Project Components : Technical

Tank Civil Works Improvement (Rs 16983.44 lakhs)

The main objective of this component would be

To improve tank storage capacity
To rehabilitate tank physical structure and infrastructure
To reduce siltation to the tanks by stabilising drainage lines and
To improve water distribution and irrigation systems in the tank command area, more specifically:
- improve tank storage capacity by de-silting,
- rehabilitate tank bunds and appurtenant works, as necessary,
- mitigate siltation by stabilising drainage inflow channels (feeder channels)
  and implementing/ coordinating/ prioritising micro-watershed plan management activities, and
- improve water distribution and irrigation systems in the tank command area.
  This would be achieved through the implementation of the following range of physical works, the actual works for each tank being determined by the ITDP for each tank.

The nature and types of works necessary would be determined on the basis of the detailed Integrated Tank Development Plans (ITDPs) to be formulated by individual TUGs. Main physical works to be undertaken would inter alia, include:

Generally the following would be the civil works

Desiltation;
Repairs to tank bunds;
Repairs to sluices and waste weirs;
Other tank structures repairs;
Command area development;
Feeder channel improvement;
Soil testing;
Preliminaries and Surveys;
Other works;
Support for constitution of dam safety Task force;
Equipments for Quality Check/Assurance of civil works

The following physical improvement measures would be taken up:

Component	Present condition	Works proposed
Feeder channel	Carrying capacity reduced due to siltation and encroachment by cropping/ vegetation	Deweeding and resectioning of the Feeder canal, construction of check dams, boulder checks, and vegetative checks
Tank bed	Storage capacity reduced due to siltation	Desilting the tank bed by removing the silt at 23% and 21% of the accumulated silt from small and large tanks respectively
Tank Bund	Scouring and erosion of bunds, reduction in top width, damaged revetment, seepage t through bunds	Bringing Bunds to MI standard including construction of revetment, and stopping leakage at bottom of the bund by providing KT on upstream wherever necessary and turfing to the bund
Tank sluices	Damaged and inoperable	Reconstruction or repairs to the sluices
Surplus weir	Major damages	Resectioning or reconstruction of pitching and body wall stopping leakage through the wall
Main distribution system and OFD	Main canal length inadequate	Deweeding and reconstruction of canal, construction of regulators for every 10 hectare. 50% of the length of the canal lining for small tanks and 50% in respect of large tanks, construction or repairs to CD wall and distribution chamber
Others	New Proposal. To be carried out in small tanks.	Formation of fish ponds in about 1 ha area (minimum 1m depth), water spread area of the small tanks.

The estimated costs for improvement of the tanks is based on the actual costs spent in respect of representative sizes of tanks under the ongoing project as also the rise in prices of materials and labour. On the basis of the study of the improved tanks and also the proposed designs for different models, the per tank cost inclusive of preliminary works, Key Trench for arresting leakage on upstream of Bund (for 25 per cent Tanks), Improvement of Other Water Bodies in Tank Area (for 25 per cent Tanks), Mobile Quality Control Testing Charges and Creation of Dead Storage for Fisheries (for 75 per cent Tanks in only 20-40 ha category) is estimated at:

9,62,123 for tanks with command area between 20-40 ha;
Rs 23,97,406 for tanks with command area between 40-100 ha.

Similarly the cost per hectare also varies among the five zones which is presented below and is exclusive of preliminary works, key trenches, fish ponds, mobile quality control testing charges and improvement of other water bodies in tank area.

Table � 5: Summary of Per Hectare Cost by Zones �
Zone	Excluding		Including
Zone	20- 40	40 -100	20- 40	40 -100
NDZ	29,532	30,165	41,223	31,441
NTZ	33,200	25,813	42,098	27,002
CDZ	36,160	37,429	46,355	38,784
STZ	30,273	30,261	39,254	31,533
HZ	24,625	26,754	32,893	27,999
All Zones	27,983	28,952	36,466	30,147

The costs are exclusive of administrative and management costs and also plantation works to be taken up in these structures under the Environment Management Plan separately to be incurred by the TUGs till the tanks are handed over to them.

The proposed physical works would result in longevity of the sluices and bunds, reduced leakages and seepage through bunds, sluices and canals and improved water use efficiency on account of appropriate on farm development works and finally, minimised resiltation of tanks due to measures taken in the catchment areas.

Feeder Canal Treatment

Feeder canal protection measures would be applied to the lower reaches of major silt carrying feeders entering the tank upto 1000 mtrs. Treatments, structure design and site selection would be determined according to local conditions. Treatment choice, placement and structure design would as far as possible be determined to maximise effectiveness, both in terms of silt trapping and in groundwater re-charge to benefit adjacent crop areas. However, the final decision on the appropriate structural treatment, its design and placement would be based on participatory discussion between the Tank Users Groups (TUGs) and the concerned villagers in the catchment area, with an advisory input from WDD taluk level staff. These decisions would be incorporated into Integrated Tank Development Plans (ITDP), ensuring consistency with micro-watershed development plans being developed by WDD for adjacent areas.

Suggested treatments will include Deweeding and Resectioning of feeder canals, loose boulder checks. Because the silt traps will be placed in the lower reaches of feeder drains it is anticipated that loose boulder checks will be the most appropriate structures in the majority of cases. Provision of vegetative checks at intervals on the upstream wherever Nala bed is flat or moderately sloppy is made under the EMP component.

Tank and Command Area Improvement

The on-farm development (OFD) works in tank command areas would require a participatory rural appraisal and walkthrough survey at the planning stages and after implementation of improvement activities. This will allow farmers to identify and propose their priorities for improving the water distribution. Farmer field training would need to be phased with some modules being undertaken before OFD works are implemented. This would be carried out by the CFT (engineer/agriculturist).

The physical activities proposed under the component comprise of: (a) Waterspread area treatment activities like Deweeding, Desilting of Tank bed, Excavation of boundary trench at FTL, (b) Tank bund improvements like Deweeding and strengthening of bunds, (c) Repairs to sluice like reconstruction of damaged sluice and repairs to sluice head walls and providing controlling arrangements, etc., (d) repairs to waste weir and appurtenant works, (e) Command area improvement like Deweeding and Resectioning of irrigation canals, Lining of Canals, Construction of Outlets, Construction of CD works, Construction of Distribution Chambers and (f) Protection to existing water bodies like Kalyani, old wells, temple etc.

The training modules provided prior to implementation of OFD works, would be used to develop a tank system and on-farm distribution/application water management plan and to prepare for system improvement and subsequent O&M. The guidelines and manuals for O&M would be provided to TUGs as part of the training. The main topics for training would be mapping, problem identification, solution finding, and water management action planning. The farmers would set priorities and provide ideas for the design of system improvements. This training would be followed by improvements to irrigation structures. Later, training sessions could cover evaluation of the results of the water management plan (including system improvement), the possibilities to strengthen the TUG organisation, cropping patterns and agricultural development plans. Evaluation and adjustment of the plans would follow at the end of each growing season. The project interventions would include the following:

These improvement works would result in: (i) extension of the useful life of existing bunds and sluices (i.e. most tanks are more than 100 years old); (ii) reduction of leakages and seepage through bunds, sluices and canals (i.e., through selective lining); (iii) increased water use availability and efficiency through on-farm development works, such as field channels desilting, construction of turnouts or drainage outlets, division boxes and water measuring structures; and (iv) reduction of the potential for resiltation of tanks.

Focus Issues for Improvement of Quality Works under Community Based Tank Management Project and Dam Safety are as under:

Improvement of Quality Works:

Utmost care to be taken to maintain the required quality of work for strengthening of bund and CC works with periodical tests.
Bund slopes to be executed as per the designed sections.
Turfing to be done on the trimmed hard surface of slope after picking.
Turf obtained from water spread area of tanks or from Nala beds to be used in place of present practice of gross seedlings in order to avoid erosion of downstream slope, there by reducing the maintenance cost and creating a small revenue resource to TUG.
Standard design of grade stones or chainage stones to be embedded at U/S top edge of the bund to serve the purpose of Indicating chainages and also scouring of top of bund.
Arresting leakage at the toe of the bund by providing key trench at the upstream toe of the bund.
Lead of channel to be excavated from pit formed due to desiltation upto sluice opening.
The tanks where the silt deposit is upto cill level without affecting live storage, silt removal is to be done to create dead storage for promoting fishery activities and also to serve as a drinking water pond for animals during summer and for improving the ground water level.
Majority of tank users are marginal and small holdings and are not afford to incur expenditure for transporting the useful silt. Hence the possibility of provision for free conveyance of silt can be looked into so that the useful silt can be used to the maximum extent.
Lining to be done to 50 per cent length of the canal to minimise transportation losses.
Sufficient number of outlet points to be provided at least one per every 10 ha of commands.
The recommended species of at least 2 year old plants to be planted for both fore shore plantation and all along canal to create some revenue bearing assets early and also to increase the rate of survival of plants.
During discussion with the farmers with many of the tanks it is ascertained that the FC which carry water to the tanks has been diverted to neighbouring valleys or obstructed otherwise for different purposes and due to which most of the tank are not surplusing regularly since fast 7 years. Hence while selecting the tank for improvement in addition to the criteria of surplusing. Through studies regarding upstream obstructions to be made and proper action to be taken for free flow of water to the tank.

Improvement of Dam Safety

Service Road to be formed at the downstream toe of the bunds for conveyance of material in case of emergencies like, breach of tank bund or waste weir.
No Plantation to be done on the slope of the bunds.
In case of removal of old trees grown on the slopes ensure the roots are removed and plugged with impervious soil to avoid the piping action along the root line.
Ensure the revetments to bunds is constructed at least 0.3 meters above the MWL Level to avoid damage to the bunds waive action.
Ensure that the floor of the apron is hard and rigid so that scouring at the downstream of waste weir will not take place.
Keep the Draft and tail channel clean without any obstruction for smooth flow of surplus water.
In case of old tank bunds where seepage below bund is observed key trench to be provided on the upstream side at the toe of the bund to arrest leakage.
In case of construction of new sluice barrel, utmost care to be taken to lay the pipeline on the C C Bed with proper leak proof jointing of pipes and the gap around should be filled with impervious soil and well consolidated manually to get required density at least upto point 0.6 meter above the barrel.