Port Underwood receives significant sedimentation loads from the Awatere and Wairau Rivers. In addition the rivers will contain the run off from farms. This run off can be a significant factor in cultural eutrophication. This is a form of water pollution and also occurs when excessive fertilizers run into lakes and rivers. This encourages the growth of algae (algal bloom) and other aquatic plants. The excess nitrogen encourages algal growth. This could be or could become a problem in Port Underwood where there are relatively low flows. 

A solution to excess nitrogen is the use of eel farms in ponds. The following link suggests a solution, although this is not recommended nor promoted by the Association. The link is provided for information purposes only:

http://raglaneels.com/

This has the dual benefit of removing nitrogen and also providing a valuable fish product.