Water Resource Associates
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Catchment Sensitive Farming Measures to reduce water pollution- an INCA modelling Study
The impacts of new catchment sensitive farming techniques have been investigated using the INCA model for N and P and applied to the River Testclimate change on water quality has been assessed using the INCA suite of Models to simulate flow, phosphorus, nitrogen, ammonia, sediments, macrophytes and epiphytes in 6 UK rivers for all the UKCIP scenarios.
Background
INCA has been applied to the River Test Catchment to simulate flow, nitrate, ammonia, total and soluble phosphorus, sediments and ecology (macrophytes and epiphytes). An important feature of the Test catchment is the relatively low slopes and the underlying geology of chalk which gives the catchment a relatively high base flow index of 0.94. This means that the groundwater is a very important component of the flow regime and will dominate the hydrology of the catchment. Land use is dominated by arable agriculture and grassland for animal production. A range of catchment sensitive farming techniques have been investigated using the model. The effect of the scenarios on phosphorus and sediment concentrations along the River Test are fairly minimal, as shown in Figure 1 below. The macrophytes and epiphytes have been simulated using INCA-P, as shown in Figure 2. The results indicate that there is a regular cycle of macrophyte growth in the summer with epiphytes also growing and these are having some impact, reducing macrophyte biomass in late summer months. What is very interesting is that in wet summers, the epiphytes do not establish a sufficiently high biomass to control macrophytes growth. This is illustrated in the years 2001 and 2002 (see day 1715) when low epiphyte biomass allows high macrophyte growth. However, the following year in 2003 there is a very dry summer and epiphytes grow to fairly high biomass levels and hence macrophyte growth is restricted. This suggests that flow is still a fairly crucial factor in chalk streams such as the Test and the threat may come from reduced summer flows under future climate change scenarios.
Figure 1: Simulated SRP along the River Test for the current situation and assuming a reduced P loading scenario.
Figure 2 Macrophyte and Epiphyte simulations for the River Test
Scope of work by Water Resource Associates Ltd
Applications of the INCA Model to assess Catchment Sensitive Farming strategies.
Results
Report to EA :- Catchment Sensitive Farming: Impacts on River Systems.
Contact Paul Whitehead for further information