What controls the partitioning between baseflow and mountain block recharge in the Qinghai-Tibet Plateau?

Mountainous areas are referred to as “water towers” since they are the source of water for many low-lying communities. The hydrologic budgets of these areas, which are particularly susceptible to climate change, are typically poorly constrained. To address this, we analyzed the partitioning between baseflow and mountain block recharge (MBR) using a regional groundwater model of the northern Qinghai-Tibet Plateau run with multiple scenarios. We found that ~19% of precipitation is recharged, approximately 35% of which becomes MBR, while 65% discharges as baseflow. This partitioning is relatively independent of the recharge rate but is sensitive to exponential depth decrease of hydraulic conductivity (K). The MBR is more sensitive to this exponential decrease in K than baseflow. The proportion of MBR varies from twice to half of baseflow as the decay exponent increases by more than fivefold. Thus, the depth dependence of K is critical for quantifying hydrologic partitioning in these sensitive areas.