High-resolution national-scale water modeling is enhanced by multiscale
differentiable physics-informed machine learning
Abstract
The National Water Model (NWM) is a key tool for flood forecasting and
planning and water management. Key challenges facing NWM include
calibration and parameter regionalization when confronted with big data.
We present two novel versions of high-resolution (~37
km2) differentiable models (a type of physics-informed machine
learning): one with implicit, unit-hydrograph-style routing and another
with explicit Muskingum-Cunge routing in the river network. The former
predicts streamflow at basin outlets whereas the latter presents a
discretized product that seamlessly covers rivers in the conterminous
United States (CONUS). Both versions used neural networks to provide
multiscale parameterization and process-based equations to provide
structural backbone, trained them together (“end-to-end”) on 2,807
basins across CONUS, and evaluated them on 4,997 basins. Both
versions show the great potential to elevate future NWMs for extensively
calibrated as well as ungauged sites: the median daily Nash-Sutcliffe
efficiency (NSE) of all 4,997 basins is improved to around 0.68 from
0.49 of NWM3.0. As they resolve heterogeneity, both greatly improved
simulations in the western CONUS and also in the Prairie Pothole Region,
a long-standing modeling challenge. The Muskingum-Cunge version further
improved performance for basins >10000 km2. Overall, our
results show how neural-network-based parameterizations can improve NWM
performance for providing operational flood predictions while
maintaining interpretability and multivariate outputs. We provide a
CONUS-scale hydrologic dataset for further evaluation and use. The
modeling system supports the Basic Model Interface (BMI), which allows
seamless integration with the next-generation NWM.