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Unformatted text preview: eady-state in which the water stock remains constant. Steady-state
systems are stable because they don’t change with time. We can model dynamic systems such as our
hypothetical lake by using stocks and flows, a topic we will explore in detail in Chapter Two. Modeling allows
us to evaluate future scenarios in which changes in the environment or in human resource use affect the supply
of renewable resources such as water over time. For example, if the inflow rate decreases during a drought, we
can model the rate of water depletion and estimate when the lake will go dry. 9 1/20/2011 The Sustainability Revolution John C. Ayers Figure 5. Illustration of the concept of steady state. Arrow size is proportional to the flow rate
(flux). In a steady state the amount of water in the reservoir does not change because inflow equals
outflow. For critical renewable resources such as water, it is wise to establish a safety margin by maintaining a
demand (rate of withdrawal) that is less than the average rate of replenishment. For example, during a drought
the rate of replenishme...
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This note was uploaded on 01/08/2014 for the course SUST 510 taught by Professor Marker during the Fall '14 term at Black Hills State University.
- Fall '14