Reservoir water quality data

Potable source-water reservoirs are the main water supplies in many
urbanizing regions, yet their long-term responses to cultural
eutrophication are poorly documented in comparison to natural lakes,
creating major management uncertainties. Here, long-term discrete data
(June 2006–June 2018) for classical eutrophication water quality
indicators, continuous depth-profile data for dissolved oxygen (DO), and
an enhanced hybrid statistical trend analysis model were used to evaluate
the eutrophication status of a potable source-water reservoir. Based on
classical indicators (nitrogen - N and phosphorus - P concentrations and
ratios; phytoplankton biomass as chlorophyll a, chla; and trophic state
indices), the reservoir was eutrophic to hypereutrophic and
stoichiometrically imbalanced. Anoxia/hypoxia occurred for 7-8 months
annually system-wide, even throughout the water column for days to weeks
in some years; and elevated total ammonia (up to ~900 µg tNH3 
L-1) in surface waters from late summer/fall through late winter/early
spring suggested substantial internal legacy nutrient loading. These
surprising DO and tNH3 phenomena may characterize many reservoirs in
urbanizing areas, and the associated cascade of negative impacts may
increasingly affect them under global warming. Total organic carbon (TOC),
seasonally influenced by phytoplankton biomass, commonly exceeded 6 mg L-1
which is problematic for potable water treatment, and significantly
trended up over time. Wet-year inflow dilution influenced an apparent
decreasing trend in nutrients within the hypereutrophic upper reservoir,
which receives most tributary inputs. Nevertheless, significant
reservoir-wide trends (increasing TP, phytoplankton chla, TOC) and mid-
and/or lower region trends (increasing TN, tNH3, decreasing TN:TP ratios)
suggest that water quality degradation from eutrophication has worsened
over time. These findings support broadly applicable recommendations to
strengthen protection of potable source-water reservoirs in urbanizing
watersheds: (i) Protective numeric water quality criteria are needed for
TOC as well as TN, TP, and chla; (ii) Continuous diel data capture more
realistic DO conditions than traditional sampling, and can provide
important insights for water treatment managers; and (iii) Assessment of
reservoir eutrophication status to track management progress over time
should emphasize classic indicators equally as statistical trends, which
are highly sensitive to short-term meteorological forcing.

城市化区域的主要供水来源多为饮用水源水库，但相较于天然湖泊，学界对其在人为富营养化（cultural eutrophication）作用下的长期响应机制记录匮乏，这给水库管理带来了诸多不确定性。本研究采用2006年6月至2018年6月的经典富营养化水质指标长期离散监测数据、溶解氧（dissolved oxygen, DO）连续剖面监测数据，结合改进的混合统计趋势分析模型，对某饮用水源水库的富营养化现状展开评估。基于经典指标（氮[N]、磷[P]浓度及其比值，以叶绿素a（chlorophyll a, chla）表征的浮游植物生物量，以及营养状态指数），该水库整体处于富营养至超富营养状态，且营养盐化学计量失衡。全库范围内每年有7至8个月处于缺氧或低氧状态，部分年份甚至整层水体持续数日至数周缺氧；夏末/秋季至冬末/初春期间表层水体总氨氮（total ammonia, tNH3）浓度最高可达约900 μg·L⁻¹，这表明水库存在大量的内源遗留营养盐负荷。这类溶解氧与总氨氮的异常现象，可能是城市化区域多数水库的共性特征；在全球变暖背景下，由此引发的一系列连锁负面效应或将愈发严重。受浮游植物生物量季节性影响的总有机碳（total organic carbon, TOC）浓度通常超过6 mg·L⁻¹，这会给饮用水处理带来极大挑战，且该指标随时间呈显著上升趋势。丰水年的径流稀释作用，使得接收多数支流来水的超富营养化上游库区的营养盐浓度呈现表观下降趋势。尽管如此，全库范围的显著变化趋势（总磷[TP]、浮游植物叶绿素a及总有机碳浓度上升）以及库区中、下游区域的变化趋势（总氮[total nitrogen, TN]、总氨氮浓度上升，TN:TP比值下降）均表明，富营养化导致的水质退化问题随时间愈发严峻。本研究结果可为城市化流域内饮用水源水库的保护工作提供普适性建议：① 需针对总有机碳、总氮、总磷及叶绿素a制定保护性量化水质标准；② 连续昼夜监测数据相比传统采样方式，能更真实地反映溶解氧状况，可为水处理管理人员提供重要决策依据；③ 若要通过水库富营养化状态评估追踪管理成效，需将经典指标与统计趋势分析同等重视——后者对短期气象扰动极为敏感。

搜集汇总

背景与挑战

背景概述

该数据集包含2006年至2018年期间美国饮用水源水库的长期水质监测数据，涵盖氮、磷、叶绿素a、溶解氧和总有机碳等关键富营养化指标。数据揭示了水库处于富营养到超富营养状态，存在季节性缺氧和总氨升高等问题，总有机碳呈显著上升趋势，为评估水库富营养化和管理提供了重要依据。