I am wondering if anyone can tell me if it is possible to sharpen or darken the brown light and dark contour lines in the attached map? They seem to be somewhat blurry and faint.
If you look at the individual Channels, you can see the contour lines have the most contrast in the Green. You can make a duplicate Channel of the Green, and use your choice of contrast enhancement tools on it, and combine it back into the image.
Here, I used Curves to make the solid blacks turn white, and make the lines darker:
Then I used Apply Image set to Color Burn, 75% opacity: