Syphon spillway are structure that use in many dams and irrigation networks and drainage. This type of spillway works under increasing discharge like an ogee spillway. In this type of spillway, since there is no provision of mechanically/electrically/manually operated iron gates, symphonic action releases flood . Gates are only provided to release water from separate head regulator through tunnel to river. The main purpose of this short case study is to evaluate how much energy & manpower have been saved by designing the structures without iron gates looking the situation at that era and to overcome draught.
- Syphon Spillway,
- Manpower, Cost
Generally spillways are installed to evacuate the excess water or over-flow that the reservoir could not store. It can be installed independently from the body of the dam or can be a part of it, similar to spillway in concrete dams.
Syphon spillway consists of closed system with the shape of inverted U. The main advantage of siphon spillway is that within minor increase in the upper part of the water level, significant increase is observed in spillway discharge. The release of water does not require any electricity, manpower or any type of diesel operated engine and thus saving of millions so far. Other main advantage is that this type of spillway works automatically and their good performance without the need of any type of instrument likes gates or other stimulants.
The Murrumsilli dam also spelled Madem Silli and Mordem Silli is an earth fill dam on Silyari river, a tributary of Mahanadi river. It is located in Dhamtari district of Chhattisgarh and about 95 km from Raipur, is one of the most prominent architectural marvels in Chhattisgarh & primary function is irrigation.
Indian famine of 1899-1900 began with the failure of summer monsoon in 1899 over west and central India and during the next year affected an area 1,230,000 Sq.Km. and population of 59.5 million. The famine was acute in central province and Berar. There was also large crop failure in India, as a result inter-regional trade could not be relied upon to stabilize food prices.
Looking to the situation of famine and to overcome the situation, then British government decided to develop irrigation system near village Rudri and in the catchment of Mahanadi. Government planned to construct dam in Silyari river, diversion scheme i.e. pick up weir near Rudri and canal system to irrigate agriculture land up to Raipur, Baloda bazaar, Mandher, Lawan and nearby area.
As the electricity at that time was not available, it was decided by engineers that syphon system should be adopted which can run without electricity. The project was completed in 1929.
On 3rd june 1929, Rajendranath Sur (Govt Civil engineer of central province) was awarded by his majesty of Britain with title “Rai Saheb” for his exemplary.
Necessity Of Syphon Spillway
This dam with siphon system was built in between 1923-29 and is the first dam in central Asia to have syphon spillway. At that time there was dense forest in this region. No electricity and no road no communication system. The only way to reach Murrumsilli was by horse. Since there was no electricity, the engineers decided to design the system that can be ‘built-run-maintain’ without electricity.
Functioning Of Syphon
Murrumsiilly syphon, due to its unique function since last 87 years is world’s most successful syphon. In this case a hood is constructed over an ordinary overflow section of a gravity dam. The inlet of this hood is kept submerged so as to prevent the entry of debris etc. When the outlet cannot be sealed by tail water, some other devices, called priming devices, are used lead to an automatic priming of syphon at certain rise of water level above the crest.
In this spillway a baby siphon is installed as a priming device. When the water level reaches slightly above the crest, the baby siphon, which is an additional syphon, starts running full. The sheet of water issuing from it, is to shoot across the lower end of the main siphon, so as to seal it from the atmosphere1.
As the water level rises, the pressure from upstream increases and sheet of water automatically breaks, thus removing of air and symphonic action gets established after the air in the bend over the crest have been completely exhausted. In this syphon all 34 gates are not at the same elevation but in different level. The main purpose of different level is that, syphon did not start simultaneously, but releases water slowly. But if water level increases all 34 syphon run as shown in figure 3.
Manually operated iron sluice gates are provided to release water from dam to river and were imported from England as shown in figure 2.
Calculation Of Cost Of Maintenance Of Gates (assumed)
The cost calculation is based on the calculation of rates of gold between 1929 & 2017. The rates of gold at 1929 was Rs 18.43 (For 10 grams ) and at present 2017 Rs 29985/- (approximate) i.e rates increases 1627 times. If the Murrumsilli would have been completed in the year 2017 the cost would be around 31.17×1627= Rs 50876.29 lakhs or 508.76 Crore. Detailed calculations are given as below.
Note- Though the cost of the maintenance for the year 2001-2010 & 2011-2017 is quite higher side but this table is only a representation of saving in maintenance cost of Murrumsilli dam. At present the charges of electricity of Gangrel dam , which is about 22 km away from Murrumsilli is approximate Rs 4.00 lakhs per month. And other charges of maintenance are separate.
So total saving is around 65.66 Crore.
Result & Discussion
The main theme of this case study is to design such type of project in which saving of electricity & manpower can be achieved by technology. Now a day’s electricity and manpower is precious. Hence projects should be so designed that saving of manpower and electricity would be main criteria in addition to other main advantages.
Think the time when this project Murrumsilli was constructed. Since there was no electricity in that area & difficulty in maintenance due to communication problem, engineers designed the structure in such a way, in which, no electricity was required for operation. And even, suppose for any reason, if staff is absent at dam site, there will not be any danger of failure of structure & will be totally safe.
Second thing is that this marvelous structure is constructed with 100% accuracy in levels & dimensions of different parts of structure. That’s why the structure satisfies all purpose.
- Based on the data presented the following conclusion may be drawn-Project should be designed taking Electricity saving as well as for minimum manpower required for maintenance.
- Flood estimation for 200 years looking to deforestation and change of climate day by day.
- It will be advantageous to use technology of structures already constructed in past. We should learn how to save water, electricity and manpower.
- Structure should designed for maximum benefit and minimum cost as observed in this project.
- SANTOSH KUMAR GARG Irrigation Engineering and Hydraulic Structures, Khanna Publishers Delhi. fifth reprint 2012
- AMIN GHAFOURIAN ANDMOHD NORDIN ADLAN, Discharge Coefficient in Siphon Spillway with Different Cross Sections, World Applied Sciences Journal 17(2); 162-167,2012
- KAMANBEDAST A, GHOLIZADEH, B, The Study of siphon spillway hydraulic by Modeling (physical and software), Journal of Applied Science Research, 8(5); 2548-2533, 2012
- Gold Rates from Penta Gold.
Images from web site of Water Resources Department, Government of Chhattisgarh, India