Blelham Tubes: In the Lake District there was work on physiology of suspended algae and recognition of which chemical substances limited growth. This resulted in development of experimental techniques, for example fertilizers. Scientists recognised that there were different levels of algae in summer and winter.
Scientists took their observations into a field experiment at Blelham. The aim was to make two water bodies in the lake. A tube (of possibly rubber) was pinned at the bottom with an inflatable collar at the top, adding nitrates and phosphates. The aim was to compare algae situation in tubes and outside, particularly effects of stratification. Out of this work came the idea that if you could avoid stratification you could limit algae growth. Engineers were able to build a reservoir where water at the bottom would keep moving; the supply of water can be ensured. Work in London started with this concept.