ABSTRACT

Impoundments in the midcontinent region of the United States provide the beneficial services of lentic waters. These impoundments were constructed long after intensified agriculture was established, and most are eutrophic. Total phosphorus (TP) increases in regional streams and reservoirs, concurrent with the proportion of cropland in the watershed, serve as a surrogate for nutrient loading from agriculture. The potential impact of external loading of TP to these reservoirs is moderated by sedimentation of particulate P and plunging interflows during summer stratification. Hydrology has a strong influence on TP; cross-system analyses show TP more than doubles across the range of flushing rates found in Missouri reservoirs when other factors are held constant. This link between hydrology and TP suggests reservoir placement on the landscape and design criteria strongly influence trophic state. Temporal variation is such that summer mean TP typically ranges 2- or 3-fold in individual reservoirs, suggesting benefits of best management practices to reduce external loading may be masked by inherent variation. Eutrophication of a midcontinent reservoir from poultry litter has been documented. Expansion of industrialized animal production throughout the region suggests legacy P, and resulting eutrophication, will likely increase over time without regulation.

摘要

美国中大陆地区的蓄水池提供了静水的有益服务。这些蓄水池是在集约化农业建立很久之后建造的，而且大多数是富营养化的。区域河流和水库的总磷 (TP) 增加，与流域中农田的比例同步，可作为农业养分负荷的替代指标。TP 的外部负荷对这些水库的潜在影响通过颗粒 P 的沉积和夏季分层期间的暴跌互流来缓和。水文对TP的影响很大；跨系统分析表明，当其他因素保持不变时，在密苏里水库中发现的冲刷速率范围内，TP 增加了一倍以上。水文和热带雨林之间的这种联系表明水库在景观和设计标准上的位置对营养状态有很大影响。时间变化使得夏季平均 TP 在单个水库中通常为 2 或 3 倍，这表明减少外部负荷的最佳管理实践的好处可能被固有变化所掩盖。已经记录了来自家禽垃圾的大陆中部水库的富营养化。整个地区工业化动物生产的扩张表明，如果没有监管，遗留的 P 及其导致的富营养化可能会随着时间的推移而增加。建议的最佳管理实践减少外部负荷的好处可能会被固有的变化所掩盖。已经记录了来自家禽垃圾的大陆中部水库的富营养化。整个地区工业化动物生产的扩张表明，如果没有监管，遗留的 P 及其导致的富营养化可能会随着时间的推移而增加。建议的最佳管理实践减少外部负荷的好处可能会被固有的变化所掩盖。已经记录了来自家禽垃圾的大陆中部水库的富营养化。整个地区工业化动物生产的扩张表明，如果没有监管，遗留的 P 及其导致的富营养化可能会随着时间的推移而增加。