Analysis of Rainfall Variability in Danda Jaya Swamp Irrigation Area Due to Climate Change

Abstract

Indonesia as an archipelago in between two oceans and located on the equator is prone to climate change. Climate change is characterized by changes in rainfall patterns that shift the beginning of rainy season and dry season. Therefore, it is necessary to conduct a test on the rainfall to determine the distribution pattern of rainfall in an area. This study aims to identify climate change through the tendency, distribution, and similarity of precipitation data with different timescales, by using precipitation data from 2000-2020. Precipitation data were obtained from the BMKG observation station in Karang Indah, Mandastana, Barito Kuala, South Kalimantan. The data were then grouped into 2 periods of observation year. Precipitation data for the rainy season in first period of 2000-2009 (October - June) and the dry season (July - September), rainy season in the second period of 2010-2020 (October - July), and the dry season (August - September). Determination of rainy season and dry season is based on Oldeman`s classification to determine the wet and dry months in the two observation periods. Then, a normality test using Smirnov-Kolmogorov was conducted to determine if the data to use have a normal distribution based on its significant value. Statistical tests were carried out using regression analysis by using the relationship among quantitative variables where one of the variables can be predicted from other variables. This study aims to identify the existence of climate change through a tendency pattern using linear regression analysis. The analysis result conducted in Danda Jaya Swamp Irrigation Area using daily precipitation data from 2000-2020 showed a tendency to increase in rainfall intensity of 18.944 mm/year. The linear regression equation is Y = 18.944x + 2449.8 with a correlation coefficient of R2 = 0.0385. Trend analysis of the annual average rainfall in rainy season in period I and II decreased by -2.663 mm/year and -11.542 mm/year respectively. In the dry season, the average value of annual rainfall increased in the first period of 4,886 mm/year and the second period of 3,083 mm/year.