Soil Infiltration and Percolation
There is no (obvious) current monitoring for Soil Infiltration or Percolation occurring in the catchment. Infiltration is important as it can help determine when overland flow may occur (contributing to flood risk) and the rate at which pollution (especially nitrates from farming in the area) may enter the ground. Percolation determines groundwater recharge so can be important from a pollution, water resources and ecology of river (base-flow) perspective.
Infiltration will be measured at the eight joint stations; along with soil moisture, vegetation interception and rainfall (as infiltration is dependant on gw level, these will be located near boreholes for correlation). These eight stations will ideally located across a range of land type and topography to examine varying infiltration rates with land use etc.
As infiltration also varies with evapotranspiration, vegetation interception, soil moisture and rainfall it will also use this data from the network in order to make predictions about soil interception. There are no automated methods to measure infiltration however infiltration is unlikely to change more frequently than seasonally - therefore infiltration will be manually measured using infiltration rings four times a year. The hope is local farmers / landowners could help with this and complete measurements themselves. In order to check this data, periodic sampling using a mobile infiltrometer (http://manuals.decagon.com/Manuals/10564_Mini%20Disk%20Infiltrometer_Web.pdf) will take place (alongise Sarah’s soil moisture core sampling) twice a year. Initial soil sampling will be required to determine soil geology and properties at each of the eight sites.
Percolation will be calculated using computer model (Modified Thornthwaite-Mather Soil-Water-Balance Code) as actual sampling method (percolation holes) is too destructive to landscape. This again will require input data from other parts of the network.