu vi, dng chy mt km pht trin. Trn lu vc dng chnh sng , s sng nhnh c chiu di trn 10 km l 223 sng, trong ti 148 sng c din tch nh hn 100 km2. 1.1.2. Cc sng nhnh chnh 1.1.2.1. Sng Nm P Nm P l ph lu ln th t ca sng thuc a phn Vit Nam. Sng c din tch lu vc l 2.280 km2, chiu di l 103 km. Bt ngun t vng ni Pu Cut, tnh in Bin, cao khong 1.000 1.500 m. Nm P chy theo hng t ty bc ln ng bc, nhp vo sng b phi ti Khang Man cch ca sng 441 km. Hng dc trung bnh ca a hnh t ty bc xung ng nam v t ty nam ln ng bc. Nham thch phn b trong lu vc kh ng nht, ch yu l sa dip thch. Lng ma nm kh ln, bnh qun lu vc ti 1.966 mm. V vy, sng sui trong lu vc tng i dy, mt t 0,5 n 1 km/km 2. C 13 sng sui di trn 10 km. Lu vc sng Nm P c hnh nan qut, tng i rng vi rng bnh qun lu vc l 24,9 km. H s tp trung nc tng i nh, khong 1,49. Tng s sng sui c chiu di trn 10 km v din tch trn 100 km 2 c 4 con (Bng 1.3).Trung tm D bo KTTV T, TS. Nguyn Vit Thi

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Nm P thuc loi sng tng i nhiu nc trn min Bc, tng lng nc bnh qun nhiu nm l 2,27 km3 ng vi lu lng bnh qun nm l 72,0 m3/s v m un dng chy nm l 31,6 l/s/km 2. Ma l t thng VI n thng IX chim 73,2 % lng dng chy nm. Dng chy ln nht trong lu vc thuc loi tng i ln, m un dng chy ln nht ti trm Nm P l 895 l/s/km2 ng vi lu lng ln nht l 429 m3/s (ngy 26/VI/1996), ln gp trn 400 ln dng chy nh nht. Rng cn rt t, nham thch ch yu l thnh phn st nhiu l nguyn nhn trc tip dn n dng chy cn rt nh. Bng 1.3: c trng hnh thi lu vc sng Nm P TT 1 2 3 4 5 sng Nm P Nm Cha Nm Nh Nm Kh Nm Nga L km F km2 H m 1.153 887 J % 36,0 44,8 B km2 24,9 7,5 15,4 7,4 10,6 Ku 1,69 1,64 1,61 1,30 1,23 Kp 2,03 0,74 D km/km2 0,53 0,71

73,5 2.280 39,0 16,0 28,0 119 129 887 84,5 1.040

1.1.2.2. Sng Nm Na Nm Na l ph lu ln nht ca sng thuc a phn Vit Nam, trn lnh th Trung Quc c tn l ng iu. Sng di 235 km v c din tch lu vc l 6.860 km2, trong c 2.190 km2 thuc Vit Nam. Bt ngun t vng ni cao trn 2.000 m thuc tnh Vn Nam Trung Quc, chy theo hng ty bc ng nam, khi ti a phn nc ta dng sng un khc ri i hng gn bc nam v nhp vo sng b tri, ti Mng Lay cch ca sng 427 km. Sng Nm Na nm gia mt bn l cao nguyn Ma Lu Thng cao trung bnh 1.000 m pha ty bc v mt bn l cao nguyn T Phnh, cao trung bnh 1.200 - 1.400 m pha ng. a th lu vc kh cao, cao trung bnh lu vc khong 1.276 m. Cc nh cao nht nm pha bc ng bc nh: Ng i Sn 3.048 m, To Leng 3.096 m, pha ty bc a hnh u cao trn 2.000 m. Hng dc chung ca lu vc sng Nm Na l t bc xung nam. chia ct su c tnh cht hm vc in hnh. Nht ct su ti 1.100 m do thung lng sng Nm Na to nn.Trung tm D bo KTTV T, TS. Nguyn Vit Thi

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Do c v tr qu v pha bc, a hnh cao nn kh hu lu vc sng Nm Na lnh v nhiu ma. y l mt trong nhng trung tm ma ln ca lu vc sng . Lng ma bnh qun nm trn lu vc sng Nm Na kh cao, khong trn 2.200 mm. Ti Phong Th 2.202 mm, Pa Tn 2.997 mm, Snh H 2.682 mm. Ma ma t thng V n thng X c lng ma chim khong 90 % lng ma c nm. Ba thng VI, VII v VIII c lng ma ln nht chim khong 50 60 % lng ma nm. Trong iu kin a hnh dc, ma nhiu, sng sui pha b phi sng Nm Na pht trin dy trn nn dip thch phn phin. Mt sng sui trn 1 km/km2. Pha b tri phn b vi, cat-xt pht trin mnh m, nn tuy cng ma nhiu nhng mt sng sui tha hn vng trn. Mt trung bnh li sng ca Nm Na thuc cp tng i dy, di 1 km/km2. Tng s sng sui c chiu di t 10 km tr ln l 21 sng, trong 12 sng c din tch nh hn 100 km2. Nhng ph lu ln u nhp vo b tri sng Nm Na (Bng 1.4). Nm trong vng ma nhiu, dc lu vc ln iu kin hnh thnh dng chy mt thun li quyt nh ngun ti nguyn nc phong ph ca sng Nm Na. Nhng ch yu tp trung vo thi k ma, l. Bng 1.4: c trng hnh thi lu vc sng Nm Na TT 1 2 3 4 5 sng Nm Na Nm Co Nm So Nm Bom Nm Cui L km 235 38 48 28 24 F km2 H m J % 31,2 37,1 37,1 40,3 41,5 B km2 28,1 8,5 16,3 7,0 7,3 Ku 1,36 1,16 1,32 1,17 1,33 Kp 0,60 0,16 2,20 0,63 D km/km2 0,60 0,75 0,66 0,50

6.860 1.276 326 750 164 175 1.368 1.253 1.307 1.021

Tng lng nc bnh qun nhiu nm ca Nm Na l 8,80 km 3 tng ng vi lu lng bnh qun 179 m3/s v m un dng chy nm l 40,7 l/s/km2. Ch dng chy sng Nm Na phn nh kh r ch ma. c im ni bt trong ch dng chy ca sng Nm Na l thi k nc ln trong ma l ti sm hn cc lu vc sng pha nam. iu ch yu l do nh hng sm ca hon lu pha ty i vi lu vc.Trung tm D bo KTTV T, TS. Nguyn Vit Thi

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Ma l ngn, t thng VI n thng IX chim khong 68,4 % lng dng chy c nm. Dng chy ba thng ln nht xut hin t thng VI n thng VIII v dng chy ln nht thng xut hin vo thng VII. Lng dng chy ca thng ny chim khong 25,3 % lng dng chy nm. M un dng chy ln nht t 507 l/s/km2. 1.1.2.3. Sng Nm Mc Nm Mc l ph lu ln th ba, vo sng b phi. Din tch lu vc l 2.930 km2 chim khong 6,75 % din tch lu vc sng thuc Vit Nam. Lu vc sng Nm Mc v tr pha cc ty ca lu vc sng , bt ngun t vng ni cao trn 1.500 m, chy trn t Lo theo hng bc nam. n gn bin gii Vit Lo, sng Nm Mc i thnh hng t ty nam ln ng bc v vo sng ti bn Hui Mc cch ca sng 409 km. Lu vc sng Nm Mc l mt vng trng so vi cc b ni xung quanh. Pha ty nam lu vc cao hn c, trung bnh khong 1.000 m, cc nh ng phn nc cao ti 2.178 m. Pha ng v ng bc lu vc h thp r rt, ch cao khong 600 m v ti ca sng ch cn 150 m. dc trung bnh ca y sng 5,55 . Lu vc Nm Mc c cao trung bnh l 934 m v dc trung bnh khong 35 %. Lng ma ti y khng ln, bnh qun ton lu vc l 1.780 mm. Pha ty nam, ti Mng Pn l 1.751 mm, Mng Mun 1.718 mm, pha ng bc ma tng hn khng nhiu, ti Nm Mc t 1.782 mm. Lng bc hi trong lu vc khong 900 mm. Trong iu kin a hnh thp, t ma, vi phn b nhiu, pha ng lu vc sng sui km pht trin. Tng s sng sui c chiu di t 10 km tr ln l 14 sng, trong 9 sng c din tch nh hn 100 km2. Cc ph lu chnh phn b lch v pha b tri (Bng 1.5). Bng 1.5: c trng hnh thi lu vc sng Nm Mc Sng Nm Mc Nm Thin Nm Mun Nm Mok L km 165 44 24 27 F km2 2.930 367 122 319 H m 934 989 866 886 J % 34,9 28,6 48,5 37,2 B km 22,6 11,3 5,5 8,8 Ku 1,62 2,26 1,36 1,60


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Tng ng vi phn b ma, dng chy trn lu vc cng tng dn t ty nam (25 l/s/km2) ln ng bc (30 l/s/km2). Ma l trn lu vc sng Nm Mc tp trung trong bn thng (VI - IX) thng c lng nc chim khong 74,8 % lng nc c nm. Thng VIII c dng chy trung bnh nhiu nm ln nht, chim 25,2 % lng dng chy c nm. Dng chy ln nht trn sng Nm Mc ln hn sng Nm P v Nm Na. Lu lng ln nht xut hin trong nhng nm gn y l 2.250 m 3/s ng vi m un dng chy ln nht l 825 l/s/km 2 (ti trm Nm Mc ngy 27/X/1961). 1.1.2.4. Sng Nm Mu Nm Mu bt ngun t vng ni cao trn 3.000 m pha ty dy Hong Lin Sn, sng chy theo hng ty bc ng nam v nhp vo sng pha b phi ti Khung Mn cch ca sng 165 km. Sng Nm Mu di 165 km v c din tch lu vc l 3.400 km 2, chim 13 % din tch lu vc sng . Lu vc sng Nm Mu thuc vng a hnh trng, cao bnh qun lu vc l 1.085 m, thung lng sng kh rng, rng bnh qun lu vc ti 26,8 km v dc bnh qun lu vc l 37,2 %. dc bnh qun y sng kh ln, khong 4,26 . Nm trong vng trung tm ma ln Hong Lin Sn, lng ma trung bnh nm ca lu vc sng Nm Mu vo loi ln trn min Bc, khong 2.454 mm. Lng ma nm tng r rt theo cao: vng thng lu ma ti 2.700 2.800 mm, trong khi h lu v cc vng thp, lng ma gim xung cn 1.800 - 1.900 mm. Trong iu kin a hnh ni, dc, ma nhiu trn mt nn dip thch, tng ph thc vt cn t l nhng thun li sng sui hnh thnh v pht trin dy c, mt sng sui trung bnh ton lu vc l 1,16 km/km2. Ph hp vi a hnh cao v ma nhiu, pha thng lu Nm Mu sng sui pht trin nhiu nht t 1,5 - 1,67 km/km 2. Tng s sng sui c chiu di trn 10 km l 4 sng, phn b tng i u theo dc sng (Bng 1.6). Hnh thnh trong vng ma nhiu, sng Nm Mu l ph lu ln v nhiu nc th 2 trong lu vc sng . Tng lng nc bnh qun nhiu nm ca ton b lu vc l 3,89 km3 ng vi lu lng bnh qun l 123 m3/s v m un dng chy nm l 36,21 l/s.km2.Trung tm D bo KTTV T, TS. Nguyn Vit Thi

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Bng 1.6: c trng hnh thi lu vc sng Nm Mu TT 1 2 3 4 Sng Nm Mu Na Gi N.T Chiang N.Cha L km 165 25 20 18 F km2 3400 219 112 65,4 H m 1085 1534 1208 J % 37,2 45,5 37,9 B km 26,8 9,1 6,2 4,4 Ku 1,67 1,26 1,18 1,31

Ma l ko di t thng VI n thng IX c lng dng chy chim 73,7% lng dng chy nm, lng dng chy 3 thng ln nht, t thng VI thng VIII, chim ti 64,1% lng dng chy nm. Thng VII c dng chy ln nht chim ti 27,4 % lng dng chy nm. Dng chy ln nht ti Nm Mu l 4.020 m3/s, ng vi m un nh l l 1.535 l/s/km2 thuc loi ln nht trn nim Bc. 1.1.3. c im ma v dng chy l 1.1.3.1. c im ma S sp xp song song ca a hnh ni, cao nguyn v thung lng sng c tc ng r rt ti kh hu trn lu vc. Dy ni cao Hong Lin Sn Pu Lung nh mt bc tng t nhin ngn cn v lm suy yu nh hng ca gi ng Bc. Cc dy ni cao bin gii Vit - Lo li to ra hiu ng fn i vi gi ma Ty Nam. iu kin a hnh v v tr ca lu vc qui nh kh hu vi hai ma: ma ng kh lnh, ma h nhiu ma vng cao v kh nng vng thp. Ma ln trn lu vc thng bt u sm, vo khong thng VI, thng VII. Vng bc v ty bc l vng ni cao c kh hu m t n rt m, lng ma trung bnh nhiu nm t 1.500 n 2.700 mm, lng ma ma h (thng V - IX) chim ti trn 70 % tng lng ma nm. Vng ni thp Sn La - Mc Chu, ma h chu nh hng ca gi ma ty nam, lng ma trung bnh nm thp, ch 1.100 n 1.500 mm, trong lng ma ma h di 1.000 mm. Khong 50 60 % lng ma nm tp trung vo 3 thng VI, VII v VIII. Trn lu vc sng tn ti nhng trung tm ma, thng xy ra phn lu vc thuc a phn Vit Nam gn bin gii Vit Trung, c lng ma nm thay i ty tng v tr t 2.400 n 3.000 mm [4, 7, 12]. Nh trung tm ma sn ty dy Hong Lin Sn thuc cc lu vc sng nhnh Nm Na, Nm Mu, lng ma trung bnh nm khong 2.500 mm: trn lu vc sngTrung tm D bo KTTV T, TS. Nguyn Vit Thi

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Nm Na c cc tm ma ln ti: Pa Tn 2.997 mm, Snh H 2.746 mm; thng lu sng Nm Mu c cc tm ma: Tam ng 2.519 mm, Bnh L 2.372 mm. Ti vng pha ty dy Hong Lin Sn thy r qui lut lng ma gim t thng lu xung trung h lu: ti Mng T 2.404 mm, Lai Chu 2.119 mm, Qunh Nhai 1.706 mm, Sn La 1.414 mm, C Ni 1.272 mm. 1.1.3.2. c im dng chy l a hnh ni cao, chia ct mnh, dc ln, thung lng su, hp vi lng ma ln li tp trung vo mt vi thng trong nm nn to iu kin hnh thnh mng li sng dy c, t sng ln, hng ca cc dng sng sui trng vi hng ca lu vc. Bng 1.7: Mt s c trng thy vn lu vc sng Din TT 1 2 3 4 5 6 7 8 9 10 11 12 13 Lu vc Ton b Lai chu T B Ha Bnh Nm P Nm Na Nm Mc Nm Mu Nm Chin Sui Sp Nm B Nm Sp Bi Sang tch (km2) 52.900 33.800 45.900 51.800 2.280 6.860 2.930 3.400 310 270 1.360 410 98 L km) 1.01 0 73,5 235 165 165 Ngun sinh dng chy quan trng nht trn sng nm phn lu vc vng sn pha ty dy Hong Lin Sn, trn cc lu vc: Nm Na, Nm Mu, Nm Chin, sui Sp, c m un dng chy nm t 40 50 l/s/km2. Tr cc lu vc Nm B (Pn) v Nm Sp c m un dng chy nh di 20 l/s/km 2,Trung tm D bo KTTV T, TS. Nguyn Vit Thi

c trng dng chy nm W (km3) 55,7 35,4 49,0 55,0 2,27 7,75 2,51 5,57 1,25 0,30 0,46 0,23 0,13 Q (m3/s) 1.170 1.125 1.550 1.744 72,0 279 79,6 177 16,0 10,6 14,6 7,5 4,3 M (l/s/km2) 33,5 33,3 34,3 33,8 31,6 40,7 27,2 50,9 51,1 39,9 10,7 18,4 44,3 0,58 0,45 0,55 0,55 0,50 0,58 0,47 0,66 0,80 0,61 0,25 0,53 0,90

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cc ni khc trn lu vc sng , m un dng chy thng t 27 - 34 l/s/km2 (Bng 1.7). Dng chy sng tp trung vo cc thng ma l, chim ti 69 78 % tng lng dng chy nm [12]. Ma l trn sng thng bt u vo thng V, kt thc vo cui thng IX u thng X (Bng 1.8). L ln nht thng xy ra vo cui thng VII, na u thng VIII. Dng chy l tp trung nhanh v khng ng b cc phn khc nhau ca lu vc l mt c im ni bt nht ca dng chy sng . iu kin a l t nhin thun li cho dng chy l hnh thnh trn cc ph lu sng , nht l lu vc Nm Na, Nm Mu. Trn dng chnh, lng dng chy l chim bnh qun t 77,6 n 78,5 % dng chy nm; dng chy thng VIII thng ln nht nm, chim ti 23,7 % (Bng 1.9). Bng 1.8: Tn sut (%) bt u v kt thc ma l trn h thng sng TT 1 2 3 Trm Lai Chu T B Ho Bnh Sng Bt u ma l VI 3 0 6 VII 87 89 74 VIII 10 11 21 IX 0 2 3 Kt thc ma l X 54 51 55 XI 46 47 42 XII 0 0 0

Bng 1.9: c trng dng chy trn sng Lu lng nh l (o c) TT Lu vcQmaxtb (m3/s) Qmax (m3/s) Thi gian

Lu lng nh nhtThi gian 27/4/63 2/5/80 8/5/60 16/5/69 5/5/69 14/5/66 4/5/80 13/5/66 8/5/60

Phn phi %Ma Ma l cn 77,4 77,2 77,6 74,7 66,5 73,2 73,9 70,4 72,1 22,6 22,8 22,4 25,3 33,5 26,8 26,1 29,6 27,9

Mmax Qmin 2 (l/s/km ) (m3/s) 325 494 415 2.147 560 840 1.534 2.048 868 114 150 180 96 42, 8, 12,0 2,4 1,5

1 2 3 4 5 6 7 8 9

Lai Chu T B Ha Bnh Nm P Nm Na Nm Mc Nm Mu NmChin Nm Bu

6.900 11.000 29/7/66 9.930 22.700 18/8/96 10.100 21.500 18/8/96 398 2.090 1.140 2.200 439 199 1.020 12/9/76 3.800 6/7/76

2.250 27/8/71 4.020 15/7/70 641 22/6/77 1.180 16/7/65


10


10 Sui Sp

140

365 29/9/62

901

0,62

28/4/60

71,8

28,1

quan trc c m un nh l rt ln trn cc sng nh: ti Nm P l 2.147 l/s/km2; ti Nm Chin l 2.048 l/s/km2 v ti Nm Mu l 1.534 l/s/km2. Trn dng chnh m un nh l cng rt ln: ti Lai Chu l 428 l/s/km2 (VIII/1945); ti T B l 494 l/s/km2 (VIII/1996) v ti Ha Bnh l 454 l/s/km2 (VII/1964). Ti Lai Chu, bin l ln nht t ti 27,5 m (VIII/1945), cao nht Vit Nam, vi cng sut l ln ln nht ti 77,4 cm/h. 1.1.3.3. H thu in Ho Bnh H Thu in Ho Bnh c xy dng trn dng chnh sng pha trn th x Ho Bnh, khnh thnh ngy 20/XII/1994. H c xy dng vi nhiu mc ch khc nhau nh: phng l h du, sn xut in, ti, giao thng thu..., trong c phng l h du v sn xut in l hai nhim v chnh. H Ho Bnh c chiu di ng vi mc nc dng bnh thng l 208 km, rng trung bnh l 1 km, din tch mt h l 208 km2 [16]. Mt s thng s k thut c bn ca h v cc cng trnh u mi nh my thu in Ho Bnh: Cao trnh nh p Cao trnh mc nc gia cng Cao trnh mc nc dng bnh thng Dung tch ng vi mc nc gia cng Dung tch phng l S t my Cng sut lp my 8 t S ca x y (kch thc) Cao trnh ngng x y Qmax x y S ca x mt (kch thc) Cao trnh ngng x mt Qmax x mt Qmax l thit k Tng lng nc nm TBNNTrung tm D bo KTTV T, TS. Nguyn Vit Thi

123 m 122 m 117 m 10,45 t m3 4,6 t m3 8 1.920 MW 12 (10 x 6 m) 56 m 21.996 m3/s 6 (10x15 m) 102 m 13.500 m3/s 49.000 m3/s 57,4 t m3 11


Mc nc thi k l sm (15/VI - 15/VII) Mc nc thi k l chnh v (16/VII - 25/VIII)

98 m 91 - 96 m

1.1.3.4. Thi gian truyn l trn sng v h Ho Bnh Theo s liu ca Phng D bo Thu vn Bc B, thi gian truyn l trung bnh cc on sng chnh t Mng T v Ha Bnh v trn cc ph lu chnh Nm Na, Nm Mu,... cho thy trong ma l thi gian truyn l c khc nhau khi l ln v l xung. Tuy nhin, trong tnh ton v d bo, thi gian truyn l trung bnh t Mng T v T B c th ly 18 20 h, t T B v Ha Bnh l 12 24 h trong t nhin, khi c h Ha Bnh thi gian truyn l gim xung cn 3 12 h ty theo mc nc h [2, 6]. Ngoi ra, thi gian truyn l trn cc on sng cng ph thuc vo tm ma trn lu vc. Vi iu kin thng tin kh tng thy vn hin nay, thi gian d kin d bo lu lng ti T B trn sng khng qu 18 h v Ha Bnh khng qu 36 h. Khi thi gian d kin trn 36 h, tr s d bo ch dng tham kho. 1.2. SNG CHY N H THC B 1.2.1. iu kin a l t nhin Sng Chy l ph lu ln th hai trong lu vc sng L. Bt ngun t vng ni Ty Cn Lnh cao nht khu ng Bc. Din tch sng Chy chim khong 16,7 % din tch ton b lu vc sng L [12]. Lu vc sng Chy c gii hn: pha Bc l vng ni cao 1.500 m, ng phn nc gia sng Chy v sng L. Dy ni con Voi ko di t ty bc xung ng nam phn cch gia sng Chy v sng Thao. Pha ng v ng nam l ng sng ni ca dy Ty Cn Lnh v dy ni thp phn chia gia lu vc sng Chy v dng chnh sng L pha trung lu. a hnh lu vc sng Chy thp dn t bc, ty bc xung ng nam. Pha bc cao hn c, trong dy Ty Cn Lnh cao khong 1.630 n trn 2.000 m vi nh cao ti 2.419 m. Pha ty, l dy ni Con Voi cao t 700 1.450 m. Pha ng nam lu vc ch cao trung bnh 200 - 300 m. Hng dc ca a hnh quyt nh hng ca dng chnh sng Chy thng lu theo hng ng ty; trung v h lu theo hng ty bc - ng nam. Phn thng lu sng Chy, cao y sng h thp rt nhanh, trong vng 20 km u, cao gim t 1.200 m xung cn 500 m. Lu vc c sn dc ln, trung bnh t 30o 45o. Sau khi qua Hong Su Ph v t Cc Pai, dng chnh sng Chy l mt hm vc su thm. Ti Lng Thng, ph lu ln nhtTrung tm D bo KTTV T, TS. Nguyn Vit Thi

12


t pha Trung Quc chy qua nhp vo sng Chy b phi. Sng Chy nhp vo sng L oan Hng, cnh ca sng L 62 km. Lu vc sng Chy hnh thnh trong mt vng a hnh c nng cao, trong vn ng to lc tr v mnh, cao tng i v tuyt i u ln hn 1.000 m. a hnh b o khot chia ct mnh. y sng chnh cao 50 - 100 m, y cc ph lu cao khong 100 - 150 m. Xm thc trn mt nn rn kt tinh thi c, thc ghnh pht trin, dng sng tr nn him tr. Ch k t Bo Nhai tr v Ph Rng c ti 41 thc ln nh v t Ph Rng v ti oan Hng di 82 km, s thc ghnh v bi ni cng c ti 82 ci. dc bnh qun sng Chy ti 24 %, cao bnh qun khong 858 m. Din tch c cao t 400 m tr xung chim trn 40 % din tch ton lu vc. Mng li sng sui pht trin mnh, trn 1,5 km/km2 (ring lu vc sng Trao Chm ti 1,85 km/km2). 1.2.2. c im kh tng thy vn lu vc sng Chy Trn lu vc sng Chy c 47 sng vi chiu di t 10 km tr ln. Dng chnh sng Chy un khc quanh co, h s un khc ln 2,32, rng bnh qun lu vc nh 26 km, h s khng cn bng ca li sng nh hn 1, cc ph lu nhp vo sng chnh tng i u theo hai bn b phi v tri. Lng ma bnh qun nm trn ton lu vc khong 1.925 mm. Nhng do v tr khc nhau i vi gi m v a hnh, trn lu vc sng Chy c s khc nhau v lng ma gia cc vng. Phn b ma c hng tng dn t thng lu v trung lu v sau li gim dn v h lu: Xn Mn 1.443 mm, Mng Khng 2.042 mm, Lc Yn 2.032 mm, Ngha 2.340 mm, Ch Ngc 2.003 mm v Thc B 1.763mm. Ring khu vc Hong Su Ph cc bc lu vc c v tr khut i vi hng gi m nn t ma (ti Hong Su Ph khong 1.667 mm). Kh nng bc hi hng nm trn lu vc khong 850 mm. Sng Chy nm trong vng ma nhiu, a hnh ni pht trin, dc lu vc ln, dng chy sng ngi sn sinh thun li. Tng lng dng chy bnh qun nhiu nm l 6,46 km3 ng vi lu lng bnh qun nm l 205 m3/s v m un dng chy nm l 31,5 l/s/km2, nhiu nc hn lu vc sng Gm. Quy lut phn b dng chy trn lu vc sng Chy cng ging phn b ma. Vng trung lu thuc b tri sng Chy nhiu nc nht lu vc, m unTrung tm D bo KTTV T, TS. Nguyn Vit Thi

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dng chy nm ti Ngha ti 57,6 l/s/km2. Vng thng v h lu t nc hn, m un dng chy nm t 31 n 32 l/s/km2 (Bng 1.10). Bng 1.10: c trng dng chy nm sng Chy Sng Chy Trm Ca sng Cc Ly Yn Chu Thc B F km2 6.498 3.290 5.030 6.170 W km3 6,43 3,3 4,9 6,0 Q m3/s 205 104 156 192 X mm 1.925 1.935 1.930 1.925 M l/s/km2 31,5 32,2 31,2 31,6 0,50 0,54 0,50 0,50

Ch nc ca sng Chy chu s chi phi ca ch ma. c im ni bt l ch l ko di. Ma l trn lu vc sng Chy ko di ti 5 thng, bt u t thng VI v kt thc vo thng X. Lng dng chy ca 5 thng ny chim ti 79,3 % lng nc c nm. Ba thng c lng dng chy ln nht l thng VII, VIII v IX vi tng dng chy chim khong 45 n 50% lng dng chy nm. Thng c lng dng chy ln nht trn lu vc sng Chy xut hin ng b vo thng VIII chim khong 19 n 20 % lng dng chy nm. c im a hnh cao, dc mnh, ma ln to iu kin cho dng chy l trn sng Chy tp trung rt nhanh v c lit. Nht l thng lu v trn cc ph lu b tri. M un dng chy ln nht nm trn sng Chy ti Cc Ly l 821 l/s/km2, ti Ngha 1.806 l/s/km2. Bin mc nc ln nht ti Cc Ly l 15,23 m thuc loi ln nht min Bc. 1.2.3. H Thu in Thc B H thu in Thc B trn sng Chy c a vo hot ng t nm 1971. Cho n nay, nh my thu in Thc B cung cp nng lng cho h thng in min Bc gp phn to ln trong vic cung cp nng lng n nh, to iu kin cho pht trin kinh t x hi. Vi p nc cao 60,8 m, din tch mt nc rng 260 km2, h Thc B c dung tch ton b l 3,6 km3, khng ch c khong 50 % lng nc hng nm ca sng Chy phc v cho pht in v ti rung. Mt s thng s k thut c bn ca h v cc cng trnh u mi nh my thu in Thc B [14]: Cao trnh nh pTrung tm D bo KTTV T, TS. Nguyn Vit Thi

62 m 14


Cao trnh mc nc gia cng Mc nc dng bnh thng Dung tch ng vi mc nc gia cng Dung tch phng l S t my Cng sut lp my S ca x mt (kch thc) Cao trnh ngng x mt Qmax x mt Qmax l thit k Dung tch nm TBNN Mc nc thi k l sm 15/VI - 15/VII Mc nc thi k l chnh v (16/VII - 25/VIII) Mc nc thi k l mun (26/VIII-15/IX) 1.2.4. Thi gian truyn l trn sng Chy

61 m 58 m 3,64 t m3 0,45 t m3 3 108 MW 3 (7x12 m) 46 m 3.230 m3/s 5.100 m3/s 6,345 t m3 56 m 56 m 58 m

Trn c s xc nh thi gian truyn l trung bnh cc on sng chnh t Cc Ly v Bo Yn; t Bo Yn v p Thc B cho thy trong ma l thi gian truyn l c khc nhau khi l ln v l xung. Tuy nhin, trong tnh ton v d bo, thi gian truyn l trung bnh t Cc Ly v Bo Yn c th ly bng 4 gi; t Bo Yn v p Thc B l 6 gi [7]. 1.3. SNG GM N H TUYN QUANG 1.3.1. iu kin a l t nhin sng Gm Sng Gm l ph lu cp I ln nht ca sng L, chim khong 44 % din tch ca ton lu vc [12]. Gii hn pha ng v ng nam lu vc sng Gm l cnh cung Ngn Sn v cnh cung Sng Gm, ng gii hn ny cao trung bnh 500 1.000 m, ring cc nh ni u cao trn 1.000 m, cao nht l nh Pia Dao 1.930 m. Pha ty v ty bc l ng phn nc gia sng L v sng Gm, cao trung bnh 200 - 1.000 m, c nh ni cao ti 1.940 m. Pha ng nam a hnh thp xung di 800 m. Nh vy, thng lu sng Gm c a hnh dc t ty bc xung ng nam, trung v h lu chuyn thnh hng gn bc - nam.Trung tm D bo KTTV T, TS. Nguyn Vit Thi

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Bt ngun t vng ni cao gn 2.000 m thuc tnh Vn Nam Trung Quc, sng Gm chy vo Vit Nam ti bn Pin Qua, ti Bo Lc, xung Bc M v Chim Ho v nhp vo sng L Khe Lau. Thng lu sng Gm pha Trung Quc chy theo hng ty bc ng nam, qua bin gii chuyn hng sang ng bc - ty nam. Di Bo Lc, sng Gm nhn mt ph lu ln, sng Nho Qu ( pha Trung Quc gi l Ph Mai) t Trung Quc chy theo hng ty bc - ng nam nhp vo sng Gm Na Mt cch ca sng Gm 178 km. Sng Gm chy qua cao nguyn ng Vn cao trung bnh trn 500 m, nn nham thch l vi v phin nham tr tri, thung lng sng ti y c dng hm vc in hnh, c ni su ti 1.000 m, vch dng ng, lng sng rt him tr. T di ng ba sng Gm v Nho Qu, sng Gm x ngang ni Lang Ca Ph cao trn 1.000 m, to thnh hm vc N Png chy v Bc M v tip nhn mt s ph lu ln khc. T di Bc M, sng Gm chy theo hng ty bc - ng nam ti Na Hang. Lng sng trn on ny nhiu bi , c ti 22 thc him tr, trong thc Thng Lm l ln nht, thuyn b khng qua li c. dc trung bnh y sng thuc a phn Vit Nam l 0,84 . V n gn Na Hang nhn thm sng Nng pha b tri, cch ca sng Gm 71,5 km. cao bnh qun lu vc ca sng Gm ti 877 m. Pha bc v ng bc cao hn c. cao t 200 m tr ln chim ti 95 % din tch lu vc, trong din tch c cao 400 - 600 m chim ti 35 %. 1.3.2. c im kh tng thy vn lu vc sng Gm Lu vc sng Gm khut sau cnh cung Ngn Sn v cnh cung Sng Gm. Gi ng v ng nam m t b ngn chn. c im ca v tr lu vc nh vy quy nh mt ch kh hu lnh v t m hn so vi dng chnh sng L. Mc che khut khc nhau i vi tng v tr trong lu vc l nguyn nhn phn ho thnh cc vng kh hu trong lu vc. Thng lu sng Gm k t Bc M tr ln c kh hu kh v lnh. Nhit trung bnh nm gim r rt, c ti 9 thng di 20 oC. Lng ma trung bnh nm t 1.100 n 1.400 mm. Vng trung lu, pha hu ngn c kh hu m t nht lu vc, nhit trung bnh nm 20 22 oC v lng ma trung bnh nm ti 1.800 n 2.200 mm, ti Thc Hc l 2.080 mm. Pha b tri, lu vc sng Nng, do c v tr khut sau cnh cung Sng Gm, lngTrung tm D bo KTTV T, TS. Nguyn Vit Thi

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ma gim r rt: Ch R 1.200 mm, Ba B 1.450 mm, Linh c 1.488 mm. Lng ma tp trung phn ln vo ma ma, chim khong 80 % lng ma nm. Kh nng bc hi trn lu vc t 600 - 700 mm. Mc d c din tch lu vc ln hn, nhng so vi sng L, sng Gm li t nc hn. iu ch yu do kh hu kh hn trong vng quyt nh. Tng lng nc bnh qun nhiu nm ca sng Gm khong 11 km3 ng vi lng bnh qun nm l 352 m3/s v m un dng chy nm 20,5 l/s.km2. Tng t phn b ma, vng thng lu sng Gm c lng dng chy nh nht, m un dng chy nm t 10 n 26 l/s/km2. Vng c lng dng chy tng i t phn b b tri sng Gm, vng sng Nng khong 20 l/s/km2. Dng chy nm trn lu vc sng Gm bin i nhiu hn pha dng chnh sng L. Nm nhiu nc gp gn 3 ln nm t nc. Ch dng chy ca sng Gm chia lm hai ma r rt. Ma l trn ton b lu vc ko di trong bn thng, t thng VI n thng IX, chim 62 73 % lng dng chy c nm. So vi ma, lng dng chy t tp trung hn. iu c lin quan ti kh nng iu tit ca lu vc, ni r l tc dng ca vi v rng. Bng 1.11: c trng dng chy nm sng Gm Sng Gm Nng Trm Ca sng Bo Lc Chim Ho Ca sng u ng F km2 17.20 0 4.060 16.50 0 2.270 1.890 W km3 11,1 0 2,08 10,9 0 1,52 1,21 Q m3/s 352 65,9 344 48,2 38,5 X mm 1.690 1.183 1.698 1.890 1.500 M l/s/km2 20,5 16,2 20,8 21,2 20,4 0,38 0,60 0,38 0,35 0,42

Vng sng Nng c h Ba B iu tit nn dng chy phn b kh u, ma l ch chim khong 63 % lng dng chy nm.


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Ba thng dng chy ln nht chim khong 51 61 % lng dng chy nm, xut hin vo thi k t thng VI n thng VIII. Thng c lng dng chy ln nht v nh nht xut hin ng b trn ton b lu vc vo thng VIII v thng III vi lng dng chy thng ln nht gp khong mi ln thng nh nht. Dng chy l trn lu vc sng Gm phn nh c tnh a dng ca iu kin a l thu vn trong lu vc. C vng l thuc loi c lit nhng cng c vng li kh n ha. Vng Ngi Qung, ni c din tch tp trung nc nh, ma nhiu, dc lu vc ln, l thng c lit nht, m un dng chy ln nht ti 1.064 l/s/km2; cng sut bnh qun ln nht l 122 cm/h, thuc loi ln nht min Bc. Ti Bo Lc, m un dng chy ln nht cng ln ti 828 l/s/km2 v cng sut bnh qun ln nht l 41,5 cm/h. Cc vng cn li thuc trung lu sng Gm v pha sng Nng, dng chy l thuc loi nh, t c lit hn, m un dng chy ln nht t 200 n 314 l/s/km2. Gi tr tuyt i ca cc c trng dng chy ln nht c s khc nhau gia cc vng, nhng tnh cht l ni th thng nht trn ton lu vc. Mc nc, lu lng bin i nhanh, t tr s ln nht trong mt thi gian ngn v xy ra bt thng. 1.3.3. Cc ph lu chnh Cc ph lu ca sng Gm phn b tng i u dc hai bn b sng. Trong c 2 ph lu ln l sng Nho Qu v sng Nng. 1.3.3.1. Sng Nho Qu Sng Nho Qu, ph lu ln nht ca sng Gm, c chiu di l 192 km v din tch lu vc l 5.387 km2, trong phn thuc Trung Quc di 145 km v c din tch lu vc l 3.380 km2. Pht ngun t vng ni cao Nghin Sn (Trung Quc) c cao t 1.500 n 1.676 m, chy theo hng ty bc - ng nam, nhp vo sng Gm ti Na Mt. Phn thuc a phn Trung Quc, sng Nho Qu c tn gi l Ph Mai. Tuy cao tuyt i ln ( cao bnh qun lu vc ti 1.235 m) nhng do tnh cht a hnh cao nguyn ca lu vc nn dc khng ln, ch khong 18%. Thung lng sng Nho Qu c dng hm vc. Din tch vi chim khong 27,7 % din tch ton lu vc.


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Tng lng nc bnh qun nhiu nm c tnh khong 2,69 km3 ng vi lu lng bnh qun nm 85 m3/s v m un dng chy nm l 15,8 l/s/km2. 1.3.3.2. Sng Nng Bt ngun t vng ni Pia-ya cao 1.980 m, sng Nng l sng nhnh ln th hai nhp vo sng Gm pha b tri ti Khun Phen cch ca sng Gm 71,5 km. Sng Nng c chiu di 113 km, din tch lu vc l 2.258 km2, c din tch vi khng ln, khong 3,4%. T thng ngun ti N Nim, sng chy theo hng ty bc - ng nam v t Ch R n gip sng Gm, sng Nng chuyn sang hng ng bc - ty nam. Vi dc y trung bnh l 4,07, c im ni bt v mt hnh thi ca sng Nng l a mo Kac-xt pht trin, trong c h Ba B ni ting (gm 3 h ln lin tip: h th nht di 4 km rng 500 m; h th hai di 2 km rng 200 m v h th ba di 3 km rng t 800 1.000 m). V mt thu vn, h Ba B c tc dng iu tit dng chy, lm cho dng chy ln nht v nh nht chnh lch nhau khng nhiu. Ti u ng, dng chy ln nht ch gp 41 ln dng chy nh nht. Tng lng dng chy bnh qun nhiu nm ca sng Nng l 1,52 km3 ng vi lu lng bnh qun nm 48,2 m3/s v m un dng chy nm l 21,2 l/s/km2. 1.3.4. H thu in Tuyn Quang H cha thu in Tuyn Quang xy dng trn sng Gm, thuc a phn x Vnh Yn v th trn Na Hang. Din tch mt nc ng vi mc nc dng bnh thng l 81,49 km2, thuc a phn huyn Na Hang tnh Tuyn Quang, mt phn a phn huyn Bc M, tnh H Giang v huyn Ba B, tnh Bc Cn. H cha Tuyn Quang c xy dng vi nhiu mc tiu, trong c 3 mc tiu chnh: Phng l h du, pht in cung cp cho li in Quc gia v cung cp nc ti cho ng bng sng Hng. Mt s thng s k thut c bn ca h v cc cng trnh u mi nh my thu in Tuyn Quang [15]: Cao trnh nh p Cao trnh mc nc gia cng Cao trnh mc nc dng bnh thngTrung tm D bo KTTV T, TS. Nguyn Vit Thi

124,5 m 123,89 m 120 m 19


Dung tch ng vi mc nc gia cng Dung tch phng l S t my Cng sut lp 3 t my S ca x y (kch thc) Cao trnh ngng x y Qmax x y S ca x mt (kch thc) Cao trnh ngng x mt Qmax x mt Qmax l thit k Tng lng nc nm TBNN Mc nc thi k l sm (15/VI - 15/VII) 1.3.5. Thi gian truyn l trn sng Gm

2,596 t m3 1 t m3 3 342 MW 8 (4,5 x 6 m) 79 m 5.232 m3/s 4 (15x15,65 m) 104,85 m 10.176 m3/s 17.258 m3/s 10,023 t m3 105,2 m

Mc nc thi k l chnh v (16/VII - 25/VIII) 105,2 m Trn sng Gm, thi gian truyn l trung bnh cc on sng chnh t ng Vn v p Tuyn Quang l 12 gi; t Bo Lc v Bc M l 3 gi; t Bc M v p l 3 gi v t u ng v p 2- 3 gi [7]. 1.4. NHNG HNH TH THI TIT GY MA SINH L TRN LU VC SNG , SNG CHY V SNG GM 1.4.1. Phn loi cc hnh th thi tit c bn gy ma ln Lu vc 3 sng , Chy v Gm nm trong vng kh hu nhit i gi ma nn thi tit chu s chi phi ca cc h thng thi tit t nhiu pha: pha bc, pha ng, pha ty v pha nam. Cc hnh th thi tit c kh nng gy ma ln vi tng lng ma trn trn 100 mm bao trm a phn lu vc trong nhng nm gn y gm c: - Rnh p thp mt t kt hp vi tc ng ca khng kh lnh (KKL). Rnh p thp (i khi c p thp ng kn Bc B) t mt t ti mc AT 850 mb, trc rnh c hng ty bc - ng nam (t Ty Bc xung ng bng Bc B) kt hp vi tc ng ca KKL km theo front lnh di chuyn


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xung Bc B, thng xy ra vo cc thng chuyn tip u ma ma, c kh nng gy ma ln ko di 1, 2 ngy, lng ma ngy ph bin l 50 100 mm. - Rnh p thp mt t kt hp vi xoy thun lnh trn cao Trng hp ny tng thp l rnh p thp c p thp ng kn Bc B, trn cao 700 500 mb c rnh di chuyn v pha ng, n khong kinh tuyn 105 0E, v 25 0N th pht trin su xung pha nam, ui rnh thng hnh thnh xoy thun dch chuyn dn xung Bc B hoc ln cn, nhit gim mc 2 3 0C/ngy (xoy lnh). y l loi hnh th c kh nng gy ma ln, lng ma ngy t 50 100 mm, c th ko di 2, 3 ngy vi tng lng ma trn t 100 n 200 mm trn ton lu vc, vi lng ma im c th ti 300 mm. Hnh th ny thng gy ma vo cc thng VI v IX. - Hi t gi theo kinh hng Bc B trn tng cao AT850 - AT700 mb Vo cc thng u ma ma, i khi xut hin s hi t hai i gi nam ty nam (c ngun gc gi ty nam t vnh Bengan ln) vi gi nam - ng nam (ngun gc gi ng nam t ra ty nam li cao p Thi Bnh Dng), gy ra ma ln ko di 1 - 2 ngy vi lng ma ngy ti 50 - 100mm, c ni t ti 200 mm. - Di hi t nhit i (DHTN) Ph bin Bc B, DHTN thng hot ng mnh vo cc thng VII, VIII trn lu vc 3 sng , Chy v Gm. Ty thuc vo cng hi t hoc cc nhiu ng trn di hi t m ma trn cc lu vc c th khc nhau c v lng v phm vi ma. DHTN c trc hng ng - ty hoc ty bc ng nam i qua ng bng Bc B, khi cng gi mt hoc hai pha di hi t mnh ln hoc xut hin cc nhiu ng di chuyn t ng sang ty (in hnh l hnh th thi tit t 16 n 18/VIII/1971) c kh nng gy ma ln, ko di 1- 3 ngy, tng lng ma trn thng gn 100 mm, c khi ln ti 200 300 mm. - Di hi t nhit i kt hp vi tc ng ca KKL Trn DHTN c xoy thun Bc B hoc ln cn kt hp vi tc ng ca KKL gy ma ln vi tng lng ma trn c th ti 200 300 mm, tm ma ti 300 400 mm. - Xoy thun nhit i Ma do p thp nhit i (ATN), bo thng xy ra vo thng VII, thng VIII, ko di 2 - 3 ngy, cng ma ty thuc vo cng , hng v tc di chuyn, thi gian tan nhanh hay chm ca bo hoc ATN. MaTrung tm D bo KTTV T, TS. Nguyn Vit Thi

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do bo, ATN thng bao trm mt din rng, c khi ton b lu vc vi lng ma ph bin ti 100 300 mm. Xoy thun nhit i phi hp vi cc hnh th thi tit khc nh khng kh lnh, li p cao cn nhit i ty Thi Bnh Dng thng gy ra ma rt ln, din rng, lng ma trn ti trn 300 mm, tm ma t ti 500 600 mm. 1.4.2. c im ma ln gy l ln trn sng , sng Chy v sng Gm 1.4.2.1. Ma ln gy l ln - Ma gy l ln trn lu vc 3 sng , Chy v Gm, thng bao gm mt s t ma (t 1 n 3 t). Tuy nhin, cng c nhng trn ch c mt t vi ma ln tp trung trong 2 - 3 ngy, hnh thnh l ln ng b trn c h thng sng. C trn ma bao gm ti 3 - 4 t ma k tip nhau do hot ng lin tip ca nhiu hnh th thi tit, trong , gia cc t ma ln l thi k ma nh hoc khng ma ko di vi gi n hn mt ngy. - Cc trn ma gy l ln thng c mt n vi tm ma, tm ma ln thng sn ty dy Hong Lin Sn, H Giang v Bc Quang, vi lng ma vng trung tm ln ti 300 500 mm ty tng trn. Vng ma ln mi trn thng bao trm mt din rng, t 100 - 200 km2 n 1.000 2.000 km2. Phn trung - thng ngun sng , sng Chy v sng Gm thng c lng ma t t 100 300 mm, c khi ti 400 mm, nh cc trn ma thng VII cc nm 1986, 2001 v thng VIII cc nm 1969, 1971, 1983, 1996,... Nh vy, nu xy ra ma u khp trn lu vc sng v sng L vi lng ma 200 300 mm, th s xy ra l ln vi lu lng ln nht n h Ho Bnh trn 10.000 m3/s; n h Thc B trn 2.000 m3/s v n h Tuyn Quang trn 3.000 m3/s. Lu thm rng, lng ma trn gy l ln trn sng v sng Chy thng ln v hn hn ma trn lu vc sng Gm cng trn . Din bin ma theo thi gian trong 1 trn thng theo mt quy lut chung: ma tng dn ln ti nh (vi lng ma ln nht thng tp trung trong 1 ngy, c khi 2 ngy v lng ma ngy ln nht ti 100 200 mm), ri li gim nhanh v ngng hn. Do, s phn b ma trn nh vy, to cho nhnh l ln v xung c dng dc ng gn cn i thng gp cc sng min ni. 1.4.2.2. Nhng trn ma ln gy l c bit ln trn sng v sng L Trong gn 4 thp k qua, trn sng c 7 trn l c bit ln vi lu lng nh l trn 14.500 m3/s (VII/1964, VIII/1969, VIII/1971, VIII/1996, VIII/2002, VIII/2006 v X/2007), trn sng Chy c 6 trn l c bit lnTrung tm D bo KTTV T, TS. Nguyn Vit Thi

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(VIII/1971, VII/1986, VIII/1995, VII/2001, VIII/1992, VIII/1978) vi lu lng ln nht n h Thc B trn 2.500 m3/s; trn sng Gm c 7 trn l c bit ln (VIII/1971, VII/2001, VII/1986, VI/1989, VIII/1969, VII/1998 v VIII/1985) c lu lng nh trn 4.000 m3/s. Loi hnh th thi tit c trng gy ra ma ln ko di hnh thnh cc trn l c bit ln c 3 c im ni bt sau: - Lun c hnh th synop ch o cho mi thi k, v d nh bo, di hi t nhit i, rnh thp trong trn l VIII/1969; rnh thp, di hi t nhit i trong trn l VIII/1971; bo, sau l hi t gi ng nam mnh hi t vo p thp tn d ca bo trong trn l VIII/1986,... - Mi hnh th synop ch o li thng phi hp vi 1 hoc 2 hnh th khc, v d rnh thp b nn bi khng kh lnh, DHTN c KKL tc ng,... - Cc hnh th thi tit hot ng k tip nhau lin tc, hnh th ny suy yu i th hnh th khc hnh thnh mnh ln thay th. Tm li: l ln v c bit ln trn sng v sng L hnh thnh do hot ng lin tip ca mt s hnh th thi tit gy ra nhng t ma ln ko di nhiu ngy, bao trm hu khp lu vc. Ch c hot ng lin tip cng t hp ca cc hnh th thi tit mi gy ra ma ln dn ti l c bit ln. 1.4.3. Ch v c im chung ca l sng , sng Chy v sng Gm 1.4.3.1. Ch v c im l Trn sng , sng Chy v sng Gm, nh l nm bin ng khng ln: lu lng nh l ln nht ln gp 2 ln lu lng ln nht TBNN; gp 3,5 4,8 ln lu lng nh l ca nm l nh. S bin ng nhiu nm ca qu trnh nh l nm kh phc tp, khng c chu k r rt. Song, c biu hin s lun phin nhm nm l ln v nhm nm l nh. Pha nhng nm l ln thng ngn, ko di 3 - 9 nm, pha nhng nm l nh ko di hn, t 5 - 15 nm. L ln trn sng Chy kh nhiu, ti h Thc B, s nm c nh l ln nht nm xp x trn trung bnh nh l nhiu nm chim 49 %. Trong khi l ln trn sng v sng Gm khng nhiu, s nm c nh l nm ln hn nh l TBNN ch chim khong 40 %.


23


nh l ln nht nm xut hin t thng VI - X, thng VIII c tn sut ln nht, t 30 36 %. nh l ln nht nm tp trung vo 2 thng VII, VIII, vi tn sut 77 - 90 % v tp trung nhiu nht vo thi k t 10/VII 21/VIII. 1.4.3.2. Mt s c im hnh thnh nhng trn l ln, c bit ln a) Khi qut chung v nhng trn l ln Vic nghin cu quy lut chung hnh thnh, chuyn ng, din bin l ln mi sng nhnh v dng chy n cc h Ho Bnh, Thc B v Tuyn Quang vi cc t hp l khc nhau ca cc sng nhnh l mt vn phc tp, nht l khi c tc ng ca cc cng trnh thy li, thu in. Vic phn tch cc c trng trung bnh ca cc trn l cc tuyn cho thy r tnh hp l ca chng trong quy lut chung: tng dn lu lng chn l v nh l t thng ngun v h du v t sng nhnh vo sng chnh; trong quy lut truyn l trn sng nhnh cng nh sng chnh; trong s gim dn mc mnh lit ca l ln (c trng bng cng sut l ln) khi i t thng ngun v h du ri vo h cha. Thi gian l ln cng c quy lut tng dn t thng ngun v h du v mc chnh lch gia chng, nhn chung, ph hp vi thi gian truyn trung bnh cc on sng. Trn sng v sng Chy l thng xy ra c lit hn (c v cng sut ln v bin l) so vi l trn sng Gm. b) Mt s c im ch yu hnh thnh l ln L ln trn sng thng tp trung nhanh v khng ng b trn cc lu vc sng nhnh; gia lu vc bn phi v bn tri ca sng chnh. Trong khi , l cc sng Chy v sng Gm thng c hnh thnh ng b trn cc lu vc t thng ngun v h cha, tuy c sm, mun so vi nhau i cht. C mt s trng hp, trn thng ngun cc sng khng c l, nhng h lu cc sng chnh v cc sng nhnh vng h vn c l ln. in hnh l trn l thng X/2007 gy l c bit vi dng chy n h l 14.500 m3/s, trong khi l T B li mc nh vi lu lng nh l l 2.700 m3/s. a s cc trn l ln u l nhng trn l kp, phc tp, thng gm 2 - 3 t l vi cc nh tng dn. S l n ch chim di 1/3 s trn vi cc nhnh ln, xung thng dc ng v kh in hnh cho l min ni. c im ny cng gy thm kh khn trong d bo v phng trnh thin tai.


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1.5. CC THNG TIN V MNG LI TRM KH TNG THU VN 1.5.1. Cc thng tin v mng li trm in bo ma l 1.5.1.1. Mng li trm kh tng thu vn trn sng Mng li trm kh tng thu vn trn sng phn b kh u, nhng mt li trm ma vn cn tha. Hin nay, trn lu vc sng c 30 trm kh tng, im o ma v 22 trm thu vn. Trong c 2 trm kh tng v 2 trm thu vn Trung Quc. Danh sch cc trm KTTV c thng k trong bng 1.12, 1.13 v hnh 1.1. Trm Ho Bnh quan trc sm nht vo nm 1902, mun nht l trm N H nm 1967. Bng 1.12: Danh sch cc trm kh tng in bo ma trn sng TT 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Tn trm TQ 56964 TQ 56977 Mng Lay Tam ng Pak Ma Pa Tn Mng T Sn H Bnh L Than Uyn Tun Gio Pha in Ta Cha Mng Nh Sn La Mng Si Mng Trai Qunh Nhai Ph Yn Bc Yn C Ni a danh Trung Quc Trung Quc TX Mng Lay TX Lai Chu Lai Chu Lai Chu TT Mng T TT Sn H TT Tam ng TT Than Uyn TT Tun Gio Tun Gio Ta Cha TT Mng Nh TX Sn La TT Mng Si TT Mng Trai TX Qunh Nhai TT Ph Yn TT Bc Yn TT C Ni V 23022 22030 22004 22025' 22032' 22035' 22022 22022 22018 21057 22035 21034 21055 22 10 21020 21042 21035 21051 21016 21015 210080

Kinh 101007 102018 103009 103029 102025' 103012' 102050 103014 103037 103053 103025 103031 103020 102 28 103054 103041 103057 103034 104038 104025 1040090

Loi trm II II I I III III II II II II II III III III I III III II II III II 25



TT 22 23 24 25 26 27 28 29 30

Tn trm Yn Chu Mc Chu Km 46 Km 22 T Khoa Thun Chu Ho Bnh Mai Chu M Cang Chi

a danh TT Yn Chu TT Mc Chu Mc Chu Mai Chu T Hc TT Thun Chu TX Ho Bnh TT Mai Chu M Cang Chi

V 21003 20050 20048' 20045' 21012 21028 20049 20039 21052

Kinh 104018 104041 104051' 104057' 104021 103043 105020 105003 104003

Loi trm III I III III III III I III II

Bng 1.13: Danh sch cc trm thu vn trn lu vc sng V tr trm TT Tn trm Tn Sng a phng Trung Quc Trung Quc Tnh Lai Chu TX Lai Chu Qunh Nhai, Sn La Mng La, Sn La Yn Chu, Sn La Ph Yn, Ngha L Kinh 102 13 101o27 102 36 103 10 103o33 104 03 104 21 104 43o o o o o o

Loi V trm 22o43 22o37 22o28 22o04 21o50 21o26 21o12 21o03 II II III I III I III III

1 2 3 4 5 6 7 8

L Tin L TinTrungiKiu A Mc

Mng T Lai Chu Qunh Nhai T B T Khoa Vn Yn


26


9 10 11 12 13 14 15 16 17 18 19 20 21 22

Ch B Ho Bnh Trung H N H Nm P Pa Tn Nm Ging Nm Mc Pa H Bn Cng Nm Chin Thc Vai Thc Mc Phing Hing

Nm Bung Nm P Nm Na Nm Na Nm Mc Nm M Nm Mu Nm Chin Nm B Nm Sp Sui Sp

Bc, Ho Bnh Th x Ho Bnh Bt Bt, H Ty

105 09 105o19 105 20o o

o

20o45 20o49 22o14 22o22 22o06 22o35 22o15 21o52 22o13 21o47 21o36 21o26 20o52 21o12

III I III II II II II II II II II I I I

Mng T, Lai Chu 102 52 Mng T, Lai Chu 102 35 Snh H, Lai Chu 103 120 o

Mng Lay, Lai Chu 103o09 Mng Lay, Lai Chu 103 17o

Snh H, Lai ChuThan Uyn, Ngha L

103 24 103o48 104 09 104 02 104 33 104 29o o o o

o

Mng La, Sn La Mng La, Sn La Mc Chu, Sn La Bc Yn, Ngha L


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1.5.1.2. Mng li trm kh tng thu vn trn sng Chy Mng li trm kh tng thu vn trn sng Chy hin rt tha v phn b khng u, ch yu tp trung trung v h du; thng lu v vng h Thc B hu nh rt t trm o ma. Hin nay, trn lu vc sng Chy n h Thc B c 8 trm o ma, 4 trm o thu vn (4 trm kh tng v 4 trm thu vn), ngoi ra, s dng thm s liu ma trm thu vn Bo H trn lu vc sng Thao, st ng phn lu lu vc sng Chy. Danh sch cc trm KTTV c thng k trong bng 1.14 v hnh 1.1. Bng 1.14: Danh sch cc trm KTTV trn lu vc sng Chy TT Tn trm a danh Kh tng 1 2 3 4 Hong Su Ph Mng Khng Bc H Ph Rng H Giang Mng Khng, Lao Cai Bc H, Lao Cai Bo Yn, Lao Cai Thu vn 5 6 7 8 9 Vnh Yn Bo Yn H Thc B Thc B Bo H Vnh Tuy, Bc Quang Bo Yn, Lao Cai Yn Bnh, Yn Bi Yn Bnh, Yn Bi Bo Yn, Lao Cai 22022' 22010' 21044' 21044' 22032' 104028 104035 105003' 105003' 102025' II I III I III 22045 22043 22032 22014' 104041 104007 104017 104028 III III II II V Kinh Loi trm

1.5.1.3. Mng li trm kh tng thu vn trn sng Gm Mng li trm kh tng thu vn trn sng Gm n h Tuyn Quang cng rt tha v phn b khng u, ch yu tp trung trung v h du; vng thng lu thuc Trung Quc hu nh khng c s liu o ma. Hin nay, trn lu vc sng Gm n h Tuyn Quang c 8 trm o ma, 5 trm o thu vn (3 trm kh tng v 5 trm thu vn). Danh sch cc trm KTTV c thng k trong bng 1.15 v hnh 1.1.Trung tm D bo KTTV T, TS. Nguyn Vit Thi

28


Bng 1.15: Danh sch cc trm KTTV trn lu vc sng Gm TT Trm Sng V tr trm a danh Kh tng 1 2 3 Ch R Nng Ch R, Bc Cn 22047 105043 105014 105010 III III III V Kinh Loi trm

ng Vn Nho Qu Yn Minh Nho Qu

ng Vn, H Giang 23017 Yn Minh, H Giang Thu vn 22008

4 5 6 7 8

Bo Lc Bc M

Gm Gm

Bo Lc, Cao Bng Bc M, H Giang Ba B, Tuyn Quang Na Hang, Gm Tuyn Quang

22058 22044 22027 22021

105040 105022 105034 105023

I II III III

u ng Nng H Tuyn Quang Na Hang (H du)

1.5.2. Ch in bo kh tng thu vn Thng tin, s liu kh tng thu vn t li trm in bo c quan trc theo Quy phm [20, 21, 22] ri truyn v Trung tm D bo Kh tng Thy vn Trung ng (KTTV T) theo ch c quy inh trong Ma lut in bao [17]: - Cc trm kh tng in bo ma synop theo thi gian 6h trong c nm. - Cc trm thu vn in bo mc nc, lu lng v ma t 1/V-31/X theo quy nh v ch in bo mua lu, khi c ma ln trn 40 mm/gi th in bo hng gi. 1.6. PHN CHIA CC LU VC B PHN TRN LU VC SNG , SNG CHY V SNG GM CHO PH HP VI M HNH NAM 1.6.1. Nguyn tc chung Lu vc sng n p h cha thu in Ha Bnh, sng Chy n p h cha thu in Thc B v sng Gm n p h cha thu in Tuyn Quang c chia thnh cc lu vc b phn theo 2 tiu ch: + Cc lu vc phi c t nht mt im nc ra sng chnhTrung tm D bo KTTV T, TS. Nguyn Vit Thi

29


+ Trm thu vn cn dng hiu chnh kt qu phi nm trong lu vc b phn. S dng phn mm ArcGIS, kt ni cc lu vc con c to ra t phn mm Watershed v Google Earth kt hp 2 tiu ch trn phn chia lu vc thnh cc lu vc b phn nh yu cu ca m hnh NAM MIKE 11. 1.6.2. Phn chia cc lu vc b phn trn lu vc sng Qua phn tch a hnh, mng sng v mng li trm kh tng thu vn trn lu vc sng , ton lu vc c chia thnh 10 lu vc b phn tnh ton dng chy t ma. Trong 10 lu vc b phn c 6 lu vc cha sng chnh v 4 lu vc cha sng nhnh (Bng 1.16, Hnh 1.2) gm:

Da1

Da2 Da3 Da4

Da8 Da5 Da6 Da7 Da9

Da1 0

Hnh 1.2: Cc lu vc b phn trn sng Trung tm D bo KTTV T, TS. Nguyn Vit Thi

30Da_ Da_ Da_ Da_

Da_

Da_

Da_ Da_ Da_


Bng 1.16: Danh sch cc lu vc b phn trn sng K hiu Da1 Da2 Tn lu vc Khu vc khng ch Din tch km2 4.405 14.845

Trung i Kiu T thng ngun sng Amc n Trung i Kiu L Tin (Th Kh H) L Tin - Mng T Nm Ging Mng T - Lai Chu Nm Mc Lai Chu - Qunh Nhai Nm Mu Qunh Nhai - T B H Ho Bnh T thng ngun sng (L Tin) v t trm Trung i Kiu trn sng Amc n trm L Tin trn sng (L Tin). Lu vc khu gia sng chnh t L Tin n Mng T; Lu vc sng nhnh Nm Na (ng iu) Lu vc khu gia sng chnh t Mng T n Lai Chu v lu vc sng nhnh Nm P. Lu vc sng Nm Mc Lu vc khu gia sng chnh t Lai Chu n Qunh Nhai. Lu vc sng Nm Mu Lu vc khu gia sng chnh t Qunh Nhai n T B. Lu vc vng h Ho Bnh t T B n p Ho Bnh

Da3 Da4 Da5

3.860 6.820 5.685

Da6 Da7 Da8 Da9 Da10

2.130 2.268 3.420 3.580 5.890

1.6.3. Lu vc sng Chy Qua phn tch a hnh, mng sng v mng li trm kh tng thu vn lu vc sng Chy, do hn ch v li trm o, lu vc c chia thnh 2 lu vc b phn tnh ton dng chy t ma trong c 1 tiu lu vc cha sng chnh v 1 tiu lu vc cha h cha Thc B (Bng 1.17 v Hnh 1. 3):


31


Bng 1.17: Danh sch cc lu vc b phn trn sng Chy K hiu Tn lu vc Khu vc khng ch T thng ngun sng Chy n trm Bo Yn T Bo Yn n p Thc B. Din tch km2 4.898 1.434

SongChay Bo Yn HoThacBa H Thc B

SongChay

HoThacBa

Hnh 1.3: Cc lu vc b phn trn sng Chy 1.6.4. Lu vc sng Gm Lu vc sng Gm c chia thnh 5 lu vc b phn ph hp vi iu kin a hnh, li trm o c kh tng thu vn. Trong 5 lu vc b phn c 3 lu vc cha sng chnh, 1 lu vc khu gia v 1 lu vc h cha, c th nh trong bng 1.18 v hnh 1.4.Trung tm D bo KTTV T, TS. Nguyn Vit Thi

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Bng 1.18: Danh sch cc lu vc b phn trn sng Gm K hiu Tn lu vc Khu vc khng ch T thng ngun sng Nho Qu n trm thu vn ng Vn T thng ngun sng Gm n trm thu vn Bo Lc Lu vc khu gia t ng Vn trn sng Nho Qu v t Bo Lc trn sng Gm v Bc M trn sng Gm. Lu vc sng Nng t thng ngun n trm thu vn u ng. Din tch km2 4.650 2.459 2.947

LV1 ng Vn LV2 Bo Lc

LV3 Bc M

LV4 u ng

2.666 1.499

Khu vc t Bc M trn sng Gm v LV5 H Tuyn Quang t u ng trn sng Nng v p Tuyn Quang.

LV1 LV2

LV3

LV5

LV4

Hnh 1.4: Cc lu vc b phn trn sng GmTrung tm D bo KTTV T, TS. Nguyn Vit Thi

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