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Watershed Health is a term used to describe how well ecological systems are functioning. The biggest challenge in defining the health of any given watershed is to decide what "well-functioning" means for each location.
A physician will decide if a human patient appears to be "healthy" based on measurements like:
while also considering the patients age and what is known about their health history.
An ecologist will decide if a watershed appears to be "healthy" based on measurements like:
while also considering the climate, geology, location and land use history of the watershed. |
One major difference is that there are not target values for ecologists to use to guide their "diagnosis". Is this watershed running a fever or not? Does this watershed have high blood pressure or not?
In most cases, instead of having a threshold value (98.6 body temperature), watershed health is measured by comparing the current condition with an estimate of how natural systems in that location would function if it was in optimal health. Of course, many places are not currently in optimal health and there may be no existing reference condition to explore and understand for comparison.
In order to move forward with sharing important information about the health of Minnesota's watersheds, the Watershed Assessment Tool uses health rankings to illustrate the range of results for a variety of measurements for watersheds across Minnesota. Eighteen Health Index values are used to compare results across Minnesota's 81 Major Watersheds. Each index is scored on a scale of 0 to 100.
Some of the index measurements look at the current condition of the landscape. In some cases, the condition that would score a "0" or "100" is known and may exist somewhere in Minnesota. Sometimes the condition that would score a "0" or "100" is unknown and other scientific information must be used to decide how to rank the index results.
Some of the index measurements look at the context in which the other information needs to be evaluated. Like using a patient's age and genetic pre-disposition to disease to inform human health decisions, a context index shows information about background risk factors such as erodible soils, steep slopes and climate conditions. For these index values, the "0" may indicate the most vulnerable watershed found in Minnesota. The context score may not be something that can be changed, but rather should inform choices about actions that are taken to minimize risk.