Phosphorus Load Reduction Research Articles

Suppression of phosphorus release from sediment by Vallisneria natans combined with iron- and zirconium-modified bentonites: Effectiveness, mechanism, and response of sedimentary microbial communities

The efficiency and mechanism in the reduction of internal phosphorus loading from sediment by Vallisneria natans combined with iron- and zirconium-modified bentonites (abbreviated as FeBT and ZrBT, respectively) were studied, and the responses of the microbial communities in sediments to Vallisneria natans combined with FeBT and ZrBT were also explored. ZrBT had stronger phosphate adsorption ability than FeBT. The greatest phosphate adsorption capacities for FeBT and ZrBT in the simultaneous presence of common ions can attain 1.60 and 4.29 mg P/g, respectively, and those for the loaded iron in FeBT and zirconium in ZrBT can attain 55.2 mg P/g Fe2O3 and 164 mg P/g ZrO2, respectively. The combined utilization of FeBT and Vallisneria natans and that of ZrBT and Vallisneria natans can effectively lower the releasing risk of phosphorus from sediment into the overlying water (OW), and the combined use of ZrBT and Vallisneria natans had a higher controlling efficiency than that of FeBT and Vallisneria natans. The passivation of diffusion gradient in thin film (DGT)-labile phosphorus in the sediment layer was vital to the control of phosphorus release from sediment by Vallisneria natans combined with FeBT and ZrBT. The bacterial communities in the sediments under the conditions of FeBT + Vallisneria natans and ZrBT + Vallisneria natans can exert well ecological functions. This work indicates that the combined utilization of ZrBT and Vallisneria natans is a better method to lower the releasing risk of phosphorus from sediment into OW than that of FeBT and Vallisneria natans.

A novel strategy of bloom forming cyanobacteria Microcystis sp. in response to phosphorus deficiency: Using non-phosphorus lipids substitute phospholipids

Despite significant reductions in phosphorus (P) loads, lakes still experience cyanobacterial blooms. Little is known regarding cellular P regulation in response to P deficiency in widely distributed bloom causing species such as Microcystis. In this study, we investigated changes in P containing and non-P lipids contents and their ratios concomitantly with the determinations of expression levels of genes encoding these lipids in cultural and field Microcystis samples. In the culture, the content of phosphatidylglycerol (PG) decreased from 2.1 μg g-1 in P replete control to 1.2 μg g-1 in P-deficient treatment, while non-P lipids, like sulfoquinovosyldiacylglycerol (SQDG) and monogalactosyldiacylglycerol (MGDG), increased dramatically from 13.6 μg g-1 to 142.3 μg g-1, and from 0.9 μg g-1 to 16.74 μg g-1, respectively. The expression of the MGDG synthesis gene, mgdE, also increased under low P conditions. Significant positive relationships between soluble reactive phosphorus (SRP) and ratios of P-containing lipids (PG) to non-P lipids, including SQDG, MGDG and digalactosyldiacylglycerol (DGDG) (P < 0.05) were observed in the field investigations. Both cultural and field data indicated that Microcystis sp. might increase non-P lipids proportion to lower P demand when suffering from P deficiency. Furthermore, despite lipid remodeling, photosynthetic activity remained stable, as indicated by comparable chlorophyll fluorescence and Fv/Fm ratios among cultural treatments. These findings suggested that Microcystis sp. may dominate in P-limited environments by substituting glycolipids and sulfolipids for phospholipids to reduce P demand without compromising the photosynthetic activity. This effective strategy in response to P deficiency meant a stricter P reduction threshold is needed in terms of Microcystis bloom control.

Gypsum and structure lime amendments in boreal agricultural clay soils: Do climate emissions compromise water quality benefits?

We examine cost-effectiveness and social net benefits of using soil amendments, gypsum and structure lime, in reducing phosphorus loading while accounting for the climate emissions from both amendments. Recent field experiments and large-scale pilots in Finland and Sweden suggest that both gypsum and structure lime improve soil structure and can reduce total P loading from clayey fields but differ as soil amendments. While gypsum does not change soil pH, structure lime helps to adjust it to a desired level. Drawing on literature, gypsum is postulated to reduce both dissolved (25%) and particulate losses (50%) of phosphorus, while structure lime is postulated to reduce only particulate phosphorus (40%). Life-cycle analysis is applied to determine greenhouse gas emissions from both soil amendments. We examine 5 and 10 years impacts on phosphorus loss by choosing doses and their timing accordingly. Both amendments provide the highest water quality benefits on erodible soils or soils with high soil phosphorus. Accounting for climate issues drastically changes the picture. Greenhouse gas emissions from gypsum production are 14.43 kgCO2e ha-1, and those from structure lime from pristine materials are 1837 kgCO2e ha-1. Cost-effectiveness of P load reduction including carbon price of GHG emissions is 59 € kg-1P for gypsum and 122 € kg-1P for structure lime. At the national level (application to 0.54 Mha), differences in greenhouse gas emissions without soil emissions are huge and in favour of gypsum (0.048 Mt and 1.04 Mt). Structure lime from recycled zero-emission materials performs well but its supply is very limited.

Hydrodynamics and phosphorus loading in an urbanized river channel influences response to future managed change: Insights from advection-dispersion modelling

There is a need to understand what makes certain targeted measures for in-river phosphorus load reduction more effective than others. Therefore, this paper investigates multiple development scenarios in a small lowland polluted river draining an urban area (The Cut, Bracknell, UK), using an advection-dispersion model (ADModel-P). A comparative analysis is presented whereby changes in concentrations and fluxes of soluble reactive phosphorus (SRP) and organic phosphorus (OP) have been attributed to specific transformations (mineralization, sedimentation, resuspension, adsorption-desorption, and algal uptake) and correlated to controlling factors. Under present day conditions the river stretch is a net source of SRP (10.4 % increase in mean concentration) implying a release of previously accumulated material. Scenarios with the greatest impact are those based on managed reduction of phosphorus load in sources (e.g., 20 % increase in afforestation causes an in-river SRP and OP reduction of 1.3 % to 12.6 %) followed by scenarios involving changes in water temperature (e.g., 1 °C decrease leads to in-river SRP reduction around 3.1 %). Measures involving increased river residence time show the lowest effects (e.g., 16 % decrease in velocity results in under 0.02 % in-river SRP and OP reduction). For better understanding downstream persistence of phosphorus pollution and the effectiveness of mitigation measures the research demonstrates the importance of establishing when and where reaches are net adsorbers or desorbers, and whether sedimentation or resuspension is important.

AquaNutriOpt: Optimizing nutrients for controlling harmful algal blooms in Python—A case study of Lake Okeechobee

We present AquaNutriOpt, a user-friendly Python package designed to tackle a complex combinatorial optimization problem aimed at optimizing nutrient management for the control of harmful algal blooms. This optimization process involves the identification of optimal Best Management Practices (BMPs) and Treatment Technologies (TTs). AquaNutriOpt is constructed based on a novel integer programming model, which we present in this paper. The package can accommodate various user inputs, automatically transforming them into an optimization model, and then solving it using a free solver. To demonstrate AquaNutriOpt’s efficacy, we conduct a series of experiments on two watersheds around Lake Okeechobee in Florida, USA. These experiments illustrate that the optimal BMPs/TTs obtained by AquaNutriOpt can significantly reduce Phosphorus loads into the lake across various budget scenarios. We validate the results by running simulations with the process-based Watershed Assessment Model (WAM), confirming that the estimated percentage reductions closely align with the reports from WAM.

Internal phosphorus loading alters nutrient limitation and contributes to cyanobacterial blooms in a polymictic lake

Clear Lake, a medium-sized hypereutrophic, polymictic lake in northern California, has had recurring harmful cyanobacteria blooms (HCBs) for over a century despite reductions in external phosphorus (P) loadings. Internal P loading can alter nutrient availability and limitation supporting HCBs but is rarely quantified or compared with external loads. We have quantified external P loads from 2019 to 2021 for the three main tributaries (accounting for 46% of the flow) and internal loadings using two methods: a P mass balance and modeled release rates of soluble reactive phosphorus from oxic and anoxic sediments. In addition, we combined high-frequency in situ measurements of water temperature and dissolved oxygen, discrete grab sampling for nutrient chemistry, and remote sensing to explore the potential drivers of the observed variability and provide a comprehensive view of the spatiotemporal dynamics of HCBs. By understanding the relative contribution of external and internal nutrient loadings and the relationship between environmental parameters and HCBs, interannual bloom variability can be better predicted. Comparative estimates of external and internal phosphorus loading indicate that internal sources accounted for 70–95% of the total P input into the system during the study period. Contrary to other lakes, the intensity of the summer bloom season was correlated to the timing and duration of anoxia rather than the magnitude of spring runoff. Internally released P shifted the system from phosphorus to nitrogen limitation during the summer, potentially favoring the proliferation of nitrogen-fixing cyanobacteria.

Legacy sediment as a potential source of orthophosphate: Preliminary conceptual and geochemical models for the Susquehanna River, Chesapeake Bay watershed, USA

Nutrient pollution from agriculture and urban areas plus acid mine drainage (AMD) from legacy coal mines are primary causes of water-quality impairment in the Susquehanna River, which is the predominant source of freshwater and nutrients entering the Chesapeake Bay. Recent increases in the delivery of dissolved orthophosphate (PO4) from the river to the bay may be linked to long-term increases in pH, decreased acidity of precipitation, and decreased acidity, iron, and aluminum loading from widespread AMD. Since the 1950s, baseline pH increased from ~6.5 to ~8 in the West Branch and “North Branch” of the Susquehanna River, which drain bituminous and anthracite coalfields of Pennsylvania. A current baseline pH of ~8 and daily maxima exceeding 9 have been documented along the lower Susquehanna River. In response to improved river quality, bioavailable PO4 now may be released into solution from legacy sediment that has filled major impoundments in lower reaches of the river. At typical pH (5–8) of natural water, aqueous PO4 species tend to be adsorbed by hydrous iron, aluminum, and manganese oxides that coat soil and sediment particles; however, PO4 may be substantially desorbed at pH >8. We created a geochemical model that simulates equilibrium aqueous/solid distributions of PO4 as pH and other solution characteristics change. Considering current conditions in the lower Susquehanna River, the model demonstrates potential for extensive release of adsorbed PO4 at pH >8. Empirical data from laboratory experiments corroborate model results. The transfer of PO4 into the water column may increase algae growth, which removes CO2 and drives pH to higher values, facilitating additional PO4 release and exacerbating the potential for harmful algal blooms. Thus, legacy sediment is a currently unquantified source of PO4 that warrants consideration by resource managers and programs collaborating to reduce phosphorus loads to the bay and similar settings worldwide.

Effects of point and nonpoint source controls on total phosphorus load trends across the Chesapeake Bay watershed, USA

Reduction of total phosphorus (TP) loads has long been a management focus of Chesapeake Bay restoration, but riverine monitoring stations have shown mixed temporal trends. To better understand the regional patterns and drivers of TP trends across the Bay watershed, we compiled and analyzed TP load data from 90 non-tidal network stations using clustering and random forest (RF) approaches. These stations were categorized into two distinct clusters of short-term (2013–2020) TP load trends, i.e. monotonic increase (n = 35) and monotonic decline (n = 55). RF models were developed to identify likely regional drivers of TP trend clusters. Reductions in point sources and agricultural nonpoint sources (i.e. fertilizer) both contributed to water-quality improvement in our period of analysis, thereby demonstrating the effectiveness of nutrient management and the importance of continuing such efforts. In addition, declining TP trends have a larger chance to occur in carbonate areas but a smaller chance in Coastal Plain areas, with the latter likely reflecting the effect of legacy P. To provide spatially explicit information, TP trend clusters were predicted for the entire watershed at the scale of river segments, which are more directly relevant to watershed planning. Among the 975 river segments, 544 (56%) and 431 (44%) were classified as ‘monotonic increase’ and ‘monotonic decrease’, respectively. Furthermore, these predicted TP trend clusters were paired with our previously published total nitrogen (TN) trend clusters, showing that TP and TN both declined in 185 segments (19%) and neither declined in 337 segments (35%). Broadly speaking, large-scale nutrient reduction efforts are underway in many regions to curb eutrophication. Water-quality responses and drivers may differ among systems, but our work provides important new evidence on the effectiveness of management efforts toward controlling point and nonpoint sources.

A mass-balance approach for predicting lake phosphorus concentrations as a function of external phosphorus loading: Application to the Lake St. Clair – Lake Erie System (Canada – USA)

Abstract A mass balance model is presented that links the total phosphorus concentration in lakes to the water residence time, Rw (lake volume divided by the annual water inflow) and the total phosphorus residence time, Rp (average standing stock of lake total phosphorous divided by the external annual total phosphorus input). Following a change in the external load, the lake total phosphorus concentration asymptotically approaches a new value that depends on the Rp:Rw ratio, with the rate of approach controlled by Rp. We applied this approach to a recent reanalysis of the water and total phosphorus budgets of the Lake Erie system of the Laurentian Great Lakes for the 2003-2016 period. We generated load–response relationships and response matrices that relate the steady state total phosphorus concentrations to external total phosphorus loads, for the whole Lake Erie system and for the individual basins (Lake St. Clair, western basin, central basin, eastern basin) and connecting channels (St. Clair River, Detroit River). These relationships and matrices provide a simple but robust framework to gauge the potential response of total phosphorus concentrations to total phosphorus load reductions, such as the 40% reduction proposed for Lake Erie under the Canada-United States Great Lakes Water Quality Agreement. The mass balance analysis further highlights the importance of inter-basin total phosphorus transfers. For example, around 70% of the total phosphorus concentration in the eastern basin is contributed by inflow from the central basin. Consequently, total phosphorus load abatements in watersheds upstream of the eastern basin, rather than in the direct watershed itself, will have the greatest impact on the eastern basin's concentration. Overall, our results illustrate how simple mass balance calculations can provide useful guidance to efforts to manage phosphorus enrichment of lakes.

Simulating Phosphorus Load Reductions in a Nested Catchment Using a Flow Pathway-Based Modeling Approach

Simulating Phosphorus Load Reductions in a Nested Catchment Using a Flow Pathway-Based Modeling Approach

Introduction to the special section: Status and approaches to assess Lake Erie Central Basin hypoxia

Seasonal hypolimnetic hypoxia has occurred in Lake Erie’s central basin since at least the 1950s. The 2012 Great Lakes Water Quality Agreement includes a lake ecosystem objective that commits Canada and the United States to minimize the extent of hypoxic zones, with a particular emphasis on Lake Erie. To meet that objective, Canada and the United States adopted a 40% total phosphorus load reduction target for the western and central basins of the lake. To help assess progress in minimizing Lake Erie’s hypoxic zones, the Cooperative Institute for Great Lakes Research (CIGLR) convened a virtual summit in October 2021 to update the state-of-knowledge regarding hypoxia in Lake Erie. This special section summarizes the recommendations for monitoring, assessment, modeling and reporting of hypoxia that resulted from the workshop and features five papers that present new information about hypoxia in Lake Erie. Recognizing that hypoxia occurs in other areas within the Great Lakes basin, a paper investigating seasonal drivers of hypoxia dynamics in Muskegon Lake a drowned river mouth that flows into Lake Michigan, is also featured.

Intercomparison of three spatially-resolved, process-based Lake Erie hypoxia models

Lake Erie hypoxia models have been developed for multiple objectives, including 1) to support development of phosphorus loading targets, and 2) to provide a real-time forecast of hypoxic zone location and movement. Nutrient management objectives have focused on spatially-averaged metrics, including the mean August-September hypoxic area or mean hypolimnetic dissolved oxygen (DO). However, the ability to model spatial patterns of bottom DO is also important for predicting impacts on drinking water intakes, benthic habitat, and biogeochemical cycling of nutrients. A previous binational effort used multiple models to develop load-response curves to guide setting phosphorus load reduction targets to achieve ecosystem objectives under the Great Lakes Water Quality Agreement. Models were assessed individually, using different sets of observations, obscuring differences in modeled spatial patterns of hypoxia. In a first binational effort, we compared three previously developed Lake Erie hypoxia models in terms of predicted hypoxic area, as well as spatial patterns of hypoxia. All models were similar in prediction of hypoxic area in 2012, but differed in 2013. Several differences in model constructs likely contributed to varying predictions of hypoxia spatial patterns, including sources and sinks of DO in the water column, parameterization of sediment oxygen demand, simulation of vertical mixing, and representation of atmospheric and riverine forcing. This study underscores the importance of comparing models, with various representations of ecological processes, using a common set of visualizations, metrics, and observations before generating ensemble modeling load-response curves to better inform lake management applications.

Detroit River load estimation; the need for a new monitoring approach

The Great Lakes Water Quality Agreement (GLWQA) established new Lake Erie phosphorus loading targets, including a 40% total phosphorus load reduction to its western and central basins. The Detroit and Maumee rivers’ loads are roughly equal and contribute about 90% of the load to the western basin and 54% to the whole lake. They are key drivers of central basin hypoxia and western basin algal production. So, accurate estimates of the Detroit River load are important. Direct measurement of that load near its mouth is difficult due to requiring real-time knowledge of flows around islands and the influence of Lake Erie’s seiches. Consequently, most estimates sum the loads to the St. Clair/Detroit River system. But this approach is complicated by uncertainties in the Lake Huron load and load retention in Lake St. Clair. Routine GLWQA reassessments will confirm or adjust over time the goals, loading targets, and approaches based on evolving information. So, there is a need to improve monitoring approaches that ensure accurate Detroit River loads. New approaches should take into account both the characteristics of this dynamic connecting channel and the uses of monitoring results: 1) determining the Detroit River loads to drive models, develop mass balances, set load reduction targets, and track progress; and 2) assessing the sources and processing of the loads to help guide reduction strategies. Herein, we review temporal and spatial variability in the St. Clair/Detroit River system, and suggest adjustments to monitoring that address those variabilities and both uses.

Modeling Lake Recovery Lag Times Following Influent Phosphorus Loading Reduction.

Internal feedback of nutrients may impede timely improvement in lake water quality. We describe a parsimonious, mechanistic framework for modeling lag times to recovery of phosphorus-enriched lakes, given decreases in external loading. The approach assumes first-order kinetics in a two-compartment system taking account of phosphorus storage in and loading from benthic sediments. Bayesian parameter modeling, published sediment phosphorus release rates, and a prior dynamic calibration for one lake are used to derive estimates of key parameters. Applications are developed for an example lake, as are maps displaying estimated times to attainment of a phosphorus criterion in lakes across a midwestern state, and lag time estimates for fractional water column concentration decrease averaged over HUC-8s. Mean lag times to 50 and 75% declines in water column phosphorus concentration were estimated as 13.1 and 39.0 years respectively, across more than 70,000 lentic water bodies in the continental United States.

Drainage water recycling reduced nitrogen, phosphorus, and sediment losses from a drained agricultural field in eastern North Carolina, U.S.A.

An experimental study was conducted to evaluate the effect of drainage water recycling (DWR) on reducing nitrogen (N), phosphorus (P), and sediment losses from agricultural fields to downstream surface water bodies. The two-year study (May 2019-April 2021) was conducted at an agricultural field in eastern North Carolina, U.S.A. A reservoir existed at the site was used to store subsurface drainage and surface runoff water during wet periods and provide supplemental irrigation during dry periods of the crop growing season. On average, the reservoir retained 14% of received inflow, with a higher flow reduction in the dry year (2019–2020; 29%) than the wet year (2020–2021; 8%). The hydraulic retention time (HRT) for the reservoir was 33.8 days for the dry year and 12.4 days for the wet year. The reservoir significantly reduced the loadings of N by 47%, P by 30% and sediment by 87%. Nitrogen load reduction was primarily driven by nitrate assimilation, the dominant form of N in the reservoir. Phosphorus load reduction was attributed to Orthophosphate assimilation as the reservoir released more particulate P than received. Reductions in both water flow and species concentration contributed to nutrient load reductions. Results suggested the removal efficiency of the reservoir would be highest during the summer and early fall months when the reservoir has a smaller water volume (due to irrigation), longer HRT, and warmer temperature. This study clearly demonstrated the potential of DWR for significantly reducing N, P, and sediment losses from agricultural land to receiving surface water. Further research is needed to investigate the physical, chemical, and biological processes that occur in the storage reservoir and affect the fate and transport of nutrients and sediment. The understanding of these processes will enable optimizing the treatment efficiency of DWR, which maximizes the system’s benefits and reduces construction cost.

High-Frequency Monitoring to Estimate Loads and Identify Nutrient Transport Dynamics in the Little Auglaize River, Ohio

New technologies allow for the in situ monitoring of nutrients, specifically nitrogen and phosphorus, in water systems at increasingly higher temporal frequencies. These technologies allow for the near-continuous monitoring of water quality, which can potentially provide new perspectives on temporal variations in nutrient concentrations and transport dynamics, ultimately supporting more targeted and sustainable water management. The current study investigated the utility of monitoring nitrate-N and soluble reactive phosphorus (SRP) in situ using wet analytical chemistry for one year at 2-h intervals in a small agricultural watershed located in northwestern Ohio. While we saw large variability in the estimated nutrient loads due to daily variations in the high-temporal resolution nutrient concentrations, the nutrient loads were fundamentally driven by high-flow events for this agricultural watershed. Concentration–discharge relations were then developed to help identify how nutrients are stored and released over time scales ranging from low-flow seasonal responses to event-driven high-flow storms. The patterns in the concentration–discharge relations indicated a potential shift in the timing of the mobilization responses for SRP at the event scale over the course of the year. These results suggest that SRP-targeted management practices would need to intercept the dominant delivery pathways of phosphorus in the watershed, such as the tile drainage runoff, to help reduce phosphorus loading. For nitrate-N, patterns in the concentration–discharge relations revealed an increased mobilization response, which was seen during the growing season with low-flow conditions, indicating the potential role of biological uptake instreams across the lowest flows and concentrations of the year. Collectively, high-frequency temporal nutrient data monitored over individual events and across seasons offer guidance for management decisions while allowing us to track progress toward water quality goals.

Can the elimination of cyanobacteria by micro-sieving be an innovative lake purity improvement method?

Abstract The removal of harmful cyanobacteria has recently become an important target in water management strategies. Various methods have been developed to eliminate these microorganisms including: (1) biological methods, especially with floating treatment wetlands and riparian vegetation; (2) physical methods with aeration, mechanical circulation, and hypolimnetic oxygenation; (3) chemical methods with coagulation and flocculation processes; (4) barley straw. We propose that the in situ mechanical-based micro-sieving process provides an opportunity for this to succeed in practice. The appropriate, selective technical parameters and techniques can result in successful water quality improvement, which is essential to meet Water Framework Directive goals and especially for public health. Additionally, micro-sieving used for removing Gloeotrichia can contribute to a significant reduction in internal phosphorus loads, a necessary step in lake restoration. The theoretically probable mean cell-bound P-content transferred with G. echinulata colonies (during strong blooms) can be as high as 48 mg L−1, and this potential P-load is usually deposited on lake bottoms. The removal of cyanobacterium can result in significant limitations of internal P-sources. The method presented above could be a promising, practical, easy-to-use, and cost-effective method for managing and limiting cyanobacterial blooms.

Comment on "Models predict planned phosphorus load reduction will make Lake Erie more toxic".

Hellweger et al. (Reports, 27 May 2022, pp. 1001) predict that phosphorus limitation will increase concentrations of cyanobacterial toxins in lakes. However, several molecular, physiological, and ecological mechanisms assumed in their models are poorly supported or contradicted by other studies. We conclude that their take-home message that phosphorus load reduction will make Lake Erie more toxic is seriously flawed.

Response to Comment on "Models predict planned phosphorus load reduction will make Lake Erie more toxic".

Huisman <i>et al</i>. claim that our model is poorly supported or contradicted by other studies and the predictions are "seriously flawed." We show their criticism is based on an incomplete selection of evidence, misinterpretation of data, or does not actually refute the model. Like all ecosystem models, our model has simplifications and uncertainties, but it is better than existing approaches hat ignore biology and do not predict toxin concentration.

Balancing multiple stakeholder objectives for floodplain reconnection and wetland restoration

Floodplain reconnection and wetland restoration projects are increasingly implemented to enhance flood resiliency, and these nature-based solutions can also achieve co-benefits of nutrient storage and improved habitats. Considering the multiple and sometimes incompatible objectives of stakeholders for uses of riverside lands, a decision-support tool linked to a hydraulic model would enable planners to simulate floodplain restoration scenarios while also quantifying and assessing the trade-offs between the stakeholder objectives to arrive at optimal restoration designs. We illustrate a simple ranking approach using an n-dimensional objective function to represent key stakeholders engaged in restoration. We applied our approach in a watershed in central Vermont (USA) that has been identified by regional and state-level stakeholders as an important location to mitigate flooding damages but also to improve water quality – all within a context of increasing development pressures on riparian lands and limited financial resources to accomplish restoration. Eleven different floodplain reconnection and wetland restoration modifications were combined in six scenarios and simulated with 2D Hydrologic Engineering Center's River Analysis System (2D HEC-RAS), along with a baseline (no-action) scenario. Only modest attenuation of peak flows for 2-, 25-, 50- and 100-year design storms was achieved by the floodplain restoration scenarios due to the steep setting, and flashy nature of the watershed. Yet, several scenarios of floodplain reconnection projects more than met the necessary annual phosphorus load reductions targeted under a Total Maximum Daily Load implementation plan. Our approach provided planners with a ranking of restoration scenarios that best met multiple stakeholder objectives and allowed effectiveness of alternate design scenarios to be quantified, justified, and visualized to promote consensus decision-making.