Abstract
Holistic water quality models to support decision-making in lowland catchments with competing stakeholder perspectives are still limited. To address this gap, an integrated system dynamics model for water quantity and quality (including stream temperature, dissolved oxygen, and macronutrients) was developed. Adaptable plug-n-play modules handle the complexity (sources, pathways) related to both urban and agricultural/natural land-use features. The model was applied in a data-rich catchment to uncover key insights into the dynamics governing water quality in a peri-urban stream. Performance indicators demonstrate the model successfully captured key water quantity/quality variations and interactions (with, e.g., Nash-Sutcliff Efficiency ranging from very good to satisfactory). Model simulation and sensitivity results could then highlight the influence of stream temperature variations and enhanced heterotrophic respiration in summer, causing low dissolved oxygen levels and potentially affecting ecological quality. Probabilistic uncertainty results combined with a rich dataset show high potential for ammonium uptake in the macrophyte-dominated reach. The results further suggest phosphorus remobilization from streambed sediment could become an important diffuse nutrient source should other sources (e.g., urban effluents) be mitigated. These findings are especially important for the design of green transition solutions, where single-objective management strategies may negatively impact aquatic ecosystems.
Highlights
Surface water ecosystems worldwide are deteriorating at an alarming rate under ever-increasing human pressures and climate change [1,2,3], threatening biodiversity and ecosystem services that link to human water security and public health [4,5,6,7]
To demonstrate the model applicability, results for both the calibration and verification period are shown for various water quantity and quality indicators
Taking advantage of the numerous stream gauging stations in the catchment, results could be shown for four locations along the Usserød stream (Grønnegade; Ådalsvej, Parallelvej, Nivemølle) and two locations along the Donse Tributary (Fredtoften, Brønsholmsdalsvej), listed here in order from up- to downstream flow locations along each water course (Figure 2)
Summary
Surface water ecosystems worldwide are deteriorating at an alarming rate under ever-increasing human pressures and climate change [1,2,3], threatening biodiversity and ecosystem services that link to human water security and public health [4,5,6,7]. Anthropogenic changes to the soil surface and sub-surface (e.g., drainage network) have resulted in important flow alterations that can have direct ecological consequences or indirect consequences via water quality impairment stemming from enhanced loads of nutrients or pollutants [8,9,10]. Bioeconomy-related pressures resulting from the drive towards green transition solutions in response to climate change threats may pose additional threats to stream water quality [11]. Streams draining peri-urban landscapes (as defined in [12]) are a prime example of such systems, with great potential to be impacted by the heterogeneous sprawl of urban, industrial, and agricultural activities coexisting with natural areas that may be found sporadically throughout a given catchment. Management decisions regarding stream flow and quality within the peri-urban landscape are extremely challenging. Integrated water quality models, i.e., considering the mutual interaction of flow and quality with potential for integration with the broader socio-economical-ecological system, are essential tools to support water resources management and facilitate decision-making, as advocated in a recent review of water quality models ([17])
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