24-Month Study Model (24MS)

Overview

The 24-Month Study Model (24MS) is one of three river system models developed and maintained by Reclamation to support operational decision-making and planning for the Colorado River Basin. All three models are implemented in the RiverWare modeling platform and share some key features, such as a monthly time-step, the same methods to estimate reservoir evaporation and bank storage, and the same current operating rules.

24MS is used for short-term (1-2 years) projections for operational decision-making, and is typically run in a deterministic mode, meaning that a single inflow scenario is used to generate a single output trace for analysis.

The results of the monthly runs of 24MS are formatted by Reclamation as a standardized set of data tables totaling 17 pages, known as 24-Month Study Reports. However, the Upper Colorado and Lower Colorado regional offices package and distribute this set of data tables differently; Upper Colorado adds a 9-page narrative summary for the Upper Colorado reservoirs, while Lower Colorado adds a single cover page with very a brief summary.

Figure 1. The Mid-term Probabilistic Operations Model (MTOM) in object view superimposed on a basin map, showing how the features of the Colorado River Basin are represented in the model. (Source: Reclamation)

Reclamation maintains primary three system models for the basin, currently implemented in the RiverWare modeling framework:

• 24-Month Study Model (24MS) -
• Mid-term Probabilistic Operations Model (MTOM) - mid-term (1-5 years) projections for risk-based operational planning
• Colorado River Simulation System (CRSS) - long-term (5-50 years) projections for planning studies and policy analysis

Relevance

The 24MS output determines the Annual Operating Plan tier determinations

Methods

RiverWare is an object-oriented modeling platform in which the objects may be inflow points, river reaches, diversions, reservoirs, canals, pipelines, and other water-resource features. Rule-based simulation with adjustable logic statements (e.g., if X then Y) are applied on a regular time-step (monthly for the three Reclamation models) to track water through the network of objects according to the rules.

Data and Tools

Data and tools for the primary Reclamation models are listed on their respective pages:

• 24-Month Study Model (24MS)
• Mid-term Probabilistic Operations Model (MTOM)
• Colorado River Simulation System (CRSS)

Additional Resources

State of the Science Report

Chapter 3 of the State of the Science report, Primary Planning Tools, describes the three primary Reclamation system models in detail.

New and Notable Research (2020-present)

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Summary