Water supply and demand management in the Galápagos : A case study of Santa Cruz Island; Dissertation, UNESCO-IHE Institute for Water Education, Delft and TU Delft.

The Galápagos Islands, a province of the Republic of Ecuador, is a volcanic archipelago of significant ecological importance. For centuries, water resources on the islands have been perceived as scarce and consequently, water issues have been recognized as an important and urgent matter. As in many other tourist islands, water resources have been severely threatened by the expansion of the tourist industry. In addition, data regarding water supply and demand are scarce since the vast research carried out on these islands focuses mainly to the conservation of endemic species, putting aside the impact of human activities on water resources. Santa Cruz Island, the hub of tourism of the Galápagos Archipelago, is experiencing significant challenges regarding water quantity and quality. There are no permanent freshwater resources in this island. The municipal system supplies only (untreated) brackish ground water (800-1200 mg/l of Chloride) intermittently. Water scarcity is felt mostly in the town of Puerto Ayora, which is the centre of tourism, where the average supply is three hours per day. In Puerto Ayora, there are no water meters and the water tariff structure is fixed. The municipal supply system has not been able to cope with the current growth in tourism and local population (7% annual growth of tourism and 3.3% annual growth of local population). Non-revenue water ranging from 35% (this thesis) to 70% (previous studies) on the island, poor maintenance and old piping systems adds also to the provision of an erratic service within this island. The research presented in this thesis focuses on water supply and water demand management on Santa Cruz Island. Firstly, water supply was analysed in order to identify the issues contributing to the current situation regarding the intermittency of water supply. Results showed three sources of supply: (1) brackish ground/crevice water distributed by the municipal supply, (2) bottled-desalinated groundwater produced by small private companies and (3) brackish ground/crevice water privately extracted and sold by water trucks. From this study, the estimated quantity supplied per capita (including all three sources) is ±370 lpcpd, which is high compared to the capital city Quito (210 lpcpd). Thereafter, water demand was estimated considering the different demand categories such as domestic households, hotels, restaurants and laundries. Water demand was assessed through approximately 400 surveys (including domestic households, hotels, restaurants and laundries), which were distributed all around the town of Puerto Ayora. The quantification of water demand was performed for each of the three sources previously identified. Results showed that the average per capita demand from the municipal supply was estimated as ±163 lpcpd, which can be considered high for an island with no freshwater resources and intermittent supply for approximately 3 hours per day. Later, in order to verify the specific domestic demand, 18 water meters were installed around the town of Puerto Ayora. In addition, the readings from approximately 300 water meters previously installed on three pilot zones established by the municipality were analysed and compared with the results of the 18 water meters add as part of this study. Both showed very high domestic water consumption, the average obtained from the 18 water meters showed an average demand of 164 lpcpd ± 94 lpcpd of standard deviation. The average domestic demand for the pilot zones were estimated at 182 lpcpd ±31, 195 lpcpd ±80 and 428 lpcpd ±70, for pilot zone 1, pilot zone 2 and pilot zone 3, respectively. In many of the pilot zones outliers were identified with average consumption as high as 4,500 lpcpd, suggesting excessive wastage of water within households and/or informal tourist accommodations, or both. A prognosis of urban water supply and demand was carried out for the next 30 years, for four different annual growth scenarios. These scenarios were: (1) slow growth- 1% for the local population and tourism, (2) moderate growth- 3% for local population and 4% for tourism, (3) fast growth- 5% for local population and 7% for tourism (current situation) and (4) very fast growth- 7% for local population and 9% for tourism. Results showed that without any intervention (business as usual) water demand coverage will barely reach 50% for the slow growth scenario and 10% for the very fast growth scenario. Consequently, five intervention strategies were developed and evaluated as options to solve current and future water scarcity. The strategies included sustainable options such as reducing per capita water demand, installing water meters, reducing leakage, rainwater harvesting and grey water recycling as well as the installation of a seawater desalination plant on the island. These strategies were assessed using several Key Performance Indicators (KPI’s), in terms of water demand coverage with supply, costs and energy use over the next 30 years. Results showed that the intervention strategy involving the installation of a seawater desalination plant is the only strategy that can completely meet the demand in a future 'rapid population growth' scenario, while simultaneously improving water quality (reducing salinity at the tap). However, this is the most expensive and energy intensive solution for the island. The intervention strategy that includes all options, except desalination, will suffice, but only for the 'slow population growth' scenario, which is very unlikely to happen. Afterwards, a Multi-Criteria Decision Analysis was performed, with the aim of evaluating the five intervention strategies assuming a 'moderate population growth' scenario. The strategies were categorized and evaluated under four criteria: environmental, technical, economic and social, and considering four groups of stakeholders: local decision-makers (governmental authorities), local experts (researchers, academia and environmentalists), domestic end-users and hotels. The proposed strategies were finally ranked based on the different stakeholder’s perspectives, providing the preferred strategy considering the selected criteria. Results differed for each stakeholder group: for local decision makers the intervention strategy including the installation of a desalination plant ranked first, while for local experts, domestic end-users and hotels, that strategy was ranked last and they preferred more environmentally friendly options. In addition, a sensitivity analysis was carried out, which showed that the most sensitive criteria are the environmental, technical and social ones, and small changes in the values of their weights may significantly change the ranking of the intervention strategies. In addition, the water supply network of Santa Cruz was evaluated with EPANET software, aiming to assess the current and future performance under the different growth scenarios, using Demand Driven Analysis (DDA) and Pressure-Driven Analysis (PDA) approaches. Each approach suggested that the current network suffices for 24 hour supply, in terms of quantity of water and pressure available within the network. Likewise, the household storage facilities were evaluated, developing a methodology (using the Emitter Coefficient feature of the software) with the aim of estimating water loss (overflow) from roof tanks for several scenarios of water consumption, leakage and storage tank capacity. Results showed that water losses from roof tanks varied from 5 to 32% of the total water supplied in the town of Puerto Ayora. The water demand estimated, as well as water losses within households is surprisingly high for an island where there are no permanent freshwater resources and intermittent supply for three hours per day. Most likely, this is a direct consequence of a fixed water tariff structure, which does not provide any incentive to people to save water. Therefore, any future growth in tourism should be limited. If the very fast tourist growth scenario is defined as a governmental target (9% annually), inevitably, a seawater desalination plant will need to be installed. This will solve water quantity and quality issues, and is independent of the amount of rainfall on the island, but many negative environmental impacts may be generated, especially regarding brine disposal, chemical discharge, energy consumption and fuel importation. For the fast and moderate growth scenarios, the proposed sustainable strategies (including leakage reduction, water meter installation, per capita demand reduction, rainwater harvesting and grey water recycling) would be partially sufficient, suggesting that at least for some activities a smaller seawater desalination plant may need to be installed as well. For the slow growth scenario, the proposed intervention strategy comprising sustainable strategies would be sufficient, suggesting that governmental tourism targets should be re-considered. If current growth trends continue, the overexploitation of brackish water from the basal aquifer may increase the salinity of the supplied water, driving the need for a desalination plant. Therefore, the amount of water that is currently consumed on the island needs to be addressed, fixed water tariffs should be abolished and the governmental targets for tourists visiting the island should be re-considered in order to preserve this fragile and unique ecosystem