Healthy Streams, Healthy Lakes

A healthy lake begins with healthy streams in the watershed, from the headwaters, to small and medium streams, to the rivermouth.  As water flows over the land, it comes into contact with sediment and dissolved nutrients and carry them down-stream into larger tributaries, and finally into the lake. In this way, a lot of nutrients can accumulate from agricultural and urban land, eventually leading to development of toxic algal blooms. In severe episodes, the shoreline is smeared with green slimy algae that is inedible and which does not enter the food chain. When the massive algal mats die and decompose, sufficient oxygen in the lake is consumed all at once that it can lead to fish kills and avian die-offs.

A section of Sulphur Spring Creek, a healthy stream in Hamilton. It has low nutrients, clear water, lots of oxygen in the water, and low epiphyton growth.

To find solutions to these pernicious problems, we need to identify all sources of nutrients from tributaries draining into the lake. For large rivers such as the Grand, the largest Canadian tributary of Lake Erie, there are thousands of small and medium-size tributaries. Because of limited time and resources, many agencies carry out monitoring programs that favour larger streams. This does not, however, identify the activities on specific land parcels that are releasing nutrients. These smaller streams need to be identified so that management plans can be put into place to prevent further loss of nutrients.

An episode of algal bloom in Lake Erie.