TREND ANALYSIS OF RAINFALL IN KONKAN REGION OF MAHARASHTRA

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Date
2016-05
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DBSKKV., Dapoli
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SUMMARY The Konkan region receives the heavy rainfall but differs from other tropical regions because of the strong influence of the Arabian Sea and the Sahyadri hilly ranges. Rainfall is one of the substantial weather indicators of climate change (Mirza and Hossian, 2004). Rising temperatures across the globe would likely results in changes in precipitation and atmospheric moisture through a more active hydrological cycle, leading to increases in water holding capacity throughout the atmosphere at a rate of about 7 per cent per °C (IPCC 2007). The present study was undertaken for Konkan region of Maharashtra which is coastal part of Maharashtra covering total geographical area of 3.09 Mha. The region receives 46 per cent of total precipitation of the state on just 10 per cent of total area of the Maharashtra state. The Konkan region has hilly topography with highly drainable lateritic and non-lateritic soils. Due to porous nature of geological strata water holding capacity of soil is less which cause the most of rainfall drains away fastly in rainy season to adjacent Arabian Sea. Even though area having heavy rainfall, it faces water scarcity in summer season.`Daily rainfall data of Jamsar, Savarkhand, Khapari, Karjat, Chowk, Varandoli, Dapoli, Karambavane, Mulde, Vengurla and Amboli, stations. The daily data was converted into weekly, monthly and annual rainfall. Trends of monthly and annual rainfall were estimated by using Mann Kendall, Sen‘s Slope, Turning point test, Moving average and Regression methods whereas trends of weekly rainfall was calculated with the help of Mann Kendall and Sen‘s Slope method. Summary of results is as follows. 5.1 Summary: Average annual rainfall for available data at Jamsar (2702 mm), Savarkhand (2547 mm), Khapari (2478 mm), Karjat (2801 mm), Chowk (3197 mm), Varandoli (3824 mm), Dapoli (3635 mm), Karambawane (3893 mm), Mulde (3330 mm), Vengurla (2922 mm) and Amboli (6981 mm).All station received more than 400 mm rainfall in June, 900 mm in July except Khapari, 700 mm in August, 300 mm in September, except Vengurla and less than 200 mm rainfall in October month, except Karambwane, Mulde and Amboli. The average weekly rainfall increased continuously from week 22nd to 26th SMW except Dapoli station. Maximum rainfall received in week number 30th at Jamsar, Savarkhand, Karjat, Karambawane and Vengurla station whereas Amboli, Mulde Varandoli, chowk received highest rainfall in 28th SMW and Khapari in 29th SMW. According to Mann Kendall method annual as well as June, July, August and October month rainfall did not show any trend all over the Konkan region where as September month 79 rainfall exhibited increasing trend in Ratnagiri and Sindhudurg district and Palghar, Thane, Raigad district did not showed any trend. Mann Kendall method also showed only decreasing trend of weekly rainfall in few SMW in Palghar district whereas only increasing trend in Sindhudurg district and Raigad, Ratnagiri district showed both increasing as well as decreasing trend in various SMW. Mann Kendall method did not exist any trend of weekly rainfall in Thane district throughout the monsoon season. Sen‘s Slope method showed increasing trend of annual rainfall in Palghar, Thane, Ratnagiri and Sindhudurg district whereas Raigad district showed increasing as well as decreasing trend at various stations. Sen‘s Slope method also showed increasing trend of June month rainfall in Palghar, Thane, Ratnagiri and Sindhudurg district whereas Raigad district showed both increasing and decreasing trend. Increasing trend of July monthly rainfall was showed in Thane and Sindhudurg district whereas Palghar, Raigad and Ratnagiri district showed both increasing as well as decreasing trend of July moth rainfall. August month rainfall exhibited increasing trend in Palghar and Thane district whereas Raigad, Ratnagiri and Sindhudurg district exhibited both increasing as well as decreasing trend. Increasing trend was exhibited in September month rainfall all over the Konkan region. October month evinced only increasing trend in Thane and Ratnagiri district whereas Palghar, Raigad and Sindhudurg district exhibited both increasing as well as decreasing trend. Either increasing or decreasing trend were exhibited in Palhgar district from 24th to 39th SMW. Except 22nd, 42nd and 43rd SMW all remaining weeks exhibited either increasing or decreasing trend in Thane, Raigad and Ratnagiri district. Sindhudurg district showed either increasing or decreasing trend in all SMW. Turning point test evinced decreasing trend of annual rainfall in Raigad and Sindhudurg district whereas Palghar, Thane and Ratnagiri district didn‘t show any trend. Decreasing trend was showed in June month rainfall in Sindhudurg district and both increasing as well as decreasing trend in Raigad district whereas Palghar, Thane and Ratnagiri district didn‘t show any trend. Turning point test showed decreasing trendof July month rainfall in Sindhudurg district whereas other district didn‘t exist any trend. Increasing trend of August month rainfall was showed in Palghar and Raigad district which are situated in north and middle part of the study region whereas south part of Konkan region didn‘t evince any trend. September month rainfall was existed only in Palghar and Raigad district had decreasing and increasing trend, respectively. Turning point test didn‘t show any significant trend of October month rainfall in the Konkan region. 80 Moving average method showed increasing trend of annual rainfall in Palghar, Thane, Ratnagiri and Sindhudurg district however Raigad district showed both increasing as well as decreasing trend. Increasing trend of June month rainfall was showed in Palghar, Thane, Ratnagiri and Sindhudurg district whereas Raigad district showed both increasing and decreasing trend. Decreasing trend of July month rainfall showed in Palghar district and increasing trend in Sindhudurg district whereas Raigad and Ratnagiri exhibited both increasing as well as decreasing trend and Thane didn‘t exhibit any trend. Increasing trend of August month rainfall was showed in Palghar and Thane district whereas Raigad, Ratnagiri and Sindhudurg district exhibited both increasing as well as decreasing trend. Moving average methods exhibited increasing trend of September month rainfall all over the Konkan region. Decreasing trend of October month rainfall was exhibited in Palghar, Raigad and Ratnagiri district whereas Sindhudurg showed increasing trend and Thane district did not exhibit any trend. Regression method showed increasing trend of annual rainfall in Palghar, Thane, Ratnagiri and Sindhudurg district whereas Raigad district showed increasing as well as decreasing trend at various stations. Regression method also showed increasing trend of June month rainfall in Palghar, Thane, Ratnagiri and Sindhudurg district whereas Raigad district showed both increasing and decreasing trend. Decreasing trend of July month rainfall was showed in Palghar and Thane district whereas increasing trend in Ratnagiri and Sindhudurg district. Raigad district showed both increasing and decreasing trend. August month rainfall exhibited increasing trend in Palghar and Thane district whereas decreasing trend Raigad and Sindhudurg district and Ratnagiri exhibited both increasing as well as decreasing trend. Increasing trend of September month rainfall was showed in Palghar, Raigad, Ratnagiri and Sindhudurg district whereas Thane didn‘t exhibit any trend. Regression method showed increasing trend of October month rainfall in Thane and Sindhudurg district and both increasing as well as decreasing trend in Raigad district where as Palghar and Ratnagiri did not show any trend.
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