Advances in Life Sciences 5(2), Print : ISSN 2278-3849, 553-564, 2016 Spatial Analysis of Rainfall Variation in Dharmapuri District Tamilnadu using GIS K. BALATHANDAYUTHAM1, D.TAMILMANI2 AND C. MAYILSWAMI3 1Department of Agronomy, PAJANCOA & RI, Karaikal 2Department of Soil and Water Conservation Engineering, AEC & RI, Kumulur 3Water technology Centre, TNAU, Coimbatore, Tamilnadu, India email: [email protected] ABSTRACT scanty in different parts. It also has great regional and temporal variations in distribution. The study Among the climatic elements the rainfall is the first of rainfall distribution pattern and its temporal index, ever thought of by farmers and climatic analyzers as it is the most important single factor variations is very important, as the country’s which determines the cropping pattern of an area in economy is highly dependent on agriculture. general and the type of crop to be cultivated and its Therefore, the study has been conducted in order success or failure in particular. It is therefore to help policymakers and developers to make more necessary to study the spatial and temporal variation informed decisions, especially, the results will help of rainfall for judging the agricultural production farmers to take necessary steps for cultivation potential and sustainability of agricultural process. production system. However, rainfall has one the Recent studies Balathandayutham et al., 2014 highest spatial-temporal variability especially in has analysed rainfall variation analysis of mountain region where in addition, there is scarcity Parambikulam Aliyar Palar (PAP) basin, Tamil of information. Planning suitable measures for Nadu, India. He has interpreted monthly, seasonal mitigating the problems requires through knowledge of the rainfall pattern. The present study variation, intensity and frequency of rainfall. The was taken up to analyze the spatial and temporal present study made to understand the rainfall of variation of rainfall in study of Dharmapuri district, the region, The south, southwest and north- Tamil Nadu and India. These results were taken into western parts of the basin experience the heavy geographical information system (GIS) platform to rainfall whereas the least rainfall areas are the east, prepare the spatial distribution maps. The highest northeast and south-eastern parts of the basin. annual rainfall recorded in Dharmapuri 981.94 mm Ishappa et al., 2010 studied the rainfall and lowest of rainfall is recorded in Perumbalai characteristics of the Coimbatore District, Tamil 622.80 mm. The annual variability ranges from 24.13 Nadu, which includes the spatial distribution and per cent to 40.61 per cent. Month of October receives variability through different seasons, precipitation highest average rainfall (180.50 mm) and the month ratio and frequency occurrences and found that of January receives the minimum with an average the south, southwest and north-western parts of of 8.00 mm. The study concludes that the Dharmapuri the district experience the heavy rainfall whereas district receives maximum amount of rainfall receive the least rainfall areas are the east, northeast and only South west monsoon (June – September) over south-eastern parts of the district. Adhikari et al., the last 34 years. 2003 reported that in Bellary, the maximum rainfall occurred during the month of September followed Keywords Spatial, temporal, rainfall variability, by October and June. It was observed that an GIS, frequency average of 240 mm rainfall occurred between January and August, out of which 210 mm Rainfall is an important element of economic occurred between May and August. In three months growth of an area or region, especially in a country i.e. September to November, the rainfall was 257 like India, where a large number of people are mm. occupied in agricultural activities. The amount of Jagannadhasarma, 2005 has analyzed the rainfall does not show an equal distribution, either in space or in time. It varies from heavy rain to rainfall pattern of the coastal zone of Krishana 554 Advances in Life Sciences 5(2), 2016 Table 1. Average annual seasonal rainfall data in Dharmapuri District S. No Station Code annual SW NE summer winter 1 Pennagaram 864.67 371.14 265.65 197.92 10.12 2 Marandahalli 828.31 848.24 313.95 170.17 5.52 3 Harur 785.30 780.70 293.15 118.57 12.49 4 Dharmapuri 981.94 468.73 300.55 199.30 10.01 5 Sitteri 795.04 358.95 290.20 145.55 3.21 6 Perumbalai 622.80 274.13 198.46 142.25 6.00 7 Papiredipati 873.24 347.94 397.18 107.80 24.99 8 Hogenakkal 697.52 287.62 239.17 156.09 5.25 9 Bommidi 840.88 375.29 300.19 143.11 8.67 10 Thopiyardam 744.65 342.22 264.21 120.06 12.28 Godavari River Basin Andhra Pradesh, India. He Study area has made analysed the annual, monsoon and no The Dharmapuri district is situated in North- monsoon rainfall and spatial and frequency western part of Tamilnadu, the region covering an distribution of rainfall intensity. Spatial variability area of 4497.77 sq.km falls between 11 47’ north of rainfall at the scales below a few kilometres is to 12 33’ North latitude and 77 02’ East to 78 40’ still a poorly explored research area (Krajewski et East longitude (Fig.1). Administratively the region al., 2003). The study was focused on the consists of 5 taluks and comprises 10 Town distribution patterns of the impacts of rainfall Panchayats. The temperature ranges between 17°C variability in terms of mapping its spatiotemporal in the month of January and 38°C in the month of impact using the modern GIS techniques such as April. The tract below 350 m above MSL can be Inverse Distance Weighted’ (IDW) interpolation divided into two portions by the watershed between technique. There is need however for an integrated the Cauvery and the Vellar river systems. The major this type of GIS modeling system, to allow crop grown in this district area is other minor agricultural producer as well as policy makers to millets, pulses, sugarcane, mango, coconut and know the impact of spatial temporal variation in tamarind. rainfall on crop yield for better management, productivity and profitability. Therefore, this study MATERIALS AND METHODS aimed at using GIS Inverse Distance Weighted (IDW) interpolation technique to examine and map The base map was prepared using toposheet the spatiotemporal variation in rainfall. on 1:50,000 scale. Monthly rainfall data for the period of 35 years from 1980 to 2014 has been Table 2. Average annual seasonal rainfall variability in (%) S. No Station Code annual SW NE summer winter 1 Pennagaram 25.83 53.14 51.00 52.88 248.54 2 Marandahalli 30.27 30.02 49.21 53.36 207.86 3 Harur 40.61 41.13 63.13 49.44 247.67 4 Dharmapuri 30.72 36.15 60.95 48.11 229.53 5 Sitteri 26.84 41.74 49.68 52.42 336.91 6 Perumbalai 24.13 37.27 54.73 48.04 290.35 7 Papiredipati 28.97 40.13 47.83 61.08 185.19 8 Hogenakkal 29.51 48.81 58.02 52.22 328.17 9 Bommidi 26.00 34.97 55.09 60.03 220.56 10 Thopiyardam 32.19 48.90 60.10 65.81 262.13 BALATHANDAYUTHAM et al., Spatial Analysis of Rainfall Variation in Dharmapuri District Tamilnadu using GIS 555 Fig. 1. Locations of rain gauge stations collected from Public Works Department, RESULT AND DISCUSSION Taramani, Chennai. There are ten in and around Monthly rainfall distribution pattern rain gauge station have been taken into consideration for analyzing long term mean monthly, seasonal The average monthly rainfall of 10 stations and annual rainfall pattern has been calculated given for Dharmapuri indicated that there exists a rainfall table 1. The coefficient of variability where worked variation in each month. The average annual rainfall out given in table.2. Their attributes are added and increases January to may and there is decline analyzed in ArcGIS 9.3 software. Spatial analysis (Fig.2). Month of October receives highest average tools were used for the preparation of interpolation rainfall (180.50 mm) and the month of January map. The maps were interpolated by using Inverse receives the minimum with an average of 8.00 Distance Weighted (IDW) spatial interpolation mm. methods to generate the spatial distribution map. 556 Advances in Life Sciences 5(2), 2016 Fig. 2. Monthly rainfall data of study area Annual rainfall distribution pattern and 47.2 percent in SW (Jun-Sept) and remaining 19.8 percent during winter and summer (Jan-May). The rainfall analysis of five rain gauge stations But, the rainfall distribution pattern is highly erratic of study area showed a wide variation in the mean and their spatial and temporal variability over the annual rainfall over the years (1980-2014) from years are given in Figs.3 and Fig.4. The annual the lowest of 607.1 mm (2006) to the highest of rainfall map of Dharmapuri district (Fig.5) reveals 1137.7 mm (1996). The mean annual rainfall for that there is huge amount of rainfall variation the period (1971 -2013) was worked out to be spatially. The rainfall pattern in the state was further 807.20 mm. The area receives nearly 33.02 percent divided into three categories moderately high rainfall of annual rainfall during NE monsoon (Oct-Dec) Fig. 3. Mean annual rainfall of Dharmapuri district (1980-2014) BALATHANDAYUTHAM et al., Spatial Analysis of Rainfall Variation in Dharmapuri District Tamilnadu using GIS 557 Fig. 4. Seasonal average rainfall for winter, summer, south-west and north-east monsoon in the study area from 1980-2014 Fig. 5. Spatial distribution of annual rainfall 558 Advances in Life Sciences 5(2), 2016 Fig.