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DELTARES, September 2016
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More reports on
www.deltares.nlT
he water in the Eems Dollard area
is getting turbid and ecological
problems are increasing. On
6 July 2016, the Dutch national
government and the provincial authority
of Groningen adopted the multi-year
programme ‘Eems-Dollard 2050’ with the
aim of improving ecological quality and
sustainable economic development. Deltares
and Imares have identified activities that will
be required and provided the basic elements
required to tackle this challenge.
After centuries of land reclamation, the
number of places where sludge can settle
in the Eems-Dollard river area has been
severely reduced. Until the mid-1990s,
excess sludge was still removed by dredging
shipping channels and ports.
The goal is to remove 1 million m³ of sludge
a year from the area in time. This sludge
can be used to strengthen dikes or for soil
improvement. Between now and 2020,
Deltares will be involved in pilot projects for
the removal of sludge from the system. The
beneficial use of sludge, and the costs and
benefits, will also be studied.
PLASTIC WASTE
A THREAT TO
PUBLIC HEALTH
Large plastics break down into particles and
even, in the end, into nanoparticles. People
are exposed to those particles through our
food, drinking water and even the air. This
represents a potential threat to human
health. The pathogens that can bond to
microplastics and spread in that way are a
new danger. For example, in more vulner-
able delta areas where sanitation facilities
are not so good, and where waste water is
hardly treated, if at all, there is a major risk
of infection and infectious diseases because
people bathe in polluted rivers. This is the
conclusion of Professor Dick Vethaak of
Deltares and the VU-University of Amster-
dam and Dr. Heather Leslie, who also works
at the VU-University, in a recently published
article. It is still unclear to what extent these
plastics endanger human health. The two
authors therefore argue for more research
into the effects of plastics on health.
FRESHWATER SUPPLIES ON ISLANDS
PROTECTED FROM SALT WATER
The small oceanic islands in the Caribbean and the Pacific are largely dependent on fresh
water lenses in the subsurface. But those freshwater supplies are seriously under threat due
to sea-level rise, coastal erosion and over-exploitation. A Deltares innovation could help to
protect them: Seepcat. Seepcat captures seepage water, the saline groundwater that flows
towards the freshwater lenses. The smart ‘seepage barrier’ was tested in the the Perk Polder
(Netherlands) last year in collaboration with Rijkswaterstaat. It consists of a series of vertical
pipes that are inserted to a depth of between 15 and 25 metres in the subsurface near the
coast. The pipes capture the saline groundwater and take it back to the sea. That prevents
the shrinkage of the freshwater lens and – in the right conditions – even allows it to grow.
Groundwater experts Perry de Louw and Gualbert Oude Essink presented their findings
in early July 2016 at the International Salt Water Intrusion Meeting (SWIM) in Cairns,
Australia. The seepage system generated a lot of interest. The Deltares researchers are now
looking for an island where they can conduct further tests with the system.
SLUDGE CLEARANCE IN EEMS DOLLARD
PHOTO: MARCEL TAAL