Heterogeneous land uses characterize river basins worldwide and result in complex landscape mosaics and mixed natural-rural-urban watersheds. Whereas the assessment of changing land use effects on runoff production is a codified practice, knowledge of the role of landscape patterns in determining water quality along streams is less developed. In particular, high yields of suspended solids triggered by intense anthropogenic land uses constitute an emerging concern worldwide due to, e.g., the environmental peril of sediment bound pollutants and light limitations endangering stream ecosystems. Understanding drivers of pollution caused by suspended solids is a growing research subject that demands robust approaches to describe the behaviours of heterogeneous watersheds, estimate loads in the receiving streams, and predict outcomes of growing urbanization and landscape restoration efforts. In the first step of the PhD project, archetypical patterns of landscape organization and related concentration-discharge relations will be identified. The second step covers the modeling of how landscape organization affects stream particulate loads and the evaluation of mosaics that are most prone to infringe regulatory thresholds. Finally, landscape mosaics that may mitigate water quality stress and buffer climate change effects will be assessed.
Safae's webpage

Stream networks collect loads of water and solutes from the catchment, and patterns of these loadings can be observed at the outlet. However, the situation of losing water from stream to groundwater can exert strong influences on the solute source composition and discharge at the catchment outlet. Long-term exploitation of groundwater and climate change may even exacerbate the losing conditions with the decline of groundwater. The first part of my PhD project will be the case study in the Bode catchment. By the build-up of the data-driven stream network model, we hope to quantify the losing conditions in this catchment and figure out their effects on the solute source composition. Meanwhile, we will simulate the situations of high and severe low flow in the model to better understand the impacts of extreme events. Following the last part, the temporal variability of losing and gaining conditions in the Bode catchment and the Suwannee River in Florida will be investigated then. Based on the research findings from the first two parts, we will work on the upscaling tasks at a larger scale possibly with the help of artificial intelligence (AI), such as in Germany or even Europe. The expected results will be the identification of losing-prone areas of the major European rivers and their trend in the future.

Nutrient concentrations in freshwaters are influenced by internal loading from sediments, which in turn rely on microbial metabolism. Specifically, benthic primary production provides labile sources of organic matter, thus increasing the mineralization of organic phosphorus (P) forms through enzymatic hydrolysis. Also, reducing conditions due to metabolic activity result in the dissolution and mobilization of mineral-bound P. These microbial processes promote substantial P-diffusive flux from sediments, increasing the risk of internal eutrophication even without additional external P inputs like wastewater. In the current climatic context and because of the higher frequency of extreme events like droughts, the role of P-release from benthic sediments is expected to gain importance due to higher temperature, longer water residence time, larger sediment/water ratio, and less external nutrient loadings. However, droughts do not occur alone but both coincide and interact with additional stressors. In this context, morphological degradation, specifically, may modify benthic nutrient uptake in freshwater ecosystems. From a floodplain perspective, morphological degradation is defined by the loss of connectivity between streams and floodplain waterbodies. In this PhD project, the influence of droughts and morphological degradation on microbial processes modifying the nutrient release from sediments will be studied. For this, the microbial processes and internal P loads in sites with varying hydrological connectivity from the Elbe river will be studied in the first step. The overarching goal of the project is to define a safe operating space to minimize the risk of internal eutrophication in floodplains.

On average about 30% of the global population experience severe water scarcity annually. The proportion is even bigger when both water quality and quantity are taken into consideration. With climatic and socio-economic changes, the water crisis will most likely worsen. This, essentially implies a multitude of conflicts among water uses and users. However, effective water governance strategies can be deployed to mitigate the water crisis and the resultant conflicts, and ensure sustainable water use and ecosystem health. In this study, we aim at developing – through reanalysis and modelling – an adaptive water governance framework that can be utilized to ensure sustainable water-use and ecosystem health. The study is piloted at the Möhne reservoir subcatchment in the North Rhine-Westphalia state, Germany. The sub-catchment represents a multidecadal time machine for hydroclimatic changes, socioeconomic dynamics and water governance by the Ruhrverband. The study will address four key questions:

i. How have the drivers and pressures of the reservoir water status changed over time?

ii. How have the water governance structures changed/responded over time?

iii. How has the water quality and quantity changed over time?

iv. What are the likely future drivers, pressures and governance structures/responses?

Faluku's webpage

My PhD project is part of the project MeskalMon that aims to improve our understanding of suspended matter routing (including mineral and organic suspended matter, as well as nutrient and contaminant transport) through river systems. MescalMon applies remote sensing techniques to detect water quality parameters Chlorophyll-a (Chla) and turbidity or suspended sediment concentration (SSC) along long river channels of several deka-km. The methodological concepts couples remotely sensed data in the form of satellite, UAV, and multispectral camera images with in-situ data gathered data by various acoustic and optical sensors, Chla probes, spectrometer probes, in-situ particle size analyzers and manual water sampling. In conjunction with ADCP (acoustic Doppler current profilers) applications the large-scale flow field if river channels will be measured, which facilitates the analysis of the hydraulics of river systems and the longitudinal, lateral and vertical mixing of suspended matter and associated nutrients and contaminants. Due to the cross-scale concept of the MeskalMon approach, my PhD aims to advance the scale transfer from local in-situ measurement to larger scale river reaches and catchments.
In context of TRACER my PhD focuses on the human induced water stresses or loading (L) in terms of the transfer of contaminated suspended matter and algae blooms through river systems. The expected outcome of the PhD - a broader understanding of Chla and turbidity/SSC dynamics within rivers - improves water quality monitoring and management and represents a key element within the field of water security. Furthermore, the cross-scale approach imbedded in the PhD potentially provides valuable information for scale-transfers from local measurements to catchment integrated understanding of anthropogenic loadings.

PFAS are ubiquitous and highly persistent in the environment because of their wide industrial applications and chemical structure respectively. PFAS can be introduced to the environment via several channels including atmospheric deposition, plant uptake, irrigation water, firefighting foams, and land application of previously anthropogenic waste including by-products of wastewater treatment plants. Beneficial reuse of biosolids and wastewater in agricultural production simultaneously promotes soil health and sustainability. However, mounting concerns over possible contamination of water sources is driving regulatory entities to consider banning all land applications of PFAS-containing residuals. Therefore, my current research considers the magnitude and the potential of groundwater contamination with PFAS from lands receiving biosolids compared to other sources of PFAS in the environment and sustainable ways to mitigate identified risks. Overall, the study involves a combination of field, laboratory, and modeling initiatives to investigate and improve the understanding of PFAS occurrence and fate in agricultural systems and their impact on rural water resources. The study investigates two major concerns, namely, impact of extended irrigation activities and biosolid applications on PFAS accumulation in soil and groundwater, and detection of PFAS in private wells serving rural communities. Furthermore, modeling data will be employed to aid in identifying landscape, hydrological, and soil characteristics that are most appropriate for receiving biosolids or treated wastewater with minimal impact on water and crop resources.

 Which parts of the landscape are the most significant sources of solutes to streams? Where in the stream network, and how frequently, should we measure solute concentrations to identify both sources and transformations? Recent technical advances of in-situ sensors enable high-frequency measurements of discharge and water quality and help to close the gap between divergent spatial and temporal scales of water quality processes and observations. High-frequency time series can shine light on the temporal variability of stream runoff, which is highly dynamic in time and strongly correlated in space. Solute source zones, however, are heterogeneously distributed in space, leading to important cost- and information trade-offs when designing monitoring programs. Recent work examining solute spatial vs temporal variability suggests spatial variability is significantly under-appreciated. The aim of this study is to setup a space-time variance framework and to understand the origins of spatial vs temporal water quality patterns in respect to geographical, anthropogenic, hydrological and climatological drivers.

Nutrient and chemical pollution of emerging contaminants (e.g. pharmaceuticals) from diffuse sources (e.g. agriculture) and point sources (wastewater discharges) are well-known pressures reported for river ecosystems. The European Water Framework Directive (WFD) implemented monitoring programs across river networks for the definition river basin management plans to achieve the required good ecological and chemical status. However, permanent and consistent monitoring of many water quality parameters at large river catchments requires huge effort by governments and environmental agencies. Moreover, measured environmental concentrations (MEC) are often constrained to fixed sampling points with low temporal resolution, from which statements about longitudinal substance dynamics at different time points are prone to be very uncertain. Here, the use of in-stream water quality models and substance-routing models is crucial to fill spatiotemporal data gaps from monitoring networks, track the behavior of waterborne substances and conduct spatial risk screening. This PhD project will focus to track longitudinally nutrient dynamics and some pharmaceuticals along river networks with high spatiotemporal resolution. Based on available lagrangian and eulerian data of MEC of water quality parameters and spatiotemporal enriched prescription data of pharmaceuticals, different in-stream water quality models and parsimonious substance-routing models will be employed depending on the river catchment scale. Multiple tailored lagrangian and multisite calibrations will be performed to identify site-specific transformation rates. With this, the environmental risk assessment across different river networks can be enhanced by accurate risk-exposure screening of critical pollution in space and time. The findings of this study are expected to help by the implementation of effective mitigation strategies.