The Water Innovation Network (EIP-Agri) is running a series of events on Water Friendly Farming (Book here). They include guidance on how to check whether a waterway is healthy.
Similar to the advice from Becky about soil health - one of the simplest ways to check water quality is to look at what is living in it.
The presence of bloodworms or sewage fungus are sure signs of pollution. Bloodworms will appear as red blotches on the bed of the river. Sewage fungus appears as a grey brown coating on the stones.
At the other end of the scale a really healthy river will have species like stonefly nymphs .
Book a place on one of the events to learn more about how to check waterways and what to do if you find pollution.