Diversion of Flood Water from Ganga at Kanpur

 Introduction  Study Area  Flow Pattern of Ganga at Kanpur  Quantification of Divertible Flood  Downstream side Flood Protection  Land Use / Land Cover ( Kanpur to Allahabad)  Different Options & Outcomes Presentation Outline #2

 CWC has been asked to make a pilot study on storing flood water in a meaningful way, in peninsular India and another in Ganga Basin.  Accordingly, a pilot study has been carried out for Diverting the Flood Water of river Ganga near Kanpur city and storing it in a Single/ Interconnected Chain of Tanks during the flood period.  Such stored water can be utilized for irrigation as well as rejuvenating Ganga in lean season. Diversion of flood water can also provide flood protection in downstream areas. Introduction #3

 In the study it has been proposed to construct a diversion structure upstream of Kanpur city and storing the flood water in a single / chain of reservoirs and releasing the same into Ganga at Shazadpur around 170 km downstream of proposed Barrage at Kanpur  The study area of reach between Kanpur and Allahabad is selected from the point of view of poor water quality in the reach during lean season.  The catchment area of Ganga upto Kanpur city is about sqkm.  Average annual rainfall of Ganga basin up to Allahabad is about 1069 mm and almost 89% (i.e. 950 mm) of it occurs during monsoon period (June- October). Study Area #4

 Hydrological data of Kanpur G&D site located on river Ganga for the period to (i.e.49 years) is used.  Average annual and monsoon (June- Oct) flows at Kanpur site are BCM and BCM respectively and remaining 3.35 BCM flows in rest of 7 months.  Three typical years representing maximum, average and minimum monsoon flows are selected and their details are tabulated below:  The rainfall and flow pattern shows almost 89% of annual flows of Ganga occurs in monsoon period resulting in floods during monsoon and shortage of watert in during rest of the year. Flow Pattern of Ganga at Kanpur #5

 The quantity of divertible flood basically depends on  Monsoon Discharge above which the flood water planned to be diverted (Q limit )  Reservoir Capacity behind the proposed hydraulic structure  Canal Carrying Capacity  Divertible flood water for different Q limit values computations: Quantification of Divertible Flood #6

 Based on the stage discharge curve and non monsoon flow pattern, the Q limit is fixed at 2000 m 3 /sec. Around BCM flood water can be diverted in an average year from Ganga without considering limitations of conveying capacity of the canal into account.  With Q limit fixed at 2000 m 3 /sec the Divertible Flood water with different canal capacities results :  Considering the existing canal capacities in India as well as general topography of the area, canal with a carrying capacity of 1000 m 3 /sec is assumed for further analysis. Quantification of Divertible Flood (contd..) #7

 Around 4.09 BCM (4090 MCM) of flood water can be diverted at Kanpur from river Ganga during monsoon with Q limit of 2000 m 3 /sec and canal capacity of 1000 m 3 /sec in an average year ( ).  Year wise divertible flood water computations show around 4.00 BCM (4000 MCM) of flood water can be diverted in 25 years out of 49 years or with an exceedance probability of 50%. #8 Quantification of Divertible Flood (contd..)

 Analysis shows not much flood reduction can be achieved either at downstream side of proposed barrage or at Patna as the diverting flood water is a small portion of the monsoon flood.  The highest flood Peak discharge at Kanpur of cumec ( ) can be reduced by 1000 cumec which is just 4%  A peak discharge at Gandhighat of cumec ( ) can be reduced by 1000 cumec which is just 1.2%  The diverting flood volume is around 15.6% of Monsoon Flows at Kanpur and 2.5% of Gandhighat  Owing to limiting canal capacity and negligible storage behind the barrage, no further flood reduction can be planned in the downstream side Downstream Side Flood Protection #9

#10 Catchment Area: sq km A peak of cumec in can be reduced by 1000 cumec which is 1.2% Downstream Side Flood Protection

#11 Downstream Side Flood Protection The highest flood peak discharge in of cumec reduces by 1000 cumec which is just 4%

Schematic Diagram of Layout of System - Plan

 In the study it has been proposed to construct a diversion structure upstream of Kanpur city and storing the flood water in a single / chain of reservoirs and releasing the same into Ganga at Shazadpur around 170 km downstream of proposed Barrage at Kanpur  Based on the stage discharge curves of Kanpur and Shazadpur sites and canal slope, the water levels at inlet and outfall points in the river are tentatively fixed as 111 m and 85 m  Based on the general topography, river levels at inlet & outfall points and different head losses, the depth of the pond / reservoir works out to be around 4m.  Approximate surface area of pond /reservoir with a depth of 4 m to accommodate 4000 MCM works out 1000 sq km (i.e.1,00,000 ha) #14 Reservoir Requirement for Storing Diverted Flood

 With the help of WRIS data, the land cover/ land use statistics for a stretch of 20 km width on either side of river Ganga between Kanpur and Allahabad is extracted and the details are as follows: Land Use / Cover in 20km stretch of Ganga ( Kanpur to Allahabad) #15

 Three options are studied  Diverting 4000 MCM flood water and storing in reservoir/ chain of tanks by acquiring the land from builtup/ agriculture land  Diverting flood water to the tune of storing in available inland wetland area  Diverting flood water to the extent of available tanks’ capacity in the vicinity Different Options #16

 The study shows sufficient flood water is available in Ganga at Kanpur during monsoon season but storing such flood water (4000 MCM) requires huge pond with a surface area of the order of 1,00,000 ha which can be done by acquiring builtup/ agriculture land etc.  The flood water during monsoon season carries a lot of sediment quantity in the order of ppm. Even after taking necessary measures, good amount of sediment enters the canal system and tanks and may lead to siltation.  Regular dredging and sediment removal techniques need to be applied to keep the canal and tanks free of sediment. A detailed study needs to be carried out to check the effects of sediment in the proposed system. Option I - Diverting 4 BCM of Flood Water #17

 Evaporation losses will be very high during non-monsoon season from ponds/ reservoirs with such a huge surface area  The diverted 4000 MCM water can augment the lean season flows by around 220 m 3 /sec at Shazadpur  The approximate cost of barrage and canal system may be in the order of 1000 crores and 500 crores respectively leaving land acquisition and other costs aside  Due to dense existing canal system the proposed canal may require cross drainage works also  Acquiring such land and construction of barrage, canal system and reservoir may not be commensurate with the benefits which will accrue upon completion of the works #18 Option I - Diverting 4 BCM of Flood Water

 The inland wetland area of around 151 sq km can be utilized to store the diverted flood water depending on its actual/ ground usage by constructing ring-bund if necessary.  By converting such inland wetland area into ponds with a depth of 4 m could lead to storing of water to the tune of 600 MCM.  The quantity of such stored water i.e. 600 MCM can augment the lean season flows by 33 m 3 /sec at Shazadpur which is around 13% of lean season average discharge  This water can also be used for irrigation purpose  Depending on the relative elevation of such area, diverting water into such ponds may require pumping / lifting of water. Option II – Diverting flood water for storing inland wetland area #19

 A detailed study to ascertain the usage of land, its profile and environmental impact assessment in case of converting these inland wetlands to pond needs to be taken up.  The system requires a diversion structure, canal system with pumping facility and additional structures also. #20 Option II – Diverting flood water for storing it inland wetland area

 From the land use statistics the tanks area approximately is 27.7 sq km. Considering the depth of such ponds to be approximately 4 m, the tanks’ storing capacity works out to 111 MCM.  Such stored water may not be sufficient enough to rejuvenate Ganga (augments the lean season flow by 6 m 3 /sec) in non-monsoon seasonan but can be used to irrigate approximately ha area.  Joining the existing tanks through canal system may require lifting of water as they may be at different elevations and far off from one another.  Diverting 111 MCM of water from Ganga, a diversion structure, lengthy canal system and additional structures needs to be established and the techno economic viabilty needs to be studied. Option III- Diverting water to store in available tanks #21

 The study has been carried out using information available with Water Resources Information System (WRIS) and hydrological data of few sites on river Ganga.  The elevation data (DEM) available in WRIS is very coarse. Possibility of storing the diverted water in tanks/ inland wetlands and inter connecting these tanks/ inland wetlands with a canal system requires detailed gound suvey.  While computing the volumes/ surface areas of reservoirs/ tanks, a regular shape is assumed.  Converting inland wetlands into ponds may have implications from environmental/ ecological point of view. Limitations of the Study #22

Schematic Diagram of Layout of System - Levels

#29

Schematic Diagram of Layout of System - Plan