Chesapeake Bay Nontidal Network 1985-2016: Short- and long-term trends

Nitrogen, phosphorus, and suspended-sediment loads, and changes in loads, in rivers across the Chesapeake Bay watershed have been calculated using monitoring data from the Chesapeake Bay Nontidal Network (NTN) stations for the period 1985 through 2016. Nutrient and suspended-sediment loads and changes in loads were determined by applying a weighted regression approach called WRTDS (Weighted Regression on Time, Discharge, and Season). The load results represent the total mass of nitrogen, phosphorus, and suspended sediment that was exported from each of the NTN watersheds. To determine the trend in loads, the annual load results are flow normalized to integrate out the year-to-year variability in river discharge. The trend in load is derived from the flow-normalized load timeseries and represents the change in load resulting from changes in sources, delays associated with storage or transport of historical inputs, and (or) implemented management actions.

针对切萨皮克湾流域（Chesapeake Bay watershed）内的河流，本研究基于1985年至2016年切萨皮克湾非潮汐网络（Chesapeake Bay Nontidal Network, NTN）站点的监测数据，计算得到了氮、磷及悬浮泥沙负荷及其变化量。本研究采用一种名为WRTDS（时间、流量与季节加权回归，Weighted Regression on Time, Discharge, and Season）的加权回归方法，确定了营养盐与悬浮泥沙负荷及其变化量。该负荷计算结果代表了各NTN流域向外输出的总氮、总磷及悬浮泥沙总质量。为确定负荷的变化趋势，研究人员对年度负荷结果进行流量归一化处理，以消除河川流量的年际波动影响。负荷变化趋势由流量归一化后的负荷时间序列推导得出，其反映了由污染源变化、历史输入物质储存或运输相关的延迟效应，以及（或）已实施的管理措施所引发的负荷变化。