Talk notes:monitoring rivers

We recently had a talk by Robin Leech on monitoring rivers (particularly, the Wylye). Robin is an ecologist employed by the Wylye farmer cluster and he spoke about some of the work he does with his farmers, involving monitoring river pollution (chemical and sedimentary) and also re-naturalisation. A lot of what he spoke about theoretically applies to our river, the Nadder.

Many of us who are interested in river pollution (to stop it!) have all probably heard by now a lot on eutrophication, nitrates and phosphates, and there was some debate at the talk on the representativity of these indicators of the extent of the chemical pollution in rivers and also on the randomness of establishing a “safe” level of pollution.

But Robin also spoke about something a bit novel: colourimetric analysis to find out where the sediments in the river come from, to target sediment run-off at source. Colourimetric analysis involves taking samples of sediment from the river, putting them in an oven to burn the organic matter and dry the grains and then put the dry remaining sample in a machine that analyses the colour - this allows to compare it with a reference collection of sediment samples from the surrounding areas of a river. 

He also spoke about their new project to restore the natural floodplains in some of the Wylye and the renaturalisation of the river system, which is something that will hopefully occupy many conservation organisations in the future. The straightened courses of rivers, with high banks, not only is detrimental to wildlife (for example, water voles) but also, in heavy rain, sends high quantities of water downstream, producing flooding in towns, and also sediments due to the erosion of the banks. Restoring the natural course of rivers not only will promote wildlife and natural processes and reduce sedimentary pollution, but it will also have the added benefit of reducing flooding in sensitive areas (the flooding needs to happen whether we want it or not, but if the river is allowed to flood a floodplain, then it won’t flood a town further down!).

​Inés López-Dóriga