Modelling a changing water cycle

Large-scale hydrological models usually treat vegetation as fixed, prescribed from a seasonal climatology that repeats each year. Vegetation, however, changes after wildfire and drought mortality, under forest treatments such as thinning and prescribed burning, and with shifts in cropping and irrigation, and it keeps changing as landscapes recover. Because vegetation governs how much water returns to the atmosphere and how much remains for soils and rivers, a model that holds it fixed misses both the loss and the recovery.

My current work addresses this gap through the California Water Information System (CWIS). CWIS is a real-time modelling framework built on the VIC land-surface model and run at 1 km resolution across California. It assimilates satellite observations of vegetation as they become available, so the simulated water balance follows the landscape through disturbance, management and recovery. The system provides current estimates of soil moisture, evapotranspiration, snow water equivalent and runoff across the state, supporting drought monitoring and post-fire assessment.

CWIS builds on my earlier work in Indian river basins, where I coupled the VIC land-surface model with the RAPID river-routing model and the LISFLOOD-FP hydrodynamic model, so that streamflow and floodplain inundation could be simulated within a single system. I later added reservoir operations to the routing model, bringing human regulation of rivers into the simulation. Together, these efforts work toward an integrated representation of the terrestrial water cycle, shaped jointly by climate, land cover and human management.