Development of a Daily Livestock Water Footprint Assessment using a Dynamic, Mechanistic Approach: Model Conceptualization and Preliminary Evaluation

The water footprint assessment method has helped to bring livestock water use to the forefront of research to address water challenges under the ecological footprint perspective. The current assessment methods of water use make a meaningful assessment of livestock water use difficult as they are mainly static, thus poorly adaptable to understand future scenarios of water use and requirements. They lack the integration of fundamental ruminant nutrition and growth equations within a dynamic context that accounts for short and long-term behavior and time delays associated with economically important beef producing areas. This study utilized the System Dynamics methodology to conceptualize a water footprint for ruminants within a dynamic and mechanistic modeling framework. The problem of beef cattle livestock water footprint assessment was articulated, and a dynamic hypothesis was formed to represent the Texas livestock water use system as the initial step in developing the Texas Beef Water Footprint model (TXWFB). The fulfillment of the dynamic hypothesis required the development of three causal loop diagrams (CLD): cattle population, growth and nutrition, and the livestock water footprint. The CLD provided a framework that captured the daily water footprint of beef (WFB) of the cow-calf, stocker, and feedlot phases and the entire beef supply chain. Preliminary simulations captured the oscillatory behavior of the Texas cattle population and overshoot and collapse behavior, under conditions when regional livestock water resources became scarce. Sensitivity analysis from the hypothesized CLD structures indicated that forage quality was less of an impact on the daily WFB of each cattle phase compared to the use of high concentrate feeds. This study provided a framework concept for the development of a dynamic water footprint model for Texans beef cattle production and water sustainability.