Climate change and subsurface drainage design: results from a small field-scale catchment in south-western Norway

Measurements on groundwater level and subsurface drain discharge have been carried in a small field-scale catchment from November 2012 to February 2013 in south-western Norway. The main objective of the measurements has been to study the interaction between the subsurface drainage discharge and groundwater level. Different methods were used to analyse the measurements. One method was to study the variation in groundwater level and drain discharge. The measurements showed there were large day to day variations. However, in addition, there were large diurnal variations in both the groundwater level and drain discharge. Also the recession of groundwater level was studied using a two-exponential decay function. During several months the precipitation largely exceeded the long-term precipitation. The measurements showed that drainage system had the capacity to react fast to precipitation-induced rise in groundwater level, resulting in a fast drawdown. The measurements at the small scale field catchment showed that the drainage system is designed and capable to react to high precipitation amounts like those predicted by climate change scenario studies.