A GATE OPERATION METHOD FOR DAMS WITHOUT SUPPORT FACILITY (A Dam Operation Method Using Only Reservoir Water Table)

Transcription

1 A GATE OPERATION METHOD FOR DAMS WITHOUT SUPPORT FACILITY (A Dam Operaion Mehod Using Only Reservoir Waer Table) April 2016 Please conac wih Dr. Nguyen i Son Hung for deails nguyen@cie.co.jp

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3 A GATE OPERATION METHOD FOR DAMS WITHOUT SUPPORT FACILITY (A Dam Operaion Mehod Using Only Reservoir Waer Table) DO YOU/YOUR ORGANIZATIONS FACE THE FOLLOWING ISSUES? (1) There are a lo of earhdams wih spillway gaes, bu no budge o build an operaion suppor sysem ha measures /calculaes inflow, discharge ec. and guides gae operaors how o do when floods come. (2) There is in shor supply of experienced expers/engineers for dam operaion. (3) Due o lack of experience, dam operaors someimes have caused very rapid discharges ha brough on serious damages of human and asse o he downsream. Namely, he dam operaions have caused human -made disasers. (4) Dambreaks by poor operaion have happened due o op dam overflows. (5) Dam operaion rules and regulaions define he reservoir waer levels or rules o be kep wih bu hey have no descripion for how o do o achieve hem. WHAT IS THIS METHOD USEFUL FOR? (1) Dam operaor may operae easily and effecively wih using only reservoir level and diagrams already prepared based on he acual rules and regulaions of dam operaion and he hydrological and hydraulic feaures of reservoir, is cachmen and downsream river channel. (2) Rapid discharges will be avoided and anybody who operaes will have he same resul. Namely, i does no require any skill or experience of he operaors. Therefore, he operaors will have no any menal sress due o dam operaion. AN EXAMPLE OF DIAGRAM USED TO OPERATE SPILLWAY GATES Figure 1 shows an example of he mehod (herein, we call as Imamura mehod) used in he case dam has no operaion suppor sysem, namely, using only reservoir waer level wih is diagram o operae spillway gaes. The main gae operaion o large floods may be sepeaed ino he following four sages: (1) Pre-flood regulaion sage, (2) Flood regulaion sage, (3) Pre-emergency sage and (4) Emergency sage. The diagram is used o operae for he four operaion sages as follows: -Pre-flood regulaion sage- Role and difficuly: The crucial roles of his sage are (1) No saring flood discharge oo early o advoid wase waer discharge, and (2) No delaying he appropriae iming o sar o flood discharge o avoid aferward having o implemen very rapid flood discharge so he users of downsream river have no enough ime o evacuae from is river waer level increase due o he flow discharge from he dam. Because hese wo roles conflic wih each oher, i is difficul o deermine he appropriae iming o sar flood discharge. Soluion: -The ligh blue verical line in Figure 1 shows he sage of waer supply (domesic and irrigaion or power generaion), he supply flow is always consan. 1

4 Reservoir Waer Level - The black dashed cuves shows he candidae relaionships beween discharge and reservoir waer level (herein call he o -H relaionship) of dam operaion, namely, each curve of hem defines he flow o discharge for corresponding revervoir waer level, in he Pre-flood regulaion sage. - The iming o sar flood discharge is he ime he operaion ransfers from waer supply sage o Pre-flood regulaion sage, namely, raferring from he ligh blue verical line o a curve of he black dashed curves. - To define he ransfer iming, he reservoir waer level incremen H in he given ime inerval will be used. Namely, when he poin describring a pair of reservoir waer level and is incremen, namely (H, H) approaches nearly o one of inersecions of ligh blue verical line and black dashed cuves, he ransfer shall be done. In Figure 1, he ransfer iming and he o -H relaionship afer being ransferred are respecively described by he poin and curve of purple color. By his mehod, he opearaion will avoid he very rapid flood discharge and ransfer o he Flood regulaion sage wihou delaying. i o H 1 os o H 1 H n H n H -Flood regulaion sage- Pre-flood conrol operaion sage Role and difficuly: The crucial roles of his sage are (1) No saring he Pre-emergency sage oo early in order o posiively decrease discharge flowing o he downsream river, and (2) No delaying he appropriae iming o sar he Pre-emergency sage o assure enough ime for downsream people o evacuae from flooding and o avoid he op dam overflow ha will cause dambreak. Because hese wo roles conflic wih each oher, i is difficul o deermine he appropriae iming o sar he Pre-emergency sage. Soluion: - Using he blue curve o operae spillway gaes in he Flood regulaion sage. - The black dashed cuve group in he Pre-emergency sage of Figure 1 shows he candidae o -H curves in his sage. 2 oc

5 - To define ransfer iming o he Pre-emergency sage, he reservoir waer level incremen H in he given ime inerval will be used. Namely, when he poin describring a pair of reservoir waer level and is incremen, namely (H, H) approach nearly o one of inersecions of he blue curve and black dashed cuves, he ransfer shall be done. In Figure 1, he ransfer iming and he o-h relaionship afer being ransferred are respecively described by he poin and curve of orange color. By his mehod, he opearaion will avoid he very rapid discharge and ransfer o Emergency sage wihou delaying. H f H f -Pre-emergency and Emergency sages- Flood conrol operaion sage Roles: Avoiding he op dam overflow ha will cause dambreak. Soluion: Operaing wih using he orange and red curves of o-h relaionship. oc of od H pe H pe H oc of ope od H e H e Pre-emergency and Emergency operaion sages FOR MORE EFFECTIVE USE OF RESERVOIR STORAGE oc ope od oe oi In he case he acual operaion rules may be changed or here is a budge o insall operaion suppor sysem, we may propose new rules and sysems based on he high-level Imamura mehod o use more effecively exising reservoir based on our professional experiences. 3

6 Reservoir Waer Level i o H 1 os o H 1 H n H n H oc H f H f oc of od H pe H pe H oc of ope od H e H e oc ope od oe oi 4

7 Reservoir waer level (m) Waer Level (Flood 1/200) Waer Level (Flood 1/100) H=0.02 m Gae openings of spillway No.2 PRE-EMERGENCY OPERATION STAGE: + Operae wih he orengy curve EMERGENCY OPERATION STAGE: open all gaes Gae openings of spillway No.1 Normal waer level in No Flood Term FLOOD REGULATION OPERATION STAGE: + Operae wih he blue curve + Based on H & H o deermine he iming o ransfer o PRE-EMERGENCY OPERATION PRE-FLOOD REGULATION OPERATION STAGE: + wih he ligh blue curve Normal waer in Flood Term + Based on H & H o deermine he iming o begin he flood discharge + Afer ha operae wih he purple curve. Noe: + H: Reservoir waer level + H: Reservoir waer level rise in he given ime inerval (herein 30 minues) oc odmax oimax Discharge 800 of spillways (m3/s) FIGURE 1 GATE OPERATION WITH RESERVOIR WATER LEVEL PRE-FLOOD REGULATION OPERATION FLOOD REGULATION OPERATION PRE-EMERGENCY OPERATION Discharge curve (Free flow) of Spillway No.1 Discharge curve (Free flow) of Spillways No.1 & No.2 EMERGENCY OPERATION 5

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