1. The component will improve availability of water for agriculture, and where feasible for fisheries, by developing new minor surface and ground water irrigation schemes. The activities will include construction of about 2,400 minor surface water irrigation systems (command area varying from 5 to 50 ha), comprising river lift schemes, gravity-fed schemes, and detention structures, and construction of about 2,260 minor ground water irrigation schemes (command areas varying from 20 to 36 ha), comprising shallow tube wells, light and medium duty tube wells, and pump dug wells (see summary table at the end of this Annex). Shallow tube wells, light duty tube wells, and pump dug wells will normally be constructed in a cluster of six, with each tube well covering six ha and each pumped dug well covering five ha. The selection of the type of scheme will be based on hydrological and technical viability, as well as on user requests where there are options. Prior to any interventions, the actual development activities will be determined for each individual irrigation scheme, summarized in a brief SDMP prepared in consultation with the users. A check list for scheme preparation and approval (see end of this Annex) will facilitate development of the SDMP. The component will also introduce, through pilots and demonstrations, water saving technologies and will also expand on the ground water monitoring program in project areas and the development of a statewide geographically referenced minor irrigation database. The former will include the introduction of sprinkler and drip irrigation in strategically selected schemes to not only show the benefits of such types of irrigation, but also to link up interested private sector suppliers with potential customers.
2. As indicated, it is estimated that about 4,660 minor irrigation schemes in 18 out of 19 districts of West Bengal will be constructed, with a total command area of about 139,000 ha, benefitting an estimated 166,000 farm families. The estimated number of proposed schemes ranges from a low of 31 in Howrah District to 1,030 in Jalpaiguri District. For most districts the number of schemes to be developed is less than 70 per district per year, which considering the decentralized level of engineering expertise down to block level and the experience with the development of minor irrigation schemes gained in the past is an acceptable number in most districts. Only two districts will have to develop between 150 and 200 schemes per year and the capacity of DWRID may be insufficient during peak periods. The project has therefore an allocation for the recruitment of engineering consultants to assist DWRID as needed with the investigation, design, and construction supervision of schemes. The project also has an allocation for the recruitment of a third-party construction supervision and quality assurance consulting firm to review the construction works at a randomly selected sample of schemes. The project will also finance a small Technical Unit attached to the SPMU to review the designs of impoundments, especially related to surface flow minor irrigation schemes and water detention structures.
3. The project proposes construction of ten different types of irrigation schemes, as listed below. The design is basically standard and the configuration and costs for each type of scheme are known with great certainty:
|a.||Medium (40 ha) River Lift Irrigation (Diesel or Electrical)||577|
|b.||Mini (20 ha) River Lift Irrigation (Diesel or Electrical)||1417|
|c.||Medium Duty (20 ha) Tube well (Electrical)||359|
|d.||Light Duty (cluster of 36 ha) Tube well (Electrical)||522|
|e.||Shallow (cluster of 36 ha) Tube well (Diesel)||1309|
|f.||Pumped Dug Well (cluster of 30 ha)||75|
|g.||Surface Flow MI Schemes (30 to 50 ha)||284|
|h.||Water Detention Structure (5 ha)||117|
4. The component will support: (i) assessment of availability of irrigation water for surface flow and river lift irrigation schemes as well as that for ground water based irrigation schemes to be developed under the project; (ii) proper design of proposed irrigation infrastructure, including electro-mechanical components; (iii) procurement of survey and quality control equipment for scheme preparation and implementation; (iv) district-level 3rd party construction supervision and quality assurance consultants to ensure that the works are carried out to acceptable construction quality standards; (v) contractual staff to bridge the gap, where necessary, between technical staff required and presently available in DWRID; (vi) a well qualified and adequately staffed Technical Unit attached to the SPMU for review of design and supervision of construction of key irrigation infrastructure to ensure adequate safety and performance quality; (vii) ground water monitoring and water quality monitoring in the project areas; and (viii) development of a statewide geographically referenced minor irrigation database to enable the DWRID plan future interventions in a better and systematic way.
5. The project does not propose any ground water structure in the areas bordering with Bangladesh. Surface water irrigation structures in the northern districts mainly comprise small capacity river lift schemes or pumped irrigation schemes from beels (local depressions or old ox-bow lakes), and are not expected to have insignificant impact on downstream flows, particularly after considering the effects of return flows. The scheme location process will be carried out keeping in view possible adverse effects, meeting the requirements of various Bank safeguard policies, while simultaneously focusing on the poor beneficiary communities in target areas.
6. Surface Flow Minor Irrigation Schemes (SFMIS). As the DWRID has limited in-house experienced technical staff in the design and implementation of surface flow structures, especially tank bunds, an adequately staffed Technical Unit will be set up in the SPMU to support field offices entrusted with the implementation of a large number of small surface irrigation schemes. The responsibility of this Unit will include guiding the field staff in investigation, planning, design, and implementation of SFMIS, reviewing and clearing designs, as necessary, and also checking if any of the proposed schemes requires special attention on engineering consideration to meet Bank's safeguard requirements.
7. All proposed SFMIS are located in five western districts bordering the states of Jharkhand and Orissa, except for an estimated 24 schemes which are located at the foot hills of Darjeeling (Siliguri Sub-division) and Jalpaiguri Districts. Average annual rainfall in the western plateau districts where most of the SFMIS will be located is about 1,400 mm. This rainfall is for about 90 percent concentrated in the main monsoon months from June through September. In addition to dry winter and pre-summer months during the rabi season, dry spells even during monsoon months are quite common which necessitate limited supplementary irrigation for the kharif crops to facilitate for assured return. No major rabi crop is possible without assured irrigation supply. Consequently, the SFMIS propose supplementary irrigation to kharif crops (paddy 85 percent, with some diversification to vegetables in about 15 percent of the culturable command area (CCA)), and full irrigation to at least 40 percent of CCA during the rabi season. The annual yield of surface water flow for SFMIS will be estimated based on hydrological studies that were conducted by external consultants during project preparation. In order to avoid inundation of areas, only a small portion of annual inflow will be stored in low height small reservoirs which are expected to be filled during the monsoon season, allowing a full storage level at the end of the kharif season. The live storage volume (above the dead storage level) together with additional water to be pumped from the dead storage will meet the above-mentioned irrigation requirements during the rabi season. Where possible, the water in the reservoir will be gainfully used for short duration fish farming.
8. The designs for evacuation of flood waters and supply of irrigation water to the agricultural areas will follow the Indian standards and practices. In the absence of precise long term hydrological data/information for the small streams that will be harnessed under the project, standard empirical formulae have been used to arrive at design floods. Standard practices have been adopted for the structural designs of the embankment, spillway, and irrigation outlets, following established guidelines.
9. River Lift Irrigation and Tube Wells. The design principles for these schemes are well defined in DWRID. The distribution system for these schemes comprises buried pressure pipelines of appropriate class and spouts for delivery of water to the fields. The design approach is sound and there are adequate numbers of technical officers who are well qualified and experienced to design and implement these systems. The key issues therefore are the selection of the best location, avoidance of the possibilities of over-abstraction, and costs and economic viability.
10. Shallow tube wells and low duty deep tube wells will cover only 6 ha CCA each, and therefore do not need any buried distribution system. However, portable lay-flat type of PVC pipes will be used to improve irrigation efficiency. Similar approach is contemplated for the pumped dug wells which can irrigate 5 ha CCA during the rabi season. Each scheme of these categories will generally comprise 6 (six) of these small structures developed as a cluster of MI structures.
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