Palaeo-hydrological reconstruction of a managed fen area in The Netherlands
Introduction
Many fen plant species have become endangered due to worldwide land reclamation and environmental degradation of fens (Millennium Ecosystem Assessment, 2005). Environmental degradation of fens consists of acidification, eutrophication and desiccation. These processes are often induced by anthropogenic interferences into the regional hydrology of fens (Lamers et al., 2002). Counteraction of these interferences by active water management aims at sustainable conservation of the remaining populations of endangered fen plant species, and the re-establishment of fen plants in areas where they have disappeared. However, hydrological restoration strategies have not been particularly effective so far, possibly, due to insufficient knowledge of the human impact on the hydrology of managed fens. The present study aims at providing new insights into the long-term changes of the groundwater supply of a managed fen area in The Netherlands.
Most endangered fen plants are typically found in nutrient-poor fens, which have a low biomass production (Wheeler and Shaw, 1991). These so-called low-productive fens develop at minerotrophic, acid-buffered, and moderately nutrient-rich sites (Bedford et al., 1999, Sjörs and Gunnarsson, 2002). These sites are usually associated with areas of groundwater discharge for two reasons. Firstly, areas of groundwater discharge receive excessive amounts of water, i.e., groundwater and precipitation, which results in shallow groundwater tables and reduced conditions in the shallow subsurface (Boomer and Bedford, 2008, De Mars and Wassen, 1999). Secondly, weathering products dissolved during flow are transported with the groundwater to the fen surface. Both reduced conditions and the presence of weathering products in the shallow subsurface, are essential for buffering the acidity at a near-neutral pH level (Almendinger and Leete, 1998) and limiting nutrient availability for plant growth (Boyer and Wheeler, 1989, Olde Venterink et al., 2002).
Many of the processes underlying the environmental degradation of low-productive fens are reinforced or induced by a decrease of the groundwater supply of fens (Barendregt et al., 1995, Fojt and Harding, 1995, Lamers et al., 2002). A decrease of the groundwater supply of fens may cause desiccation if the consequent water deficits are not counterbalanced by an increased supply of precipitation (Schot et al., 2004) or surface water (Van Wirdum, 1991). However, these shifts in the origin of water supply affect the biogeochemical processes determining the acidity and nutrient availability in fens (Almendinger and Leete, 1998), and may cause acidification or eutrophication of fens (Beltman et al., 2000, Smolders et al., 2006). Therefore, the restoration of groundwater flow to low-productive fens is thought to be a prerequisite for the preservation of threatened fen plant species in intensively managed areas (Fojt and Harding, 1995, Wassen et al., 1990).
The design of effective hydrological fen restoration strategies requires insight into the causal relation between water management and the evolution of groundwater systems. Numerous studies have been performed on the evolution of groundwater systems in the past by analysing (Lamentowicz et al., 2007) or reconstructing (Pons and Oosten, 1974) botanical peat deposits, performing groundwater model exercises (Schot and Molenaar, 1992) and comparing intensively managed areas with near-natural areas (Wassen et al., 1996). These studies suggest that the groundwater supply of managed fens decreased with anthropogenic developments. However, none of these studies provided a quantitative analysis on the evolution of groundwater systems driven by natural and anthropogenic developments. Obtaining this lacking knowledge may improve the current insights into the anthropogenic impacts on the hydrological key-processes that underlie the environmental degradation of low-productive fens in intensively managed regions like The Netherlands.
In this paper, we analyse the naturally and anthropogenically driven evolution of groundwater systems that discharge into an intensively managed fen in The Netherlands using a series of three-dimensional palaeo-groundwater models at a high spatial and temporal resolution. These palaeo-groundwater models are based on a thoroughly underpinned and complete reconstruction of geohydrological conditions in the past. The purpose of this model exercise is to analyse past shifts in the groundwater supply of fens, and to disentangle the effects of subsequent natural and anthropogenic developments on the groundwater supply of fens.
Section snippets
Study area and its historical development
The palaeo-hydrological reconstruction was performed for the Gooi- and Vechtstreek area in The Netherlands (52°03′N–52°20′N and 5°00′E–5°18′E; Fig. 1). The study area was selected because (1) sufficient geo-scientific knowledge and data is available to perform a reconstruction of past geohydrological conditions on a high spatial resolution and (2) human domination of the current hydrology is large, due to a series of hydrological changes that have occurred in the past, many of which are
General
Five time slices were defined according to the timing of natural and anthropogenic developments that were expected to underlie the major transformations of the groundwater system configuration in the past (Fig. 2). From a comparison of these five time slices, insight into the evolution of the groundwater systems in response to natural and anthropogenic developments was deduced.
For each time slice, groundwater flow was simulated with a stationary groundwater model based on the MODFLOW-code (
Results
The results of the palaeo-hydrological reconstruction are depicted in Table 5 and Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8. We distinguish three phases of landscape development according to the evolution of geo-hydrological properties of the river valley (Fig. 4): the accumulation phase, the stagnation phase and the degradation phase. Below we describe the co-evolution of geo-hydrological properties and groundwater systems during these phases.
Methodological approach
In this study, we analyzed the naturally and anthropogenically driven evolution of groundwater systems using a series of three-dimensional palaeo-groundwater models. Similar to many palaeo-groundwater models such as presented by Sanford and Buapeng, 1996, Piotrowski, 1997 and Van Weert et al. (1997), the palaeo-models presented in this paper could not be validated, because quantitative reference data is only available for the last few decades, and not for the past time slices. Nevertheless, we
Conclusion
The results of the present study provide new insights into the impact of anthropogenic hydrological interferences on the groundwater supply of fens on a regional scale. The finding of an increased groundwater discharge flux into managed fens after the initiation of water management opposes the hypothesis that a decreased groundwater flux to fens underlies the environmental degradation of fens in intensively managed regions (Barendregt et al., 1995, Fojt, 1994). Instead, the palaeo-hydrological
Acknowledgements
The authors would like to thank Henk Weerts and Jan Gunnink for their contribution to the palaeo-geographical reconstruction of the studied fen during natural conditions, Ype van der Velde and Ruth Heerdink for their technical support with the construction of the groundwater models, Henk Kramer for providing the historical land use map of The Netherlands, Rebecca Elkington for proofreading the manuscript, and two anonymous reviewers for their suggestions to improve the manuscript.
References (66)
- et al.
Hydrological systems beyond a nature reserve, the major problem in wetland conservation of Naardermeer (The Netherlands)
Biological Conservation
(1995) - et al.
Influence of nested groundwater systems on reduction–oxidation and alkalinity gradients with implications for plant nutrient availability in four New York fens
Journal of Hydrology
(2008) Dehydration and the threat to east anglian fens, England
Biological Conservation
(1994)- et al.
Long-term effects of drainage on species richness of a fen meadow at different spatial scales
Basic and Applied Ecology
(2005) Subglacial hydrology in North-Western Germany during the last glaciation: groundwater flow, tunnel valleys and hydrological cycles
Quaternary Science Reviews
(1997)- et al.
Regional changes in groundwater flow patterns and effects on groundwater composition
Journal of Hydrology
(1992) - et al.
Calcium concentrations in wetland groundwater in relation to water sources and soil conditions in the recharge area
Journal of Hydrology
(1993) - et al.
The dynamic form of rainwater lenses in drained fens
Journal of Hydrology
(2004) - et al.
Water-level changes in the Flevo area, central Netherlands (5300–1500 BC): implications for relative mean sea-level rise in the Western Netherlands
Quaternary International
(2005) - et al.
The effects of Pleistocene glaciations on the geohydrological system of Northwest Europe
Journal of Hydrology
(1997)
Quarternary geological mapping of the lowlands of The Netherlands, a 21st century perspective
Quarternary International
Peat characteristics and groundwater geochemistry of calcareous fens in the Minnesota River Basin, USA
Biogeochemistry
Seepage, a new modflow drain package
Ground Water
Patterns in nutrient availability and plant diversity of temperate North American wetlands
Ecology
Internal eutrophication in peat soils through competition between chloride and sulphate with phosphate for binding sites
Biogeochemistry
Modeling hydraulic conductivity of a complex confining layer at various spatial scales
Water Resources Research
Draining–digging–dredging; the creation of a new landscape in the peat areas of the low countries
Vegetation patterns in spring-fed calcareous fens, calcite precipitation and constraints on fertility
Journal of Ecology
Simulation of the influence of solar radiation variations on the global climate with an ocean-atmosphere general circulation model
Climate Dynamics
Redox potentials in relation to water levels in different mire types in The Netherlands and Poland
Plant Ecology
Efficiency and accuracy of per-field classification for operational crop mapping
International Journal of Remote Sensing
Thirty years of change in the vegetation communities of three valley mires in Suffolk, England
Journal of Applied Ecology
Palaeoecological evidence for anthropogenic acidification of a kettlehole peatland in northern Poland
The Holocene
The restoration of fens in The Netherlands
Hydrobiologica
Cited by (17)
Flood mapping with remote sensing and hydrochemistry: A new method to distinguish the origin of flood water during floods
2011, Ecological EngineeringCitation Excerpt :However, palaeo-ecological studies have revealed that a distinct zonation in species composition of plant remnants occurs in river floodplains, indicating a spatial distribution of different water types (Bakker et al., 1976; Oświt, 1994). The three potential sources of water are precipitation water (or chemically similar snowmelt water), groundwater discharging into the floodplain or river water (Schipper et al., 2007; Van Loon et al., 2009). Testing if the spatial distribution of current vegetation is linked to these different water sources during floods is at present impossible in most floodplains since they are reclaimed and used for agriculture.
Linking habitat suitability and seed dispersal models in order to analyse the effectiveness of hydrological fen restoration strategies
2011, Biological ConservationCitation Excerpt :Subsequent land subsidence has resulted in the current ground surface levels being below sea level (Fig. 1a). This has resulted in a complex spatial configuration of exfiltration zones, and exfiltrating groundwater has become increasingly intercepted by drainage networks instead of being laterally redistributed by throughflow (Van Loon et al., 2009a,c). Particularly the latter is thought to contribute to the fragmented configuration of habitat remnants within a matrix unsuitable for fen plants.
Influence of organics and clastic lake fills on distributary channel processes in the distal Rhine-Meuse delta (The Netherlands)
2009, Palaeogeography, Palaeoclimatology, PalaeoecologyThroughflow as a determining factor for habitat contiguity in a near-natural fen
2009, Journal of HydrologyMaximum Holocene groundwater levels and associated extension of peat in the border zone of 'Het gooi' (the Netherlands): A reconstruction based on the study of soil transects
2020, Geologie en Mijnbouw/Netherlands Journal of GeosciencesRestoration of brook valleys by rewetting
2021, Landschap