Impacts of Climate Change and Human Activities on Streamflow in the
upper basin of the Yongding River, North China
Abstract
Quantitative assessment of the effects of climate change and human
activities on runoff is very important for regional sustainable water
resources utilization. Determining abrupt changes in runoff could
enhance identification of the main driving factors for the sudden
changes. In this study, the double mass curves analysis combined with
field investigation is used to determine abrupt changes in runoff in two
sub-catchments of Upper Yongding River Basin(UYRB), while trend analysis
via the traditional Mann–Kendall test for the period 1961–2017 is used
to identify the basic trend of precipitation, temperature and potential
evapotranspiration(E0). The results suggest an insignificant change in
precipitation, a significant increase in temperature and a significant
decline in E0 in both sub-catchments. For both of the sub-catchments,
abrupt changes in runoff occurred in 1982 and 2003. Both Budyko’s curve
and double mass curves are used to evaluate the potential impacts of
climate variability and human activities on mean annual streamflow. The
results showed that, from the 1960s to the 1980s, runoff declined by
20.01% and 22.28% for Xiangshuibu and Shixiali, respectively; from the
1980s to the 2000s, runoff declined by 68.23% and 67.77% respectively.
In the variation stage Ⅰ (1983~2003), human activities
contributed 90.6% and 62.7% of the mean annual streamflow change in
YRB and SRB, respectively. In the variation stage
Ⅱ(2004~2017), human activities contributed 99.5% and
93.5% of the change in YRB and SRB, respectively. It is also noted that
the first abrupt decline in runoff was actually at the beginning of
China’s land reform, when the land reform motivated farmers to
productively manage their reallocated lands, agricultural water
consumption therefore increased. The second abrupt change point occurred
in 2003, when “Capital water resources planning” implemented including
water conservation projects and irrigation district construction. In
general, human activities, including soil and water conservation
projects and water consumption, are found to be the dominant factors
responsible for the significant decline in the annual streamflow in the
UYRB over the last six decades.