Modeling the impacts of climate change on nitrogen retention in a 4th order stream

Abstract

Climate induced changes of temperature, discharge and nitrogen concentration may change natural denitrification processes in river systems. Until now seasonal variation of N-retention by denitrification under different climate scenarios and the impact of river morphology on denitrification have not been thoroughly investigated. In this study climate scenarios (dry, medium and wet) have been used to characterize changing climatic and flow conditions for the period 2050-2054 in the 4th order stream Weiße Elster, Germany. Present and future periods of nitrogen turnover were simulated with the WASP5 river water quality model. Results revealed that, for a dry climate scenario, the mean denitrification rate was 71% higher in summer (low flow period between 2050 and 2054) and 51% higher in winter (high flow period) compared to the reference period. For the medium and wet climate scenarios, denitrification was slightly higher in summer (3% and 4%) and lower in winter (9% and 3% for medium and wet scenarios, respectively). Additionally, the variability of denitrification rates was higher in summer compared to winter conditions. For a natural river section, denitrification was a factor of 1.22 higher than for a canalized river reach. Besides, weirs along the river decrease the denitrification rate by 16% in July for dry scenario conditions. In the 42 km study reach, N-retention through denitrification amounted to 5.1% of the upper boundary N load during summer low flow conditions in the reference period. For the future dry climate scenario this value increased up to 10.2% and for the medium climate scenario up to 5.4%. In our case study the investigated climate scenarios showed that future discharge changes may have a larger impact on denitrification rates than future temperature changes. Overall results of the study revealed the significance of climate Climatic Change (2012) 113:981-999 change in regulating the magnitude, seasonal pattern and variability of nitrogen retention. The results provide guidance for managing nitrogen related environmental problems for present and future climate conditions.

High frequency measurements of reach scale nitrogen uptake in a fourth order river with contrasting hydromorphology and variable water chemistry (Weiße Elster, Germany)

“…Natural rivers are assumed to have a higher removal capacity than modified systems [ Kemp and Dodds , ; Opdyke et al ., , Boyacioglu et al . ] and restoration efforts can have a positive effect on nitrogen uptake [ Bukaveckas , ; Stanley and Doyle , ]. Channelization shortens water residence time, one of the primary predictors of N retention [ Seitzinger et al ., ; Wollheim et al ., ].…”

A Review of Water Quality Responses to Air Temperature and Precipitation Changes 2: Nutrients, Algal Blooms, Sediment, Pathogens

“…; Boyacioglu et al. ; Alam and Dutta ) have been shown to increase with temperature. Decomposition and mineralization rates of organic nutrients in soils increase at higher temperatures (Shrestha et al.…”

“…Warmer temperatures generally increase nutrient availability, solubility, and cycling in aquatic and terrestrial ecosystems (Murdoch et al 2000;Kundzewicz et al 2008;Duan and Kaushal 2013). Rates of nitrification (Murdoch et al 2000;Kundzewicz et al 2008;Pourmokhtarian et al 2012), mineralization (Brooks and Williams 1999;Andersen et al 2006;Hartman et al 2014), and denitrification (N loss to the atmosphere) (Murdoch et al 2000;Andersen et al 2006;Battarbee et al 2012;Boyacioglu et al 2012;Alam and Dutta 2013) have been shown to increase with temperature. Decomposition and mineralization rates of organic nutrients in soils increase at higher temperatures (Shrestha et al 2012).…”

“…Decomposition and mineralization rates of organic nutrients in soils increase at higher temperatures (Shrestha et al 2012). The net effects of these changes determine nutrient availability, affecting transport and fate of constituents (Worrall et al 2003;Andersen et al 2006;Boyacioglu et al 2012;Shrestha et al 2012;Alam and Dutta 2013;Hartman et al 2014;Ryberg et al 2018).…”

Challenges and opportunities of German-Chinese cooperation in water science and technology

“…Modeling, amongst experiments and monitoring, is an important tool to explore these relationships (Jeltsch et al 2013). While much progress has been made e.g., to simulate the hydrology, water demand, water quality, biotic communities and ecological functions of river ecosystems or predictions of effects of climate change in running waters (Hejazi et al 2014;Kuemmerlen et al 2014;Schuwirth and Reichert 2013;Jähnig et al 2012;Venohr et al 2011;Döll et al 2009;Schöl et al 2006;Boyacioglu et al 2012;Rode et al 2007;Jiang et al 2014), many modelling approaches are not very realistic in their assumptions, e.g., assuming linear behavior, ignoring regime shifts, uncertainty, or responses of humans to decisions taken, which are typical elements of complex ecoystems, as Schlüter et al (2012) argue. For future water management special attention should be given to the hierarchical organization and longitudinal structure of rivers (Wagenschein andRode 2008, Domisch et al 2015), e.g., to analyse how the biodiversity of specific water bodies are influenced by the spatial arrangement of neighbouring water bodies or to consider scale-dependence in stream networks and their catchments.…”