INTERNATIONAL JOURNAL OF GEOMATICS AND GEOSCIENCES Volume 2, No 4, 2012

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1 INTERNATIONAL JOURNAL OF GEOMATICS AND GEOSCIENCES Volume 2, No 4, 2012 Copyright 2010 All rights reserved Integrated Publishing services Research article ISSN Spatial distribution of rainfall in Salem and Namakkal districts Jegankumar.R 1, Nagarathinam S.R 2, Kannadasan.K 3 1- Assistant Professor, Department of Geography, School of Geosciences, Bharathidasan University, Tiruchirappalli 2- Associate Professor & Head, Department of Geography, Govt., Arts College (Autonomous), Coimbatore 3- Guest Lecturer, School of Geosciences, Bharathidasan University jegankumar@gmail.com ABSTRACT The spatial distribution of rainfall shows a unique pattern in Salem and Namakkal Districts. By analyzing the long term rainfall data, the results shows that Summer contributes 18.73%, Southwest monsoon produces 40% and North east 40%. The average mean rainfall of the study area is mm. The variability indicates higher variability in winter to compare other seasons. Similarly precipitation ratio is carried out to bring out the anomalies in the distribution and the rainfall frequency is calculated to understand the occurrences. GIS is effectively used in this attempt to compute and produce maps. Keywords: Rainfall, rainfall variation, Salem district rainfall, Namakkal district rainfall. 1. Introduction Rainfall is unique variable, which reflects multiple factors locally and globally. The distribution of rainfall depends upon various factors existing at regional scale. Rainfall is being a single most important factor for success of crops in the farming areas. South west monsoon (June September) is the most important season as it brings more amounts of rainfall to major parts of India and the northeast monsoon is the returning monsoon from October to December, it pours supplementary rainfall and apart from conventional rainfall during summer. Study of rainfall over a long period is called rainfall climatology. It brings out the general pattern and characteristics of rainfall of a particular region (Sahu, 2003). Usually rainfall is studied as weekly, monthly, seasonally and annually. The best understanding of rainfall is useful for various agronomic activities (Mavi, 1994). In this study GIS is effectively used to interpolate the rainfall for various analysis and preparation of maps. 2. Study area The study area lies between 11 00' and 12 00' North latitude and 77 40' and 78 50' of East longitude. It occupies an area of 8, 658 sq.km. The present study area is land locked by Erode in the west, Karur and Tiruchirappalli in the south, Perambalur and Cuddalore in the east, Villupuram in the northeast and Dharmapuri in the northern direction. It has many hills and valleys. Many structurally controlled hills of the Eastern ghats are present in the study area. They are Shevorys, Kolli hills, Cheteri hills, Kalarayan hills and Pachamalai. In the North of study area Shevorys (Yercaud) is present with the maximum elevation of 1,652m. East of shevorys part of Cheteri Hills and Kalrayan Hills are present. Kolli hill is located in the south eastern direction. The maximum elevation of the Kolli hill is about 1,300m and a part Submitted on April 2012 published on May

2 Pachamalai is present in eastward of Kolli hills. The well marked Attur Gap is located between Kalrayan hill and Pachamalai. In the Northwestern part of study area Stanley Reservoir is located and it is surrounded by hills elevation with 768m. Apart from the major hills few hillocks also seen in the plain region. Kongu upland is located in the west, Karur plain and Musri plain in south and Ponnaiyar plain and Vellar plain are located in the east. The present study area comprises of two districts such as Salem and Namakkal Districts of Tamilnadu. At present Salem District contains 9 Taluks, 20 Blocks, 33 town panchayats, four revenue divisions, 631 revenue villages, four municipalities and one corporation. The District occupies an area of 5, sq.kms. The Namakkal District consists of four taluks, fifteen blocks, two revenue divisions, nineteen town panchayats, 391 revenue villages, 331 panchayat villages and five municipalities, the Namakkal district is spread about 3, km 2. The total area of the study area is 8, sq.kms. The population of Salem district is 34,80,008 according to 2011 Census. It ranked fifth among the District in population of the Tamilnadu. Similarly Namakkal district consists of 17,38,376 people and it is in 21 th position among the districts. The location of the study area is given in the figure1. The figure 2 illustrates the location of rain gauge stations in and around the study area. Figure 1: Study area map 977

3 2.1 Data and analysis Figure 2: Location of rain gauge stations There are thirty seven rainfall stations selected for the present study. The daily rainfall data for the period of have been collected for major stations and available rainfall stations which are installed in last five years. The daily rainfall data has been tabulated as monthly for the respective rain gauge stations. The tabulated data are analyzed to calculate mean rainfall, coefficient of variation, precipitation ratio and frequency. The results are mapped in GIS environment by applying spline interpolation. 2.2 Mean annual rainfall The location of the study area is an important factor for the distribution of rainfall. In the study area, three seasons have significant amount of rainfall out of the four seasons. The well marked hills in the north and south directions play a key role in the spatial distribution of rainfall. 978

4 Table 1: Annual mean and seasonal rainfall Sl. Southwest Northeast Mean Station Winter Summer No Monsoon Monsoon Annual 1 Salem Junction Salem Attur Omalur Namakkal Paramathi Mettur Yercaud Rasipuram Puduchatram Edappadi Pottaneri Kolathur Sankari Tiruchengode Erode Ammapet Kumarapalayam Mohanur Senthamagalam Thampampatti Dainshpet Karur Musri Thathaiangarpet Anaimadu Penagram Dharmapuri Harur Modakurichi Paramathi Karia Kovil Kullampatti Pillukurichi Vazaphadi Mangalapuram Gangavalli Average There are thirty seven rainfall stations found in and around the study area. The general pattern of the rainfall over this area shows that the southwest monsoon and northeast monsoon shares 80% totally, but spatial pattern is different, summer showers due to conventional rainfall contribute % and winter rain is about 1% annually. The annual average rainfall is about mm, mm during northeast monsoon, mm occur in southwest, mm in summer and 7.69mm occur in winter 979

5 2.3 Mean annual rainfall Spatial distribution of rainfall in Salem and Namakkal districts The mean annual rainfall is the sum of twelve month long term monthly average is computed. The annual average rain fall of the study area is mm, the annual mean varies from mm to mm. Southwest and northeast monsoon shares 80 percent of rainfall and summer contributes by 18 percent and winter shares 1%. The stations Yercaud and Gangavalli record more than 1000mm rainfall, the following stations receive between 900mm and 1000mm. They are Kolathur, Anaimadu, Salem, Omalur, Pillukurichi, Edappadi, Kariakovil, Erode and Salem Jn. Less than 500mm of rainfall occurs in Mohanur and Paramathi. The mean annual rainfall of the study area is classified into five categories less than 700mm of rainfall occurs in north of Kadayampatti, Paramathi, Kabilarmalai, Senthamagalam and Veerapandi blocks of the study area. Rainfall between 700 and 800mm is found on west of Senthamagalam, eastern part of Tiruchengode, Vennandur, Panamarathuppatti, Vazaphadi, East of Attur and in Mettur in the western part of the study area. The mean annual rainfall for the all stations shown in table 1 and figure 3 illustrates the mean annual rainfall of the study area. 2.4 Winter Figure 3: Mean annual rainfall The winter season contributes small amount of rainfall to the annual share. In this season rainfall varies from 2mm to 22mm. In the winter season the maximum rainfall occur in the hilly areas of Yercaud. Apart from the Yercaud block all parts of the study area receive less than 10mm of rain fall during winter season. The seasonal pattern of rainfall of the study area is shown in figure Summer The average rainfall of the summer season is about mm (20%) of total annual rain of the study area, ( mm). During the summer season showers were common in this study area (Ramanan, 2006) in the summer season rainfall varies from 80.4mm at Paramathi and mm at Yercaud. Less than 100mm of rainfall was found in north of Kadayampatti, Kabilarmalai and northern part of Erumaipatti. From 100 to 125mm of rainfall occurs in 980

6 Gangavalli, Attur, Senthamagalam, Namagiripettai, Erumaipatti, northern part of Kabilarmalai, Paramathi and few parts of Kadayampatti. Between 125 and 150mm amount of rainfall during the summer season occurs in Vazaphadi, northern parts of Pethanaickanpalayam, Vennandur, Veerapandi, west of Namakkal, and few parts of northern Omalur block. More than 150mm of rain fall is present during the summer in the following blocks namely Thalaivasal, Tiruchengode, Pallipalayam, Edappadi, Kolathur, and Yercaud. 2.6 Southwest monsoon The winds from Arabian Sea bring more rainfall to the western part of the country. A few places in Tamilnadu receives more rainfall during the southwest monsoon season. A Branch of wind belongs to southwest monsoon is able to reach over Salem and Namakkal through Palaghat Gap, it was obstructed by hills present in the study area. As result of orographic effect, the windward side around Namakkal, Sankari, Omalur, Salem and Yercaud gets more rain. Areas between Kolli hills and around Attur become rain shadow during this period. During the southwest monsoon the rainfall varies between 119 mm at Mohanur and 828mm at Yercaud. The average rainfall of this season is about mm (40%) of the total mean annual rainfall. Less than 150mm of rainfall is found only in the northern part of Kadayampatti, western part of Kolathur, and southern part of Kabilarmalai. Between 150 and 250mm of rainfall occurs in few parts of Kolathur, Mecheri, southern part of Tiruchengode, and Erumaipatti. This category ( mm) of rainfall occur in vast area, which include, Sankari, northern part of Tiruchengode, Senthamagalam, Kollimalai, western part of Gangavalli, Attur, southern Vazaphadi & Ayothiyappattinam, and Tharamangalam in west. From 350 to 450mm of rainfall found in the following areas of Omalur, Veerapandi, Namakkal, Panamarathuppatti, northern part of Pethanaickanpalayam and western part of Thalaivasal and eastern part of Gangavalli. More than 450mm of rainfall prevails over Yercaud, Salem and Thalaivasal. 2.7 Northeast monsoon The retreating monsoon is called northeast monsoon, it is prevail in the period from October to December. From this monsoon, east cost of Peninsular India and interior parts of Tamilnadu receive rain; through the depressions originate from Bay of Bengal. The study area receives 40.34% of total mean annual rain fall from northeast season and the table 2 indicates the northeast monsoon season rainfall of the study area. The rainfall varies during the season from 229mm at Paramathi to 558mm at Kolathur. Attur Gap Plays significant role, it provides a path to the rain clouds from Bay of Bengal to the inner parts of the study area. The Yercaud and Kolli Hills create a rain shadow effect on the west of each hills, it is clearly seen in the spatial distribution. During this period Kolathur and Mettur located straight to the Attur Gap is benefited in the season by receiving more than 475mm rainfall. The windward side of Kolli hills, Yercaud and Southern side of Kalarayan receive more than 475mm of rainfall. Rainfall between 150 and 250mm occur only in the few places of southern part of Kadayampatti, Veerapandi, Senthamagalam, and Kabilarmalai. Rainfall from 250 to 300mm is found in Kolathur, Omalur, Salem, Attur, Sankari, Tiruchengode, Veerapandi, Rasipuram, Paramathi, Erumaipatti, Vennandur, Puduchatram and middle parts of Magudanchavadi. Rainfall of 350 and 450mm is the second major category found in this region, which covers south of Thalaivasal, eastern part of Gangavalli, Yercaud, northern parts of Pethanaickanpalayam, eastern part Kolathur and central Edappadi. 981

7 Figure 4: Seasonal rainfall distributions 982

8 3. Rainfall variability Spatial distribution of rainfall in Salem and Namakkal districts The coefficient of variation (CV) defined as the standard deviation divided by the mean value of rainfall. It shows the variability of rainfall in percentage. The higher the variability percentage, the lower is the dependability and vice versa. For the monthly case less than 100% of CV is dependable, while more than 100% not dependable rainfall. CV = (SD/Mean) X 100 where SD = Standard deviation Mean annual variability The mean annual variability of the study area is calculated for the thirty eight rainfall gauge stations located in and around the study area. Coefficient of variability is calculated from the long term mean annual rainfall and standard deviation of the each rainfall station. The annual variability is 30.41% and it varies from 20% to 50% in the study area. The minimum variability is found at Kariakovil at north (14%) and the Maximum variability is found at Paramathi in the south (53%). The low variability (less than 20%) is found in the east, northeast and northwestern part of the study area, which includes around Gangavalli and Thalaivasal in the east, the area around Kariakovil in the northeast, Pottaneri and Pillukurichi on the northwestern part of the study area. The Salem, Omalur, Kolathur, Pillukurichi, Mangalapuram, Paramathi, Kumarapalayam, Mettur dam, Tiruchengode, Yercaud, Sankari, Edappadi, Puduchatram, Senthamagalam and Namakkal are covered with percentage of variability. The variability range of percentage is found in the following places Vazaphadi, Kullampatti, Attur, Rasipuram, Thampampatti and Dainshpet. Areas around north of Dainshpet in the north and areas around Mohanur in south were under percentage of variability. More than 50 percentage of variability is found in the west of Yercaud and down south of Paramathi. The mean annual variability shown in figure 5 and in table 3 annual and seasonal variability is shown. Figure 5: Mean annual variability 983

9 3.2 Winter rainfall variability Spatial distribution of rainfall in Salem and Namakkal districts The mean rainfall variability of winter season is % and varies between 66.20% and 318%, maximum variability is found in Gangavalli and minimum is present over Kariakovil. The low variability of less than 150% is present around Kariakovil in the northeast, Attur and Vazaphadi in the east and the portions of east face of Yercaud are in less than 150% of variability. Similar conditions prevail over Puduchatram in the central part of Namakkal District. Variability of % is seen over in the following places, Middle portions of Yercaud, Kullampatti, Anaimadu and Edappadi. The variability range of percentage is seen over in the following places Ammapet, Attur, Tiruchengode, Mettur, Pottaneri, Rasipuram, and Kolathur. The range variability between 175 and 225 concentrates over northeast and southwest central portions of the study area. High variability range between % is seen more in the study area than other variability categories, it spreads around central, southeast and a small area in the north. The places records high variability include Pillukurichi, Salem, Senthamagalam, Mangalapuram, Thampampatti, Paramathi, Omalur, Namakkal, Kumarapalayam and Sankari. The very high variability of more than 300% is seen towards east of Gangavalli, Mohanur south of Omalur and north of Dainshpet. The high variability in winter season of among all season states that the occurrence of less rainfall during winter. Table 3: Annual and seasonal rainfall variability Sl.No Stations Winter Summer Southwest Northeast Annual monsoon Monsoon Mean 1 Salem Junction Salem Attur Omalur Namakkal Paramathi Mettur Yercaud Rasipuram Puduchatram Edappadi Pottaneri Kolathur Sankari Tiruchengode Erode Ammapet Kumarapalayam Mohanur Senthamagalam Thampampatti Dainshpet Karur Musri Thathaiangarpet

10 26 Anaimadu Penagram Dharmapuri Harur Modakurichi K. Paramathi Kariakovil Kullampatti Pillukurichi Vazaphadi Mangalapuram Gangavalli Average Summer rainfall variability The summer variability of the study area is percentage, it varies between 24.6 and 104 percentage of variability. Less than 50 percentage of variability is found in the east of Attur and around Thalaivasal, similar variability prevails also in Kariakovil, Edappadi, Yercaud, Salem Jn, Salem, Omalur, Mettur, and Namakkal, the central part of Namakkal, around Thampampatti in the east and north of Mettur in the percentage variability range. The variability between 60 and 70 percentage occur in the following areas Kolathur, Sankari, Dainshpet, Mohanur, and Kumarapalayam. The high variability of more than 70% is found in the southeast of Kollimalai, west of Paramathi north of Dainshpet. The drastic down variability during summer season indicates that the rainfall during this season is higher than winter. The summer showers contribute mm (18.73%) of rainfall to the total annual rain. In general the central part and the eastern sector receive more rain which was indicated by the less variability. 3.4 Southwest monsoon rainfall variability The rainfall variability of the southwest monsoon is about 42.79%. The season contributes 40 % of total annual rainfall as equal to northeast monsoon. The variability of southwest monsoon season varies between 21% at Edappadi and 71 % at Paramathi. The regions influenced by southwest monsoon have less variability than other places. Less than 30 percentage of variability is found along the west around Omalur, Edappadi, Sankari and Kolathur. The block around Thalaivasal and places around Attur exhibit less than 30% of variability. The zone of percentage of variability is found periphery of the zone of less than 30 percentage of variability, the places include Salem Jn, Kariakovil, Pillukurichi, Sankari, Attur, Gangavalli, Mettur, Kumarapalayam and Puduchatram. The moderate amount of variability between 40 and 50 percentage of variability covers the major parts of Rasipuram, Namakkal, Tiruchengode and other parts of Namakkal and the northern boundary of the study area. The major portions of southeast and few places around north were covered by 50 to 60 percentage of variability. High variability of more than 30 percentage of variability exists in the north of Yercaud, the west of Kolathur and the south of Mohanur. 985

11 Figure 6: Seasonal rainfall variability 986

12 3.5 Northeast monsoon rainfall variability The variability of the northeast monsoon had shown the strength of the northeast monsoon. The spatial pattern clearly indicates that the prominent hills located in the study area create rain shadow effect in the northeast monsoon season. The regional variability of the northeast monsoon season is 91% and it varies from % at Kariakoil and 31.8 % at Namakkal. The eastern part of the study area, north of Kolli hills and west of Mettur are found in less variability of < 45%. Variability of percentage is found in the western part of the study area, similar variability occur in the area between Attur, Salem and around Thampampatti and west of Gangavalli. A linear area in the central and the west of Kolathur is covered under percentage of variability. The maximum variability more than 75 percentage is found in the west of Kollimalai and west of Yercaud hills. This region may have a shadow during the northeast monsoon. Even though this season shares equal rain along the southwest monsoon and the spatial distribution pattern is different. 3.6 Precipitation ratio The abnormalities of rainfall at a specific region can be drawn through a simple ratio of precipitation. The ratio may give the stability of rainfall with spatial pattern. Higher the ratio is the higher the abnormality in rainfall and the lower in ratio indicates the less anomaly. The formula used to calculate precipitation ratio is as follow. Precipitation Ratio = (P x P n )/P m x 100 Where: Px = Maximum of Rainfall, Pn = Minimum of Rainfall and Pm is the mean rainfall. 3.7 Mean annual precipitation ratio The mean annual precipitation ratio of the study area is 19.75%, the ratio calculated from the monthly mean of the respective season., It varies between 14% at Penagram and Maximum at 28% at Mohanur. The majority of the area under less than 20 percentage area Yercaud, Namakkal, Edappadi, Mangalapuram, Senthamagalam, Dainshpet, Salem, Kullampatti, Sankari, Salem Jn, Omalur, Rasipuram,,Vazaphadi, Mettur Dam, Attur, Puduchatram, Tiruchengode and Erode. The mean annual precipitation ratio between 20 and 25 percentage is found in the following areas Kariakovil, Pillukurichi, Anaimadu, Kolathur, Paramathi, Thampampatti, Gangavalli and more than 28 % found in Mohanur. (Table 4) 3.8 Winter precipitation ratio The seasonal precipitation ratio is shown in the figure 6. It is depicts the seasonal and annual precipitation ratio. During the winter season the average precipitation ratio of this region is %, it varies at maximum of 1381 % at Salem Jn and minimum of % at Anaimadu. Zones with less than 500% cover the northeastern portion and areas around Namakkal. The following regions such as such as Kullampatti, Yercaud, Attur, Tiruchengode, Musri, Pillukurichi, Rasipuram, Gangavalli, Paramathi and Mohanur were under percentage of precipitation ratio. The central part of the study area intercepted by precipitation ratio zone of , the following areas were partly covered in this category, Senthamagalam, Mettur, Paramathi, Dainshpet, Namakkal. More than

13 percentage of Kolathur. precipitation ratio is found in southeast of Namakkal, west of Salem and 3.9 Summer precipitation ratio The summer precipitation ratio of the study area is % and it varies between 13% and 443%. The south eastern sector, west of Mettur and towards north of Yercaud express high precipitation ratio of more than 250 % and following areas show high abnormality during this season they are K. Paramathi, Salem, Senthamagalam, Sankari, Attur, Dainshpet, Thampampatti, Pillukurichi, Mangalapuram and Gangavalli. Less than 150 percentage of precipitation ratio is found in and around of the following places Paramathi, Kariakovil, Anaimadu, Edappadi, Puduchatram and Vazaphadi, these areas under 150 % have fewer anomalies to compare the other areas Southwest precipitation ratio Southwest monsoon season is an important monsoon season for the study area, it contributes 40% rain to annual total. The average precipitation ratio of the region in southwest season is %, which is lesser than other three seasons. The precipitation ratio varies between 51 % and 287 %. The lower category of less than 100 percentage is found in northeast portion of Attur Thalaivasal, Anaimadu, Kariakovil and west of Sankari, Yercaud along Omalur. The category percentage prevails most part of the Namakkal Districts of the study area, places around Yercaud and west of Kolathur percentage of precipitation ration prevails around Rasipuram west of Thampampatti and Mettur. The maximum amount of precipitation ratio is found over Yercaud hills and a small area around Thampampatti and the west of Kolathur Northeast precipitation ratio Northeast monsoon equally shares 40% rainfall as southwest monsoon to the total annual rainfall. The seasonal average precipitation is 188% prevails in this region during this period. The northeast precipitation ratio varies between Kariakovil at minimum of 83 % and maximum of 371% over Namakkal. The categories and percentage occupies western part of the study area. The eastern part of the study area has minimum abnormality, which is indicated by the lower precipitation ratio. The precipitation ration between 200 and 250 percentage prevails over the western middle part of the study area, it covers the areas include Paramathi, Rasipuram, Omalur, Salem and north of Dainshpet. The maximum precipitation ratio is found in Namakkal, east of Paramathi and north of Rasipuram. Table 4: Precipitation ratio Sl. No. Stations Winter Summer Southwest Northeast Monsoon Monsoon 1 Ammapet Anaimadu Attur Dainshpet Dharmapuri Edappadi

14 7 Erode Gangavalli Harur Paramathi Kariakovil Karur Kolathur Kullampatti Kumarapalayam Mangalapuram Mettur Modakurichi Mohanur Musri Namakkal Omalur Paramathi Penagram Pillukurichi Pottaneri Puduchatram Rasipuram Salem Salem Junction Sankari Senthamagalam Thampampatti Thathaiangarpet Tiruchengode Vazaphadi Yercaud Average Rainfall frequency Rainfall frequency is the number of time rainfall occurs at a specific class interval. There are 28 rainfall stations which have more than 15 consecutive years of rainfall data are having been taken for the frequency analysis. The mean annual rainfall data is classified into following categories less than 600, , , and more than 900. There are 730 times rainfall occurred in the study area for the selected period. More than 900mm of rainfall occurred 270 times in the study area, which accounts maximum contribution. Less than 600mm of rainfall occurred 133 times. Rainfall amount of mm and mm rainfall events occurred 115 and 112 times respectively. The range of 600mm to 700mm of rainfall occurred 100 times. The station wise frequency of occurrence is given below in the table

15 Sl. No. Rain Stations Figure 7: Seasonal precipitation ratio Table 5: Rainfall frequency (Annual) Gauge < > Attur Dainshpet Kolathur Kullampatti Kumarapalayam

16 6 Mettur Namakkal Nangavalli Omalur Paramathi Pillukurichi Rasipuram Salem Salem Jn Sankari Senthamagalam Thampampatti Musri Thathaiangarpet Karur Penagram Erode Modakurichi Tiruchengode Yercaud Mangalapuram Total number of occurrences Figure 8: Frequency curve for selected station from the above table 991

17 4. Conclusion The study of thirty seven rainfall station with long term rainfall data shows the annual mean rain is mm, south west and northeast monsoon season contributes and mm respectively. Both the monsoon seasons give 40% of rainfall each to the annual rain. The spatial distribution pattern is different because of the hills with different elevation spread across the study area. Significantly the summer season contributes 18.73%. The winter season receives minimum rainfall among the other season. The variability indicates more 100 % of variability observed in the winter season and the other three season the variability was below 100%, which indicates the dependable rainfall is available during these period. By observing the precipitation ratio of the east and south eastern side, more abnormality is found than the western side. In the south west and northeast season the area having more abnormality is very less. The rainfall frequency indicates more than 900 mm rainfall has higher frequency followed by 133 for less than 600. The overall observation shows except winter season, all seasons have rainfall without much variability. 5. References 1. A Gazetteer of Southern India with the Tenasserim provinces and Singapore, Printed and Published by Pharoah and Co, Madras, pp Afzal Sharieff et al., (2010) Agricultural Meteorology, Sarap Book Publishers private, Ltd, New Delhi. 3. Alaguraja. P Manivel.M, Nagarathinam, S.R Sakthivel. R and Yuvaraj D., (2010), Rainfall Distribution Study in Coimbatore District Using GIS, Recent Trends in Water Research Remote Sensing and General Perspectives, I.K International Publishing House Pvt. Ltd. New Delhi, pp Ananthakrishnan R., (1979), Some feature of the southwest monsoon rainfall along the west coast of India, Proceedings in Indian academy of Science, 88 A, Part II, pp Bishnoi, O.P., (2010), Applied Agroclimatology, Oxford Book Company, Jaipur, India. 6. Gadgil A., (1986), Annual and weekly analysis of rainfall and temperature for Pune: A multiple time series approach, Institute of Indian Geographers, 8(1), pp Gangai, P., Aruchamy, S., and Selvam, K., (2008), Rainfall Characteristics and Drought Prone Area of Pudukkottai District, Tamilnadu, Indian National Geographer, 23(1&2), pp Hema malaini, B., (1986), Climate and landuse of Ananthapur Dt, Andhra Pradesh, Transactions, Institute of Indian Geographers, 8(1), pp Ishappa Muniyappa Rathod, Aruchamy S., (2010), Spatial Analysis of Rainfall Variation in Coimbatore District Tamilnadu using GIS International Journal of Geomatics and Geosciences, 1(2), pp

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