Abstract
Groundwater is the most unexplored element of the hydrologic cycle on the Tibetan Plateau (TP) due to harsh climate conditions. This study aims at delineating and characterizing the unexplored Zhanongtang–Ganmanong aquifer, situated in the Zhagu subcatchment of the Nam Co catchment, south-central TP. Multiple hydrogeophysical and lithological in situ field and laboratory methods are applied: depth-to-water-table measurements, grain size analysis, hydraulic empirical and field methods to estimate hydraulic conductivity (K), and analysis of electrical resistivity tomography profiles. Integration of these methods revealed the existence of a Quaternary hydrostratigraphic unit that was found to be unconsolidated, laterally heterogeneous and homogeneous over depth. The results revealed consistent K ranges of three K zones, which is in accordance with local lithology. The K ranges are applicable to other locations within the Nam Co catchment with similar lithology as in the study area without further field experiments. Permafrost was found to be absent in the study area ranging from 4730 m a.s.l. to 5200 m a.s.l. altitude. These results provide insight into the hydrogeological conditions of the TP and are useful for conceptual and numerical groundwater flow modeling to predict future changes of water fluxes and water budgets caused by climatic change, especially in remote areas.
Highlights
The study area is located on the Tibetan Plateau (Figure 1a), where the Nam Co
Our study shows that the delineated aquifer formation can be classified as a Quaternary hydrostratigraphic unit
During the Holocene, the Ganmanong formation was overlain by the Zhanongtang formation with a thickness of 3 m, showing that the entire Quaternary formation has a total thickness of 17 m
Summary
The Tibetan Plateau (TP), called the Asian Water Tower [1] provides water for billions of people supraregionally in India, Bangladesh, China and Southeast Asia, representing over 20% of the global population [2,3]. [4] postulated that rivers originating from the central TP are influenced by discharging melt- and groundwater, contributing to significant and variable amounts of water towards streams. This underpins the importance of groundwater from the TP as a globally important fresh water resource. Assessment of regional subsurface structures and the hydrogeologic environment is crucial to understand the hydrologic cycle of the TP, which sustains the water supply to the Asian Water Tower
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