What our ammonia, nitrate and phosphate tests tell us about pollution Rivers need nutrients, but only in the right amounts. Nitrogen, phosphorus and ammonia occur naturally in soils, plants, animals, decaying leaves and animal waste. They are also found in fertilisers, sewage, treated effluent, road and farm runoff. Problems start when too much nutrient pollution reaches the river, especially during warm, low-flow conditions but also during prolonged storm overflows. Excess n

April was an exceptionally dry month across the River Mole catchment. With only around 5 mm of rain recorded before testing, river levels fell and pollution concentration strengthened. This month’s citizen science results show what often happens as the catchment moves from winter into spring: nutrient concentrations begin to rise, some streams remain in good condition, while others, including those shown below, showed a significant increase in pollution pressure. See foot of

March brought a marked spring shift in River Mole catchment water quality. Across our 33 monitoring sites, phosphate, nitrate and conductivity all rose noticeably compared with February as less rainfall fell, river flows dropped and dilution decreased. This month we review those changing seasonal conditions, examine the main pollution hotspots emerging in the River Mole and tributaries, and compare the latest storm overflow data with recent years to assess whether progress is

River Mole River Watch citizen science reveals how storm overflows pushed pollution higher during the season rivers should have lowest pollution concentration. This winter our dedicated citizen scientists have been out testing in rain and flood conditions, and their data are now revealing a clearer and more detailed understanding of how the River Mole behaves during winter high flows and prolonged periods of sewage overflow activity. Within this growing dataset, some concerni