What are hydrographic maps and how can you use them?

Photo credit www.noaa.gov

Hydrographic maps are a valuable source of information both above and below water. Detail varies greatly but if a tackle store has a hydrographic chart or map of a lake you will be boating and fishing, pick one up and study it. 

Above water, these maps or nautical charts provide information such as the shoreline shape, and the location of boat ramps, coves, points, and any dam. A hydrographic map also will give scale. It is important to have a good idea just how far it is from Point A to Point B.  

But perhaps just as valuable is the information a hydrographic map can supply below water, in the form of contour lines. When learning how to read a lake map for fishing, make sure to pay attention to lines in the water that kind of trace the shore line. Widely spaced contour lines mean a gradual slope or similar depth. Closely spaced contour lines are locations of steeper slopes, ridges, or drop-offs.

Why is this important?

This information about the depth and how it changes can help you locate fish. Deeper sections will be a source of cooler water during the heat of summer and may remain weedless because of the lack of sunlight reaching the bottom. Large flat areas may be spawning areas in the spring. An area with a steep slope can be a source of upwelling or current movement which hungry fish know, often carries food. And you may be able to locate channels that can act as fish “highways” during some parts of the year as fish move to or from spawning areas.

Hydrographic maps will help you find underwater humps, rock piles, and other places where the bottom changes. These transition areas often attract fish. When you are renewing your fishing license, see if you can find any hydrographic maps of lakes or rivers in your area. It can help make the outing a success.


Andy Whitcomb

Andy Whitcomb

Andy Whitcomb is a columnist, outdoor humorist, and stressed-out Dad. He says there are “people who fish”… and there are “fishermen”.  One of the few things he knows is that he is a “fisherman”...  To the point it could be classified as borderline illness.  Sharing this obsession is rewarding, therapeutic. He likes to encourage people to “stop and smell the crappie."  Enjoys catching fish, but gets a greater thrill out of helping someone else hook up.
Born in Florida, but raised on the banks of Oklahoma farm ponds. Now relocated to western Pennsylvania. He has fished, worked, lived all around the US.  He has a B.S. in Zoology from Oklahoma State as well...
And he met his wife while electrofishing. He has been contributing weekly to www.takemefishing.org since 2011.