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Understanding the groundwater system of a heavily drained coastal catchment and the implications for salinity management

By Trevor Baylie Simpson

Abstract

The Thurne catchment in north-east Norfolk, UK, is an extremely important part of the Broads National Park, an internationally important wetland environment. Extensive engineered land drainage of the marshes of this low-lying coastal catchment over the past two centuries has led to land subsidence and the need for drainage pumps to control water levels sufficiently below sea-level to maintain agricultural productivity. Consequently, seawater from the North Sea has intruded into the underlying Pleistocene Crag (sand) aquifer and brackish groundwater enters into land drainage channels, thereby raising their salinity. Powerful pumps discharge these brackish drainage waters into a Special Area of Conservation (SAC) and RAMSAR site, leading to adverse ecological impacts on salt-sensitive species. Chloride concentrations within drainage channels throughout the network have been found to significantly vary, with several influential factors affecting channel salinity such as proximity to the sea and connectivity to the underlying aquifer. A thorough understanding of the surface-water/groundwater system and a subsequent quantification of the various processes has been necessary for the development for the drain/aquifer interactions and a numerical groundwater model. These models are used to estimate the long-term distribution of the salinity within the drainage system under current conditions. The model credibility is justified by comparable aquifer-drain water balance, a comparable coast water inflow/ total groundwater ratio and the particle tracking from the coastal reaches trace to previously-measured saline-vulnerable locations. The numerical groundwater model has demonstrated that the average daily inflow of saline groundwater into the Crag aquifer of the Thurne catchment is 3,081 m3/day, of which the HempsteadMarshes main drain is one of the main conduits for saline inflow into the Brograve system, which discharges directly into the SAC. Various changes to the engineering design or operation of the drainage system have been proposed to minimise the saline inflow to the SAC, but the implementation of any proposals must be considered in conjunction with the current dynamics of the system. Three separate management or engineering remedial measures have been modelled: (i) raising the water levels in the drains of the Hempstead Marshes in the north east of the catchment (ii) lining the main drain of the HempsteadMarshes with low permeability material, and (iii) The construction of a new coastal open ditch drain which is intended to ‘intercept’ the saline intrusion and prevent ingress into inland drains of the Brograve system. The results suggest that raising the water levels in the Hempstead Marshes will reduce the saline inflow into the Brograve sub-catchment substantially, and decrease the overall saline inflow into the Thurne catchment from 3081 m3/day to 2822 m3/day). The lining of the main drain in Hempstead produces a less than 10% decrease in saline inflow into the catchment from 3,081 m3/day to 2,958 m3/day. The simulated coastal interceptor drain could in theory through maintaining a low groundwater head near the coast, prevent the inflow of saline groundwater into the Brograve system. However, such a drain would increase the saline inflow across the coastal boundary by around six times (from 3,081 m3/day to 19,750 m3/day), remove large quantities of fresh groundwater from the Pleistocene Crag aquifer and lead to high energy and pumping costs. The research has shown that there are partial solutions to reducing the saline inflow into the drainage systems in this lowland coastal catchment. However, any intended alterations must first consider other potential impacts, such as changes to flood risk, land management restrictions or hydrodynamic effects on the receiving watercourse through changed discharge volumes

Publisher: Cranfield University
Year: 2007
OAI identifier: oai:dspace.lib.cranfield.ac.uk:1826/2460
Provided by: Cranfield CERES

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Citations

  1. (1968). (Notes on the probable results of well drilling near Amsterdam) Tijdschrift van het Koninklijk Instituut van Ingenieurs :
  2. (2001). A continuous radon monitor for assessment of radon in coastal ocean waters.
  3. (1984). A finite element-finite difference alternating direction algorithm for three-dimensional groundwater transport. doi
  4. (1959). A note on the Crag in Norfolk. doi
  5. (1996). A practical guide to groundwater and Solute Transport Modelling.
  6. (1994). A review of techniques for parameter sensitivity analysis of environmental model. doi
  7. (1988). An investigation of uncertainty and sensitivity analysis techniques for computer models. doi
  8. (2003). Anisotropy and depth-related heterogeneity in bog peat II: modelling the effects on groundwater flow. doi
  9. (2002). Applied Contaminant Transport Modelling: Theory & Practice.
  10. (1992). Applied Groundwater Modelling: Simulation of flow and Advective Transport. doi
  11. (2001). Applied Hydrogeology, 4 th edn,
  12. (1987). Assessment of recharge components for a chalk aquifer unit. doi
  13. (1990). Atoll island hydrogeology: flow and freshwater occurrence in a tidally dominated system, doi
  14. (2003). Beach response to shore-parallel breakwaters at Sea Palling. doi
  15. (1961). British Regional Geology East Anglia and Adjoining Areas.
  16. (1984). Chloride ion concentration in dyke water in the Thurne catchment area in 1974 and 1983. Unpublished Report for NCC,
  17. (1984). Comparison of finite difference and finite element methods. In: doi
  18. (1995). Computational Fluid Dynamics: The basics with applications.
  19. (1993). Conceptualisation and Characterization of Hydrological System.
  20. (1994). Controls on saline intrusion in the Crag aquifer of north-east Norfolk.
  21. (1901). Die Wasserversorgung einiger Nordseebaeder (The water supply of parts of the North Sea coast in
  22. (1985). Digital models of groundwater flow in the Cape Cod aquifer system,
  23. (1985). Does the regional groundwater-flow equation model vertical flow? doi
  24. (1972). Dynamics of Fluids in Porous Media. doi
  25. (2007). Effects of Sea-Level Rise on Ground Water Flow in a Coastal Aquifer System doi
  26. (1998). Estimating runoff-recharge in the Southern Lincolnshire Limestone catchment, doi
  27. (2004). Evaluating the use of canal seepage and solute concentration observations for aquifer parameter estimation. doi
  28. (1984). Experiences in the use of East Anglian sands and gravels ('Crags') as a source of water supply.
  29. (1975). Faden's map of Norfolk. Norfolk Record Society.
  30. (1971). First survey of resources and demands Water Resources Act.
  31. (1950). Flow of ground water,
  32. (1990). FLOWPATH, Two-dimensional Horizontal Aquifer Simulation Model. Waterloo Hydrogeologic Inc.,
  33. (2005). Fresh and saline groundwater interaction in coastal aquifers: Is our technology ready for the problems ahead? doi
  34. (1970). Fundamentals of Transport Phenomena in Porous Media,
  35. (2005). Geochemical identification of fresh water sources in brackish groundwater mixtures; the example of Lake Kinneret (Sea of Galilee), Israel, doi
  36. (1994). Geology of the country around Great Yarmouth. London : doi
  37. (1980). Ground-Water Modeling: Numerical Models . doi
  38. (1986). Ground-water resources of Cape Cod,
  39. (1984). Groundwater chemistry in south east Suffolk (UK) and its relation to Quaternary geology. doi
  40. (2005). Groundwater Hydrology, 3 rd edn.
  41. (2006). Groundwater modelling to assess the effect of interceptor drainage and lining. doi
  42. (1990). Groundwater Recharge. A Guide to Understanding and Estimating Natural Recharge 8. International Contributions to Hydrogeology, Verlag Heinz Heise.Trevor Baylie Simpson PhD Thesis
  43. (1985). Horizontal and vertical components of flow deduced from groundwater heads. doi
  44. (2006). Horizontal wells in shallow aquifers: Field experiment and numerical model. doi
  45. (1986). Hydraulic conductivity and related physical properties of peat. Lost River Peatland Northern Minnesota. doi
  46. (1979). Hydraulics of Groundwater. doi
  47. (2001). Hydrogeochemistry of groundwater in coastal wetlands: implications for coastal conservation in Scotland, doi
  48. (1995). Hydrology of soil types: a hydrologically based classification of the soils of the United Kingdom: Report No.
  49. (2006). Improved soil moisture balance for recharge estimation. doi
  50. (2005). Institute of Water and Environment
  51. (2006). Intercomparison of submarine ground water discharge estimates from a sandy unconfined aquifer. Journal of Hydrology 327: 411– 425.Trevor Baylie Simpson PhD Thesis doi
  52. (2002). Inversely estimating soil hydraulic functions using evapotranspiration fluxes. doi
  53. (2007). It Is the Discharge. doi
  54. (1998). Land drainage and saline intrusion in the coastal marshes of northeast Norfolk. doi
  55. (2002). Land Drainage From The Field To The Sea , Wiltshire:
  56. (1987). Lowland Peat In England and Wales. Soil Survey.
  57. (2006). Ltd and Halcrow Group Ltd
  58. (1974). Method of additional seepage resistances theory and applications.
  59. (1977). Middle Pleistocene stratigraphy in southeast Suffolk. doi
  60. (2005). Modeling stream-aquifer interactions with linear functions. doi
  61. (1987). Modelling Groundwater Flow and Pollution. doi
  62. (1970). Modelling partially penetrating rivers on aquifer models. doi
  63. (2002). Modelling stream-aquifer seepage in an alluvial aquifer: an improved losing-stream package for MODFLOW. doi
  64. (2007). Modelling the impacts of land-use and drainage density on the water balance of a lowland-flood plain landscape in northeast Germany. doi
  65. (1992). Modelling transport in transient ground-water flow; an unacknowledged approximation, doi
  66. (1948). Natural evaporation from open water, bare soil and grass. doi
  67. (1990). Nitrogen Inputs to a Marine Embayment: The Importance of doi
  68. (1977). Permissible mesh spacing in aquifer problems solved by finite differences. doi
  69. (1997). Physical and Chemical Hydrogeology. doi
  70. (1979). Possible mechanisms for leakage between aquifers and rivers. doi
  71. (1998). Prediction of regional groundwater flow to streams Ground Water Vol. doi
  72. (1991). Principles and confidence in hydrological modelling.
  73. (2004). Rainfall-runoff Modelling: The Primer. doi
  74. (2000). Recharge through a regional till aquitard: threedimensional flow water balance approach . doi
  75. (2006). Representation in regional models of saturated river-aquifer interaction for gaining/losing rivers. doi
  76. (1992). Research Centre Ltd Unpublished NRA report,
  77. (1996). Runoff curve number. Has it reached maturity? doi
  78. (2004). Saline intrusion and refreshening in a multilayer coastal aquifer in the Catania Plain (Sicily, Southern Italy): dynamics of degradation processes according to the hydrochemical characteristics of groundwaters, doi
  79. (2001). Salt water intrusion in a three-dimensional groundwater system in The Netherlands: a numerical study.
  80. (1992). Salt-water upconing in an aquifer overlain by a leaky confining bed . doi
  81. (1987). Saltwater intrusion in aquifers: Development and testing of a three-dimensional finite element model. doi
  82. (2007). Saltwater intrusion in the unconfined coastal aquifer of Ravenna (Italy): A numerical model. doi
  83. (1979). Seepage and groundwater flow. doi
  84. (2003). Sensitivity analysis for four pesticide leaching models. doi
  85. (2004). Simulated effects of pumping and drought on groundwater levels and the freshwater-saltwater interface on the north fork of Long Island,
  86. (1983). Soil Survey of England and Wales doi
  87. (2001). Submarine groundwater discharge: An unseen yet potentially important coastal phenomenon. Florida Sea Grant publication USGEB–54.
  88. (1984). SUTRA-A Finite Element Simulation Model for Saturate-Unsaturated, Fluid-density-Dependent Groundwater Flow with Energy transport or Chemical reactive Single-Species Solute Transport, U.S. Geological Survey Water Resources Investigation Report.
  89. (1976). The agricultural climate of England and Wales. doi
  90. (2001). The Broads The People's Wetland.
  91. (1991). The effect of tidal fluctuation on a coastal aquifer in the U.K. doi
  92. (1979). The estimation of groundwater recharge. doi
  93. (1964). The flow of fresh water and salt water doi
  94. (1904). The fresh and brackish water crustacea of east Norfolk.
  95. (1981). The Limnology of the Thurne Broads. Unpublished PhD Thesis,
  96. (1960). The making of the Broads. doi
  97. (1939). The Norfolk Sea Flood,
  98. (1938). The Norfolk Sea Floods,
  99. (1980). The record of peat wastage in the East Anglian fenlands at Holme Post,1848-1978. doi
  100. (1984). The reliability of packer tests for estimating the hydraulic conductivity of aquifers. doi
  101. (1979). The sensitivity of parameters in the Penman evaporation equations and direct recharge balance. doi
  102. (1989). The Significance of Vertical Components of Flow in Groundwater, with Special Reference to the Bromsgrove Aquifer. Unpublished PhD thesis
  103. (1962). Unpublished Report for the Happisburgh-Winterton Internal Drainage Board Harr,
  104. (1975). Upconing of the salt-water-fresh-water interface beneath a pumping well. doi
  105. (2004). Validation of Numerical Ground Water Models Used to Guide Decision Making. doi
  106. W (1888) Nota in verband met de voorgenomen putboring nabij
  107. (1999). Water exchange between canals and surrounding aquifer and wetlands in the Southern Everglades, doi
  108. (2000). Water Level Management Plan for Brograve, Including Calthorpe Broad SSSI. Unpublished Report for the Kings Lynn Consortium of IDBs,

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