Distinguish between a fresh-water lake and a salt-water lake with respect to a contour plot.

• A. A fresh-water lake has streams flowing both into and out of it; a salt-water lake has streams flowing only into it (no outlet).
• B. A fresh-water lake has streams flowing only into it; a salt-water lake has streams flowing both into and out of it.
• C. A fresh-water lake has no streams; a salt-water lake has streams flowing both into and out of it.
• D. A fresh-water lake has streams flowing into it; a salt-water lake has streams flowing out of it.

Answer: (A)

Contours show how water drains from higher to lower ground, so you can read drainage patterns directly from a map. A lake that has both an inlet and an outlet sits in a connected drainage system: you can trace streams feeding into the lake and another stream leaving it to continue downstream. A freshwater lake is typically part of that kind of system, so the contour map would show streams flowing into the lake and also a path carrying water away. A salt-water lake, especially one in an endorheic basin, lacks a surface outlet; streams may feed into it, but there is no channel leaving toward lower ground that continues downstream, so there’s no outward drainage from the lake on the map. Thus, the description that matches the contour-pattern logic is: freshwater lakes have streams flowing into and out of the lake, while salt-water lakes have streams flowing into it but not out.