How does it work? what does it output? and how is it used?
To understand how a water system performs today and to evaluate the impacts of future changes, planners build water resource system models.
Water resources systems can be small, like a city and its water supply sources, or large, like a country with many different rivers, water infrastructure assets and water users. Whether you're trying to evaluate the reliability of current sources, or evaluating new interventions under plausible future conditions, such a computer model helps track water throughout the system (spatially) and over time.
Given data on hydrological flows and climate, water demands and use, and water management rules and allocation, a water system model outputs water flows and volumes at each modeled location and time-step. When these results are aggregated, they provide an accurate picture of how different water interventions (changes to water policies or infrastructure) might perform.