CHAPTER 4 STUDY AREA DESCRIPTION

Transcription

1 88 CHAPTER 4 STUDY AREA DESCRIPTION 4.1 GENERAL For the purpose of evaluating the impact of tank restoration on livelihoods, three restored tanks in two districts of Kancheepuram and Thiruvallur in Tamil Nadu have been selected. These tanks are grouped as ones restored prior to and post STUDY AREA Tamil Nadu is located in the southern part of India, having a land area of 1,30,058 km 2 (50,216 sq. mi), which constitutes 3.96% of the Country. It lies between 8 05 l 00 ll and l North Latitudes and between l and l East Longitudes and it is the eleventh largest state in India. Physiographically, the state can be divided into four major regions, namely coastal plain, Eastern Ghats, central plateau and higher elevation mountains. Palar, Cauvery, Pennaiyar, Vaigai and Tamiraparani are the major rivers flowing through the state. Southwest monsoon feeds the plateau and retreats the Northeast monsoon brings rain to the East Coast. The temperature in the state ranges from 2 C in the hills to 45 C in other areas. The average rainfall ranges from 925 mm to 1170 mm.

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3 90 If any deviation occurs from normal rainfall either during the Southwest monsoon or during the Northeast monsoon in a year, the water availability in Tamil Nadu would be always under stake in all the three sources of irrigation viz. tanks, canals and wells. The temporal distribution of rainfall over Tamil Nadu is 46.4 mm during cold weather period (January- February); during hot weather period (March May); mm during the Southwest monsoon period (June September) and mm during the Northeast monsoon period (October December). The study was carried out in two tanks namely Avalur and Puliambakkam as shown in Figure 4.1, which are located in the villages of Avalur at Kancheepuram block and Puliambakkam at Walajabad block of Kancheepuram district and one tank is Ponpadi, which is located in the village of Ponpadi in Thiruthani block of Thiruvallur district in Tamil Nadu, India. 4.3 GEOGRAPHICAL DETAILS Avalur tank is on the Southern side of Palar river (Figure 4.2) in Kancheepuram block, which is located at 40 km from Chennai. It lies at l East Longitude and l North Latitude. Figure 4.2 Location of Avalur and Puliambakkam tanks

4 91 Puliambakkam tank is on the Northern side of Palar river in Walajabad block. It lies between l and l East Longitudes and between l and l North Latitudes. The Palar River is the most important river running through the Kancheepuram district. Through most of the year, it remains dry as attributed to the construction of dams across the river in Andhra Pradesh. It is an interstate river, originating in Andhra Pradesh and running through Tamil Nadu. Kancheepuram district is situated on the Northern East coast of Tamil Nadu and is adjacent to the Bay of Bengal and Chennai city. The district is bounded on the West by Vellore and Thiruvannamalai districts, on the North by Thiruvallur and Chennai districts, on the South by Villuppuram district and on the East by the Bay of Bengal. The predominant soil orders found in this area are inceptisol, Alfisol, Entisol and Vertisol. Due to different stages of weathering of parent material, the above soil types are met in combination. They are red, brown and grey in colour with surface horizon more developed than sub surface. They are developing soils, moderately deep to deep, coarse loamy to loamy suited for commonly grown crops with exceptions due to soil problem, moderately drained to well drain soils. The study area has a tropical monsoon climate. December and January month have cool and dry weather. The maximum daily temperature does not exceeding 40 C. The total annual average rainfall is mm. The district is mainly dependent on the monsoon rains. Failure of monsoon leads to distress condition. Northeast and Southwest monsoons are the major donors, with 54% and 36% contribution each respectively to the total annual rainfall. During normal monsoon, the district receives a rainfall of 1200 mm. The climate is normal during winter but very hot in summer. The maximum and minimum temperatures range between 37.6 C and 21.4 C respectively.

5 92 Ponpadi tank is situated in Thiruthani block of Thiruvallur district in Tamil Nadu. The Latitude and Longitude of the tank are l 58 ll N and l 59 ll E respectively with an altitude of 99 m above M.S.L. It is situated about 0.6 km from Ponpadi village. The Thiruvallur district is geographically positioned at North Latitudes between l and l and at East Longitudes between l and l. It is bound by Kancheepuram district on the South, Andhra State on the North, Bay of Bengal and Chennai district on the East and Vellore district on the West. Its headquarters is at Thiruvallur. The monthly average maximum temperature varies from C (December) to C (May) and the average minimum temperature varies from 20 C (January) to C (May). The monthly average pan evaporation varies from mm (December) to mm (May). Evaporation is one of the main factors causing hydrologic cycle particularly in arid and semi arid regions. The loss of water is caused due to evaporation particularly in arid and semi arid regions. The monthly average relative humidity varies from 54.26% (May) to 78.57% (November) and the monthly average sunshine hours vary from 5.37 hours/day (July) to 9.41 hours/day (April) 4.4 RAINFALL AND CLIMATE For Avalur and Puliambakkam, Kancheepuram is the nearest rain gauge station and for Ponpadi, Thiruthani is the nearest. Figure 4.3 presents the rainfall distribution during at Kancheepuram to be considered for Avalur and Puliambakkam tanks. Figure 4.4 presents the rainfall distribution during at Thiruvallur for Ponpadi tank. The year was divided into 2 periods, June - December and January- May, and

6 93 frequency analysis was carried out for annual rainfall at 50% and 75% dependability, which is presented in Table 4.1. Figure 4.3 Rainfall during at Kancheepuram Figure 4.4 Rainfall during at Thiruvallur Table 4.1 Frequency analysis of Annual Rainfall Sl. Rain gauge No station Year of occurrence Dependable rainfall ( mm) Probability (%) 1 Kancheepuram 2 Thiruthani

7 94 The monsoon period is further sub-divided into Southwest monsoon from June to September (4 months) and Northeast monsoon from October to December (3 months). Similarly, the non-monsoon period is further sub-divided into winter period between January and February (2 months) and summer period from March to May (3 months). 4.5 CROPPING PATTERN Paddy is a principal crop grown in the study area of Avalur Village. In the double cropped period, farmers use the short duration (107 days) variety (Kuruvai) as first crop and medium duration (135 days) variety (Samba) as second crop. Land preparation for Kuruvai crop is started in August month and harvested in November month. For Samba crop, land preparation starts in November month and harvest in March. Ayacut area for this study area is about 140 ha. In Puliambakkam village 75% farmers mainly depend upon the tank water and marginally dependent on well water as a supplementary source for irrigation. Farmers cultivate paddy and sugarcane as major crops and also go in for different types of vegetables like ladies finger, cucumber, pumpkin etc. Since the village is located nearer to the city they are selling their produce at wholesale rate, which is highly remunerative for them. In Ponpadi village, paddy and vegetables are major crops and also some farmers cultivate sugar cane. Ponpadi tank, which is a nonsystem tank, has only one sluice. The command area for the Ponpadi tank is about ha. 4.6 TANK IRRIGATION SYSTEM IN STUDY VILLAGES Agriculture is the major source of income in all these three study villages. In most of these villages well irrigation is very well adopted for cultivation. Both open and bore wells exist in these villages. Well irrigation

8 95 complements tank irrigation. As a result, the income from agriculture has been increased abnormally when tank restoration programme was taken up. Avalur tank, which is a system tank, has three sluices. The tank is located on the right flank of the River Palar on the southern side of Kancheepuram block, and it falls in between the Rivers Cheyyar and Palar. In general, irrigation depends more on open wells than on bore wells and the numbers of bore wells are less in number when compared to open wells. Water user association is not functioning well in this village. But tank related decisions are taken by the village Panchayat Councilor in this village in close cooperation of the tank farmers. Tank farmers community accepts him as their leader and has full confidence in him. Hence, the major problems of this tank namely encroachment, siltation in both water spread area and supply channel and catchment area. Puliambakkam tank is a system tank and has two sluices. The command area for this tank is about 75 ha. It is located on the left flank of the River Palar and on the northern side of Walajabad block. In this tank also irrigation depends more on open wells than on bore wells. The numbers of bore wells are less in number when compared to open wells as like Avalur. Ponpadi tank, which is rainfed, receives drainage from its free catchment of km 2. The catchment is classified as good. Irrigation depends on the tank as well as bore and open wells. Unlike other two tanks, bore wells are more in number when compared to open wells. The hydraulic particulars are shown in Figures 4.5, 4.6 and 4.7 respectively for Avalur, Puliambakkam and Ponpadi. Hydrological and Hydraulic particulars of all the three tanks are given in Table 4.2. Tanks and their components are shown in Figure 4.8, 4.9 and 4.10 respectively for Avalur, Puliambakkam and Ponpadi.

9 96 Table 4.2 Details of hydrology and hydraulic particulars Sl. No Tank components Quantity and Quality Puliam Avalur Ponpadi Bakkam 1 Type of tank System tank System tank Rainfed tank 2 Chain of the tank - - Murrukanpattu tank and Velanchery tank 2 Tank bund level m m No of Sluices Crop Paddy Paddy & Vegetables Paddy & Sugarcane 5 Full tank level m m 95.20m 6 Maximum water level m m 95.60m 7 Command Area 140 ha 75 ha ha 8 Water spread area m m - 9 Catchment area Sq.km 9 Number of sluices Number of wells People Participation Women Participation Yes Yes No Leadership Yes Yes No

10 97 Figure 4.5 Avalur Tank Figure 4.5 Avalur Tank

11 98 Figure 4.6 Puliambakkam Tank

12 Figure 4.7 Ponpadi Tank 99

13 100 AVALUR TANK SLUICE SLUICE Figure 4.8 Avalur tank with its components

14 101 PULIAMBAKKAM SLUICE SLUICE Figure 4.9 Puliambakkam Tank with its components

15 102 PONPADI TANK SLUICE SLUICE WEIR Figure 4.10 Ponpadi Tank with its components