Water balance under climate and land use changes in Taiwan’s mountainous watersheds

Climate change induced precipitation pattern changes along with the increasing forest area have affected the hydrological processes in Taiwan’s mountainous watersheds. Recent studies pointed out that despite the increasing rainfall, the ratio of precipitation that turns into runoff decreases, implying more water storage in watersheds. However, a contradictory decreasing trend in groundwater level was also discovered, highlighting the importance of water budget reassessment. To figure out where the missing water is stored, observed precipitation, runoff data and model evapotranspiration data from Taiwan Climate Change Projection Information and Adaption Knowledge Platform (TCCIP) will be integrated to infer total dynamic storage by water balance equation. To further distinguish the composition of total dynamic storage, recession analysis and sensitivity function will be applied to derive direct storage and indirect storage, which represent the storage that drives streamflow and the remainder of it, respectively. Finally, the combination of total water storage data (from GRACE or GNSS), soil water content data (such as TerraClimate), observed groundwater levels or other potentially relevant data will be used to validate the results. The objectives of this study include: (1) Accessing the water budget under climate and land use changes in Taiwan’s mountainous watersheds and (2) Identifying the distribution of the water stores in the watersheds.