|dc.description.abstract||This report discusses the findings of a social and environmental impact study under the
proposed integrated water resource management project in Gadhdhoo, Gaafu Dhaalu Atoll.
The project is proposed by United Nations Office for Project Services (UNOPS).
The project is targeted at providing potable water to the community and improving the
rainwater recharge. Potable water is provided by a combination of rainwater and desalinated
water, which is a new and unique project for the Maldives. The recharge well system is even
more unique. Consequently, several discussions have been held with the Ministry of
Environment (represented by EPA), Ministry of Housing and Infrastructure and UNOPS to
discuss the several issues. The issues were re-visited during the scoping meeting, the main
issues identified by the EPA being the size of the rainwater tanks and good management of
the system to ensure that most of the rainwater is used and desalinated water is depended
upon as a supplementary source. EPA also has issues with the proposed recharge wells with
the main concern lying in the possibility that the recharge wells may help to cause flooding
during storm water. However, the project engineer is quite certain that this was not likely and
this was also backed by the EIA Consultant.
At present Gadhdhoo does not have a piped water supply system and groundwater is used
unanimously for all purposes with the exception of bottled water and rainwater for drinking.
Several efforts have been made in the past including the construction of public rainwater
tanks with public tapbays, which was later replaced by household rainwater tanks of 2500l at
each household for easier access but with some compromise on water quality issues.
Rainwater, however, could not be depended upon during long, dry periods during the
northeast monsoon. With changing climatic patterns worldwide, rainwater can rarely be
depended upon. With lack of space for appropriate rainwater collection facilities combined
with groundwater contamination and salinization has been seen to cause various health and
environmental problems including water-borne diseases. The dependence on groundwater and
untreated rainwater is often a cause for concern. Therefore, an integrated water supply system
with sustainable groundwater resource is an immediate need for the people of Gadhdhoo,
which has a population of over 2899 people in September 2012. The proposed integrated water supply system is designed for maximal use of rainwater
supplemented by desalinated water for an average water demand of 50-70 litres per person per
day. Raw water is proposed to be drawn from a borehole with 8’’ casing and pumps to pump
the raw water to the treatment plant. The treatment for the water is proposed by using Reverse
Osmosis technique. The plant will be run by diesel engine and the possibility of alternative
energy options such as solar and wind will be considered. The pure water after treatment is
collected in glass or fibre-reinforced plastic tanks of adequate capacity determined for
Gadhdhoo to be 900m3 based on EPA guidelines. The water thus collected is introduced in the
network so as to reach all the households, institutional and commercial areas with adequate
residual pressure through HDPE pipes. The distribution network is designed for over 35 years
while the water tank capacity has been based on 15 years as per Government requirements.
The proposed IWRM project also comprises of a mechanism to recharge groundwater using a
collection of recharge wells made of concrete that will run along the main roads as well as the
island periphery. Direct recharge of groundwater is minimized due to urbanisation as
permeability is reduced and infiltration surface is minimized. Therefore, this process is
assisted by the use of recharge wells that will direct the excess rainwater from roofs to the
groundwater lens. However, it must be noted that these recharge wells are not anticipated to
cater for storm water drainage. The sole purpose of these wells is to assist groundwater
recharge so that the groundwater lens may be sustainably managed.
Environmental impacts were assessed for both the construction and operation phase of the
project. Most of the environmental impacts of the project have been identified as positive
resulting mainly from easy access to safe water supply, improvements to groundwater quality
and resulting reduction in water-borne and water-related diseases and improved health of the
population. The socio-economic benefits of the project may be considered to outweigh the
negative impacts of the project. There are a few negative impacts of the project including the
minor impacts of landuse related to the project, however, no clearing is envisaged. The impact
of clearing, if any, would be compensated by replanting mature trees in other areas of the
island and, if necessary, planting additional trees. The impact of brine discharge is also
considered minor or negligible especially due to the fact that there is no coral cover in the
proposed brine discharge location and good mixing will occur due to currents in the area.
Since the pipeline is a pressure system, the pipes will be laid above the water table and no
dewatering will be required. Hence, no effect on the groundwater lens. Other minor negative impacts include excavation to lay the water distribution network and brine discharge pipe.
One of the impacts of the proposed recharge wells would be space constraints to services on
the road and the impact would be mitigated by appropriate planning for locating recharge
wells and sewerage manholes as well as other such services. The other impact of the proposed
recharge wells would be that there may be clogging of the pipes and such clogging may lead
to unnecessary flooding in some areas where clogging occurs, especially in areas easily prone
to flooding following rain. However, clogging is expected to occur over the long-term,
therefore, it is not possible to do field tests to verify this.
It has also been seen that recharge is also not much of a use if pumps are used to draw water
from the groundwater aquifer, which leads to rapid salinization of the water lens during the
dry period. Recharge of groundwater lens also occurs over a large surface due to rainfall. If
we consider the sustainable yield estimated for Gadhdhoo, it can be seen that no amount of
recharge will help to overcome the problems related to salinization due to increasing use of
pumps. In fact, the Maldives receives well over 2000mm of rainfall, which would be more
than sufficient to recharge the aquifer. Yet, the aquifer, similar to a rainwater tank, has its
maximum capacity limits and cannot overgrow the impact imposed by high rates of
abstraction. Therefore, only sustainable rates of pumping can ensure sustainable management
of the aquifer. It has been observed from studies carried out for Malé that freshwater exists in
pockets. Where the drawn down effect is high, due to the size of pumps and rate of pumping,
there is a tendency for the water lens to become more saline at the location where the
drawdown is greater. This draw down or lowering of the water table at the point of
abstraction, sometimes referred to as the “coning effect” for the freshwater lens, can only be
avoided with the use of appropriate technology such as skimming wells and infiltration
The main mitigation measure for the proposed project would be to identify measures to
minimize drawdown on the aquifer including the introduction of skimming wells by
improving existing wells and enhancing water conservation techniques. The proposed concept
of recharge wells is still at a preliminary stage, therefore, it is proposed that the detailed
design takes into consideration the findings of this Environmental Impact Assessment, and
consultations with the community and relevant government agencies, especially the EPA.
After discussions with the engineers, it is believed that the system will retain water and about
500m3 of rain will be retained to slowly recharge the aquifer during the dry period or periods with prolonged duration without rain. However, the main problem with the salinization of the
aquifer and the making full use of the sustainable yield of the island’s small aquifer lies with
the fact that drawdown and coning effect due to the use of pumps in household wells and not
with recharge. Also, the potential impact of recharge wells contributing to flooding in a floodprone
island like Gadhdhoo is of significance, such a system is not recommended.
It is inevitable that there would be some negative environmental impacts. However, most of
the impacts of the proposed water supply system are minor compared to the positive effects of
the proposed system. Yet, monitoring to ensure the effectiveness of the proposed system
would be necessary. Therefore, a monitoring component has been suggested which takes in to
consideration, the most important elements that require regular checks. This monitoring
component will be adhered to and will allow the assessment of changes due to construction
and implementation of the proposed water supply system and aquifer recharge system.
Monitoring is specifically focussed on water quality, to include feedwater from the borehole
(or other source), collected rainwater, groundwater, product water at designated locations and
seawater at brine discharge location (upstream and downstream). Reef or marine ecological
monitoring may be considered if the proposed location of the brine discharge or intake is
found to be of ecological significance.
In conclusion, it appears justified from a technical and environmental point of view, to carry
out the proposed project to install and operate a piped water supply scheme using rainwater
supplemented by desalinated water. However, the recharge well scheme needs to be further
evaluated and possibly replaced by or integrated with an alternative scheme such as
converting existing household wells to skimming wells to minimize salinization of the