System Dynamic Model for Estimating Water Scarcity in Maldives

Water scarcity has been a major concern for the Maldivians for a long period of time. Limited land area restricts the freshwater quantities, increasing the demand for freshwater. The availability of water is extremely limited due to a fluctuating pattern of rainfall and climate. System dynamic models can be applied to identify the existence of water shortage in a country, as it depends on time with complex interaction between variables. The Maldives consists of 1,200 small islands formed as sandy soil, coral atolls, or limestone islands, where surface water resources are non-existent and freshwater resources are very limited. According to the Maldives Environment and Energy Ministry (2007), the Maldives agriculture sector is already under stress due to poor soil, limited arable land for cultivation, and water scarcity. Rainfall deficiency over the last 18 years indicates that the Maldives islands suffer drought and flood events, with drought events occurring every 9 years and flood events occurring once every 6 years. The factors affecting water balance in the Maldives include precipitation, evapotranspiration, infiltration, groundwater availability, runoff, water usage, and escape water amount to sea. The basic equation for water balance is Water availability for Usage = Precipitation - Evapotranspiration - Runoff. Freshwater lenses occur in coastal regions in many islands and are essential for the local water supply. The freshwater lens is dependent on the width of the island. The availability of water is limiting in the Maldives, as most small islands depend on a single water resource, such as groundwater, rainwater, surface water, or imported water. Per capita consumption of freshwater in most small island countries is increasing, with a growing expectation of 100-150 L/capita per day. The first desalination plant in Malé was installed in 1988 with a capacity of 200 m3/day, and the capacity has been increased steadily to 5,800 m3/day. In Malé, 100 percent of the population has access to piped desalination water. System dynamic models can be applied to identify the existence of water shortage in a country, as it depends on time with complex interaction between variables. Vensim-software for creating system dynamic models is used to identify the water scarcity of each month in Malé, Maldives. The recharge and runoff are calculated using inserted precipitation climatology data, while evapotranspiration is estimated in terms of two sections as potential and actual evapotranspiration. Population and tourist data are extracted from the statistical yearbook of Maldives 2013, and desalination water contribution is considered according to the reports and talks of MWSC. The water scarcity availability is checked by the difference between water demand and water availability in Malé, Maldives. Most of the time, the shortage of water demand is fulfilled by desalination plants in the island. The nature of the freshwater, water demand, management, water availability, and water scarcity availability according to the month are discussed for Malé, Maldives. Results imply that the extractable freshwater availability is low during the first 3-4 months relatively to the last months. The rainwater harvesting water volume is also estimated as a low value due to low rainfall during the first few months, which leads to high water demand in Malé. Overall, the conclusion can be made that the shortage of water is high during the first 7-8 months in Malé, whereas it is low comparatively in other months.