Having completed data collection prior to the application of practical measures, we now have a large data base of biology and chemistry.
This will build a story towards phase two of the project where we will be observing whether mitigating against farming using designs, such as those set by Stewardships Schemes, can be successful.
The top graph shows the total phosphorus (TP) concentrations found upstream and downstream of sewage treatment systems in Eye and Stonton brook. The TP concentration from the sewage systems is the highest found anywhere in both catchments as a result of the high nutrient loads produced by these urban areas. TP concentrations on the Stonton brook are almost half of those found on the Eye brook. The second graph shows a comparison between the stream discharges, it highlights the larger variation of water flow in the Eye compared to Stonton and with higher peaks of water movement.
This graph shows nitrate concentrations in the Eye and Stonton brooks. Nitrate levels do not vary greatly upstream or downstream of the sewage treatment works.
Fertiliser in the form of nitrate is more soluble than phosphorus. Phosphorus containing fertiliser is not applied on the land as frequently as nitrate and has a tendency to bind to soil particles, making it less likely to move in to aquatic systems unless sufficient rainfall has caused soil particles to move. As a result TP and suspended sediment appear to have a strong relationship as shown in the graph below.
Coupled with the inability of land to retain its structure as a result of agricultural disturbance, top soil and nutrients are lost from catchments through rainfall, run-off and erosion. The delivery of excessive levels of suspended sediment in to waterbodies can have significant deleterious impacts on the physical, chemical and biological properties of the waterbody. The graphs directly above show the loss, per arable hectare, of sediment and total phosphorus in each of Stonton brook and Eye brook catchments as a result of land run-off and erosion. With its higher stream discharges and increased potential for greater peak flows, the Eye brook is observed to have greater capacity for loads each year.
We have also determined the fish abundances across the streams and tributaries in all catchments. The following maps identify sub-catchments, as determined by a digital elevation model, and show the health of fish assemblage diversity in the sub-catchments of each brook before the installation of mitigation measures. Barkby brook catchment appears to have more diverse fish populations with a community of bullheads, minnows, sticklebacks and stone loach found at one site. Bullheads were encountered most regularly and appeared in 19 out of 31 sites at an average density of 46 fish/100m². Three spined sticklebacks were encountered in 12 out of 31 sites at an average density of 123 fish/100m². Salmonids were only found in the Eye brook, were caught in 5 out of 31 sites, and at an average density of 6 fish/100m².