Understanding the main drivers of runoff availability has important implications for water-limited inland basins, where snow and ice melt provide essential input to the surface runoff. This paper presents an analysis on the runoff response to changes in climatic and other controls of water-energy balance in an inland glacierized basin, the Urumqi River basin, located in the arid region of northwest China, and identifies the major control to which runoff is sensitive across the basin’s heterogeneous subzones. The results indicate that the runoff is more sensitive to change in precipitation in the mountainous headwaters zone of the upper reach, and followed by the impact of basin characteristics. In contrast, the runoff is more sensitive to changes in the basin characteristics in the semiarid and arid zones of the mid and lower reaches. In addition, the change in basin characteristics might be represented by the distinct glacier recession in the mountainous upper reach zone and the increasing human interferences, i.e., changes in land surface condition and population growth, across the mid and lower reach zones. The glacier wasting contributed around 7% on average to the annual runoff between 1960 and 2012, with an augmentation beginning in the mid-1990s. Findings of this study might help to better understand the possible triggers of streamflow fluctuation and the magnitude of glacier wasting contribution to runoff in inland glacierized river basins.

In this study, a new approach is developed to compute groundwater flow rate and hydraulic head distribution in a two-dimensional discrete fracture network (DFN) in which both laminar and inertial flows coexist in individual fractures. The potential errors in both flow rate and hydraulic head, from the approach based on uniform flow assumption in relation to DFN and flow characteristics, are examined. The cubic law is used to calculate hydraulic head distribution and flow behaviors in fractures in which flow is laminar, whereas Forchheimer’s law is used to quantify inertial flow behaviors. The Reynolds number is used to distinguish flow characteristics in individual fractures. The combination of linear and nonlinear equations is solved iteratively to determine flow rates in all fractures and hydraulic heads at all intersections. Applying the cubic law in all fractures regardless of actual flow conditions overestimates the flow rate when inertial flow may exist whereas applying Forchheimer’s law indiscriminately underestimates the flow rate in the network. The contrast of apertures of large and small fractures in the DFN has significant influence on the potential error of using only the cubic law or Forchheimer’s law. Both the cubic law and Forchheimer’s law simulate similar hydraulic head distributions, as the main difference between these two approaches lies in predicting different flow rates. Fracture irregularity does not significantly affect the potential errors from using only the cubic law or Forchheimer’s law if the network configuration remains similar. The relative density of fractures does not significantly affect the relative performance of the cubic law or Forchheimer’s law.