Available online at www.sciencedirect.com ScienceDirect Aquatic Procedia 4 (2015 ) 713 720 INTERNATIONAL CONFERENCE ON WATER RESOURCES, COASTAL AND OCEAN ENGINEERING (ICWRCOE 2015) Spatial and Temporal Variability of Rainfall in Anand District of Gujarat State Khadeeja Priyan Civil Engineering Department, G H Patel College of Engineering & Technology,Bakrol Road,Vallabh Vidyanagar, Gujarat,388120,India Abstract Rainfall Variability is one of the key factors that affect agricultural production in any region. Hence the proper understanding of rainfall pattern and its trends may help water resources development and to take decisions for the developmental activities of that place. The present study is an attempt to evaluate the spatial and temporal rainfall variability of Anand district of Gujarat State in Western India. Anand in Gujarat State popularly known as the milk capital of India is located in the Southern part of Gujarat near Gulf of Cambay. The district has eight Talukas with district headquarter at Anand. Khambhat Taluka of this district has natural border with Gulf of Cambay. The normal rainfall of this district is 687 mm from South-West Monsoon with an average of 40 rainy days. The normal onset of monsoon is from 3 rd week of June and the normal cessation is in the 4 th week of September. In the present study the spatial and temporal rainfall characteristics of this district are studied. Long-term annual and monthly rainfall data (Monsoon months) are considered from 1901 to 2014. The daily rainfalls of monsoon months of all the eight Talukas are analysed for the last five years from 2010 to 2014. It was found out that spatial and temporal variability is high in the District. 2015 2015 The The Authors. Authors. Published Published by by Elsevier Elsevier B.V. B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of ICWRCOE 2015. Peer-review under responsibility of organizing committee of ICWRCOE 2015 Keywords: annual and monthly rainfall, rainfall variablility, daily rainfall, number of rainy days. * Corresponding author. E-mail address: khadeeja.priyan@gmail.com 2214-241X 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of ICWRCOE 2015 doi:10.1016/j.aqpro.2015.02.092
714 Khadeeja Priyan / Aquatic Procedia 4 ( 2015 ) 713 720 1. Introduction Rainfall variability is considered as an important factor in agricultural and other economic development. Hence understanding its nature and trend at any place has a great significance in water storage for future use. McCartney and Smakhtin (2010) stated that rainfall variability due to climate change and insufficient capacity to manage it, lead to poverty and food insecurity in Africa and some parts of Asia. Gujarat is one of the leading states in industrial developments in India, but the percapita water availability in this state is only 908 cum per annum which is far behind the national average. Though the State Government has taken a lot of steps to improve the water scenario, Sen (2010) recommended that all the stakeholders from the public and the private sectors should join together to create and manage the water resources. 1.1 Rainfall Variability Rainfall variability has been defined as the deviation of rainfall from the mean or the ratio of standard deviation to the mean or the variability of coefficient of variation (Rathod and Aruchami, 2010). Rainfall variability has been discussed and studied in the context of climate change at global level, regional level and local level. Gadgil (2007) emphasized that there should be a clear understanding of the basic systems responsible for monsoon and the factors that lead to its variation before developing any predictability model. Rangarajan and Sant, (2004) used fractal dimentional analysis to analyze the time series data of three major climatic variables temperature, pressure and precipitation, to study variability changes and the variability of south-west monsoon and north-east monsoon in India at local level and regional level using predictability indices. They concluded that the precipitation during south west monsoon is affected by the temperature and pressure variability of the preceding winter. Large sets of rainfall and temperature data are examined using spectral and time series analysis to analyse climatic trends and interactions (Tularam and Elahee, 2010). 1.2 Rainfall Variability in Gujarat The rainfall in Gujarat varies from 300 mm in the North and Northwest to gradually increasing to 2500 mm in the Southern districts (GEC, undated). The coefficient of variation of rainfall in the state is as high as 50%. Many hydrology projects have been taken up in the State with the objective of understanding the present institutional arrangement, technical capacity and physical facilities to the best level (Brahmbhatt, 2009). Many researches have been done in different parts of India to predict the rainfall variability. Varshneya, et al., (2009) forecasted the rainfall based on Astro-meteorology. Tripathi (2009) prepared a crop pattern by considering weekly rainfall pattern to help extension agencies to advise the farmers to prepare the crop plan which in turn helps to increase the agricultural productivity. The present study is an attempt to understand the spatial and temporal variability of rainfall in Anand district of Gujarat and the study reveals that high spatial and temporal variability over the period studied. 1.3 South West Monsoon in Gujarat State Gujarat state in India gets rainfall through South-West monsoon during June to September. The intraseasonal and inter annual variability of the summer monsoon has a great socio-economic impact in the agricultural and other economic development in India (Krishnamurthy and Kinter III, 2002). The study of the rainy season of India has been started even before 17 th century and the scientific studies have been progressed in the post independence era with more understanding and prediction models (Sikka, 2012). It has been estimated that there is a large spatial variation in the annual rainfall of the country with a lower value of 35% in the sub-divisions of Tamilnadu & Pondicheri and with a maximum value of 95% in the subdivisions of Gujarat (Guhatakurta, 2012). Gujarat is one of the states in India where the highest one day rainfall exceeds 40 cm. As per the analysis of IMD for the period 1875-2009 maximum number of droughts occurred in Rajastan (31 years) followed by Gujarat (30 years). In the year 2008, the State experienced delayed and deficient monsoon and hence the net sown area was very less (Samui, 2012). Hence rainfall variability studies are having great significance in the State. Since the rainfall in the State varies from less than 500 mm in the arid Kutch regions to more than 2500 mm in the South Gujarat region, the
Khadeeja Priyan / Aquatic Procedia 4 (2015 ) 713 720 715 study may be appropriate at micro-level only. 2. Study Area Anand district of Gujarat State in Western India popularly known as the milk capital of India is located at 22 0 6 to 22 0 43 N latitude and 72 0 2 to 73 0 12 E longitude with an altitude 43 m above MSL. This district is located in the Southern part of Gujarat near Gulf of Cambay. The district has eight Talukas with district headquarter at Anand. It is bounded by Kheda district on the North, Ahmedabad district on the West, Baroda district on the East and Gulf of Cambay on the South. Khambhat Taluka has a natural border with Gulf of Cambay. Amul (Anand Milk Union Ltd) Dairy, the largest dairy Cooperative of India and National Dairy Development Board are situated here. Ahmedabad Mumbai Expressway is passing through the district. The district has a total area of 2951 sq.km and the total population is 2,092,745 as per 2011Census. There are eight Talukas in the district and out of the total geographical area of the district 70.5% area is cultivable area. The normal rainfall of this district is 687 mm from South-West Monsoon with an average of 40 rainy days. The normal onset of monsoon is from 3 rd week of June and the normal cessation is in the 4 th week of September. For the present study, rainfall data from Gujarat State Disaster Management Agency (GSDMA), Gandhinagar and Long sequence of district wise data available with Indian Meteorological Department (IMD) have been collected and analysed. Figure 1. Administrative Boundary of (a ) Gujarat (b) Anand District There are eight Talukas (Anand, Anklav, Borsad, Khambat, Petlad, Sojitra, Tarapur and Umreth) in Anand
716 Khadeeja Priyan / Aquatic Procedia 4 ( 2015 ) 713 720 District and the spatial and temporal variations in rainfall are very high in these Talukas. The average rainfall in the district from 1984-2013 was 763 mm where as the State average was 797 mm. The average rainfall values of last 30 years in these Talukas are shown in Figure 2. The average annual rainfall of last 30 years (1984-2013) shows that the highest value 910 mm was recorded in Anklav Taluka and the lowest value 599 mm was recorded in Umreth Taluka. The same pattern for highest and lowest rainfall was observed in Anklav Taluka and Umreth Taluka respectively when the 10 years averages of (2000-2009) and (2001-2010) are considered. Umreth Taluka is the farthest Taluka of this district from the sea coast. Anand, Anklav, Borsad, Khambat and Petlad recorded above normal rainfall of the district. Sojitra, Tarapur and Umreth have received below average rainfall only. In general, Talukas in the northern side of the district recorded below average rainfall during the last 30 years. Talukas of central part and southern side near to Gulf of Cambay received good rainfall. 1000 900 800 700 600 500 400 300 200 100 0 Talukawise Annual Average Rainfall in mm (1984-2013) Anand Anklav Borsad Khambat Petlad Sojitra Tarapur Umreth Figure 2.Talukawise Annual Average Rainfall for the Last Thirty Years (1984-2013). 3. 1 Annual Rainfall in Anand District The annual average rainfall in the district from 1901 to 2014 is 672 mm. However, the last 10 years (2005-2014) average value is 911 mm. Out of these ten years, the rainfall was above normal in nine years and only in the year 2009 the rainfall was below 400 mm. The linear line in Figure 3 shows an upward trend in the annual rainfall. The highest anuual rainfall was 1518 in the year 2005 and the lowest (209 mm) was in the year 1918. Out of 113 years (data is not available for the year 2003), above normal rainfall was recorded for 61 years and the remaining 52 years the rainfall was below normal. The annual rainfall was above 1000 mm for eight years and below 400 mm for 15 years. Figure 3 below depicts the distribution of annual rainfall from 1901 to 2014.
Khadeeja Priyan / Aquatic Procedia 4 (2015 ) 713 720 717 Annual Rainfall in mm (1901-2014) 1600.00 1400.00 1200.00 1000.00 800.00 600.00 400.00 200.00 0.00 1901 1905 1909 1913 1917 1921 1925 1929 1933 1937 1941 1945 1949 1953 1957 1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2006 2010 2014 Figure 3.Annual Rainfall in mm from 1901 to 2014 The Figure below shows ten years moving average of the rainfall in the district. An increasing trend in rainfall was observed in the district from 1990. The last five years average (2011-2014) the rainfall is appreciably high with an average of 926 mm. 1000.00 800.00 600.00 400.00 200.00 0.00 10 Years Moving Average Rainfall in mm Figure 4. Ten Years Moving Average Rainfall (1901-2014) The following Table shows the details of Talukas having the highest and lowest rainfall in the district. Khambat Taluka which is having natural border with Gulf of Cambay is having the highest or next to highest rainfall. Umreth Taluka which is the farthest from the sea coast is continuously getting the lowest or next to lowest rainfall in the district. The variability is very high whether a particular year is a good year or a bad year. Table 1.Talukas Having Highest and Lowest Rainfall. Particulars Highest Name of Taluka Having Highest and Lowest Rainfall and its Value in mm in paranthesis 2010 2011 2012 2013 2014 Khambat (1117) Anklav (910) Khambat (794) Khambat (1500) Borsad (1400)
718 Khadeeja Priyan / Aquatic Procedia 4 ( 2015 ) 713 720 Lowest Umreth (505) Umreth (492) Umreth (420) Umreth (772) Tarapur (703) 3.2 Monthly Rainfall in the District June, July, August and September are the four monsoon months in the district. The probability of getting highest rainfall in July is 0.52 if the whole period (1901-2014) is considered and it is 0.6 if the last 10 years are considered. However, in the last five years (2010-2014), August month received the highest rainfall in three years. The percentage rainfall in four monsoon months in the last 10 years are 10%, 39%, 31% and 20% in June, July, August and September respectively. However, this pattern is changed to 6%, 36%, 35% and 23% when the last five years rainfall is considered for the corresponding monsoon months. Percentage Rainfall in Each Monsoon Month September in the Last 10 Years 20% June 10% August 31% July 39% Figure 5. Percentage Rainfall in Monsoon Months The highest monthly rainfall recorded is 552 mm in July, 2006. The Borsad Taluka recorded a maximum of 732 mm in July, 2014. It has been noticed that the rainfall was 1000 mm or more in the years 2013 and 2014, and the rainy season in these years was extended to October month also. The mean rainfall and the standard deviation is the highest in July month only. Variability is calculated as: variability = standard deviation *100/ mean The result shows that highest variability is in the month of June and the lowest in the month of August. The variability is comparatively low in Khambat Taluka where rainfall is high and it is high in Umreth Taluka where the rainfall is very low. Sojitra is having very low variability in September month. The following Table gives the monthly variability of rainfall at different Talukas. Table 2.Rainfall Variability in Different Talukas. Name of Taluka June (%) July (%) August (%) September (%) Anand 142 51 30 59 Anklav 139 52 53 54 Borsad 149 50 40 65 Khambat 131 48 58 50 Petlad 118 68 41 43 Sojitra 173 50 49 23 Tarapur 174 47 56 55 Umreth 193 56 35 68
Khadeeja Priyan / Aquatic Procedia 4 (2015 ) 713 720 719 3.3 Daily Rainfall Analysis The rainfall anomaly is determined by considering the daily rainfall in five categories; no rainfall, low rainfall, medium rainfall, heavy rainfall and very heavy rainfall. The following Table gives the details. Table 3.Rainfall Anomaly in Different Talukas. Name of Taluka Average Number of Rainfall Days (2010-2013) No rainfall Low Medium Heavy Very Heavy (zero rainfall) (0-2mm) (3-10 mm) (11-40 mm) (>40 mm) Anand 76 6 16 16 5 Anklav 81 2 12 17 8 Borsad 83 2 13 15 8 Khambat 76 4 16 14 9 Petlad 76 8 19 14 3 Sojitra 78 3 16 17 6 Tarapur 80 7 12 14 7 Umreth 76 7 19 17 2 The highest single day rainfall for the period 2010-2013 was 165 mm observed in Petlad Taluka in the year 2013. The number of rainfall days in the district varied in each year and it was 43, 36, 33 and 53 in different years 2010, 2011, 2012 and 2013 respectively. It is worth notice that the average rainfalls in these years were 813 mm, 722 mm, 623 and 1138 mm. So it is in the same order of average rainfall in the district in these years. 4. Discussion & Conclusion The present study is an attempt to evaluate the spatial and temporal rainfall variability of Anand district of Gujarat State in Western India. The district has eight Talukas with district headquarter at Anand. Khambhat Taluka of this district has natural border with Gulf of Cambay. When the annual rainfall from 1901-2014 is considered, high rainfall of above 1000 mm was observed in 9 years and below 400 mm rainfall in 15 years. The linear line of annual data analysis shows an increasing trend in rainfall. Talukawise rainfall analysis shows that central and southern part of the district (five Talukas) received good rainfall and the remaining three Talukas on the northern side of the district received only below normal rainfall. The mean rainfall of the district in the last 30 years is 763 mm with a maximum of 910 mm rainfall in Anklav Taluka and minimum of 599 mm in Umreth Taluka. Sojitra, Tarapur and Umreth had below average rainfall of the district. The same trend is observed when the 30 years average is considered from 1982-2011, 1983-2012 and 1984-2013. Even the same result is obtained in the last 10 years average of 2000-2009 and 2001-2010. The mean rainfall from 1983 to 2012 (30 years) records show that July month received highest rainfall followed by August. The result shows that highest variability is in the month of June and the lowest in the month of August. The number of rainy days and frequency vary in different Talukas and different years. The variability is the highest in June month and the lowest in August. Similarly, highest daily rainfall was also observed in Khambat Taluka only in the year 2010, 2011 and 2013. Lowest rainfall in all four years was observed in Umreth Taluka which is the farthest from the Gulf of Cambay. References
720 Khadeeja Priyan / Aquatic Procedia 4 ( 2015 ) 713 720 Brahmbhatt, V. S., 2009, Hydrology Scenario of Gujarat, Journal of Applied Hydrology, Vol XXII No.I, Jan 2009, pp63-67. Gadgil, S., 2007. Indian Monsoon:Physics of the Monsoon, Resonance, May 2007. Guhathakurta, P., 2012. Extreme Weather Events: Floods, Droughts,Heavy Rains, Monsoon Monograph (Volume 1), Tyagi A., et al, (Eds.), Government of India, Ministry of Earth Sciences, India Meteorological Department. Gujarat Ecological Commission, undated. State Profile, Government of Gujarat. Krishnamurthy, V., and Kinter III, J.L., 2002, The Indian Monsoon and Its Relation to Global Climate Variability, Rodo, X (Ed), (To Appear in) Springer Verlag. McCartney, M., and Smakhtin, V., 2010. Water Storage in an Era of Climate Change: Addressing the Challenge of Increasing Variability, IWMI Blue Paper. Pisharoty, P. R., 1990. Characteristics of Indian Rainfall, Monograph, Physical Research Laboratories, Ahmedabad Rathod, I. M., and Aruchami, S., 2010. Spatial Analysis of Rainfall Variation in Coimbatore District Tamilnadu using GIS, International Journal of Geomatics and Geosciences Vol 1. No.2. Sen, S., 2010, Rational Water Management: Aligning the Interests of Stakeholders, Gujarat /Water Summit special session. Samui, R. P., 2012. Scientific Studies on the South West Monsoon Past, Present and Prospects, Monsoon Monograph (Volume 1), Tyagi A., et al, (Eds.), Government of India, Ministry of Earth Sciences, India Meteorological Department. Sikka, D. R., 2012. Scientific Studies on the South West Monsoon Past, Present and Prospects, Monsoon Monograph (Volume 1), Tyagi A., et al, (Eds.), Government of India, Ministry of Earth Sciences, India Meteorological Department. Tripathi, S. K., 2009, Rainfall Ananlysis for Cropping Planning: A Lesson from Uttarakhand, Journal of Applied Hydrology, Vol XXII No.I, Jan 2009, pp42-54. Tularam, G. A., and Elahee, M., 2010, Time Series Analysis of Rainfall and Temperature Interactions in Coastal Catchments, Journal of Mathematics and Statistics 6(3), 372-380 Varshneya, MC., Vaidya,VB.,Pandey, V, Chimote, LD, Damle KS, /shekh AM, and Karande, /BI., 2009, Forecasting of Rainfall for Gujarat Based on Astro-meteorology, Asian Agri-History, Vol. 13, No. 1, 2009(25-37).