Water & Wastewater Asia March/April 2022

IN THE FIELD
and finally emptying into the Gulf of
Thailand, the Chao Phraya was the
birth site of Bangkok, an area that
would blossom into the “Venice of
the East”, attracting commerce and
tourists worldwide.
With growing concern of SI in the
Chao Phrya, the Office of the National
Water Resources released a tender in
2017 for the installation of a series of
continuous water quality monitoring
stations along the river to collect and
transmit data – particularly salinity – to
key stakeholders helping to manage
and mitigate the effects of SI. Green
Banyan, a Xylem Analytics’ partner
in Thailand, was awarded the tender
and began work in 2018, installing 16
monitoring stations along the Chao
Phrya. Each site was equipped with a
Xylem YSI EXO water quality sonde,
along with power and communications
to support the collection and
transmission of water quality data to
monitor the location and magnitude
of saltwater mass intrusion. Each EXO
was cabled to a logger system, where
data was transmitted via modem to the
customer’s server.
without interrupting the collection of
data.
One of the key stakeholders of the
SI-monitoring data programme were
the upstream dam controllers along
the Chao Phraya, who use the data
to help decide when to release water
to help push back the encroaching
saltwater mass; a procedure known
as the “water hammer method”. If
the reservoirs have the available
capacity, the dams can release a
volume of upstream freshwater to
limit the intrusion. Unfortunately,
as has happened in the past, if the
reservoirs are well below capacity
due to drought, front line defences
are compromised, and the “hammer”
option is limited. The decisionmakers
also face the difficult choice
of reservoir water allocation and
utilisation; a trade-off in reserving
freshwater for “hammer ops” at
the expense of farmer’s crops. The
farmers often get the short end of the
stick. They rely on river and reservoir
water to irrigate their crops but have
often been deprioritised when a
significant intrusion occurs, with any
available volume being reserved for
driving saltwater seawards.
WHERE DO WE GO FROM HERE?
This is an extremely complicated
situation with a diverse and expansive
stakeholder list and its concomitant
conflicts of interests, both locally,
nationally and internationally. But
ultimately, something needs to change
before these historically and vital fertile
lands collapse. A variety of solutions
have been proposed, from innovative
integrated farming techniques to
incentivising a reduction in upstream
development like sand mining and dam
building. But so far, the only tangible
actions have been taken at the local and
personal levels.
“Dead fish and dead shrimp, and if
we don’t have a solution soon, dead
farmers too,” explained a Mekong Deltabased
shrimp farmer, who at 62 years
old, has farmed the delta all her life but
is now realising, among many others in
the community, that their way of life may
be coming to an end.
Greg Weiss is South East Asia business
development manager for Xylem (Analytics).
TOOLS OF THE TRADE
For Green Banyan and its customers,
the EXO is at the front lines in the
battle to stay ahead of the salty
silent invader. Its autonomous and
multiparameter capabilities provide
a means to continually monitor
the location and magnitude of an
encroaching saltwater mass. Although
the signature parameter is salinity,
the EXO also provides the flexibility to
measure other parameters, to help fully
characterise the intruding water mass,
such as turbidity, dissolved oxygen,
temperature and others. With its active
biofouling protection in a central wiper,
it can be deployed autonomously for
weeks at a time without cleaning or
calibrating, and more importantly,
30 WATER & WASTEWATER ASIA | MARCH/APRIL 2022