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Tank Selection

The selection procedure is divided in to three stages for prioritizing the areas and the tanks in each district for project interventions. Three stages are district, mandal and tanks in a descending order. The strategy for tank selection is to select areas where tank irrigation is predominant form of irrigation and surface water yield is favourable to justify the investment on tank restoration. The criteria also take into account the hydrological parameters, community willingness and tank status. The project will be covering about 3000 minor irrigation tanks.

District Selection
In the first stage districts are prioritized on the basis of predominance of tank irrigation vis-à-vis the total irrigated area on the basis of predominance of irrigation (>75% area irrigated by tanks)  during the years 1989-91. The districts are prioritized accordingly and the first 15 districts out of 23 districts of the state are chosen for implementation in the first phase. Out of the remaining 8 district, 6 districts will be taken up in the 2nd phase of the project implementation. Of the remaining two districts one district does not have any tanks and other one is an urban area. The project will be initiated in mandals of these 15 districts.

Mandal selection

The next stage of selection involves identification of mandals in three batches according to predominance of irrigation by minor irrigation tanks:

  • more than 75 %
  • 50 to 75 %
  • 35 to 50 %

Using these criteria 163 mandals in 15 districts are identified to be taken in batch 1. These mandals contain about 2400 eligible tanks. In Batch 2 the project would be extended to 236 additional mandals where tank irrigation is more than 50% in 1991. In batch 3 the project will be extended to 130 mandals in these 21 districts where area irrigated by tanks is more than 35 %


Tank selection criteria

In the third stage individual tanks to be rehabilitated will be selected within these identified mandals. This would be through a self-selection process that would be based on:

(i)     Hydrological assessment to determine the hydrological viability of rehabilitating the tank system with 75% dependability.

(ii)   Community willingness to participate in the rehabilitation by

  • Contributing 10% of the cost of rehabilitation (5% upfront in cash)
  • To undertake operation, maintenance & management.
  • To undertake responsibility of collection of water charges and management of the fund for undertaking satisfactory maintenance of works.  
    (iii)      Technical parameters for selection:
    • No Land acquisition should be involved.
    • Tanks in which major repairs and rehabilitation works taken up during last 5 years are not taken up.
    • No revival or restoration to be taken up in new tanks completed during last 5 years under various programs.
    • No major irrigation system tanks are eligible for revival & restoration
    • No Head works to be taken up under super standard tanks (where top width of the bund is more than 5 m and revetment thickness is more than 0.6 m), components such as weir, sluice and distribution system should be taken up for revival/restoration
    • No revision of hydraulic standards is allowed in the revival/ restoration estimates.
    • Gap ayacut in a tank should be more than 25%.
    • No tank should be included under the project which is going to be influenced by any of the schemes being undertaken / contemplated by the Government.
    • Priority to be given to bigger tanks having ayacut between 1000 to 5000 acres followed by the tanks having below 1000 acres.

Hydrological assessment

Revival and restoration of tanks proposed under the project have to satisfy the hydrological criteria. It is essential to assess the inflows availability into the tank due to the changing scenario in the catchment, rainfall conditions and other hydrological criteria. A.P. State Remote Sensing Application Centre (APSRAC), a government agency has developed a simple protocol for the hydrological assessment of the tanks for I&CAD Department, which has been tested on 100 batch 1 tanks and is proposed to be used for the selection of the remaining project tanks.

The protocol is developed in MS-Access for estimation of available surface water yield (Runoff) for a selected MI tank based on weighted curve number derived from catchment area characteristics like soil and land use /land cover, rainfall, utilized yield in the catchment under different command areas using Soil Conservation Service (SCS) method. Queries are built based on daily rainfall (mm), antecedent five days rainfall for all years - of the stations in and around of the selected tank catchment. These queries will be administered sequentially to run through the protocol. Different queries built in the sequence are as follows:

  • Antecedent Moisture Condition (AMC)
  • Curve Number
  • Potential Maximum Retention
  • Runoff (Daily, monthly, seasonal, yearly)
  • Rainy days above threshold (monthly, yearly)
  • Total Yield for total catchment area
  • Balance Yield after interceptions
 
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