Refactor: Reuse efficiencies to avoid redundancy
Refactor: Reuse efficiencies to avoid redundancy

Previously the literal values were specified in two
separate places, carrying the risk of inconsistency
if one was updated without the other. By exporting
and importing the values to reuse them, we ensure
that the literals are specified only once, and now
can be updated in a single place, to have consistent
effect throughout the app.

WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed