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Salt intrusion


Two potential operations are at risk. First, the abstraction of the low-flow compensation water at the mouth of major rivers (e.g. the River Exe). Abstraction generally occurs as low down the system as possible, i.e. close to the tidal limits of a particular channel. Sea level rise solely or in combination tidal surges may lead to a greater incidence or further penetration of up-river saline penetration on the high tide (1). This could result in periodic shut-down of the major abstraction pumps. As several abstraction points are relatively close to current maximum saline incursion limits, this is viewed as a long-term threat. A more significant threat is the potential for saline intrusion of key aquifers (2). Others, however, report that saline intrusion into coastal aquifers is currently assessed as a relatively minor issue (3).

In Eastern England saline intrusion into coastal aquifers is already a fact (4). Pumped land drainage for agricultural purposes over the past centuries has lowered the groundwater in the underlying Pleistocene sand and gravel aquifer, with consequent saline intrusion into the coastal portion of the aquifer (5). The ecological impact of increased salinity in the Broads is episodic algal blooms of Prymnesium parvum which can be fatal to fish and some gill breathing invertebrates (6).

A rise in sea-level in the 2080s to an elevation of 57 cm and a 60% decrease in annual actual groundwater recharge under a Medium-high gas emissions scenario may potentially cause saline water to advance 1700 m further inland into the coastal sand and gravel aquifer (7). As a consequence of the shallow depth of saline water in the coastal aquifer, the chloride concentration in coastal drains may increase to about 4000 mg/l in the 2080s.

Salt water intrusion due to sea-level rise is mostly a very slow process that may take several centuries to reach equilibrium (8). Even small rates of groundwater pumping from coastal aquifers are expected to lead to stronger salinization of the groundwater than sea-level rise during the 21st century (9).


The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for the United Kingdom.

  1. Holman et al. (2002)
  2. C-CLIF and GEMRU (2003)
  3. Land Use Consultants, CAG Consultants and SQW Limited (2003b)
  4. Hiscock and Tanaka (2006)
  5. Holman and Hiscock (1998), in: Hiscock and Tanaka (2006)
  6. Holdway et al. (1978), in: Hiscock and Tanaka (2006)
  7. Hiscock and Tanaka (2006a)
  8. Webb and Howard (2011), in: IPCC (2014)
  9. Ferguson and Gleeson (2012); Loaiciga et al. (2012), both in: IPCC (2014)

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