Mobilisation or dilution? Nitrate response of karst springs to high rainfall events

peer-reviewedNitrate (NO3−) contamination of groundwater associated with agronomic activity is of major concern in many countries. Where agriculture, thin free draining soils and karst aquifers coincide, groundwater is highly vulnerable to nitrate contamination. As residence times and denitrification potential in such systems are typically low, nitrate can discharge to surface waters unabated. However, such systems also react quickest to agricultural management changes that aim to improve water quality. In response to storm events, nitrate concentrations can alter significantly, i.e. rapidly decreasing or increasing concentrations. The current study examines the response of a specific karst spring situated on a grassland farm in South Ireland to rainfall events utilising high-resolution nitrate and discharge data together with on-farm borehole groundwater fluctuation data. Specifically, the objectives of the study are to formulate a scientific hypothesis of possible scenarios relating to nitrate responses during storm events, and to verify this hypothesis using additional case studies from the literature. This elucidates the controlling key factors that lead to mobilisation and/or dilution of nitrate concentrations during storm events. These were land use, hydrological condition and karstification, which in combination can lead to differential responses of mobilised and/or diluted nitrate concentrations. Furthermore, the results indicate that nitrate response in karst is strongly dependent on nutrient source, whether mobilisation and/or dilution occur and on the pathway taken. This will have consequences for the delivery of nitrate to a surface water receptor. The current study improves our understanding of nitrate responses in karst systems and therefore can guide environmental modellers, policy makers and drinking water managers with respect to the regulations of the European Union (EU) Water Framework Directive (WFD). In future, more research should focus on the high-resolution monitoring of karst aquifers to capture the high variability of hydrochemical processes, which occur at time intervals of hours to days.Teagasc Walsh Fellowship Programm

A model ensemble generator to explore structural uncertainty in karst systems with unmapped conduits

Karst aquifers are characterized by high-conductivity conduits embedded in a low-conductivity fractured matrix, resulting in extreme heterogeneity and variable groundwater flow behavior. The conduit network controls groundwater flow, but is often unmapped, making it difficult to apply numerical models to predict system behavior. This paper presents a multi-model ensemble method to represent structural and conceptual uncertainty inherent in simulation of systems with limited spatial information, and to guide data collection. The study tests the new method by applying it to a well-mapped, geologically complex long-term study site: the Gottesacker alpine karst system (Austria/Germany). The ensemble generation process, linking existing tools, consists of three steps: creating 3D geologic models using GemPy (a Python package), generating multiple conduit networks constrained by the geology using the Stochastic Karst Simulator (a MATLAB script), and, finally, running multiple flow simulations through each network using the Storm Water Management Model (C-based software) to reject nonbehavioral models based on the fit of the simulated spring discharge to the observed discharge. This approach captures a diversity of plausible system configurations and behaviors using minimal initial data. The ensemble can then be used to explore the importance of hydraulic flow parameters, and to guide additional data collection. For the ensemble generated in this study, the network structure was more determinant of flow behavior than the hydraulic parameters, but multiple different structures yielded similar fits to the observed flow behavior. This suggests that while modeling multiple network structures is important, additional types of data are needed to discriminate between networks

The stochastic simulation of karst conduit network structure using anisotropic fast marching, and its application to a geologically complex alpine karst system

Anisotropic fast-marching algorithms are computationally efficient tools for generating realistic maps of karst conduit networks, constrained by both the spatial extent and the orientation of karstifiable geologic units. Existing models to generate conduit network maps are limited either by high computational requirements (for chemistry-based models) or by their inability to incorporate the effects of elevation and orientation gradients (for isotropic fast-marching models). The new anisotropic fast-marching approach described here provides a significant improvement, though it imitates rather than reproduces actual speleogenetic processes. It can rapidly generate a stochastic ensemble of plausible networks from basic geologic information, which can also be used as input to karst-appropriate flow models. This paper introduces an open-source, easy-to-use implementation through the Python package pyKasso, then describes its application to a well-mapped geologically complex long-term study site: the Gottesacker alpine karst system (Germany/Austria). Groundwater flow in this system is exceptionally well understood from speleological investigations and tracer tests. Conduit formation primarily occurs at the base of the karst aquifer, following plunging synclines. Although previous attempts to reproduce the conduit network at this site yielded implausible network maps, pyKasso quickly generated networks faithful to the known conduit system. However, the model was only able to generate these realistic networks when the inlet-outlet connections of the system were correctly assigned, highlighting the importance of pairing modeling efforts with field tracer tests. Therefore, a model ensemble method is also presented, to optimize field efforts by identifying the most informative tracer tests to perform

Intergenerational family caregiving in welfare policy context

Definition Intergenerational family caregiving refers to exchanges up and down family lines aimed at nurturing the needs of others. Caregiving is more than a task; it involves emotional and relationship work

Timing preferences for women's family life transitions: Intergenerational transmission among migrants and Dutch

This study examines the transmission of preferences regarding the timing of family-life transitions of women among migrant and native Dutch families. We study how and to what extent parental preferences, migrant origin, and family characteristics affect the child’s timing preferences. We use parent and child data (N ¼ 1,290) from the Netherlands Kinship Panel Study (2002, 2003) and the Social Position and Provisions Ethnic Minorities Survey (2002). Regression analyses reveal that parental timing preferences regarding family-life transitions are strongly associated with the timing preferences of their children. Analyses also show that these preferences strongly vary by migrant origin, educational level, and religious involvement.The process of intergenerational transmission, however, is found to be very similar among migrants and Dutch

Parents’ Economic Support of Young-Adult Children: Do Socioeconomic Circumstances Matter?

This paper assesses how the economic support provided by parents to young adults as they complete their education and enter the labor market is related to the family's socioeconomic circumstances. We address this issue using detailed survey data on intergenerational co-residence and financial transfers merged with nearly a decade of administrative data on the family's welfare receipt while the young person was growing up. We find that young people who experience socioeconomic disadvantage are more likely to be residentially and financially independent of their parents than are their peers growing up in more advantaged circumstances. This disparity is larger for financial transfers than for co-residence and increases as young people age. Moreover, there is a clear link between parental support and a young person's engagement in study and work which is generally stronger at age 20 than at age 18 and is often stronger for advantaged than for disadvantaged youths. We find no evidence, however, that a lack of parental support explains the socioeconomic gradient in either studying or employment

Change in the Gender Division of Domestic Work after Mummy or Daddy Took Leave: An Examination of Alternative Explanations

This study investigates how the duration of child care leave taken by mothers and fathers relates to changes in couples' division of housework and child care after postnatal labour market return in Germany. It explores whether take-up of child care related leave may impact the gender division of domestic work beyond the period of leave and examines three theoretical explanations: 1) development of domestic work skills, 2) bargaining power based on economic resources, and 3) adaptations in gender role or parenting identities. Using data from the German Socio-Economic Panel (1992-2012) on 797 and 762 couples with a first or second birth, respectively, we applied OLS regression models with lagged dependent variables in combination with Heckman selection correction. The results suggested that dual-earner couples where mothers took longer leaves experienced a greater shift towards a gender-traditional division of domestic labour after childbirth even in the medium-term after labour market return. The linear relationship and stronger effects on the division of child care than for housework lent support to identity-based explanations. Paternal leave take-up was associated with a more equal division of housework and child care after first births but not after second birth transitions. The relationship with the leave duration was less clear. In terms of explaining the mechanisms for fathers, the findings provided greatest support for explanations relating to domestic skills development possibly in combination with changes in fathering identities