Cau 45:Dinh nghia chuan dong chay namva y nghia cua chuan dong chay nam cua 1 con song o 1 mot vi tri nhat dinh?Dong chay namduoc bieu hien boi cac dai luong nao?cach xd chung?

-Dinh nghia:ladai luong tb nhieu nam cua dong chay binh quan hang namvoi dk canh quan dial y ko thay doi cung thuoc thoi dia chat ngay nay va cung muc do khai thac kinh te cua con nguoi.

- Y nghia:No danh gia duoc kha nang tiem tang ve nguon nuoc trong 1 luu vuc hay so \sanh kha nag nay giua cac luu vuc hoac long song khac nhau.Nocungla dac trung co ban nhat dugn trong thiet ke ho chua va cac cong trinh t ren song khac.

-Mot cach so luoc co the noi dong chay nam duoc tinh bang tb so hoc cua chuoi dong chay tb nam cua mot tram thuy van thuong ky hieu bang chu so "0" duoi dang dai luong can xem xet.

1.-Luu luong dong chay namtb nhieu nam Q0(m3/s)

2.-Tong luong dong chay nam tb nhieu nam W0 (m3,km3..)

3.- Mo dun dong chaynam tb nhieu nam M0(1/s.km2)

Cau47 neu toom tat phuog phap va cac buoc tinh chuan dong chay khi co it so lieu va ko du so lieu.

*tinh toan dong chay nam khi co it so lieu.

-it so lieu tuc la dung luong mau n nho hon so nam doi hoi trong truong hop nay ta can tin bien phap keo dai so lieu dong chay theo 2 pp suu:

a. keo dai chuoi dong chay theotuong quan voi mua nam.

- loai nay ap dung o nhung noi thoa man cac dk sau:

1) xet thay luong mua anh huong quyet dinh toi dong chay

2)cac tram do mua khong che duoc luong mua trong luu vuc

3)co nhung nam do song song ca dong chay va mua

4)quan he giua dong chay va mua tot ,dam bao sai so cho phep.

* cach lam:xay dung Phuong trinh hoi quy roi ngoai suy dong chay(Q) tu mua(X)

b. keo dai chuoi dong chay bang pp tuong quan voi luu vuc tuong tu.

Hai luu vuc F1 va F2 duoc goi la tuong tu ve dong chay nam va co the noi suy so lieu cua luu vuc nay cho luu vuc kianeu thoa man 3 yeu cau .

1)tuong tu ve cac nguyen nhan hinh thanh dong chay: dieu kien dia ly tu nhien khi hau,co the thuoc mot quan he tram tren tram duoihay 2 con song khac nhau.

2)mot luu vuc co dung luong mau dong chay du dai: hai luu vuc co cung mot so nam quan trac dong chay.

3)dien tich 2 luu vuc xap xi nhau.

Cach lam

1) keo dai bang pp tuong quan don gian.

Cham cac diem luu luong trong thoi gian dong quan trac cua 2 tram tren do thi.neu cac diem phan bo tao nen mot bang diem hep co xu the duong thang , ta ve duong trung binh va keo dai so lieu theo duong nay voi dk quan he nay co he so tuong quan >=(0.7-0.8) Q

2)keo dai bang pp ty le.

Dung khi mph tren do thi the hien ko ro.Neu gia thiet rang dao dong dong chay nam cua 2 tram A va B trong cung mot khoang thoi gianla nhu nhau , tuc la:

QoA/Qob=QtbA/QtbBtu do suy ra QoA=.....

Trong do:

QoA= chuan dong chay cua tram can timnhung it so lieu

Qob=chuan dong chay cua tram co du so lieu

QtbA &QtbBla Qtb cua so nam quan trac song song.

Cau48luong dong chay nam thiet ke la gi? Neu cac buoc tien hanh de xac dinh luong dong chay namthiet ke tai mot vi tri tren song trong truong hop du so lieu quan trac.

Luong dong chay nam thiet ke la luong dong chaynam ung voi tan suat thiet ke cho truoc

-luong don gchay nam thiet ke la dai luon gco ban dugn de tinh toan thiet ke cac cong trinh tren song

-Luong dong chay nam thiet ke duoc bieu thi duoi cac dang sau:

+Luu luong dong chay nam thiet keQp(m3/s).

+Mo dun dong chay nam thiet ke Mp(l/s/km2).

+Lop dong chay nam thiet ke Yp(mm).

+tong luong dong chay namthiet keWp(m3,km3).

-Cach tinh:

a. Dung tinh duong tan suat kinh nghiem:dung dung tan suat kinh nghiem theo cac buoc sau

1).Lap bang tinh va ve duong tan suat kinh nghiem

2).Tra giatri luu luong dong chay nam tren duongtan suat kinh nghiem

-neu tan suat thiet ke can tra nam ngoai cho phep cua duong tansuat kinh nghiem thi

+Neu khoang can keo dai ngan thi ta keo dai theo xu the

+neu khoang can keo dai qua lon va can do chinh xac cao thi dua vao duong tan suat lu luan(PIII,Kriski-Melken,ham mu...)nhu trinh bay sau day:

b .Dung duong tan suat ly luan de keo dai de keo dai duong tskn

b1. dung dung PIII:cac buoc tien hanh nhu sau

1).tu c huoi so lieu thuoc do suy ra tinh cac tham so thong ke Qtb,Cv,Cs.

2).Voi gia thiet luat phan bo xs cua duong tansuat kinh nghiem co the xap xi boi phan bo PIII tren co so cac tham so thong ke duoc tinh o trensuy ra ve duong tan suat ly luan

3).Dung pp thu duong de chinh lai cac tham so thong ke sao cho tren do thi duong tan suat ly luan va duong tskn phu hop nhau(gan trung nhau)

4).voi duong tsll da hieu chinh nay, hoac dung do thi or dung cong thuc tim ra gia tri dong chay nam thiet ke

*1 so diem chu y:

1).nen dung cong thuc tinh t strong tinh toan va ve P=(m-0.3)/(n+0.4)*100%

2).Khisu dung hamPIII chu y gioi han thay doi cua Cs phai la 2Cv=Cs>=2Cv/(1-Kmin) chi ca 2 ve cho 2Cv ta co 1>=1/(1-Kmin)  Kmin vay khi Cs Kp

-De khac phuc nhuoc diem n ay ta dung duoc K-M .

Dung duong kriski-melken.

Khi ko ap dung duoc duong PIII (khiCv

Cau49. trinh bay pp tinh toan luong dong chay nam thiet ke trong truong hop chuoi so lieu ngan va ko co so lieu.

* Khi so nam quan trac dong chay it can tim bien phap keo dai dong chay.

-viec keo dai dong chay noi chung co the phan thanh 2 loai sau:

1. keo dai theo quan he tuong quan giua mua nam va dong chay nam.

- pp nay can co tai lieu do mua tren luu vuc trong nhieu nam trong do co nhung nam do dac song song ca 2 yeu to mua va dong chay; pp nay chi su dung duoc voi nhung vung ma luong mua co anh huong quyet dinh doi voi dong chayva tram do mua khong che duoc luong mua trong luu vuc.

2. keo dai tai lieu bang pp tuong quan dong chay cua luu vucnghien cuu va luu vuc tuong tu.

- de keo dai tai lieu trong truong hop nay can chon luu vuc tuong tu co tai lieu quan trac dong chay trong nhieu nam quan he giua dong chay nhieu nam o 2 luu vuc co the co dang :Mx = k.Ma+B.

Mx ,Ma cac mo dun dong chay cua luu vuc nghien cuu va luu vuc tuong tu.

K: he so.

*khi khong co so lieu quan trac.

Khi hoan toan ko co so lieu quan trac dong chay ta co the dung mot so pp sau:

1. xac dinh dong chay chuan theo pp luu vuc tuong tu:

+van de co ban cua pp nay la chon luu vuc co dieu kien hinh thanh dong chay tuong tu nhu luu vuc nghien cuu.do 2 luu vuc ko the going nhau hoan toan nen ta phai hieu chinh laic ac dac trung dong chay cho phu hop voi cac dac trung o luu vuc nghien cuu thuong co the muon o luu vuc tuong tu mot trong cac dac trung sau:modun dong chay chuan hoac he so dong chay nam binh quan.

1) pp mun modun dong chay chuan

trong truong hop luu vuc tuong tu va luu vuc nghien cuu co cac dieu kien thuy van va khi hau tuong tu thi co the muon modun dong chay cua luu vuc tuong tu(Mo) cho luu vuc nghien cuu.

Ta co Mo=Mca.

2) pp muon he so dong chay nam binh quan

3) dung he so dong chay nam binh quan cua luu vuc tuong tu cho luu vuc nghien cuuta co the tinh duoc lop dong chay chuan bang cong thuc

Yo =n.Xo=Yoa/Yon.Xo.

2.xac dinh dong chay chuan tren modun dong chay.

Modun dong chaycua luu vuc tinh theo cong thuc:

Mo=(m1f1+m2f2 +....+Mnfn)/F

m :modun dong chay tinh binh quan cho cac dien tich cuc bo fi khong che boi cac duong dong muc ke nhau.

3. dung cong thuc kinh nghiem de tinh dong chay chuan.