THE PAMPA IRRIGATION PROJECT

Transcription

1 Chapter - 4 THE PAMPA IRRIGATION PROJECT 4.1 Introduction 4.1 Introduction 4.2 Description of the study area 4.3 Salient Features of the PIP 4.4 Context 4.5 Objectives of the Pampa Irrigation Project: 4.6 Other Benefits: 4.7 Alignment of Canals. 4.8 Design of canals. 4.9 The Ayacut Details Extent of Irrigation Lands Cropping Pattern in the Project Area Before and After PIP 4.12 Irrigation Intensity (PIP) in Pathanamthitta and Alappuzha districts aims at the utilization of the tail-race water of Sabarigiri Hydro Electric Project for irrigation purposes. The tail race water is let into the river Kakkad and is picked up at Maniyar by a barrage. The water thus collected is diverted through a canal on the left bank of the river. The project was declared completed in The potential of the project is Ha in Ranni, Kozhencherry, Mallappally and Thiruvalla taluks in Pathanamthitta district and Chengannoor, Mavelikkara, Karthikappilly and Kayamkulam taluks in Alappuzha district. The ayacut is generally on the right and left bank of the river Pampa which is in between the rivers of Manimala and Achancoil on the right and left respectively and at the tail end reaches Onattukara and eastern fringes of the paddy fields in Kuttanad of Kerala. Contents

2 4.2. Description of the study area The study area spreads across two districts viz. Pathanamthitta and Alappuzha. The total population of Pathanamthitta district is with a density population of 434 per sq.km as per the 2001 census (GOK, 2008). The district is irrigated mainly by two rivers viz. Pampa and Kallada. The major tributaries of Pampa River are Achenkovil, Manimala, Kakki, Arudai, Kakkad and the Kallar that flow through major parts of the district. Almost 57% of the district area is occupied by forest and only about 31% is the net area sown. Important crops are coconut, rubber, paddy, banana and pepper. The irrigation facilities are confined to valleys in the midland area. Only 2.2% of the district area (6119 hectares) has irrigation facilities and the groundwater irrigation is restricted to 1891 hectares only. A small part (600 hectares) of the command area of major irrigation project of the Pampa falls in the district. The project uses the tail end water from the Sabirigiri Hydroelectric Project located in the upstream of the Pampa river. Only approximately 32 percent of surface land of this district is irrigated by government canals which mainly come under the PIP (Table No.4.1). Alappuzha is one of the well-developed coastal districts in the southern part of Kerala State covering an area of 1,414 sq.kms and is the smallest district accounting 3.64% of the area of the State. Kuttanad, also known as the rice bowl of Kerala constitutes a major part of the district. The district has a population of 21,05,349 persons as per the 2001 census. The population density is 1489 persons/sq.km, the highest among all the districts of the State. Alappuzha district is mainly irrigated by the Pampa river and its tributaries viz. Achankovil and Manimala rivers. The Pampa river irrigates an area of 804 sq.km of district and forms a deltaic region skirting the south eastern, southern and south western fringes of the Vembanad Lake. There are no major irrigation projects in Alappuzha district. However, about 19 sq.kms in the southwestern part of the district is benefited by the Pampa Irrigation Project. Minor and lift irrigation projects irrigate an area of about 181 sq. kms. Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 73

3 Table 4.1 Source-wise Area under Irrigation for Alappuzha and Pathanamthitta Districts, (in hectares) Alappuzha Pathanamthitta Source Net area % area of district Net area irrigated, % area of district irrigated Govt. Canal Pvt.Canal Govt. Tanks Pvt.Tanks Govt. Wells Pvt.Wells Minor Irrigation Other sources Tube Wells Total Source: Department of Economics & Statistics Department, Govt of Kerala,Trivandrum, Salient Features of the PIP The PIP consists of a barrage of length m with FRL at 34.62m. Details of canals are given below. 4.4 Context of PIP Table.4.2 Salient Features of the PIP Canal Length in Kms Main canal 26 Right bank canal Right bank distributory Left bank canal Left bank distributory The project area is well inhabited from very early times, and in the absence of major industries of any sort in the area, the population is mostly dependant on agriculture. Flow irrigation on a large scale does not exist anywhere in the project area. A small portion of the ayacut is served by small tanks. From early times, water was lifted from the water course by means of wells, buckets, scoop etc. for irrigating the fields. But this practice, being costly and impracticable for fields at Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 74

4 higher levels, could not be adopted to irrigate large areas. It has been only about fifteen years, since lift irrigation envisaging the raising of water from the river using pumps was established at a few points along the river to serve isolated plots. As all other lands at present dependent upon the seasonal rains to meet their water requirement, only a single crop is raised in a major portion of the ayacut. The first crop which is raised between the months of May and September gets sufficient water from the south-west monsoon, if the showers are normal. The second crop, between October and January usually fails as it depends on the north-east monsoon which is not always dependable, in this area. The third crop which is raised during the period from December to April is attempted only in the low lying areas which are submerged during the first two crop seasons. The average annual rainfall in the ayacut is about 284 cms (112.5 inches). It may appear that the first two crops do not need any further irrigation water. But the rainfall is not evenly distributed and about 90 per cent of the total annual rainfall occurs during the monsoon months. To prevent crop failure due to this uneven distribution of rainfall, artificial irrigation is essential in this area. In addition to such protection, provision of irrigation facilities will also enable the raising of additional crops and encourage the adoption of intensive forms of cultivation. A major irrigation scheme is, therefore, vital to the development of this area and hence the Pampa Irrigation Scheme. To embark on the project of PIP the government of Kerala started the preparation of the project; and the main steps initiated could be chronologically summarized as: The Government of Travancore started a preliminary investigation for a hydroelectric scheme in the Pampa River in Detailed investigation was again started in 1957 with a view to enlarge the scope of the irrigation project corresponding to the hydro project. Another investigation was carried out by the Government of Kerala in Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 75

5 According to this report, a suitable barrage site across the Kakkad River was selected and a necessary canal alignment was taken. The new canal was joined to the originally aligned canal at Edakulam. The direct ayacut was increased to hectare requiring a discharge of cusecs. The balance of the tail race flow was proposed to be utilized in the Kuttanad region. For economical reasons the proposal was modified and it was decided to continue the canal up to Kurudamannil, 20 kms, from the weir-site along the left bank before the take off of right bank canal. The capacity of the canal has also been increased to cumec (720 cusecs). Based on the detailed studies made henceforth, the water requirement of paddy was worked out and revised cropping pattern was proposed after the implementation of the project. Accordingly, hectares would be benefited by this project,out of which hectares would be paddy cultivated land. The PIP was sanctioned in the year 1964 at an estimated cost of Rs.3.84 crores. The construction of the project was started by the end of year the Due to the increased cost of construction, a revised estimate was prepared in July 1970 for Rs crores. The World Bank team visited the project in July 1971 for conducting a detailed study. The study focused mainly on the problems of submergence of a portion of the ayacut and on the infiltration losses in the portion which consists of sandy soil with high permeability values. The economic aspects of the project were also worked out, taking into consideration the pre-project conditions of the ayacut area and the proposed crop pattern and other details based on the data collected from the Agriculture Department. Following the suggestions made by the Central Water and Power Commission and also from the Word Bank, the project estimate had been revised to Rs crores. Upto 2002, an average amount of Rs 79.3lakhs was expected for the maintenance work of the project. As per the project report, the scheme was to be completed in six years. The barrage and the head stream were programmed to be completed in three years, along with 30 miles of canal. The residue work was to be completed during the remaining three years. Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 76

6 4.5 Objectives of the Pampa Irrigation Project: 1. Utilisation of the tail-race water of the Sabarigiri Hydroelectric scheme for irrigation. 2. The project consists of a barrage for diverting the tail water and a network of canal system taking off from the barrage and commanding an ayacut of hectares (49,500 acres) mainly in Alappuzha and Pathanamthitta districts. 3. The canal system includes a main canal of 20 km length, a right bank canal with about 20 km length and left bank canal of 46.6 km length with about 220 km length of subsidiary branches. 4. The ayacut being generally on the right and left banks of the river Pampa between the rivers of Manimala and Achencoil on the right and the left respectively, its tail reaches Onattukara and the eastern fringes of the Kaayal(backwaters) lands of Kerala, known as Kuttanad. 4.6 Other Benefits: 5. Water supply for drinking: The 86 km length of the canal system, which meanders along the banks of the river through the inhabited places, will thus help in conveying the needed water, apart from irrigation, for the purpose of drinking and domestic use of the people. However, the possibility of supplying protected water to the residents of the area is to be looked into. 6. Fish culture: With the construction of the barrage, about 30 hectares of water spread will be formed. In the artificial lake thus available, fresh water fish like talopia which breeds and multiplies rapidly can be cultivated. 7. Recreation: By providing good hotels, catering to the needs of the various classes of tourists, information houses, etc. and over and above by constructing beautiful parks with shady trees and exquisite lawns where the visitors can relax and enjoy the beautiful scenery should also be provided. The lake can be used for boating and angling. The area Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 77

7 upstream of the head works is best suited for conversion into a wild-life sanctuary. 8. Overall development: Adoption of scientific cultivation, backed up with artificial irrigation, will fetch continuous work for the people of the area. Poverty and unemployment will thus be wiped out from the project area. 4.7 Alignment of Canals. The canal system as finally aligned would consist of left bank canal taking off from the barrage at Maniyar. At the 20 th km. at Kurudamannil it bifurcates into two branches, one branch continuing along the left bank and the other branch crossing over to the right bank by means of an reinforced cement concrete aqueduct from the right bank canal. Between the head works and Kurudamannil, the canal serves negligible ayacut. After bifurcation, the left bank canal continues for a length of 46.6 kms before tailing off at Kareelakulangara. The Ranny,Thiruvalla and Mallapally taluks of Pathanamthitta district and Chengannoor, Mavelikara and Karthikapally taluks of Alappuzha district are served by the canals. The main canal of Pampa was originally designed for a discharge of 650 cusecs. The right bank canal was then apportioned a discharge of 305 cusecs of which 100 cusecs was meant for the lift irrigation ayacut in the Manimala basin in the Pampa river. The remaining 345 cusecs was intended for the ayacut served by the left bank canal. Subsequent investigation of the basin showed that there is considerable scope for increase in the ayacut of the left bank canal even within the Pampa basin. There is also a possibility in future for the construction of a storage scheme in the Manimala River to serve the ayacut of lift irrigation schemes within its basin. Hence, it was decided that the quantity of 100 cusecs included in the design of right bank canal should be ultimately transferred to the additional ayacut of the left bank canal from the date the ayacut of the left bank canal is fully developed. In addition to 100 cusecs proposed to be diverted as above, the additional ayacut of the left bank canal requires an additional quantity of 70 cusecs. Design calculations show that the capacity of the main canal up to the bifurcation point could be enhanced to 720 cusecs by partial encroachment on the free board and without any increase in section. Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 78

8 Left Bank Canal(LBC). After bifurcation the left bank canal passes through rough country for a few kilometers and then through mid and low lands before tailing off. Except for a small ridge which is to be crossed by a tunnel of 490m length, the left bank canal does not cross any high ridges. But it has several valleys to cross for which aqueducts are proposed. The L.B.C. has a length of 46.6 kms. From the bifurcation point to the tail-end it has 33 branches extending to a total length of 170 kms. Twenty nine aqueducts are proposed in this canal to cross the valleys. Right Bank Canal (RBC) starts from Kurudamannil, the bifurcation point and it crosses the Pampa river by an aqueduct and passes through rocky areas for a few kilometers near Ayroor and then through the lateritic areas in the midland region, mainly in Thiruvalla taluk. It has a length of 20kms and has 16 branches extending to a total length of 50kms. Nine aqueducts are proposed in this canal to cross the valleys. 4.8 Design of canals The main canal is designed to carry a discharge of 20.93m 3 /Sec. based on a peak demand consideration for the ayacut. The free board given is 0.9m and the bed fall adopted is 1 in 5000 for the open canal section. The transmission losses have been calculated at 8 cusecs/million sq.ft for the main canal and 6 cusecs/million sq.ft for the branches. Throughout the length of the canal the side slope is fixed as 1:1; but where the canal passes through rocks, the side slopes are varied suitably during actual execution. A 3.2m wide jeep track is provided along one side of the canal for inspection purposes and on the other side a footpath 2m wide in embankments and 1m wide in cuttings is provided. The outer slope of the embankment is provided to cover an arbitrary saturation gradient of 4:1 at F.S.L. with sufficient depth of earth over it. In places where the canal is carried in cutting, small drains have been provided along the top of the canal to carry away storm water. 4.9 The Ayacut Details. The Project area is made up of different types of soil. A detailed preirrigation soil survey has been conducted by the Department of Soil Conservation of Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 79

9 the State. A scientific grouping and classification of the soil in the area has been classified under six different series viz 1) Ayroor 2) Elanthoor 3) Koipuram 4) Mannar 5) Mezhuveli and 6) Thiruvanvandoor. Each series differs from the other in certain morphological and other characteristics that ultimately affect suitability for agriculture. These six different series are briefly described below. The Ayroor Series. (Ayr). Ayroor soil represent very deep moderately drained dark brown alluvial deposits occurring along river banks and other low lying areas and subject to frequent footing. The surface texture varies from loam to clay loam followed by somewhat heavy textured clay loam to clay sub-soils. The soil is poorly drained with moderately slow internal permeability. Elanthoor Series (Elr). Consists of very deep reddish brown laterite soils coming under the textural grade of gravelly loam to gravelly clay loam surface soil followed by gravelly clay loam to gravelly clay sub-soil. The soils rest on a thick layer of quarriable type of laterite. The soil is well drained with moderate permeability. Koipuram Series (Kpm). This series represents imperfectly drained from moderately deep to very deep brown soils, with loam to clay loam surface texture occurring on the low lying areas in between the mid-up land region. The topography is flat to very gently sloping lands. The series is distributed in Thiruvalla and Chenganoor Taluks and has moderately low permeability. Mannar Series (Mnr). Mannar soil consists of very deep grey-coloured sandy alluvial deposits spreading in between the coastal and laterite region along the western portion of the ayacut area. The Mannar soil is generally encountered in level to gently sloping lands with average slope below 3%. The soils have taken shape as a result of weathering of recent alluvial deposits. The drainage is a problem in most of the areas due to high water table. The soil is moderately well drained with moderately low permeability. The series is distributed in Karthikapally Mavelikkara and part of Chengannor taluks. Mezhuveli Series (Mzh). Mazhuveli soil represents very dark yellowish brown loamy sand to silty clay loam, paddy lands. This soil is generally seen within Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 80

10 flat to gently sloping lands with the slope below 3 percent. Water table is moderately high. This series is slowly permeable when moist. Thiruvanvandoor series (Tdr). This type is very deep imperfectly drained soil occurring on level to gently sloping soil of the commanded area. The colour ranges with depth from dark yellowish brown to dark grey with textural grades ranging from loam to clay loam. The clay content decreases with depth. The water table is moderately high. The soil is poorly drained with slow permeability. The distribution of the above series of soil in the ayacut area is given below. Table 4.3 Soil Series in the PIP Area Name of soil series Area in hectares 1 Ayroor Elanthoor Koipuram Mannar Mezhuveli Thiruvanvandoor 4940 Source: PIP 4.10 Extent of Irrigation Lands. The gross commendable area of the project is hectares (66500 acres) and the net irrigable area is hectares (60,500). Out of the above acres are coconut garden lands. The acres of coconut gardens and 1000 acres of tapioca garden lands are not proposed to be irrigated and the net irrigated area of the project is, therefore, taken as hectares (49500 acres). This area comprises of hectares (41000 acres) of existing paddy fields, 1215 hectares (3000 acres) of sugarcane cultivation, 1012 hectares (2500 acres) of vegetable cultivation and 1215 hectares (3000 acres) of tapioca gardens proposed to be converted to paddy fields. In the lower portion of the ayacut, flooding is common during periods of heavy monsoon rainfall. An area of acres of the ayacut is liable to flooding and at present only a single crop is raised in this area. Out of these 2000 acres, known as oru mundakan fields lie on the eastern fringes of Kayamkulam lake and Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 81

11 flooding is not very serious here. But there are chances of salt water entry into these fields. Necessary salt water regulators have already been constructed to prevent salt water intrusion to this area. It is only necessary to construct a bund on the eastern boundary of the lake to prevent salt water intrusion. This is a minor work proposed to be constructed under the minor irrigation programme even before the commissioning of the Project. So there is no difficulty in raising an additional crop in this area where the 2 nd crop alone is cultivated now. In the remaining acres of flooded area, the present practice is to drain the area by pumping and cultivating only a single crop starting from December. The first crop is now tried in about 4000 acres of high level fields, but this is not a stable crop acres of the ayacut area are viruppu lands in which the 1 st and the 2 nd crops are now cultivated by depending upon the natural rainfall. Scarcity of water is felt in the early days of the last crop season and almost for the entire period of the 2 nd period crop season when the post monsoon rains are relied on. It is impossible to try a 3 rd crop anywhere in this area. Another attempt of the PIP is to raise a short term crop of sesame in about 5000 acres of the above fields; but generally this crop is uncertain. The tapioca cultivation in the garden lands and the sugarcane and vegetable cultivation are entirely dependent upon the rains. By commissioning the project, the intention is to bring the maximum area under paddy cultivation. As explained above, an additional 1 st crop is proposed in 2000 acres of Orumudakan fields. The cultivation of the 1 st crop will be discontinued in the 4000 acres of submersible fields. Instead the crop pattern in the acres of punja lands are proposed to be regulated as follows acres of the submersible fields are deep punja lands where the depth of submergence is about 6ft. during the months from June to November. The present practice of draining and cultivating the single crop in the area will continue even after the implementation of the project. The balance of acres are shallow punja fields when the period and depth of submergence lasts only till the middle of October, when the flood waters recede through natural drainage courses without any difficulty. It is possible to bring this area under cultivation by the middle of October. In the remaining 9000 acres, the submergence varies from 3 to 6 ft. during Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 82

12 the months from July to October; and by the middle of October the depth of water will not be more than 3 ft. It is possible to pump out the water and bring this area also under cultivation by the middle of October. The only work to be done to facilitate this is to bund this properly and to do the draining. This work is even now done by the ryots themselves when they attempt at the single crop in these fields. It is proposed to do the permanent bounding in this area under the Minor Irrigation Programme; and the draining is expected to be done by the ryots themselves. So, after the implementation of the Project, by suitably adjusting the crop period, it is possible to raise a second and third crop in acres of these submersible fields. In addition to the stabilization of the 2 crops in the acres of viruppu lands it is proposed to cultivate a third crop of paddy in acres of the above fields. This restriction is necessary as sufficient water will not be available for raising paddy in the entire area. But, by suitably adjusting the crop period, it would be possible to raise a crop of sesame in 8000 acres of the above fields and vegetables in the balance of 2000 acres Cropping Pattern in the Project Area Before and After PIP Table 4.4 Cropping Pattern in the Project Area Before PIP Crops Area in acres Yield in tones 1. Khariff season a. Irrigated crops Nil Nil b. Paddy c. Vegetables Rabi Season(Rain fed) a. Irrigated crops Nil Nil b. Paddy 2 nd crop c. Paddy 3 rd crop d. Sesame e. Vegetables Perennials (Rain fed) a. Sugarcane b. Tapioca c. Banana d. Coconut Source: Pampa Irrigation Revised Projects Report Volume-1 Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 83

13 Before the commissioning of the project, the intention is to bring the maximum area under paddy cultivation, an additional 1 st crop is proposed to 2000 acres of orumundakan fields. The cultivation of the 1 st crop will be discontinued in the 4000 acres of submersible fields. Instead, the crop pattern in the acres of punja lands is proposed to be regulated as follows; 3000 acres of the submersible fields are deep punja lands where the depth of submergence is about 60 ft during the months of June to November. The present practice of draining and cultivating of single crop to this area will continue even after the implementation of the project. The balance of acres are shallow punja fields where the period and depth of submergence varies from place to place for nearly 7000 acres and the submergence lasts only till the middle of October. In the remaining 9000 acres, the submergence varies from 3 to 6 months during October and by the middle of October, the depth of water will not be more than 3 ft. It is impossible to pump out the water and bring this area also under cultivation by the middle of October. The only work that can be done to facilitate this is to blend this properly and do the draining. So, after the implementation of the project, by suitably adjusting the crop period, it is possible to raise a second and third crop in acres of these submersible fields. Table 4.5 Cropping Pattern in the Project Area after PIP Crops Area in acres yield in tonnes Cost (Rs.) 1. Khariff season a. Irrigated crops Nil Nil b. Paddy c. Vegetables Rabi Season(Irrigated crops) a. Paddy 2 nd crop b. Paddy 3 rd crop c. Sesame d. Vegetables Perennials (Irrigated crops) a. Sugarcane b. Banana Perennials (Rain fed) -- a. Tapioca b. Coconut Source: Pampa Irrigation Revised Projects Report Volume-1 Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 84

14 4.12 Irrigation Intensity There are three distinct crop seasons in the ayacut, 1 st crop viruppu, 2 nd crop mundakan and 3 rd crop punja. The crop periods in the ayacut for different reaches are proposed to be suitably adjusted, as described earlier, to bring in the maximum area under paddy cultivation. Table 4.6 Irrigated Crops Envisaged by the PIP Irrigated Crops Area Ha. 1. Paddy 1 crop, double crop orumundakan & Tapioca converted land ( ) 2. Shallow punja land Third crop a. In double crop viruppu land b. Shallow punja land c. Deep punja land Sesame Vegetables Bananna Sugarcane Non-irrigated Crop a. Coconut b. Tapioca 1000 c. Submerged land 3000 d. Foliage land(dry land) 5000 e. Land under preparatory cultivation Source: Pampa Irrigation Revised Projects Report Volume-1 In the foregoing section the original plan objectives and technical features of PIP have been presented. As is obvious from the description, this project aims at increasing the irrigated area under its catchment places spreading across two districts viz. Alappuzha and Pathanamthitta. Besides this overall objective, it also envisages to enhance the cultivation of paddy in the catchment area. It has been mentioned that the study aims at analyzing the impact of the PIP on the area under cultivation, yield, income and productivity that farmers would generate from Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 85

15 cultivating different crops in the catchment area of the PIP. Along with this the study proposes to examine the influence of non-economic factors on the impact of PIP on the above said key economic variables. Now, let us proceed with the analysis of the impact of the PIP on the basis of the objectives..... Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 86

16 Works Cited 1. GOK (1998). Economic Review, Government of Kerala, State Planning Board, Thiruvananthapuram. 2. GOK (1972). Pampa Irrigation Project, Department of Irrigation, Thiruvananthapuram. 3. GOK (2009). Ground Water Information Booklet, Irrigation Department, Thiruvanathapuram. Impact of Pampa Irrigation Project- A Case Study with Special Reference to Pathanamthitta and Alappuzha Districts in Kerala 87