The Identification of Sites and Farming Systems Prone to Pollution by Surface Runoff.

Abstract

There is mounting evidence that overland flow from land contributes to pollution of surface water. No convenient method exists to identify fields that generate overland flow. Therefore the WT model has been developed to predict overland flow from any small parcel of land. Water table tubes and flow meters were installed in three sites in Wexford and Carlow. The water table data, along with rainfall and evaporation data, were entered into the WT model to calculate overland flow and other parameters over a 7-month period. Additional measurements of water table level were taken using maximum level indicators with a view to reducing field costs. All three sites had layers of sand in the sub-soil. It is likely that the sand allowed water to flow under the soil and contributed to overland flow. Values from the WT model matched the field measurements of water table closely and predicted overland flow with reasonable accuracy. One pipe in each field was identified which could indicate when the field was sufficiently dry for spreading slurry. The maximum level indicators recorded water table accurately. However, the lack of synchronisation of this data, with weather data, reduced slightly the precision of the model. The WT model can identify fields prone to overland flow and show when a field is sufficiently dry to accept slurry. Proposed economies promise to reduce the cost of investigation.