scholarly journals Assessing Impacts of Changes in External Nutrient Loadings on a Temperate Chinese Drinking Water Reservoir

2021 ◽  
Vol 9 ◽  
Author(s):  
Qingchuan Chou ◽  
Anders Nielsen ◽  
Tobias K. Andersen ◽  
Fenjuan Hu ◽  
Weiyu Chen ◽  
...  

The safety of drinking water is constantly being evaluated. In the last few decades, however, many drinking waters sources in the world, including in China, have undergone serious eutrophication and consequently water quality deterioration due to anthropogenic induced stressors such as elevated external nutrient inputs. In this study, we used the state-of-the-art complex, dynamic, mechanistic model GOTM-FABM-PCLake (a coupled one-dimensional hydrodynamic-lake ecosystem model) to quantitatively assess the impacts of external nutrient loading on the temperate Jihongtan reservoir in Shandong Province, China. Simulated values of all variables targeted in calibration (water temperature, dissolved oxygen, total nitrogen, total phosphorus, and chlorophyll a) agreed well with observations throughout the entire calibration and validation period and generally mimicked seasonal dynamics and inter-annual variations as found in the monitoring data. A series of scenarios, representing changed external nutrient loadings (both increasing and decreasing compared to the current nutrient load), were set up to quantify the effects on the reservoir water quality. Changes relative to the current external nutrient load had a significant effect on the simulated TN and TP concentrations in the reservoir. Our impact assessment indicate that TN will meet the Chinese water quality requirements of the water source (Class III) when the external nitrogen load is reduced by 70%, whereas TP will meet the requirements even if the external phosphorus load is increased by 100% relative to current loads. The model predicts progressively higher summer and autumn phytoplankton biomasses in the scenarios with increasing external phosphorus loading and potential toxic cyanobacteria will become more dominant at the expense of diatoms and other algae. Strict control of the external nutrient loading is therefore needed to maintain good drinking water quality in the reservoir.

2020 ◽  
Vol 25 (4) ◽  
pp. 565-579
Author(s):  
Azadeh Golshan ◽  
Craig Evans ◽  
Phillip Geary ◽  
Abigail Morrow ◽  
Zoe Rogers ◽  
...  

2020 ◽  
Vol 79 (17) ◽  
Author(s):  
Johanna M. Blake ◽  
Jeb E. Brown ◽  
Christina L. Ferguson ◽  
Rebecca J. Bixby ◽  
Naomi T. Delay

Author(s):  
Tiina Nõges ◽  
Orlane Anneville ◽  
Jean Guillard ◽  
Juta Haberman ◽  
Ain Järvalt ◽  
...  

<p>Through cascading effects within lake food webs, commercial and recreational fisheries may indirectly affect the abundances of organisms at lower trophic levels, such as phytoplankton, even if they are not directly consumed. So far, interactive effects of fisheries, changing trophic state and climate upon lake ecosystems have been largely overlooked. Here we analyse case studies from five European lake basins of differing trophic states (Lake Võrtsjärv, two basins of Windermere, Lake Geneva and Lake Maggiore) with long-term limnological and fisheries data. Decreasing phosphorus concentrations (re-oligotrophication) and increasing water temperatures have been reported in all five lake basins, while phytoplankton concentration has decreased only slightly or even increased in some cases. To examine possible ecosystem-scale effects of fisheries, we analysed correlations between fish and fisheries data, and other food web components and environmental factors. Re-oligotrophication over different ranges of the trophic scale induced different fish responsesIn the deeper lakes Geneva and Maggiore, we found a stronger link between phytoplankton and planktivorous fish and thus a more important cascading top-down effect than in other lakes. This connection makes careful ecosystem-based fisheries management extremely important for maintaining high water quality in such systems. We also demonstrated that increasing water temperature might favour piscivores at low phosphorus loading, but suppresses them at high phosphorus loading and might thus either enhance or diminish the cascading top-down control over phytoplankton with strong implications for water quality.</p>


1995 ◽  
Vol 32 (5-6) ◽  
pp. 235-243 ◽  
Author(s):  
C. W. Randall ◽  
T. J. Grizzard

The high dam on the Occoquan River of Northern Virginia, United States of America, was constructed in 1957, forming a drinking water reservoir with a capacity of 37.1 × 106m3 formed by drainage from a 1 460 km2 watershed, and providing a safe yield of 189 251 m3 per day. Deteriorating water quality in the late 1960s led to a special “policy” for the watershed, designed to preserve the reservoir as a drinking water supply. Key provisions of the policy mandated replacement of the watershed's 11 publicly owned wastewater treatment works with a single advanced wastewater treatment plant (AWT), and establishment of the Occoquan Watershed Monitoring Programme. Early results from the programme established non-point nutrient pollution as a major cause of water quality deterioration and resulted in the implementation of non-point pollution controls throughout the watershed during the late 1970s. The AWT plant went on-line in July 1978. Continuous monitoring since 1973 has demonstrated both the necessity and the effectiveness of point and non-point nutrient controls for the preservation of the reservoir's water quality. The AWT plant provides excellent removal of organics and phosphorus, plus complete nitrification. The nitrates are discharged to the receiving stream to enhance conditions in the reservoir. Control policies include land-use management for the preservation of this essential water supply for 750 000 people in the Washington, D.C. suburbs. Land-use management decisions are based on the results obtained with a watershed-reservoir linked computer model which predicts water quality changes resulting from land-use changes.


2010 ◽  
Vol 28 (4) ◽  
pp. 209-217 ◽  
Author(s):  
Sarah A. White ◽  
Milton D. Taylor ◽  
Stewart L. Chandler ◽  
Ted Whitwell ◽  
Stephen J. Klaine

Abstract Agricultural operations face increasing pressure to remediate runoff to reduce deterioration of surface water quality. Some nursery operations use free water surface constructed wetland systems (CWSs) to remediate nutrient-rich runoff. Our objectives were twofold, first to examine the impact of two hydraulic retention times (HRT, 3.5 and 5.5 day) on CWS performance, and second to determine if increased nutrient loading from internal CWS and nursery sources during the spring contributed to nutrient export in excess of regulatory limits. We quantified nutrient loading and removal efficiency in a free water surface CWS from late winter through late spring over three years and monitored various water quality parameters. Total nitrogen in runoff was reduced from 20.6 ± 2.8 mg·liter−1 (ppm) to 4.1 ± 1.3 mg·liter−1 (ppm) nitrogen after CWS treatment. Phosphorus dynamics in the CWS were more variable and unlike nitrogen dynamics were not consistently influenced by water temperature and hydraulic loading rate. Phosphorus concentrations were reduced from 1.7 ± 0.8 mg·liter−1 (ppm) PO4-P in influent to 1.2 ± 0.6 mg·liter−1 (ppm) PO4-P in CWS effluent, but substantial variability existed among years in both phosphorus loading and removal rates. The CWS was able to efficiently remediate nitrogen even under high spring loading rates.


PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8174 ◽  
Author(s):  
Samuel F. Atkinson ◽  
Matthew C. Lake

Background Riparian corridors can affect nutrient, organic matter, and sediment transport, all of which shape water quality in streams and connected downstream waters. When functioning riparian corridors remain intact, they provide highly valued water quality ecosystem services. However, in rapidly urbanizing watersheds, riparian corridors are susceptible to development modifications that adversely affect those ecosystem services. Protecting high quality riparian corridors or restoring low quality corridors are widely advocated as watershed level water quality management options for protecting those ecosystem services. The two approaches, protection or restoration, should be viewed as complementary by watershed managers and provide a foundation for targeting highly functioning riparian corridors for protection or for identifying poorly functioning corridors for restoration. Ascertaining which strategy to use is often motivated by a specific ecosystem service, for example water quality, upon which watershed management is focused. We have previously reported on a spatially explicit model that focused on identifying riparian corridors that have specific characteristics that make them well suited for purposes of preservation and protection focused on water quality. Here we hypothesize that focusing on restoration, rather than protection, can be the basis for developing a watershed level strategy for improving water quality in urbanizing watersheds. Methods The model described here represents a geographic information system (GIS) based approach that utilizes riparian characteristics extracted from 40-meter wide corridors centered on streams and rivers. The model focuses on drinking water reservoir watersheds that can be analyzed at the sub-watershed level. Sub-watershed riparian data (vegetation, soil erodibility and surface slope) are scaled and weighted based on watershed management theories for water quality, and riparian restoration scores are assigned. Those scores are used to rank order riparian zones –the lower the score the higher the priority for riparian restoration. Results The model was applied to 90 sub-watersheds in the watershed of an important drinking water reservoir in north central Texas, USA. Results from this study area suggest that corridor scores were found to be most correlated to the amount of: forested vegetation, residential land use, soils in the highest erodibility class, and highest surface slope (r2 = 0.92, p < 0.0001). Scores allow watershed managers to rapidly focus on riparian corridors most in need of restoration. A beneficial feature of the model is that it also allows investigation of multiple scenarios of restoration strategies (e.g.,  revegetation, soil stabilization, flood plain leveling), giving watershed managers a tool to compare and contrast watershed level management plans.


2020 ◽  
Vol 20 (5) ◽  
pp. 1862-1870
Author(s):  
Jung Eun Lee ◽  
Seok-Jae Youn ◽  
Myeongseop Byeon ◽  
Soon-Ju Yu

Abstract In 2012, a large concentration of geosmin was found in the Paldang reservoir, which is the primary source of drinking water in Seoul, Korea. In June and September 2012, we measured the concentrations of cyanobacteria and actinomycetes, and geosmin, to identify the source of geosmin in the Paldang reservoir. A total of 68 water samples were collected from two sampling sites (Sambong, Paldang), and used to analyze the correlation between cyanobacteria, actinomycetes, and geosmin. The cell density attained a maximum of 24,722 cells/mL on August 11, 2012 and geosmin occurred at a high concentration of 3,934 ng/L on August 13 in Sambong. After July 31, 2012 a rapid increase in growth and cell density occurred with a peak value of 11,568 cells/mL on August 6, 2012. At the same time, the geosmin concentration increased to 3,157 ng/L in Paldang. The number of cyanobacteria positively correlated with geosmin concentration (R2 = 0.84, P &lt; 0.0001), while actinomycetes were not significantly correlated with geosmin (R2 = 0.01, P = 0.709). In addition, the number of actinomycetes was associated with increased turbidity (R = 0.507). Among the various water quality constituents, temperature affected cyanobacteria in the Paldang reservoir (R = 0.803). These results suggest that cyanobacteria are the main source of geosmin in the Paldang reservoir, which might be providing useful information for managing the unpleasant taste of its drinking water.


<em>Abstract</em>.—A CE-QUAL-W2 water quality model was used to characterize the availability of striped bass <em>Morone saxatilis</em> habitat in Lake Greenwood, South Carolina, during 2004 and 2005. Although the lake has a productive fishery, water quality and aquatic habitat are affected by nutrient loading, algal blooms, and extensive oxygen depletion in the bottom waters. The main objectives were to characterize habitat availability and predict the implications of a change in phosphorus loading from the Saluda and Reedy rivers. The baseline scenario of the model showed that habitat was most critical during July and August, when as little of 5% of the reservoir contained tolerable habitat (temperature <28°C and dissolved oxygen >2 mg/L). Favorable habitat (temperature <25°C and dissolved oxygen >2 mg/L) was usually absent for most of July and August. Pulses of higher inflow or freshets produced short-term increases in tolerable habitat, especially in the upper end of the reservoir. Phosphorus-loading scenarios predicted that large reductions (50% or more) would be required to improve habitat substantially during midsummer. For the manager of a striped bass fishery, water quality models can be useful tools for evaluating habitat, especially under marginal conditions, and for predicting the impact of altered water management practices.


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