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Title: Environmental impact assessment for the proposed integrated water resource management project AA. Ukulhas
Authors: Sandcays
Keywords: Legislative and regulatory consideration
Project description
Stakeholder consultations
Existing environment
Environmental impacts
Project alternatives
Socio - ecocomic aspects
Environmental management plan
Issue Date: Sep-2013
Citation: Sandcays. (2013). Environmental impact assessment for the proposed integrated water resource management project AA. Ukulhas. Male': Maldives
Abstract: This report discusses the findings of an Environmental and Social Impact Assessment carried out for the proposed Integrated Water Resource Management (IWRM) project in Ukulhas, Alif Alifu Atoll. The project is proposed by Ministry of Environment and Energy. The project is targeted at providing potable water to the community through a water supply scheme based on rainwater harvesting supplemented by desalination during the dry period. This kind of scheme has not been previously introduced to the Maldives and is considered a unique project for the Maldives. One of the primary objectives of the project is climate adaptation and mitigation of impacts of climate on basic human needs such as water supply. The project is undertaken with support from the EU/Aus.AID funded Climate Change Trust Fund (CCTF) managed by the World Bank. At present Ukulhas 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. 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 salinisation 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 that incorporates maximum rainwater harvesting supplemented by desalination and sustainable groundwater management is an immediate need for the people of Ukulhas, which has a population of over 1,000 people in mid-2013. It shall be noted that sustainable groundwater management is not within the scope of this project or the EIA report, although it is considered an integral part of any IWRM project in the Maldives. The proposed water supply scheme is designed for maximal use of rainwater supplemented by desalinated water for an average demand of 70 litres per person per day and a minimum of 20 litres per person per day for cooking and drinking during emergencies and extreme climatic conditions, as recommended in the Guidelines for IWRM Projects. The proposed scheme consists of rainwater collection from public roofs to a number of storage tanks, treatment works including desalination and chlorination and final distribution to households. Project Engineers have come up with various scenarios using different combinations of harvested water and RO water for supply. Among the scenarios, harvested water from public building roofs along with RO plant has been found to be the best option. As per the prevailing requirements by EPA, a minimum of 25% supply has to be from rainwater harvesting. It has been worked out that optimum supply of water is 25 lpcd which balances both the need of the people and follows the standard. 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. The main negative impact of the project is the diesel-based power system and resultant emissions, which has minor to moderate negative cumulative impacts. However, since rainwater is the primary source and desalination is supplementary to the proposed rainwater system, the power requirement is expected to be much lower than depending on RO desalination technology alone. There are a few negative impacts of the project including the minor impacts of landuse. 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. 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 Ukulhas, 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 galleries. The main mitigation measure for the proposed project would be to identify maximum public roof areas for rainwater collection and measures to minimize drawdown on the aquifer including the introduction of skimming wells by improving existing wells and enhancing water conservation techniques. Awareness on water conservation and sustainable groundwater management is key to sustainable water supply schemes, therefore, increasing awareness is considered an important mitigation measure. Mitigation measures have also been identified for the proposed reverse osmosis process including the use of solar desalination technology, however, this is not a must due to the small size of the project although it is desirable. Also, the use of lagoon intake wells instead of sea intakes or deep boreholes are important measures to mitigate the high energy costs related to the desalination component. It is inevitable that there would be some negative environmental impacts. However, these 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. Monitoring is specifically focussed on water quality, to include feedwater, collected rainwater, groundwater, product water at designated locations and seawater at brine discharge location (upstream and downstream). Reef or marine ecological monitoring has not been considered under the project. 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.
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