Flood Routing By Reservoir

Safety Inspection Of Dams

Ø The dams are national property – constructed for the development of the national economy and

in which large investments and other resources have been deployed.

Ø The safety of the dam is a very important aspect for safeguarding the national investment

and the benefits derived by the nation from the project.

Classification Of Dams

Ø Dams should be classified in accordance with size and hazard potential in order to formulate a basis for selecting dams.

ØThe height of the dam is established with respect to the maximum storage potential measured from the natural bed of the stream or

watercourse at the downstream toe of the barrier.

Size Classification

Selection Of Dams To Be Investigated

Ø The selection of dams to be investigated should be based upon an assessment of existing developments in flood hazard area. Those dams

possessing a hazard potential classified high or significant

Investigation

Purpose:The primary purpose of the Phase I investigation programme is to identify expeditiously those dams which may pose hazards to human life or property.

Scope:The investigation will develop an assessment of the general condition with respect to safety of the project based upon available data and a visual inspection, determines any need for emergency measures and conclude if additional studies, investigation and analyses are necessary and warranted

Evaluation Of Structural Stability

ØDesign and construction data

ØOperating records

ØPost construction changes

ØSeismic stability

Various flood routing Strategies:

(i) Inter-Basin water transfer assessment

(Ganga & Brahmaputra Basins)

(ii) Flood Management by Reservoir in Pakistan

(Tarbela & Mangla Reservoir)

(iii)Extended Muskingum method for flood routing

(Hirakud Reservoir)

The Indian River System:-

1)Himalayan component:- the sources of which are the glaciers of the Himalayas and the monsoon rains.

2)Peninsular component:-consisting of water mainly from the monsoon rains.

Methodology

Ø Based on the problems , aims, the data available, and technological know-how and its implementation.

Ø Various methods can be used to identify possible locations for dams and reservoirs , and to determine the best route of canals.

Meteorological Aspects

Ø Floods in Mangla catchment of river Jhelum and catchment of river Chenab occur due to monsoon depressions emerging from Bay of Bengal which travel to Rajasthan in India before moving to these catchments.

Hydraulic Aspects

The flood waves in river Jhelum and river Chenab join at about 5 km upstream Trimmu Barrage. In such a case the resulting flood peak may exceed the capacity of Trimmu Barrage which is 18300 cumecs endanger life and property in the flooded areas

Procedure used to ensure proper reservoir operation

1. Meteorological tracking of weather system as it originates from Bay of Bengal.

2. Quantitative rainfall forecast/measurement on Mangla Reservoir catchment.

3. The forecast/measured rainfall will be used to compute the inflow hydrograph at Mangla Reservoir using the rainfall-runoff models.

Conclusions

Ø Large storage volume is available in Mangla Reservoir can be utilized efficiently only if a proper decision support system is available. outflow scenarios should be formulated using the reservoir routing modules in which the maximum Mangla release is limited to avoid damage.

Ø The time of concentration of flood peaks at Mangla Reservoir and Marala Barrage are similar and travel in almost same time to point of confluence i.e. damage at Trimmu and downstream in river Chenab. Therefore it is essential that any Mangla release scenario should be checked for possible discharge.

Ø With outflow hydrograph from Marala Barrage by channel routing use combined hydrodynamic flow model of river Jhelum and river Chenab.

References

1.K.H.V. Durga Rao ,V. Bhanumurthy , P.S. Roy ,2009 .Application of Satellite – based Rainfall Products and SRTM DEM in Hydrological Modelling of Brahmaputra Basin .Indian soc. remote sens. (december 2009) 37:587–600.

2. Niladri Gupta, Petter Pilesjo, and Ben Maathuis, 2009. Use of Geoinformatics for Inter -Basin Water Transfer Assessment . ISSN 0097-8078, Water Resources, 2010, Vol. 37, No. 5, pp. 623–637.

3. Dr. shahbaz khan. Decision support system for reservoir operation to manage severe floods in Pakistan, National Engineering service of Pakistan pvt. Ltd.,576.

4. D. Nagesh Kumar , Falguni Baliarsingh , K. Srinivasa Raju ,2011.Extended Muskingum method for flood routing. Hydro-environment Research 5(2011) 127-135.