Statistical Assessment of Some Water Quality and Rainfall Data in Ciliwung River, Indonesia

Abstract

Ciliwung is the river that flows from upstream in the Puncak area of Bogor Regency to Jakarta Bay. Water quality parameters have been monitored each month at three stations in the Ciliwung River watershed by the Indonesian Ministry of Environmental and Forestry and Meteorological, Climatological, and Geophysical Agency. The data analyzed in this study are rainfall and water quality data for the period 2017-2020 with water quality variables including pH, temperature, Dissolved Oxygen (DO), electrical conductivity (EC), Turbidity, Total Dissolved Solids (TDS), and Nitrate-N. This paper aimed to analyze the time series data using statistical methods and describes certain chemical parameters and rainfall data, that show Ciliwung water quality during 2017-2020. Descriptive analysis was used to determine the mean, skewness, and kurtosis values based on time and location. Histogram and boxplot graphs were used to describe distribution of the data set. Test of Kolmogorov-Smirnov was used to evaluate the normality of the data set. The descriptive analysis resulted in the mean of each water quality parameter showing a value that did not show a significant difference between observation locations except for the TDS parameter. From the histogram and boxplot graphs, it can be seen that the data shows an abnormal distribution and there are many outliers. Kolmogorov-Smirnov test resulted in better normality of data distribution. The main problem of pollution is the use of oxygen by organic matter contained in river water. Ciliwung River downstream was changed into open accumulator wastewater from the food industry, livestock, and settlements.