Sediment characteristics and accumulation rates in constructed ponds

Abstract

Pond densities have increased rapidly during recent decades within the Brandywine Watershed, southeastern Pennsylvania. Sediments trapped by these ponds are prevented from impairing stream networks, but also reduce pond longevity and increase management costs. This study investigates spatial variation of sediment characteristics within ponds as a function of pond morphology and related variation in sediment accumulation rates among ponds to differences in pond size and watershed attributes. Increasing distance from shore was accompanied by decreasing sediment dry bulk density, decreasing percentage of sand, and increasing organic content; pond area-specific sediment accumulation rates and rates of area-specific organic matter sequestration declined with increasing pond size and were significantly higher among ponds with stream inflows. Sediment delivery rates per unit catchment area declined with increasing watershed size. Because excessive sediment loading is perhaps the most important cause of stream impairment in many regions, the interception of sediments by ponds within stream networks may be of critical importance to downstream water quality. Results of this study also provide evidence that small, constructed ponds can be important tools for estimating sediment yield and stream-borne sediment transport within small catchments.