My fieldwork in Northumberland on Thursday was not particularly successful. After several days of dry weather, it started to rain on Wednesday night and, by Thursday morning, the rivers I wanted to sample were running very high. First rule of sampling: the ecologist is a benthic organism. Never planktonic. Second rule of sampling: discretion is the better part of valour. However, as I drove towards the raging torrent that was Wooler Water, salvation appeared in the guise of an Environment Agency van. The two guys whose van it was knew the Northumberland rivers well and assured me that, with no more rain forecast, the rivers would be low again by the next morning. Fortunately, I had decided to stay overnight in Rothbury, so I was able to reorganise my itinerary and return to Wooler Water and the nearby River Coquet in the morning.
This is a good example of the “streamcraft” I mentioned in my recent post (“Slow science and streamcraft”): I have a good idea of how my local rivers react to rainfall but, here in Northumberland, I needed to draw upon the experience of people who visited these rivers regularly. Once settled in my hotel, I was able to test their advice in real time, using the Environment Agency’s excellent system of hydrographs (see “The River Ehen in January”). The closest hydrograph whose results are available online was at Rothbury, a few hundred metres from my hotel and, assuming Wooler Water was behaving in a similar manner, my visit earlier in the day had coincided with the peak flow for this particular rainfall event. Over the next 12 hours, however, the flow gradually decreased and, by Friday morning, though the river was still higher than normal, it was possible to wade in and collect my samples. I should, in retrospect, have checked the hydrograph before I went out on Thursday, but it is useful to have some local knowledge in order to “calibrate” the readings in terms of the activities you want to perform.
A screenshot of the Environment Agency’s hydrograph at Rothbury between 30 April and 2 May (see http://apps.environment-agency.gov.uk/river-and-sea-levels/120694.aspx?stationId=8173). My first visit was at 14:00 on 1 May; my return visit at about 10:00 on 2 May.