General Assessment of the Operational Utility of National Water Model Reservoir Inflows for the Bureau of Reclamation Facilities

Abstract

This work investigates the utility of the National Oceanic and Atmospheric Administration’s National Water Model (NWM) for water management operations by assessing the total inflow into a select number of reservoirs across the Central and Western U.S. Total inflow is generally an unmeasured quantity, though critically important for anticipating both floods and shortages in supply over a short-term (hourly) to sub-seasonal (monthly) time horizon. The NWM offers such information at over 5000 reservoirs across the U.S., however, its skill at representing inflow processes is largely unknown. The goal of this work is to understand the drivers for both well performing and poor performing NWM inflows such that managers can get a sense of the capability of NWM to capture natural hydrologic processes and in some cases, the effects of upstream management. We analyzed the inflows for a subset of Bureau of Reclamation (BoR) reservoirs within the NWM over the long-term simulations (retrospectively, seven years) and for short, medium and long-range operational forecast cycles over a one-year period. We utilize ancillary reservoir characteristics (e.g., physical and operational) to explain variation in inflow performance across the selected reservoirs. In general, we find that NWM inflows in snow-driven basins outperform those in rain-driven, and that assimilated basin area, upstream management, and calibrated basin area all influence the NWM’s ability to reproduce daily reservoir inflows. The final outcome of this work proposes a framework for how the NWM reservoir inflows can be useful for reservoir management, linking reservoir purposes with the forecast cycles and retrospective simulations.

Quantifying patterns of streamflow peaks over the southeastern United States using a long‐term retrospective data set

“…Generally, the limitations of model‐based approaches in the calculation of flow values, as with the case of the NWM, come from limited infiltration quantification abilities, especially noted in semiarid regions (Lahmers, et al, 2021), lack of subsurface tile drainage representation (Valayamkunnath et al, 2022), channel routing schemes (Frame et al, 2021), or general simplified hydrologic process representations, and forcing errors (Viterbo, Mahoney, et al, 2020; Viterbo, Read, et al, 2020). Additionally, it must be noted that in the current version of NWM data (v2.1) only about 5000 reservoirs across the United States are represented in the model in terms of simplified input–output rules, and the model efficiency in representing real conditions is largely unknown (Viterbo, Mahoney, et al, 2020; Viterbo, Read, et al, 2020). The impact of reservoir operations on high and low flow peaks is critical; however, with the currently available data, it cannot be assessed in a consistent, distributed manner either by the use of the NWM v2.1 data set or by observed USGS data.…”

NOAA's National Water Model: Advancing operational hydrology through continental‐scale modeling

“…To date a number of published works have documented various performance aspects of the NWM. These works have analyzed several aspects of the skill of reservoir inflow forecast performance (Viterbo, Read, et al., 2020) and snow model performance (Garousi‐Nejad & Tarboton, 2022). Viterbo, Mahoney, et al.…”

Comprehensive analysis of the NOAA National Water Model: A call for heterogeneous formulations and diagnostic model selection

“…Some applications have also focused on using the the historic data to study issues such as seasonal low flow in the Colorado River basin (Hansen et al, 2019), the one-way surface-groundwater flux in the Northern High Plains Aquifer during extreme flow events (Jachens et al, 2020), operational flood map generation (Johnson et al, 2019); cross section representation (Brackins et al, 2021); and reservoir inflow performance (Viterbo et al, 2020). In the latter, the authors specifically found that NWM inflows in snow-driven basins outperformed those in raindriven and that basin area, upstream management, and calibrated basin area influenced the ability to reproduce daily reservoir inflows.…”