APPLICATION OF NON PARAMETRIC TEST FOR TREND DETECTION OF RAINFALL IN CHAMKHARCHHU BASIN OF BUMTHANG, BHUTAN

Author Name: 1. Leki Dorji 2. Jamyang Seldon

Volume/Issue: 02/01

Country: Bhutan

DOI NO.: 08.2020-25662434 DOI Link: https://www.doi-ds.org/doilink/07.2021-59719426/UIJIR

Affiliation:

1. Lecturer, Civil Engineering and Engineering Geology Department, College of Science and Technology, Royal University of Bhutan, Bhutan.
2. Student, Civil Engineering Student, Royal University of Bhutan, Bhutan.

ABSTRACT

Bhutan is one of the sensitive regions to climate variation particularly to temperature and precipitation changes as there is indication of melting Glaciers in the northern part of the country. This study attempts to an effort to analyze one of the most important climatic variable i.e., rainfall for analyzing its trend in Chamkhar area as the Royal Government of Bhutan is planning to come up with small hydropower in that region. Historical available data form 1996 to 2020 have been processed to determine the monthly variability of rainfall using Mann-Kendall test and Sen’s Slope Estimator specially to observe trend and slope magnitude of rainfall. Correlation between rainfall and river discharge can be established, so as to achieve the objective of hydropower sustainability can be forecasted with the available of 25 years of data. The application of a trend detection framework resulted in the identification of insignificant trends from January to December. It has been observed with maximum decreasing rates of rainfall in some of the seasons particularly in summer season and autumn seasons of -2.003 and -0.754 respectively. However, june month indicates the maximum value of decreasing trend based in Sen’s slope and Mandell Test. Mandell test and sen’s slope obtained by these statistical tests suggesting overall insignificant changes in the area. In contrast, most of the seasons represent slight precipitation either increase or decrease (which are not statistically significant) annually, spring, autumn and winter. However, summer is the most significant season of decreasing, followed by annul average decreasing trend and autumn indicated the least decreasing trend. The main objective of this study is to observe the rainfall trend so far in Chamkharchhu .Mann-Kendall’s (MK) nonparametric test and Sen’s slope estimation techniques were used to quantify the overall statistical significance of the results.

Key words: Climate Variation, Precipitation, Mann-Kendall, Trend, nonparametric