Erosion and Weathering Processes in the Delaware River Basin

Total suspended sediments and the total dissolved solids (TDS) from three river gaging stations, near Delaware Water Gap, Riegelsville and Trenton on the Delaware River measured by the USGS were used to estimate the physical erosion, chemical weathering and total denudation rates of the Delaware River Basin. The denudation rates are 28 and 128 tons/km 2 /yr for the upper stream and downstream stretches. Overall, the chemical weathering is more prominent in the basin than the physical weathering due to the low gradient of the region and sufficient moisture levels in the regional soil. The total suspended sediments are high during March and April when snow melting and ground thawing occur, and low during the summer when the river discharge is low. The response of TDS to the river discharge is more complicated. Overall, higher temperatures increases the chemical weathering, and low discharge increases the ion concentration in the water. The saturation indices calculated using the WATEQ4F program indicate that calcite and dolomite are more saturated in the summer, while silica and halite show opposite patterns. While the saturation index of silica may be explained by its thermodynamic property, the saturation index of the halite that deviates from the normal pattern is thought to be related with the application of winter deicing salt in the region. Soil cores were also collected from four sites in the basin. Data from a 15-foot soil core indicates that weight percentage of quartz decreases with depth, while the weight percentage of feldspar increases. Various mineral types and abundance were also recognized from other shallow soil cores. These diverse mineral patterns reflect the diverse ion species in the river basin. INTRODUCTION Because of the effect of weathering on water quality and landscape in a basin, there are always interests in better understanding the weathering processes (Blum et al., a : Corresponding author’s e-mail: [email protected] Proceedings of GANJ XXV Environmental and Engineering Geology of Northeastern New Jersey, October, 2008. p.27-38.