The results of the three methods suggest that climate variability is a greater contributor to streamflow decrease than change in catchment properties for the UHRB, whereas the relative contribution from change in catchment properties increases from 17% in the upper parts to 54% in the lower parts, which is likely linked to the population growth.
Climate projections also suggest greater variability in streamflow with more frequent high and low discharge periods [36], [37], [38].
At MSSP-GR and MSSP-TH, increases at low and moderate streamflows were greater than decreases at high streamflows, whereas decreases at IOWA-WAP, OHIO-GRCH, and MSSP-OUT at high streamflows were more comparable to increases at low and moderate streamflows, particularly in the spring and summer.
In contrast to traditional models either in the lumped ANN or in empirical regression forms, the new approach of integration of Artificial Neural Networks has shown great potential in streamflow modeling.
At these and most other sites, however, increases in nitrate concentration at low to moderate streamflows were greater than or comparable to changes at high streamflows.
The contour plots show that concentrations increased at low and moderate streamflows at most of the study sites and the magnitude of changes in concentration at low and moderate streamflows was greater than or comparable to that at higher streamflows.
Climate variability has a greater effect on the streamflow reduction in the Beiluo River and Yan River, while human activities accounted for more of the streamflow changes in other tributaries, especially in the northern catchments.
In south-western Australia, significant declines in annual rainfall in recent decades have been accompanied by even greater declines in annual streamflow.
Although most models show a greater variability in daily streamflow than the observations, the models with the greatest variability (as much as double the observed variability), produce most of their runoff through fast response, surface runoff mechanisms.
Streamflow declines are greater in areas that are restocked with conifers than in those restocked with hardwoods.
