Lakes and reservoirs are an integral part of the terrestrial water cycle. In this work, we present the implementation of water balance models of lakes and reservoirs into mizuRoute, a vector-based routing model. The developments described here are termed mizuRoute-Lakes. The capabilities of mizuRoute-Lake in simulating the water balance of lakes and reservoirs are demonstrated. The main advantage of mizuRoute-Lake is flexibility in testing alternative lake water balance models within a given river and lake network topology. Users can choose between various types of parametric models that are already implemented in mizuRoute-Lake or data-driven models that provide time-series of the target volume and abstraction from a lake or reservoir from an external source such as historic observation or water management models. The parametric models for lake and reservoir water balance implemented in mizuRoute-Lake are Hanasaki, HYPE, and D{\"o}ll formulations. In general, the parametric models relate the outflow from lakes or reservoirs to the storage and various parameters including inflow, demand, volume of storage, etc. Additionally, this flexibility allows to easily evaluate and compare the effect of various water balance models for a lake or reservoir without needing to reconfigure the routing model. We show the flexibility of mizuRoute-Lake by presenting global, regional and local scale applications. The development of mizuRoute-Lake paves the way for better integration of water management models with existing and future observations such as the Surface Water and Ocean Topography (SWOT) mission, in the context of Earth system modeling.

The implementation of elevation bands is a common strategy to account for vertical heterogeneity in hydrology and land surface models; however, there is no consensus guidelines for their delineation. We characterize hydrological implications of this choice by configuring the Variable Infiltration Capacity (VIC) model in nine mountainous basins of the Andes Cordillera, central Chile, using six different setups: no elevation bands (benchmark model), and elevation bands with vertical discretizations of 1000, 750, 500, 200 and 100 m. The analyses are conducted in a wet period (April/1982-March/1987), dry period (April/2010-March/2015) and a climatological period April/1982-March/2015). The results show that adding elevation bands yield little variations in simulated monthly or daily streamflow; however, there are important effects on the partitioning of precipitation between snowfall and rainfall, snowmelt, sublimation, and the spatial variability in September 1 SWE, suggesting a model-structure equifinality. Incorporating elevation bands generally yields less basin-averaged snowmelt, and more (less) catchment-scale sublimation across water-limited (energy-limited) basins. Further, the implications of elevation bands vary with the analysis period: fluxes are more affected during the wet period, while variations in September 1 SWE are more noticeable during the dry period. In general, the effects of adding elevation bands are reduced with increasing vertical discretization, and can differ among catchments. Finally, the grid cells that yield the largest sensitivities to vertical discretization have relatively lower mean altitude, elevation ranges >1000 m, steep slopes (>15°) and annual precipitation amounts <1000 mm, with large intra-annual variations in the water/energy budget.

Regional climate change impacts show wide range of variations under different levels of global warming. Watersheds in the northeastern region of United States (NEUS) are projected to undergo most severe impacts from climate change in the forms of extreme precipitation events, floods and drought, sea level rise etc. As such, there is high possibility that hydrologic regimes in the NEUS may get altered in the future which can be absolutely devastating for managing water resources and ecological balance across different watersheds. In this study, therefore, we present a comprehensive impact analysis using different hydrologic indicators across selected watersheds in the NEUS under different thresholds of global temperature increases (1.50C, 2.00C and 3.00C). Precipitation and temperature projections from fourteen downscaled GCMs under RCP8.5 greenhouse gas concentration pathway are used as inputs into a distributed hydrological model to obtain future streamflow conditions. Overall, the results indicate that majority of the selected watersheds will enter into a wetter regime particularly during the months of winter while flow conditions during late summer and fall indicate a dry future under all three thresholds of temperature increases. The estimation of time of emergence of new hydrological regimes show large uncertainties under 1.50C and 2.00C global temperature increases, however, most of the GCM projections show strong consensus that new hydrological regimes may appear in the NEUS watersheds under 3.00C temperature increase.