Change in rainfall pattern Gujarat region in the last 116 years (1901-2017): A case study

Introduction

India's economy is dependent on the agricultural production, which in turn is dependent one of the monsoon rainfall and its distribution. The year to year fluctuation in rainfall as well as the fluctuation within the monsoon season governs the crop growth, development and yield. Earlier studies on rainfall probability in India have been carried by many workers (Singh et al., 2009; IMD, 2010 and Halikatti et al., 2010) [5,2,1] . Rainfall, the main driver of the hydrological cycle, has been varying in part of the world in various ways. Rainfall is the main source of water. But rainfall is scares and erratic in Gujarat especially in Saurashtra region. So, its preservation and conservation has become the most important aspect in relation to the water resources development planning. Its magnitude, variation and distribution plays important role in hydrological response of the area. The analysis of rainfall records for long period provides information about rainfall pattern and variability. And also rainfall studies are utmost utility for understanding nature and behavior of climate change. (Solanki et al. 2014) [6] . Climate change is one of the main challenges in the world that is being studied by scientists and researchers. Rainfall is a key input in management of agriculture and irrigation projects and any change in this variable can influence on sustainable management of western resources, agriculture and ecosystems. Mainly, studies of climate change science are focused on the probable changes in the annual series of a variable such as rainfall and variability of this is important for crop planning. Globally the averaged precipitation is projected to increase; both increases and decreases are expected at the regional scale. The impact change on water resources has received much attention globally. The analysis of rainfall records for long period provides information about rainfall pattern and variability (Lazaro et al. 2001) [3] . The main objective of this paper is to analyses the rainfall data to study variation in rainfall pattern.

Material and Methods

Study area

Gujarat is divided into eight agro-climatic zones based on rainfall. Based ion the annual rainfall of different agroclimatic zone, the mean annual rainfall varies between 442.3 mm in North-West Gujarat zone and 1651.4 mm in south Gujarat heavy rainfall zone. The number if rainy day varies between 18 in North-west zone and 63 in South Gujarat heavy zone. (M.C. Varshney et al. 2009) [4] Gujarat is a serene and pristine land where the azure seas meet sparkling sands. Gujarat is positioned between 20° 6′ N to 24° 42′ N latitude and 68° 10′ E to 74° 28′ E longitude. www.extensionjournal.com

Data and Methodology

In this paper average of total mean rainfall (mm), maximum rainfall intensity of the month (mm/day) and rainy days data was used during 1901 -2017 (116 years). The trend is determined by the relationship between the two variables as rainfall and time. The statistical method such as linear regression analysis and coefficient of determination R 2 are used. The equation of a linear regression line given as:

Where, y is the observation on the dependent variable, x is the observation on the independent variable, a is the slope of the line and b is an intercept of the vertical axis. The drawing of the scattered diagrams and fitting of the regression lines were done in Microsoft Excel.

Results and Discussion

Trend Analysis for the month of June

Trend Analysis of Monthly Mean of Total Mean Rainfall (TMRF)

The linear regression trends with their linear regression equations and coefficient of determinations for the months from June to October (Monsoon season) are represented in figure 2.

It is evident from figure 2 Climate change is a continuous process but it is analyzed in this study that there is a significantly change in rainfall over last decade.

Conclusion

Long term data analysed for 116 years (1901-2017) annual data suggest that there is a significantly change in rainfall over last decade. However an annual rainfall is the erratic with wide range from 1620.1 mm maximum and 392.6 mm minimum in Gujarat region. It observed total mean rainfall June to October, total mean rainfall observed an increasing trend having an increase 0.24 mm per year. This implies that in Gujarat region annual rainfall has increased by 24 mm. From the average monthly rainfall analysis, it is observed that rainfall variation for first 20 years (1901-1920 & 1921-1940) and second 20 years (1941-1960, 1961-1980) are similar rainfall pattern whereas it differs for last decade (2000-2017) because of the change in magnitude however the overall trend is similar. Average monthly rainfall analysis indicates there is maximum rainfall in month of July and minimum rainfall in month of October.

Acknowledgement

Authors are thankful to Head, Department of Agricultural Meteorology, BACA, AAU, Anand for their inspiring guidance, and valuable suggestion her constant support.

References

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