Prairie Watersheds Research Articles

Escherichia coli efflux from rangeland ecosystems in the southcentral Great Plains of the United States.

Bacterial contamination of surface water is a public health concern. To quantify the efflux of Escherichia coli into ephemeral and intermittent streams and assess its numbers in relation to secondary body contact standards, we monitored runoff and measured E. coli numbers from 10 experimental watersheds that differed in vegetation cover and cattle access in north-central Oklahoma. Escherichia coli numbers were not significantly different among the watersheds, with one exception; the grazed prairie watershed (GP1) had greater numbers compared to one ungrazed prairie watershed (UP2). Median E. coli numbers in runoff from ungrazed watersheds ranged from 260 to 1482 MPN/100mL in comparison with grazed watersheds that ranged from 320 to 8878 MPN/100mL. In the GP1 watershed, higher cattle stocking rates during pre- and post-calving (February-May) resulted in significantly greater bacterial numbers and event loading compared to periods with lower stocking rates. The lack of significance among watersheds is likely due to the grazed sites being rotationally (and lightly) grazed, data variability, and wildlife contributions. To address wildlife sources, we used camera trap data to assess the usage in the watersheds; however, the average number of animals in a 24-h period did not correlate with observed median E. coli numbers. Because of its impacts on E. coli numbers in water, grazing management (stocking rate, rotation, and timing) should be considered for improving water quality in streams and reservoirs.

Learning from hydrological models’ challenges: A case study from the Nelson basin model intercomparison project

Intercomparison studies play an important, but limited role in understanding the usefulness and limitations of currently available hydrological models. Comparison studies are often limited to well-behaved hydrological regimes, where rainfall-runoff processes dominate the hydrological response. These efforts have not covered western Canada due to the difficulty in simulating that region’s complex cold region hydrology with varying spatiotemporal contributing areas. This intercomparison study is the first of a series of studies under the intercomparison project of the international and interprovincial transboundary Nelson-Churchill River Basin (NCRB) in North America (Nelson-MIP), which encompasses different ecozones with major areas of the non-contributing Prairie potholes, forests, glaciers, mountains, and permafrost. The performance of eight hydrological and land surface models is compared at different unregulated watersheds within the NCRB. This is done to assess the models’ streamflow performance and overall fidelity without and with calibration, to capture the underlying physics of the region and to better understand why models struggle to accurately simulate its hydrology. Results show that some of the participating models have difficulties in simulating streamflow and/or internal hydrological variables (e.g., evapotranspiration) over Prairie watersheds but most models performed well elsewhere. This stems from model structural deficiencies, despite the various models being well calibrated to observed streamflow. Some model structural changes are identified for the participating models for future improvement. The outcomes of this study offer guidance for practitioners for the accurate prediction of NCRB streamflow, and for increasing confidence in future projections of water resources supply and management.

Sediment sources and transport dynamics in large, regulated river systems with multiple lakes and reservoirs in the subarctic region of Canada

AbstractThe Burntwood River (BR) and Upper Nelson River (UNR) are regulated rivers in the subarctic region of Canada. They merge at Split Lake and then discharge into Hudson Bay via the Lower Nelson River (LNR). The BR water discharge was increased eight‐fold by a cross‐watershed diversion in 1976. The UNR drains the 11th largest lake in the world, Lake Winnipeg, which itself receives discharge from a large North American Interior Plains watershed. Sediment loads and the source fingerprinting approach in these rivers were used to: (a) identify the sediment sources; (b) examine the impact of climate change and flow regulation on the BR and UNR sediment loads; and (c) assess the influence of Split Lake on downstream delivery of sediment into the LNR. Lake Winnipeg effectively decouples the UNR from the sediment sources in its prairie watershed. Fluvial riverbank and reservoir shoreline erosion in the UNR increased in the late 1990s, in response to a multi‐decadal increase in discharge forced by climate change in the Lake Winnipeg watershed. The BR sediment load was increased seven‐fold by diversion. Since diversion, flow regulation near the licenced limit has muted the response to variability in local precipitation and runoff; however, erosion processes independent from discharge (bank failures and subaerial processes) add variability in the sediment load record. Based on sediment budgeting, Split Lake conveys almost 80% of the BR and UNR sediment load into the LNR. The greater sediment load in the UNR (~1100 Gg year−1, compared to ~530 Gg year−1 from the BR) reveals that the UNR is the primary sediment source into the LNR, so that downstream sediment transport dynamics are more sensitive to the environmental changes in the UNR than to disturbances in the BR. Whether this may change in the future depends on changes in climate and engineering responses to increasing demand for hydroelectric power.

Evidence for pulse-shunt carbon exports from a mixed land-use, restored prairie watershed

Evidence for pulse-shunt carbon exports from a mixed land-use, restored prairie watershed

Evaluation of Soil Water Content Using SWAT for Southern Saskatchewan, Canada

Soil water content (SWC) is one of the most important hydrologic variables; it plays a decisive role in the control of various land surface processes. We simulated SWC using a Soil and Water Assessment Tool (SWAT) model in southern Saskatchewan. SWC was calibrated using measured data and Soil Moisture Active Passive (SMAP) Level-4 for the surface (0–5 cm) SWC for hydrological response units (HRU) at daily and monthly (warm season) intervals for the years 2015 to 2020. We used the SUFI-2 technique in SWAT-CUP, and observed daily instrumented streamflow records, for calibration (1995 to 2004) and validation (2005–2010). The results reveal that the SWAT model performs well with a monthly PBIAS < 10% and Nash–Sutcliffe efficiency (NS) and R2 ≥ 0.8 for calibration and validation. The correlation coefficient between ground measurement with SMAP and SWAT products are 0.698 and 0.633, respectively. Moreover, SMAP data of surface SWC coincides well with measurements in terms of both amount and trend compared with the SWAT product. The highest r value occurred in July when the mean r value in SWAT and SMAP were 0.87 to 0.84, and then in June for r value of 0.75. In contrast, the lowest values were in April and May (0.07 and 0.04, respectively) at the beginning of the growing season in southern Saskatchewan. Furthermore, calibration in the SWAT model is based on a batch form whereby parameters are adjusted to corresponding input by modifying simulations with observations. SWAT underestimates the abrupt increase in streamflow during the snowmelt months (April and May). This study achieved the objective of developing a SWAT model that simulates SWC in a prairie watershed, and, therefore, can be used in a subsequent phase of research to estimate future soil moisture conditions under projected climate changes.

Screening and scoping-level assessment of beneficial management practices in a Canadian prairie watershed

In the Canadian prairies, eutrophication is a widespread issue, with agriculture representing a major anthropogenic nutrient source in many watersheds. However, efforts to mitigate agricultural nutrient export are challenged by the lack of coordinated monitoring programs and the unique hydrological characteristics of the prairies, notably, the dominance of snowmelt in both water flows and nutrient loads, variable runoff, variable contributing area and the issues of understanding how scale affects nutrient concentrations and prevalence of dissolved nutrient transport (over total nutrients). Efforts are being made to integrate these characteristics in process-based water quality models, but the models are often complex and are not yet ready for use by watershed managers for prioritizing implementation of beneficial management practices (BMPs). In this study, a screening and scoping approach based on nutrient export coefficient modeling was used to prioritize BMPs for the 55,700 km2 Qu’Appelle Watershed, Saskatchewan. By integrating land use information, in-stream monitoring data, stakeholder input and nutrient export coefficient modeling, the study assessed potential efficiencies of six BMPs involving fertilizer, manure, grazing, crop and wetland management in nutrient load reductions for nine tributaries of the watershed. Uncertainty around the effectiveness of the BMPs was assessed. Field-level export coefficients were adjusted with nutrient delivery ratios for estimating watershed-level exports. Of the BMPs examined, in general, wetland restoration had the greatest potential to reduce both nitrogen and phosphorus loads in most tributaries, followed by fertilizer management. The importance of wetland restoration was supported by positive, significant, linear correlations between nutrient delivery ratios and drainage intensity in the tributaries (nitrogen: R 2 = 0.67; phosphorus: R 2 = 0.82). Notably, the relative ranking of BMP efficiencies varied with tributaries, as a result of differing landscape characteristics, land uses and nutrient inputs. In conclusion, the approach developed here acknowledges uncertainty, but provides a means to guide management decisions within the context of an adaptive management approach, where BMP implementation is partnered with monitoring and assessment to revise ongoing plans and ensures selected practices are meeting goals for nutrient abatement.

Predictive Mapping of Solute‐rich Wetlands in the Canadian Prairie Pothole Region Through High‐resolution Digital Elevation Model Analyses

Prairie Pothole Region wetlands are integral in reducing nutrient mobility in prairie watersheds. Wetland soil CaCO3 content likely plays an important role in wetland phosphorus retention capacity. Accurate predictions of the spatial distributions of wetlands with CaCO3-enriched soils would allow for further study on these relationships and prioritized wetland conservation efforts to encourage this ecosystem service. Solute accumulations (including CaCO3) within wetlands are largely determined by the wetland’s topographic position and relationship with groundwater. These characteristics were estimated by predicting spill channel connections between wetlands using LiDAR-derived digital elevation models. Spatial distributions of solute-rich wetlands were predicted with a simple decision tree model that predicts wetlands as either fresh or solute-rich based on approximated hydrologic characteristics (Strahler order and terminal status) determined from the predicted active spill channel networks. The model was trained and tested using measurements of wetland pond water and soil electrical conductivity (i.e., solute-richness) in three study areas within the Saskatchewan Prairie Pothole Region. The model achieved acceptable predictive accuracies based on training and independent validation tests. The proposed methodologies could be incorporated into more complex multivariate models for the purposes of predictive soil mapping or hydrologic studies in the Prairie Pothole Region.

Toward Simple Modeling Practices in the Complex Canadian Prairie Watersheds

AbstractThe prairie region in Canada has been characterized as a graveyard of hydrological models due to its challenging cold-regions processes and complex landscape with numerous land depressions ...

Identification of Hydrological Models for Enhanced Ensemble Reservoir Inflow Forecasting in a Large Complex Prairie Watershed

Accurate and reliable flow forecasting in complex Canadian prairie watersheds has been one of the major challenges faced by hydrologists. In an attempt to improve the accuracy and reliability of a reservoir inflow forecast, this study investigates structurally different hydrological models along with ensemble precipitation forecasts to identify the most skillful and reliable model. The key goal is to assess whether short- and medium-range ensemble flood forecasting in large complex basins can be accurately achieved by simple conceptual lumped models (e.g., SACSMA with SNOW17 and MACHBV with SNOW17) or it requires a medium level distributed model (e.g., WATFLOOD) or an advanced macroscale land-surface based model (VIC coupled with routing module (RVIC)). Eleven (11)-member precipitation forecasts from second-generation Global Ensemble Forecast System reforecast (GEFSv2) were used as inputs. Each of the ensemble members was bias-corrected by Empirical Quantile Mapping method using the Canadian Precipitation Analysis (CaPA) as a training/verification dataset. Forecast evaluation is performed for 1-day up to 8-days forecast lead times in a 6-month hindcast period. Results indicate that bias-correcting precipitation forecasts using verifying datasets (such as CaPA) for a training period of at least two years before the forecast time, produces skillful ensemble hydrological forecasts. A comparison of models in forecast mode shows that the two lumped models (SACSMA and MACHBV) can provide better overall forecast performance than the benchmark WATFLOOD and the macroscale Variable Infiltration Capacity (VIC) model. However, for shorter lead-times, particularly up to day 3, the benchmark distributed model provides competitive reliability, as compared to the lumped models. In general, the SACSMA model provided better forecast quality, reliability and differentiation skill than other considered models at all lead times.

Streamwater ages in nested, seasonally cold Canadian watersheds

AbstractThe mean transit time (MTT) is an important descriptor of water storage and release dynamics in watersheds. Although MTT studies are numerous for many regions around the world, they are rare for prairie watersheds where seasonally cold or dry conditions require adequate methodological choices towards MTT estimation, especially regarding the handling of sparse data records and tracer selection. To examine the impact of such choices, we used timeseries of δ18O and δ2H from two contrasted years (2014 and 2015) and relied on two metrics and two modelling methods to infer MTTs in prairie watersheds. Our focus was on nested outlets with different drainage areas, geologies, and known run‐off generation mechanisms. The damping ratio and young water fraction (i.e., the fraction of streamflow with transit times lesser than 3 months) metrics, as well as the sine‐wave modelling and time‐based convolution modelling methods, were applied to year‐specific data. Results show that young water fractions and modelled MTT values were, respectively, larger and smaller in 2014, which was a wet year, compared with that in 2015. In 2014, most outlets had young water fractions larger than 0.5 and MTT values lesser than 6 months. The damping ratio, young water fraction, and sine‐wave modelling methods led to convergent conclusions about watershed water storage and release dynamics for some of the monitored sites. Contrasting results were, however, obtained when the same method was applied using δ2H instead of δ18O, due to differing evaporation fractionation, or when the time‐based convolution modelling method was used. Some methods also failed to provide any robust results during the dry year (i.e., 2015), highlighting the difficulty in inferring MTTs when data are sparse due to intermittent streamflow. This study therefore allowed the formulation of empirical recommendations for MTT estimation in prairie environments as a function of data availability and antecedent wetness conditions.

Hydrological variability affects particulate nitrogen and phosphorus in streams of the Northern Great Plains

Study regionThe study area is located in southern Manitoba, in the prairie region of Canada Study focusThis study examined the impact of hydrological variability on the timing and magnitude of nutrient export from seven agriculturally-dominated watersheds in the Red River Valley, Manitoba, Canada. New hydrological insights for the regionIn 2013, discharge showed a seasonal pattern typical of streams traversing the Canadian prairies: high discharge during snowmelt followed by cessation of flow in early June due to lack of precipitation. In 2014, discharge still peaked during snowmelt but, compared to 2013, was 49% lower during snowmelt yet 21% higher during summer and fall due to greater rainfall. These hydrologic differences were associated with differences in fractionation of nutrients between years. Thus, higher concentrations and loads of particulate phosphorus (P) and nitrogen (N), and a greater (p < 0.05) share of the total nutrient pool in particulate forms (particularly for P), were observed during the snowmelt- dominated year (2013). Our findings show that the nutrient concentrations, fractionation and export from prairie watersheds differ between years, and amongst hydrological seasons, in relation to hydrological conditions. Additional management actions may be required to address changes in the quantity, timing and fractionation of nutrient export associated with rainier summers forecasted under future climate scenarios.

End-Member Selection in Two-Component Isotope-Based Hydrograph Separation

The science that underpins our knowledge and understanding of Isotope-Based Hydrograph separation (IHS) has gained grounds, over the last few decades, in the identification of streamflow sources. However, challenges still exist in identifying appropriate tracers and the right combination of end-members for the IHS process. In a two-component IHS analysis, the application of the dual isotopes tracers, δ18O and (or) δ2H, is regarded as the simplest method. We undertook an IHS study within a nested system of eight Prairie watersheds located in South central Manitoba, Canada. The work evaluated about 17,000 results emanating from the application of a combination of two potential tracers (δ18O and δ2H) and eight each of potential “old” and “new” water end-members in a two-component IHS process. The outcome showed occurrences of many mathematically possible but hydrologically unacceptable IHS results. The observation was particularly predominant within relatively larger perennial sub-catchments of the watershed. It is also shown that inter-site sub-catchment isotopic end-member transferability is possible within watersheds of similar physio-hydrographic characteristics. We suggest that a careful evaluation of the physio-hydrographic characteristics of catchments be considered in IHS studies in addition to the recommended guidelines in the selection of tracers and end-members.

Phosphorus Retention in Intact and Drained Prairie Wetland Basins: Implications for Nutrient Export.

Draining of geographically isolated (no defined inlet or outlet) freshwater mineral soil wetlands has likely converted areas that acted historically as important P sinks to sources of P. To explore the role of wetland drainage on nonpoint-source P pollution, differences in the chemical characteristics and P sorption parameters of drained and intact wetlands were investigated in a small watershed situated in the Prairie Pothole Region of southwestern Manitoba, Canada. Chemical characteristics and P sorption parameters varied across landscape positions, particularly for landscape positions that were submerged. Intact wetlands had slightly higher concentrations of organic and total P relative to drained wetlands, which is indicative of their P trapping capacity. More importantly, the maximum P sorption capacity and P buffering capacity of intact wetlands were 3.6 (1752 vs. 492 mg kg) and 17 (1394 vs. 84 L kg) times greater than those in drained wetlands. Conversely, equilibrium P concentrations and bioavailable P concentrations in drained wetlands were an order of magnitude greater than those in intact prairie wetlands. Our study suggests that intact prairie wetlands may be effective sinks for P. As a result, prairie wetlands may play an important role in mitigating nonpoint-source pollution. Conversely, our findings suggest that drained prairie wetlands are potentially a high risk for P export and should be treated as important critical source areas within prairie watersheds.

Evaluation of four hydrological models for operational flood forecasting in a Canadian Prairie watershed

ABSTRACTThe complexities of the Prairie watersheds, including potholes, drainage interconnectivities, changing land-use patterns, dynamic watershed boundaries and hydro-meteorological factors, have made hydrological modelling on Prairie watersheds one of the most complex task for hydrologists and operational hydrological forecasters. In this study, four hydrological models (WATFLOOD, HBV-EC, HSPF and HEC-HMS) were developed, calibrated and tested for their efficiency and accuracy to be used as operational flood forecasting tools. The Upper Assiniboine River, which flows into the Shellmouth Reservoir, Canada, was selected for the analysis. The performance of the models was evaluated by the standard statistical methods: the Nash-Sutcliffe efficiency coefficient, correlation coefficient, root mean squared error, mean absolute relative error and deviation of runoff volumes. The models were evaluated on their accuracy in simulating the observed runoff for calibration and verification periods (2005–2015 and 1994–2004, respectively) and also their use in operational forecasting of the 2016 and 2017 runoff.

Impact of climate variability and wetland drainage on watershed response in depression dominated landscapes

ABSTRACTThis study investigates changes in run-off production behaviour which may have occurred due to climate change/variability and/or as a result of draining of wetlands over Canadian portion of North American Prairies. The study uses statistical methods to quantify changes in precipitation/run-off over various spatial and temporal scales. The major results indicate dominated upward trends in some run-off metrics over some Prairie watersheds, whereas there is no concrete evidence of statistically significant precipitation trends during the observation period. The observed changes in run-off response, therefore, are interpreted to represent the possible effects of intensive wetland drainage. The remaining unchanged metrics over the majority of tested watersheds are interpreted to be due to varying progressive land use/cover disturbances which may have conflicting impacts on watershed response in the Prairies. The absence of significant changes in precipitation and observed changes in hydrology of some parts of the study area may support the narrative that loss of wetlands has led to increased flood risks in this area. However, information on major land cover indices like intact forests, agricultural land, urban areas within the study area, and landscape best management practices would be necessary to fully comprehend land use change and its impact on the Prairie’s hydrology.

Incorporating climate change scenarios and water-balance approach to cumulative assessment models of solution potash Mining in the Canadian Prairies

Changing hydroclimatic conditions on the Canadian Prairies include significant shifts in the intensity, duration, and frequency of precipitation events, as well as temperature and seasonal shifts that affect water availability and quality. Concurrently, high-water-use-intensity industrial development, such as solution potash mining, is also lessening availability of timely water resources in agricultural regions and southern Prairie watersheds. This study used a three-pronged approach to (1) incorporate climate change projections within CEA, (2) identify the impact of projected and trending population and industry growth to inform water-balance calculations and recommendations within the study area, and (3) calculate the net impact on water availability of changing hydroclimate on a specific industry (solution potash mining) using a case study methodology for application to the Qu’Appelle Watershed. The results indicate that an implemented process approach is a good option for incorporating climate change models and methods within cumulative effects monitoring and assessment programs, despite challenges associated with regional variance and lack of long-term data. The outcomes of case study development and review indicate a climate change impact (26% difference) on the available water resources anticipated within the area. And combining this with the water-balance approach, it is recommended that water and climate modeling be completed at the regional scale to account for assumptions and scenario/model-based projections.

Evaluating the Effects of Tracer Choice and End‐Member Definitions on Hydrograph Separation Results Across Nested, Seasonally Cold Watersheds

AbstractIsotope‐based hydrograph separation (IHS) is a widely used method in studies of runoff generation and streamflow partitioning. Challenges in choosing and characterizing appropriate tracers and end‐members have, however led to presumably highly uncertain IHS results. Here we tested the effects of end‐member definitions and tracer choices on IHS results in nested Prairie watersheds of varying size and landscape characteristics. Specifically, the consideration of eight potential “new” water end‐members, eight potential “old” water end‐members, and two stable water isotope tracers led to 80 potential IHS results for each stream water sample. IHS‐related uncertainty was evaluated using a Gaussian error propagation method. Results show that choosing an appropriate “new” water end‐member is most challenging during the freshet: highly variable “old” water fractions associated with high uncertainties were attributed to changing conditions from melting snow only to rain‐on‐snow. In summer and fall, it was rather the choice of an appropriate “old” water end‐member that was most problematic. IHS results obtained using δ18O versus δ2H as a tracer were significantly different except in the flattest and most wind‐sheltered watersheds examined. Overall, δ2H‐based IHS results were more uncertain than their δ18O‐based counterparts. Recommendations are therefore made toward careful selection of a tracer and a sampling strategy aimed at characterizing the most appropriate end‐members for IHS, especially when dealing with seasonally cold watersheds.

Probing whole‐stream metabolism: influence of spatial heterogeneity on rate estimates

Summary Whole‐stream metabolism has been estimated by measuring in‐stream oxygen (O2) concentrations since the method was introduced over 50 years ago. However, the influence of measurement location and estimation method on metabolism rates is understudied. We examined how the placement of O2 probes (i.e. depth, separation from the thalweg), differences in methodology (1‐station, 2‐station, area‐weighted) and reach lengths influenced estimated rates of whole‐stream metabolism in a tallgrass prairie watershed. Metabolism estimates made in the thalweg differed from estimates made in backwaters due to disconnection in flow, and estimates made in deep pools differed from surface estimates due to thermal stratification (temporary flow disconnection). The 1‐station respiration estimates differed from short 2‐station reach‐scale estimates (c. 20 m) but were more similar to larger 2‐station reach‐scale estimates (c. 100 m). In contrast, the 1‐station gross primary production was most similar to the short 2‐station reaches occurring immediately upstream and became less similar at longer 2‐station reach lengths. The different estimation methodologies (1‐station, 2‐station, area‐weighted) accounting for the longest reach scale did not result in different metabolism rates. The temporary phenomena of thermal stratification of stream pools during a warm day, which disconnected pool bottoms from the surface waters, likely affected not only the pool estimates but also estimates made in the downstream thalweg (i.e. an O2 deficit accrued from respiration during the day in the bottom of the pool abruptly moved downstream during mixing). Oxygen probe placement mattered and affected rate estimates according to habitat type and reach length (i.e. scale) due to the influence of small‐scale heterogeneity on community respiration. Selection of reach length can be critical for studies depending on whether local heterogeneity is of interest or should be averaged. We conclude that the intuitive use of thalwegs and reaches that are at least 10 times the stream width are likely appropriate for whole‐stream metabolism estimates, although the exact reach length necessary and potential stream‐specific characteristics, such as stratified pools, need to be carefully considered in probe placement. We encourage other studies to report the placement characteristics of O2 probes in streams as well as consider the potential confounding factor of local habitat heterogeneity.

Modeling of nutrient export and effects of management practices in a cold-climate prairie watershed: Assiniboine River watershed, Canada

Non-point source pollution due to agricultural activities is an important problem that has been threatening water resources in Canadian prairie watersheds. The development of strategies to prevent nutrient loss depends on the quantification of nutrient mobilization and transport across a watershed. Integrated eco-hydrological models can play an important role in this regard. However, current model applicability to cold-climate Canadian prairie watersheds is limited due to the complex dynamics of nutrient export under the existence of numerous landscape depressions and freeze-thaw cycles. The aim of this study was to evaluate an eco-hydrological model for nutrient export prediction and assess the impacts of management practices for a cold-climate prairie watershed. To achieve the objectives, a new version of the SWAT model called SWAT-PDLD, which combines SWAT and a Probability Distributed Landscape Depressions (PDLD) model, along with a seasonally varying soil erodibility factor, was applied to a Canadian prairie watershed (the Assiniboine River watershed, Saskatchewan, Canada). The PDLD module is used to simulate the effect of the numerous landscape depressions that exist in these watersheds on streamflow, whereas a seasonally varying soil erodibility factor is used to take into account seasonal variation of sediment and nutrient generation due to the cold climate conditions. Model calibration and uncertainty analysis were performed using the Sequential Uncertainty FItting (SUFI-2). The study shows that the SWAT-PDLD model with seasonally varying soil erodibility simulates the daily nutrient export in a cold prairie watershed satisfactorily as confirmed by both graphical plots and statistical measures. A sensitivity analysis of sub-watershed discretization revealed that the streamflow is relatively insensitive to sub-watershed discretization but it did affect sediment and nutrient export. Importantly, the model shows that both filter strips and cover crops decreased sediment, phosphorous, and nitrogen export, while conservation tillage increased phosphorous export in the study watershed.

Integrated Economic-Hydrologic Modeling for Examining Cost-Effectiveness of Wetland Restoration Scenarios in a Canadian Prairie Watershed

This study develops an integrated economic-hydrologic modeling to examine cost-effectiveness of wetland restoration scenarios in the 75-km2 South Tobacco Creek watershed in the Canadian prairie region. The modeling results show that spatial variations of wetland restoration costs are driven by forgone cropping returns while wetland restoration benefits in terms of total phosphorus (TP) reductions are related to wetland drainage area characteristics including slope, soil, and land use, and wetland features such as size, volume, and position relative to the stream network. For a TP reduction goal of 141.1 kg/yr or 4.3 % at the watershed outlet, the spatial targeting scenario based on economic cost to environmental benefit ratios identifies 28.8 ha of wetland restoration costing $3,058.6/yr. The cost ceiling scenario based on minimizing economic costs only would have to restore 80.1 ha of wetlands costing $8,032.6/yr. In comparison, the cost ceiling scenario requires 178.2 % more wetland restoration areas and would cost 162.6 % more than those of the spatial targeting scenario. The study contributes to develop integrated economic-hydrologic modeling to inform wetland restoration decision at farm field scale. The modeling results demonstrate the importance of spatially targeting wetland restoration based on economic cost to environmental benefit ratios in order to achieve cost-effectiveness.