Water Quality Impacts of Natural Filter Strips in Karst Areas

Naturally occurring riparian filter strips are widely recommended as a technique for removing chemicals fromflow prior to entering a stream. Data on their effectiveness is sparse as is information on the partitioning of chemicalstrapped by various mechanisms in these strips. Studies were conducted on the effectiveness of natural riparian grassbuffer strips in removing sediment, atrazine, nitrogen and phosphorus from surface runoff. The strips were located in akarst watershed. No-till and conventional-tillage erosion plots served as the sediment and chemical source area. Runofffrom the plots was directed onto 4.57, 9.14, and 13.72 m filter strips where the inflow and outflow concentrations and flowrates were measured. Trapping percentages for sediment and chemicals typically ranged above 90%. An evaluation wasmade of the distribution of trapped chemicals among infiltrated mass and mass stored in the surface layer. The analysisshowed that most of the chemicals were trapped by infiltration into the soil matrix and that trapping efficiency increasedwith filter stip length and with fraction of water infiltrated.