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Studies of regional drought history will be helpful for understanding current hydroclimate variability with global warming as well as predicting future hydroclimate shifts. Long‐term tree‐ring records are scarce in the western Qilian Mountains of northwestern China, which is also the western boundary of the natural distribution of Qilian Juniper (Juniperus przewalskii Kom.) in this area. Here, we present an 850‐year (AD 1161–2010) reconstruction of May–July self‐calibrating Palmer Drought Severity Index (scPDSI) in the western Qilian Mountains that is based on two nearly millennia of ring‐width chronologies derived from long‐lived Qilian Juniper trees. The reconstruction suggests a relatively dry phase from the 15th century to the 18th century during the Little Ice Age (LIA) and a relatively wet period over the past two centuries. This reconstruction is consistent with other tree‐ring‐based hydroclimatic reconstructions from the northeastern Tibetan Plateau, as well as the corresponding century‐scale solar activity during the LIA. The three mega‐drought periods (AD 1260s–1340s, 1430s–1540s and 1640s–1740s) recorded by the tree‐ring series also correspond to the Wolf, Spörer and Maunder solar activity minimum periods. Results of the multi‐tape method analysis and wavelet analysis further confirmed the relationship between regional hydroclimate variability and solar activity forcing.

The dominant source of streamflow in many mountainous watersheds is snowmelt recharge through shallow groundwater systems. The hydrological response of these watersheds is controlled by basin structure and spatially distributed snowmelt. The purpose of this series of two papers is to simulate spatially varying snowmelt and groundwater response in a small mountainous watershed. This paper examines the spatially and temporally variable snowmelt to be used as input to the groundwater flow modelling described in the second paper. Snowmelt simulation by the Simultaneous Heat and Water (SHAW) model (a detailed process model of the interrelated heat, water and solute movement through vegetative cover, snow, residue and soil) was validated by applying the model to two years of data at three sites ranging from shallow transient snow cover on a west-facing slope to a deep snow drift on a north-facing slope. The simulated energy balances for several melt periods are presented. Snow depth, density, and the magnitude and timing of snow cover outflow were simulated well for all sites.Influence de la variabilité spatio-temporelle de la fonte des neiges sur l'écoulement de subsurface de bassins versants de montagne: 1. Simulation de la fonte Résumé La principale source de l'écoulement des cours d'eau de nombreux bassins versants montagneux réside dans la recharge de systèmes aquifères superficiels due à la fonte des neiges. La réponse hydrologique de ces bassins est commandée par leur structure et par la distribution spatiale de la fonte. Le but de cet article en deux parties est de montrer comment on peut simuler les variations spatiales de la fonte des neiges et la réponse des eaux souterraines dans un bassin versant montagneux de petite taille. La première partie de l'article s'intéresse aux variations spatiales et temporelles de la fonte des neiges, en relation avec l'écoulement souterrain dont la modélisation sera décrite dans la seconde partie de l'article. Le modèle de fonte SHAW (Simultaneous Heat and Water, un modèle fin des processus conjoints de transfert de la chaleur, de l'eau et des solutés à travers le couvert végétal, la neige, les résidus de fonte et le sol) a été validé en l'appliquant sur deux ans en trois sites