Approach and methodology of Technoeconomical issues

Approach and methodology of Technoeconomical issues for Koyna let out water utilization

Introduction

Koyna dam is in Satara district of Maharashtra state. It has been constructed about 35 years before. Since then it is giving a very good service to the country. Amongst the other uses the prime importance of this dam that it is very successful Hydroelectric Project in the country. Having a natural site in the Sahyadri ridges on Western Ghats, the catchment provides for a reliable rainfall of about 3700-mm per year. It has a huge storage of 98 TMC at an altitude of 650 m above sea level.

Power generation is being done taking the advantage of fall available. It has IV stages. Total power generation in these stages is about 1920 MW. Potential energy of Waterfall is used to generate the electricity. Initial used water is collected in Kolkewadi dam which is having a capacity of 1.3 TMC at an altitude of 137 m. Further this head is also used for electricity generation. Finally water is let out through tailrace.

Every year, 67.5 TMC water is being let out from Koyna Hydroelectric Project to the Vashisthi River and it then merges to the Arabian Sea. After electric power generation the tailrace water finds its way to sea without any fruitful utilization. In quality it is sweet water and can be treated to drinking water level standards. Quantity is equivalent to cater for the needs of about 2 crore population at the urban standards of 250 lpcd. Drinking water is a prime issue with the Maharashtra state and it has not been solved upto the level of satisfaction. Availability of tailrace water and demand for water in the influence zone of this hydroelectric project is required to be ascertained.

There are alternative uses of water. It is required for drinking. It is required for agriculture and industry. It can be used for development of fisheries, and it can be alternatively used for navigation and recreation. At present huge quantity is just running to sea. To transform it into better usable entity some financial input is required. Naturally, any project has to become financially viable. Equivalent returns are expected.

Level at which the tailrace water is available is about 10.00 m. It meets River, which further merges into sea. This distance is hardly 7 to 8 km.
Sweet water is turned into saline water. This is not suitable for drinking.
Nearest town Chiplun is getting water through Vashisthi River. The demand is much less compared to the available quantity. Diversion to any other area is remote, as level at which it is available is just 10 m. Hence, something different has to be thought of.

Brief details of the existing project.

Koyna dam storage capacity 98 TMC
Average rainfall in the catchment 3700 mm
FRL 657 m
Power generation at the foot of dam 50 MW
Header Tunnel to Pophali length 3800 m
Power generation at Pophali 300 MW
Tailrace water tunnel length upto Kolkewadi 4200 m
Kolkewadi dam FRL 132 m
Kolkewadi dam capacity 1.3 TMC
Headrace tunnel length 1400 m
Power generation at Allore 1000 MW
Tailrace water tunnel start level 22 m
Tailrace water tunnel ends level 10 m
Quantity of tailrace water coming out 67.5 TMC per year
185 mcft/day
5.28 mcum/day
5280 MLD

Urban water requirement in Mumbai urban aglomeration

Urban requirement for drinking water may vary according to size of city and the configuration of industrialization. Present urban supply in Mumbai, Thane etc.is 250 lpcd . Major population in the urban agglomeration of Mumbai, Thane, Kalyan, New Mumbai corporations is 1.5 crores. The prospective population will be 4 crores. Vaitarana is higher level and avialability of water is by gravity near the city. They are reliable sources and time proven for dependability.

Present water supply availability to this aglomeration is from Vaitarana and Bhatsa dams. They are about 80 to 120 km away from these agglomerations. There is a substantial contribution from Barve and Morbe dam. Industrial demand in this agglomeration is very high and it is taken care of by these additional sources.

As far district boundaries are concerned Vaitarana is situated in another region.It is possible to divert water from Vaitarana to Nasik Region. A short length tunnel may be required to be constructed. But considering the
requirement of the Urban agglomeration, Vaitarana stage I,II,III are planned.
If any economical alternative can replace this source it will boost economy of Nasik and Marathwada region.

Tailrace water conveyance to Mumbai urban aglomeration

With the prospective demand of the Urban agglomeration of 4 crores after 30 years will be 4*10^7*300 =12000 MLD. This demand will be generated in a span of 30 years. It has to be planned to be developed well before. Maintaining the existing sources and developing new sources might be in process. It may cost considerable amount. Equivalent quantity is available at the talirace of the project. It is running to sea unutilized. The quantity is available practically at the same ground level. The distance is much more i.e. about 250 km. frictional head will be about 175 m. Total pumping head can be 200 m.

Conveying water to Mumbai Thane Urban agglomeration from Koyna tailrace is a substantial task. Eight no. of 4000 mm dia. pipes will be required.

Approximate cost of pipes can be worked out as following,
Weight of 4000 mm dia. Pipe 15 mm thickness per meter is 1.48 MT
Weight of 250 km, 8 No. pipes 2957880 MT.
Approximate cost Rs. 12423 cr.
Approximate cost including land acquisition, laying, lining, Rs. 18000 cr.

Pumping cost required from Koyna tailrace to 250 Km away and at 200 m head for the whole quantity of water will be as following,

Pumping 5280 MLD at 200 m head will require 244444 HP.
At Rs.5000/HP Installation cost would be Rs.122 cr.
With 20 hr working Energy cost will be Rs. 1.82 cr per day.
Annual pumping cost will be Rs.666 cr.

Assuming 60 days storage for pumping about 11.1 TMC capacity storage will be required. At Rs.2.5 cr per TMC total cost Rs.28 cr will be required.

Approximate capital cost Rs.18000 cr
Rs. 122 cr
Rs. 28 cr
Total Rs.18150 cr

Cost of raw water can be approximately calculated as following,
Capital cost Rs.18150 cr
Annual M&R cost Rs. 1815 cr
Annual Repayment cost Rs. 2270 cr
Energy charges Rs. 666 cr
Estt.cost Rs. 300 cr
Total Annual burden Rs. 5051 cr
Annual water supply 1927200 ML
Cost of water Rs. 26216 per ML
Rs. 26 per 1000 lit.

Cost sensitivity of the components

Cost sensitivity does not seem to be related to pumping or gravity type of system. Major cost is due to cost of pipe. Length involved is much more. Also the diameter required is huge. Tailrace water is available at very low level. Hence local pumping for creating head will also involve similar costing.

Tunnel alternative

Conveying tailrace water through a tunnel of 250 km long and of appropriate size is another alternative to 4m dia. 8 number of pipes. Its economics will have to be worked out. Considering the huge land cost required above ground tunnel may be economical. Approximate size can be about 8 m dia.
For checking this alternative rock strata available, underground water,necessity of lining, etc., parameters will have to be studied.

For taking water from tailrace to Mumbai the possible locations to receive are Pise or at Bhandup water works. If sufficient head is not available then Pise is only alternative.In case sufficient head is available then Bhandup water works can be thought of.

At present for BMC and Thane water lifting point is at Pise. Water from upstream storages of Vaitarana and Bhatsa Dams comes by gravity to Pise.
In case of conveying water through tunnel the needy towns and villages on way can get this water by local pumping. This being raw water necessary treatment will have to be considered.

Alignment of the tunnel can be preferably along the National Highway 17.
It can cover major locations onway. For Mumbai urban agglomeration this is not the only source. However, remaining water will supplement the existing source.

To compensate for the head loss during the transit initial level at the entry of the tunnel will have to be higher. Present tailrace water level is about 10 m. An artificial storage will have to created to pump the water to a suitable location. The best alternative is to use Kolkewadi dam.



Recycling tailrace to Kolkewadi

Pumping water to Kolkewadi is fruitful in view of power generation also. It is nothing but recycling of tailrace water to upsteam in Kolkewadi dam.
Dam FSL is 137.50 m .Tailrace water level is about 15 m average.
Lift involved is 122.5 m.
Quantity is 5280 MLD or 61111 lit per sec.
HP required 140915 HP
Annual energy cost will be 384 crores.This is quite a huge amount. Its economics will have to be studied.
For this purpose both the alternatives will be required to be studied in details.

Generation capacity
Phase I & II 65 MW 4 No. 260 MW
75 MW 4 N0. 300 MW
20 MW 2 MW 40 MW

Phase III 80 MW 4 No. 320 MW

Phase IV 250 MW 4 No. 1000 MW

Total 1920 MW

Daily 1920 MW generation capacity can get Rs.77 lakh per day and about Rs.280 crores per year at minimum rates. Prima facie pumping tailrace water does not seem to be practical.

Power generation is very important as far as the State income is concerned. It is important from the industries point of view also. Hence, any change in the infrastructure will have to be weighed against all economical angle.

Rough costs of pumping tailrace water either to Kolkewadi dam or to Mumbai through conveyance system show that they are not economical as they involve comparatively much more cost in the maintenance itself. If it is absolutely required then it should be viable only for the commercial utilization. Rate for commercial utilization is normally 4 to 5 times more than the domestic rate for water.

Further the capital cost required for conveying the water to Mumbai is huge and its financial analysis itself is a job. Lot of data will be required as far as the future industrial development is concerned. Similarly private sector involvement needs to be assesed.

Availability of power and availability of water in the Kokan area can be further developed and industries can be attracted to this area. It is also required to be verified, that non-forest area and their present land use pattern
marks availability of land for industrial purpose. Presently the communication to Mumbai has become easier because of Kokan Railway.
With all these parameters planning of water base industry has to be identified.

Overall Quantity balance

Koyna dam is a multiutility dam. It is useful for Power generation, Irrigation, Drinking water, flood control and number of other purposes.
As far power generation is concerned water balance seems to as following,

Koyna capacity 98 TMC
Kolkewadi capacity 1.3 TMC
Total capacity 99.3 TMC
Tailrace water let out 67.5 TMC
% of tailrace water 68 %
Approximate cost of let out water at the Irrigation normal rates is Rs.25 cr.
per year.

As far as the quantity of tailrace water running to sea is substantial compared to the overall storage. Considering to the other uses of water it is huge. Particularly, referred to drinking water supply this quantity is more cognizable. Quantity running to sea is sweet water. In the fair season the water is available for drinking in this area. However, in the summer season the water is scarce in the rural wadies and in some parts of the urban areas.


Tailrace water mixing effects

Tailrace water is let out in the River Vashsthi, which in turn reaches to sea. This process is continued for about 35 years. The quantity is varying according to generation activity. River Vashsthi has absorbed these changes in its course to sea. Accordingly the the banks and the bed is readjusted .Any change in the pattern will have to be studied as to how it is getting reflected in the set pattern of the river. It is quite likely that salinity of water due to sea intrusion has been substantially reduced due to addition of tailrace water in the river course. The stretch of sweet water zone in balance with sea water has to be identified.

Tourism and navigation

The level at which the tailrace water is mixing into the River Vashisthi is about 10. The stretch of combined flow is about 45 km upto sea water. The river water in the summer is comparatively less. Tailrace water is fairly constant over the period. Hence, river is having a flow in the summer period. This flow has become a partial means of conveyance. It is not developed fully. It can be systematically developed. River banks can be strengthened and developed for tourism. It can be a systematic master plan to develop as a tourist attraction center. Navigation for tourism purpose is not yet established. It also needs attention. The rough cost estimates and planning strategy is to be detailed out. Though it is planning area of civil engineers, planning and modifying structures as well as hydraulics is a specialized area. It can better be dealt with by Landscape Architects. Gross economics can be worked out while giving shape to the tourism center. It may include navigation. Development of huge parks and sloping gardens will be planning canvas for the architects having a wide angle, with lots of other attractions for the tourists. When the cost of water itself is about Rs.25 cr per year, such a development will need a sizeable amount. However, it will create a job potential for local youth.

Industrial demand

In Raigad district two major industries are developed. One is electrical power generation in Dabhol. Other one is petrochemical industry. After full development they will require major quantity of water. This quantity can be provided to them at reasonable rates. They can put a major treatment facility and provide a surplus capacity. They can utilize this surplus capacity by planning a regional scheme of nearby towns and villages. They can select a total taluka for such a purpose. They can give services and get the revenue also. As they will be a major benefit to the nearby population Irrigation may apply the rates for the domestic use. Planning in such a way will be fruitful to all concerned. Electric power generation will be commissioned at Dabhol within 1 to 2 years. It was stopped for a period,but the issues are resolved now. When the main industry is commissioned the other satellite industries are also sure to flourish. They will also need water.

It is essential to asses the future plans of Industrial Deptt. It is necessary to know the scope to develop the industries in this area. Nearness to Mumbai and easy connections by Kokan railway can identify major inputs by the private sector. Availability of water has to be spelled out. It will give further inclination to the intending industries.

Agricultural sector

Raigad, Ratnagiri and Sindhudurg districts are known for rice growing. In rainy season the rainfall is substantial and hence, there is no question of water requirement for agriculture. Land available for agriculture is mainly on slopes and not large pieces. Quality of soil available does not permit to take rabbi crops fruitfully. Water is not available in plenty to the rabbi crops. Lift irrigation facilities are not in common. Hence, the prospective farmers take some support varieties. Even with available water change in crop pattern seems to be difficult.

Instead, with given facilities farmers can be encouraged to evolve fruit cultivation. Land permits such cultivation. Environment also suits for Mango, coconut, cassuenuts, papai and others. Agricultural produce will have to be marketed by organized sector. Food processing industries also can emerge in this area. This area has good communication with Mumbai area at the personal level. Its institutionalization is necessary. Cash flow increase in this area is very essential. Labour is available but trained or skilled inputs are required.

Use of water for agricultural purpose at the personal level seems to be difficult. Organized sector can take up such farming. It may become profitable. Cooperative sector is not flourished in this area. At least in the Raigad district revenue land is available for farming by the organized sector.
An information about these developments will have to be considered from the concerned department. Prospective demand for water and usability of tailrace water will have to be worked out. Present land use under cultivation, agricultural proceeds from these areas, present use of water etc. is to be collected and analyzed.

Cash crops in this area are lagging. Farmers are marginal. In the heavy rains farming is painstaking. Change of pattern is not traditionally accepted. Hence, organizational support is expected. Financial capacity is very meager. From the social angle, water availability be extended to the farmers.
It is difficult to expect the cash returns from the agricultural sector in this area unless some different strategy is adopted.

Koyna stage V and Kolkewadi acting as balancing storage

In stage IV water is taken from Dam to power station using new technique. It has been successful. It has added 1000 MW power generation. It is encouraging technique and it can be repeated. Power generation may increase using the available water. The important aspect in this regard is that whether this possible stage is to add in the tailrace water quantity. If tailrace water is being increased then its quantification is necessary. It should be taken into account.

In case of stage III to stage stage IV transformation, record is to be verified as to what quantity is added to the tailrace water, by each stage. It is also likely that ex-Kolkewadi there may not be any change in the tailrace water. It will ensure that water quantity in the main dam is utilized in such a way that power generation is enhanced using same quantity of water.

In such a case, if stage V really comes, then Power generation will be balanced, even if the ex-Kolkewadi power generation is stopped. In that case tailrace water will be available at 137 m. Kolkewadi will act as the balancing tank. Any distributions from that level will become easier and economical. Power generation and utilization of water in the tailrace will have to be economically evaluated. Kolkewadi acting as a storage tailrace water running to sea will be reduced. Other utilization will be given priority and balancing storage of 1.3 TMC in the dam will be used as per necessity.

Other uses can be for drinking water, tourism, navigation and combination of all. The uses have seasonal importance. They can be identified accordingly. Water requirement for each use can be calculated and reserved for particular purpose. Obligatory letting out can have control.

Diversion of tailrace water of stage II

Tailrace water from stage II reaches to Kolkewadi dam. It is at higher level. Approximate level is 137 m. A contour tunnel at this level can be taken on both the sides of the outlet. The capacity of canal can be decided as per the demands. For this purpose the prospective demands can be calculated. These may include demand for industrial, agricultural, and for drinking water purpose.in the area through which it is passing. Topographical study is necessary for the feasibility of this proposal initially.


Record for the stage wise tailrace quantity can be verified. Stage IV has come into operation for last 6 years. Changes in the tailrace water quantity are to be noted. Fall involved in both the cases is different. Velocity at which they are approaching may be different. Similarly the residual energy level in the water flow will be different. Combination effects are to be verified.

A study will have to be made whether there is any additional site for the construction of dam of equivalent capacity of Kolkewadi, to accommodate for any additional tailrace water coming in future after completion of possible Stage V

If such a site is available towards south side, part tailrace water can be taken to this area. Storage at this place may have advantage to divert water to Warna basin either by a tunnel or by pumping. The connected area on the otherside of the ridge is drought prone. Some benefits can be given to this area. A study shall have to done as to whether this technically feasible. From Kolkewadi to possible dam site, it is to be checked whether contour tunnel conveying is technically possible. Its economics is to be studied. Detailed maps including the land use pattern shall have to studied. During this range if there is a possibility of any tapping for drinking water, it has to be verified.

Recent heavy rainfall and floods

Recent heavy rains in July 2005 have created a typical situation. In June 2005 there were a crisis of electricity. Rains were somewhat delayed. Every body was waiting for mansoon. In July last week heavy rains poured in this area. Mumbai rains created the record pouring of 946 mm in a day. Similar was the situation in Kokan area. In Koyna catchment area heavy rainfall was contiued and dam was filled to 95 % capacity. Letting out of water from dam was unavoidable. Few days before power generation was required to stopped for want of inadequate quantity of water in the dam. However, situation changed with heavy rainfall. River Vashisthi was flooded. Water was spreading in the areas and in the Chiplun city. In such a case addition of tailrace water in the River Vashisthi would have worsened thew situation of floods.

Collector Ratnagiri reviewed the situation. He declared that tailrace water to be stopped for mixing in the River Vashisthi. For this purpose power generation was required to be stopped. Importance of power generation was already known. But situation was such, that generating power at the cost of floods was not making any sense. Hence, Collector took a correct decision to stop the relevant power generation so that tailrace water can be stopped from mixing in the River Vashisthi.

Decision taken by the administration speaks about important aspect. Power generation is important. State was going through the energy crisis. But the inordinate situation created by nature overshadowed the importance of power generation. It was stopped for a period. Letting out water in already flooded river was expected to be more criticized. Power generation was stopped as letting out of water was required to be stopped. It becomes clear that these two issues can be delinked. Power generation has its own importance. At the same time let out water has also a potential and it can be saved and used in other fruitful way.

Decision was taken at the District level and not at the Govt. level. This indicates that the decision was natural and distinct. Technical authorities
are expected to review the situation. It is important to consider the views of Administration in this respect. These authorities might have crystallized some ideas. Technical and financial viability will have to be studied in details.

Administration has to face the difficulties regarding drinking water supply in the summer period in their area of control. Every year tankers are required to be engaged. Practically all the villages and wadies have the source in fair season. These sources deplete in summer and the problem starts. They get replenished in rainy season. Situation is created every year. The permanent solution is visualized in the let out water from the tailrace. Since it is not felt economical, the proposal does not take shape. A systematic study in this regard is required. It will need the discussion with the concerned officers in the Districts. Alternative expenditure figures are required to be taken into account.

Opinion of selected group of local dignities in Kokan area

The issue of letting out of tailrace water is being in the limelight for last 35 years. Local residents in this area might have a good apprehension of the issue. They may have some useful ideas in their mind. They might not have opened out because of the feasibility grounds. All such issues will have to taken for consideration and checked roughly for the technical and financial feasibility. Their economics can be openly discussed.

No wastage parameter

The principle adopted for the industry for identifying the fullfledgeness is that there should not be any wastage and all the byproducts are also utilized.
The same Principle shall have to be utilized, in case this tailwater issue. Whatever is being wasted is worth Rs.25 cr per annum. This cost is calculated considering the domestic rate for raw water at Rs.1.30 per 10000 lit. When it made available to Mumbai raw water rate rises to Rs.4 per 1000 lit. Cost involved at this rate for let out quantity comes to Rs.771 cr per year. In addition, for it has not been utilized for specific uses, Govt. has to put in about Rs. 5 cr per year, i.e for scarcity purposes.

Till the tunnel conveyance system is materialized power generation in stage III will continue and to that extent tailrace water will reach the Sea.


Irrigation Deptt. has elaborately checked the issue. May be because financial constraints proposal might not have taken shape. However, lots of developments have taken place in last 35 years. Parameters have changed. In general, it can be seen that the issue is identified as a separate project. It is multidimensional. Economic feasibility will be dependent on considering all the issues.

Prima facie it is a high cost project. Raising of funds will be major issue. Apart from the State Govt,. beneficiaries also will have to contribute. External funding may also be required. Initially development of tourism can be taken on priority and then main project be processed. Initial cost in such development will be comparatively much less but the benefits will be area specific.

Evaluation and arriving at a viable proposal

Kirloskar Consultants have in-house expertise to deal with such issue and
can study all the parameters. However, considering the multi-angles of this issue some local expertise can be involved.

The team may visit the sites and also discuss the parameters with field staff.
The discussions will also be held with officers of the other concerned departments. Similar issues tackled with in other countries will also be taken cognizance of through web sites.

Activity-wise schedule of man-days involved is enclosed herewith for ready reference..