Assessment of variable trend of rainfall and water discharge in the lo river basin, Ha Giang province

Abstract

This paper presents assessment results of variable trends of rainfall and water discharge in Lo river basin (Ha Giang province) in the period from 1972 to 2018 using statistical analysis, cumulative standard error line and non-parametric Mann-Kendall test. The results show that (i) averaged values of annual rainfall at Ha Giang and Bac Quang stations are 2430 mm and 4510 mm, (ii) the annual rainfall at Ha Giang and Bac Quang stations tend to decrease by 4 mm/year, (iii) the high continuous rainy periods are 1972-1990 and 1994-2006, while the low continuous rainfall periods are 1990-1994 and 2006-2018, (iv) the averaged value over the considered period of monthly rainfall has the largest decrease (by 6.0 mm) in May. At Dao Duc station, the averaged value over the considered period of annual water discharge equals 150 m3 /s, and has a decrease variable trend with a value of 1.24 m3 /s/year. The monthly water discharge has a decline variable trend from May to February, in which September is the largest reduction (3.73 m3 /s). At Vinh Tuy station, the averaged value over the considered period of annual water discharge is 304 m3 /s and has a drop variable trend with a value of 2.45 m3 /s/year.