Upward trend of streamflow and precipitation in a small, non-snow-fed, mountainous watershed in Nepal

Hydroclimatic trend assessments of one of the rural, agricultural, non-snow-fed watersheds – the Jhikhu Khola Watershed (JKW) – in Nepal using a non-parametric trend estimation method (Mann–Kendall, Spearman’s rho, and modified Mann–Kendall for autocorrelated data) showed that annual average, maximum, and minimum flows are increasing. This trend of increasing flow is also seen in the annual average flow measured by one of the river gauging stations in the river basin that the watershed drains into, and is corroborated by Seasonal Kendall Test as well. This increase in streamflow coincides with the increasing rainfall trend of the yearly monsoon (June–September) and pre-monsoon (March–May) periods. The post-monsoon (October–February) period does not show any statistical trend. No consistent trend is observed in temperature changes for the whole watershed. Apparently there is no paradox in terms of scale (watershed and basin) and consistency between rainfall and runoff trends in this watershed. However, lack of a consistent trend in temperature changes in the study area may indicate a greater effect from local climatic control than global change on temperature. The lack of shift in the peak month of streamflow in this non-snow-fed watershed may also indicate that there are no major changes in the arrival of monsoon patterns in the study area.