FLOW FORECAST AT DOWNSTREAM LOCATIONS OF RED RIVER SYSTEM

RED RIVER SYSTEM Hanoi hydro. station

SCHEMATIZATION OF RED RIVER NETWORK FOR FLOW FORECAST

METHODS USED FOR FLOW FORECAST IN RED RIVER SYSTEM 1. Traditional methods - Using graphs - Correlative water levels between up and down stations 2. Mathematical models - MIKE11 - SH2 model

Traditional methods 1. Using graphs: Based on long term data at the stations along the river, number of graphs H Hà Nội(t+36h) = f(∑Q BenNgoc+PhuTho+VuQuang ) ( Both water rising and going down phases ) H Hà Nội(t+24h) = f(∑Q BN+PT+VQ ) (Both water rising and going down phases) H max Hà Nội = f(∑Q BN+PT+VQ ) max Advantage: simple, easily applying and quickly Disvantages: low accuracy

Traditional methods

2. Correlative water level between stations - Based on the rule “water flows from upstream to downstream” - Travelling time of flow depends to hydraulic regimes and topography Relationship form Hdt = f [H u1 (t-k 1 ), H u2 (t-k 2 ), …, H uj (t-k j )] Advantage: simple, easily applying and quickly using H(Q) both up and downstream Disvantages: Applied only for river sections where its bed slope is high; limited number of branches; low affacted by backwater; travelling time is not much changed Applied during low flow

Mathematical models 1. Mike11 2. SH2 model

It was built up and put into practice for flood forecast at lower part of Red and Thai Binhf river system from Forecasting results by using this methods is quite good and it becomes main method applied now. River system is schematized as figure with - Cross section: updated every year when having new investigation - Boundary conditions: + Upper: Q + Lower: H APPLICATION OF MIKE11 FORECASTS FLOOD AT LOWER PART OF RED RIVER SYSTEM Thái Bình Bến Ngọc Phú Thọ Vụ Quang Thái Nguyên Chũ Cầu Sơn Cửa Đáy Ninh Cơ Cửa Cấm Văn Úc Ba Lạt Trà Lý Lạch Tray Đá Bạch Trạm TV Hà Nội

PROCEDURE USED FOR FLOOD FORECASTING BY APPLICATION OF MIKE11 Step 1: Updating observed data (H,Q) at upper boundaries. These data are extracted from data base with real time Discharge at boundary points is taken by H-Q graph.

Step 2: Checking H,Q at upper boundaries It can be used extra methods to interpolate lacking data at special point in time series of water level and discharge if needed. Checking and revised data before they are put into model.

Step 3: Continuous updating upper boundary: Based on 4 obs/day, next 4 forecast data are done. Boundary data can be revised with 4 observed above before putting to the model in the next step. Step 4: Prepare simulated file (1): Updating forecasting time Updating simulated duration

Step 4: Prepare simulated file (2) Updating forecasting time for data synchronization (updating latest time having observed data)

Step 4: Prepare simulated file (3) Updating forecasting discharge at 6 upper boundaries. Data and drawing in left side to check visually the consistency of data.

Step 4: Prepare simulated data (4) Updating simulated duration. Starting time of forecast is at 7 a.m every day Ending time of each forecasting is 48 hours later. Step 5: Running MIKE 11

Step 6: Announcement of forecasting results at certain locations along the red and Thai Binh rivers Using Mike View, H(Q) for 48 hours at any locations can be seen. - Sơn Tây: (SONGHONG 29807) - Cầu Nhật Tân: (SONGHONG 66252) - Hà Nội: (SONGHONG 72392)…

Conclusions Advantages: -More accuracy results using this package. -It can be received forecasting results at any location along the river. -It is taken into hydraulic interaction between river branches of Red and Thai Binh system. Disadvantages: -Forecasting flood peak value is litter bit higher than real one. -Forecasting value will be not correct if getting wrong input at upper boundaries or/and high fluctuation of release water from reservoirs such as Hoa Binh, Son la, Tuyen Quang.

SH2 MODEL 1.Discription on SH2 model Equation governing in the model is used in SSARR: In which : is average discharge at node j between t and t+1 K is considered as travelling time: K = P.Q m j+1 P, m – parameters determined by optimization method. SH2 is applied to simulate flow H (Q) at Son Tay from H(Q) of Hoà Binh, Phú thọ, Vụ Quang về Sơn Tây  t  t Q (t+1)ST = (QHBVQ - QtST1 ) + ( QPT - QtST2) + QtST k1 +  t/2 k2 +  t/2 k1 = 150.Q 0.25 HBVQ k2 = 160.Q 0.33 PT

SH2 MODEL This model is also used to forecast flow at Ha Noi and Thuong Cat from flow at Son Tay. Mô hình mô phỏng dòng chảy từ Sơn Tây  t Q t+1 HNTC = ( Q ST - Q t HNTC ) + Q t HNTC k 3 +  t/2 k 3 : Travel time in river sections of ST-HN and HN-TC Advantage: - Results is more accuracy in case of slow changing flow. Disadvantages: - Total discharge in upper boundaries is needed for this model - This model is invalid for areas affacted by tide.

SH2 MODEL SH2 PACKAGE is included flowing modules: Automatic softwave to exploit data. Supporting module with 3 functions: simulation, error treatment and interpolation. Software to draw graphs and time series Softwave to create menues. Forecsting module and restoration of flood series. Translated module to connect all modules into package.

APPLICATION OF SH2 PACKAGE TO FOREAST FLOW AT LOW AREAS OF RED RIVER Running SH2 package Data extraction Step 1: Reading and checking observed data

Input total discharge at: Hoà Bình, Phú Thọ, Vụ Quang for 48hours forecasting Step 2: Forecasting at low sections of red river

Step 3: to see forecasting results BẢN TIN DỰ BÁO MỰC NƯỚC HÀ NỘI Thời gian phát báo :10h Tham số phân phối : 0.81 Hoà Binh mở/đóng : 01 Thời gian TGDK Lưu lượng Mựcnước

Summary and result analysis Drawing results of different scenarios Analysis and selecting reasonable results Discussion in the staff group and select value for announcement officially Editing the forecasting news

Conclusions and Kết luận và kiến nghị Conclusions -At present, The traditional and mathematical models are jointly used to forecast flow parameters at low parts of Red and Thai binh rivers. It can make use of advantages of each methods and select the best forecasting results at downstream part of red river. -Traditional methods need less input data and quick results for that we can recognize the flood situation, specially flood peak. -Mathematical models need detail input data, but we can get flow parameters at any location and time. -At present, there are many reservoirs built in upstream rivers, so it affects much to forecasting results. So the combination of different forecasting methods is necessary, but improvement of forecasting quality by using mathematical models is prioritized. For example using parallel models of MIKE11 and SH2 daily and deciding final results for forecasting news.

Recommendations -Updating regularly data and new graphs for traditional methods. -In order to improve forecasting quality, the combination of MIKE NAM, reservoir regulation into MIKE11 and SH2 is neccesary. -For getting good forecasting results and extension of forecasting duration at downstream points, upper input data need to improved both in value as well as longer time of forecasting

Thank you for your attention!