Investigating the changes in streamflow regimes is useful for
understanding the mechanisms associated with hydrological processes in
different watersheds and for providing information to facilitate water
resources management. In this study, we selected three watersheds, i.e.,
Sandu River, Hulu River, and Dali River on the Loess Plateau, to examine
the changes in the streamflow regimes and to determine their responses
to different soil and water conservation measures (terracing,
afforestation, and damming). The daily runoff was collected continuously
by three hydrological gauges close to the outlets of the three
watersheds from 1965 to 2016. The eco-surplus, eco-deficit, and degree
of hydrological change were assessed to detect hydrological alterations.
The Budyko water balance equation was applied to estimate the potential
impacts of climate change and human activities on the hydrological
regime changes. Significant decreasing trends (P < 0.05) were
detected in the annual streamflow in the Sandu and Dali River
watersheds, but not in the Hulu River watershed where afforestation
dominated. The annual eco-surplus levels were low and they decreased
slightly at three stations, whereas the eco-deficit exhibited dramatic
increasing trends in the Sandu and Dali River watersheds. In the Sandu
River watershed (dominated by terraces), the runoff exhibited the most
significant reduction and the eco-deficit was the highest among the
three watersheds. The integral degrees of hydrological change were
higher in the Sandu River watershed than the other two watersheds,
thereby suggesting substantial variations in the magnitude, duration,
frequency, timing, and rate of change in the daily streamflow. In the
Dali River watershed (dominated by damming), the changes in the extreme
flow were characterized by a decreasing number appearing in high flow.
In these watersheds, human activities accounted for 74.1% and 91.78%
of the runoff reductions, respectively. In the Hulu River watershed
(dominated by afforestation), the annual runoff exhibited an
insignificant decreasing trend but with a significant increase in the
low flow duration. Rainfall changes accounted for 64.30% of the runoff
reduction.
Soil and Water Conservation Measures in Ethiopia: Importance and Adoption Challenges: Review
