Lateral and longitudinal chloride dynamics in an urbanizing watershed in Southern Ontario: a spatial cross-correlation modelling approach

The application of spatial cross-correlation modelling was tested on continuous time series of electrical conductivity to estimate lateral and longitudinal chloride dynamics in an urbanizing watershed in Southern Ontario. Overall, the model appeared more robust for the winter salting season than for the summer growing season. The winter results showed shorter travel times with higher velocity longitudinally (upstream to downstream) in an urban stream reach with more impervious surfaces than in a rural reach with more permeable surfaces. The lateral exchange rates (stream-hyporheic zone) were observed to be affected by both local and catchment-scale land use and soil profiles. Cross-correlation results and time series data also indicated that road-salt applications in the urban catchment may be leading to underground storage of chloride, contributing to the streams in summer and producing year-round peaks of chloride in the urban stream reach.

Lateral and longitudinal chloride dynamics in an urbanizing watershed in Southern Ontario: a spatial cross-correlation modelling approach

The application of spatial cross-correlation modelling was tested on continuous time series of electrical conductivity to estimate lateral and longitudinal chloride dynamics in an urbanizing watershed in Southern Ontario. Overall, the model appeared more robust for the winter salting season than for the summer growing season. The winter results showed shorter travel times with higher velocity longitudinally (upstream to downstream) in an urban stream reach with more impervious surfaces than in a rural reach with more permeable surfaces. The lateral exchange rates (stream-hyporheic zone) were observed to be affected by both local and catchment-scale land use and soil profiles. Cross-correlation results and time series data also indicated that road-salt applications in the urban catchment may be leading to underground storage of chloride, contributing to the streams in summer and producing year-round peaks of chloride in the urban stream reach.

Modelling The Transport and Return of Chloride Using INCA-Cl in an Urbanizing Watershed

1.0 Introduction In northern environments such as Canada, road salt (e.g. sodium chloride, NaCl) has been used as a de-icing agent to improve winter driving conditions since the 1950’s (Godwin et al., 2003). While research has shown that the application of salt to roadways can reduce accident rates by up to 88%, the use of road salt has been linked to increasing concentrations of chloride (Cl) in ground and surface waters in urbanized watersheds (Godwin et al., 2003). A recent study (Dugan et al., 2017) which tested 371 lakes in north eastern North America found that 44% trended towards long term salinization – levels at which Cl concentrations may begin to impact freshwater ecosystems. High Cl concentrations have been found to be potentially lethal to aquatic organisms, and long-term exposure can have detrimental effects on human health (Howard and Beck, 1993; Kelly et al., 2008). Keeping lakes and rivers “fresh” is important for the maintenance of ecosystem services associated with freshwater resources such as drinking water, fisheries and aquatic habitat.

Modelling The Transport and Return of Chloride Using INCA-Cl in an Urbanizing Watershed

1.0 Introduction In northern environments such as Canada, road salt (e.g. sodium chloride, NaCl) has been used as a de-icing agent to improve winter driving conditions since the 1950’s (Godwin et al., 2003). While research has shown that the application of salt to roadways can reduce accident rates by up to 88%, the use of road salt has been linked to increasing concentrations of chloride (Cl) in ground and surface waters in urbanized watersheds (Godwin et al., 2003). A recent study (Dugan et al., 2017) which tested 371 lakes in north eastern North America found that 44% trended towards long term salinization – levels at which Cl concentrations may begin to impact freshwater ecosystems. High Cl concentrations have been found to be potentially lethal to aquatic organisms, and long-term exposure can have detrimental effects on human health (Howard and Beck, 1993; Kelly et al., 2008). Keeping lakes and rivers “fresh” is important for the maintenance of ecosystem services associated with freshwater resources such as drinking water, fisheries and aquatic habitat.

The Performance of Physically Based and Conceptual Hydrologic Models: A Case Study for Makkah Watershed, Saudi Arabia

Population growth and land use modification in urban areas require the use of accurate tools for rainfall-runoff modeling, especially where the topography is complex. The recent improvement in the quality and resolution of remotely sensed precipitation satisfies a major need for such tools. A physically-based, fully distributed hydrologic model and a conceptual semi-distributed model, forced by satellite rainfall estimates, were used to simulate flooding events in a very arid, rapidly urbanizing watershed in Saudi Arabia. Observed peak discharge for two flood events was used to compare hydrographs simulated by the two models, one for calibration and one for validation. To further explore the effect of watershed heterogeneity, the hydrographs produced by three implementations of the conceptual were compared against each other and against the output of the physically-based model. The results showed the ability of the distributed models to capture the effect of the complex topography and variability of land use and soils of the watershed. In general, the GSSHA model required less calibration and performed better than HEC-HMS. This study confirms that the semi-distributed HEC-HMS model cannot be used without calibration, while the GSSHA model can be the best option in the case of a lack of data. Although the two models showed good agreement at the calibration point, there were significant differences in the runoff, discharge, and infiltration values at interior points of the watershed.

Prioritizing Sponge City Sites in Rapidly Urbanizing Watersheds Using Multi-Criteria Decision Model

Spatial planning is crucial for Sponge City (SC) construction; however, prioritizing SC sites at the watershed scale has not been fully explored. In this study, a multi-criteria decision model, considering demand and suitability of SC construction, was established by monitoring, model simulation and index calculation. This new model was then tested in a rapidly urbanizing watershed, Beijing, China and the priority of SC construction at both grid scale (1km 1km) and subwatershed scale was ranked. The results showed that the highest priority was found in emerging regions where urbanization is ongoing, and followed by urban core areas. In addition, six indexes were identified by clustering heatmaps as key factors affecting the priority of SC planning, including topographic index, water pollution index, pollution rate based on the state standard of surface water environment quality, urbanization planning, urban levels, and vegetation index, which could guide SC planning in data-lacking regions. The approach and findings in this study can not only provide helpful references for watershed managers and urban planners but also can be easily used in other regions.

Assessing impacts of future climate change on hydrological processes in an urbanizing watershed with a multimodel approach

The sensitivity of hydrological processes to the changed environment is of great concern. The integrated impacts of climate change and urbanization in the future have been assessed in a watershed in Northwest China through a multimodel approach based on the combined application of Generalized Watershed Loading Functions, the Long Ashton Research Station Weather Generator, and the Land Change Modeler. The results showed that both climate change and urbanization would lead to more watershed streamflow, and their combination would have synergistic effects on additional increases. In addition, there would be different seasonal distributions of streamflow with a greater proportion of runoff. These study results are helpful in supporting projects and/or decision-making processes for managers by providing more insights into the regional hydrological changes affected by climate change and urbanization. The proposed methodology of the combined multimodel approach may be applicable in other areas with similar conditions.