Paired riparian water table monitoring to quantify hydraulic loading to a saturated buffer

Abstract

The use of saturated buffers for reducing NO3-N loads from tile-drained croplands is increasing in the US Midwest and there is a need to develop options for estimating reductions at riparian sites. In this study, we present a paired water table monitoring approach to estimate hydraulic and NO3-N loading into a saturated buffer in eastern Iowa. One well was located within the saturated buffer (treatment) and a second well was installed in the same section of the riparian buffer but without the saturated buffer (control). Over a season of monitoring, water table depths were remarkably consistent between the two wells but the water table beneath the saturated buffer was consistently 0.22m higher than the non-saturated buffer control. The increase in water table height increased the amount of water discharged from a 162m long buffer by 468.2 m3/year and, assuming concentration reduction of 15mg/l, resulted in a N reduction of approximately 7kg. Although more work is needed to document this paired monitoring approach elsewhere, the method may hold promise for inexpensively quantifying the performance of conservation practices at landowner-led sites.