Development of reservoir geometry and discharge parameters for National Water Model waterbodies

Abstract:

Realistic representation of geometry and discharge parameters of lakes and reservoirs (“waterbodies”) is the foundation for modeling hydrologic systems with significant waterbody storage. Continental-scale hydrologic models like the NOAA National Water Model (NWM) require accurate and realistic estimates of physical and discharge (e.g. weir and orifice) parameters for thousands of waterbodies, in both natural and highly managed systems. Some data do exist, for example, the National Inventory of Dams provides some basic discharge and physical parameters for many managed reservoirs, and U.S. agencies are making advancements in hosting near-real time reservoir release data, such as the U.S. Army Corps of Engineer’s “CWMS” and the Bureau of Reclamation’s “RWIS”. However, these do not provide bathymetry or geometry parameters for the reservoirs and for any natural lakes. Given the lack of systematic and widespread data services to provide bathymetric and discharge parameters for lakes on a continental scale, this work describes the development of such a dataset for the NWM. Specifically, we test several shapes and functional forms to describe the height-area-volume (h-A-V) relationships across 5,781 lakes in the NWM version 2.1. We also develop functions for estimating the orifice and weir discharge parameters where observed values are unavailable. We validate the parameters with observational data and test the impact on streamflow and waterbody storage through retrospective simulations using the NWM.