Screening of Annual Rainfall Time-Series Data in Kala Oya Basin: Case Study in Sri Lanka

Hydrometeorological data screening is essential analysis conducted prior to the use of such data for modelling and designing of water development schemes as inconsistencies can occur during the data collection or data entering. There are many methods adopted to perform screening of data by various publishers, but this paper presents a prominent method which has been used for the rainfall annual time-series of Kala Oya basin. Adequate numbers of rainfall gauging stations and outliers have been checked using statistical analysis and percentage significance level outlier constant for normal distribution. Trend analysis and absence of persistency have been estimated by the Mann-Kendall test and the first serial correlation coefficient method. Homogeneity of the region was checked by doing two statistical tests based on L-Moments of the time-series data. The first criterion was Discordancy measure (Di) and the second criterion was Heterogeneity measure (Hi) which have been based on L-moments of the time-series data. The results confirmed that the selected annual time-series data can be considered as homogeneous and consistent with minor deviations.