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Costa Rica is divided into three major drainage basins encompassing 34 watersheds with numerous rivers and tributaries, one major lake used for hydroelectric generation, and two major aquifers that serve to store 90% of the municipal, industrial, and agricultural water supply needs of Costa Rica.〔 Agriculture is the largest water user demanding around 53% of total supplies while the sector contributes 6.5% to the Costa Rica GDP. About a fifth of land under cultivation is being irrigated by surface water. Hydroelectric power generation makes up a significant portion of electricity usage in Costa Rica and much of this comes from the Arenal dam. Both total and per capita water usage is very high in comparison to other Central American countries but when measured against available freshwater sources, Costa Rica uses only 5% of its available supply. Urbanization is increasing and as it does, demand for water is expected to rise exponentially in the coming decades. There exists ample water but the threat of widespread contamination to the aquifers is legitimate as untreated wastewater, stormwater, and industrial effluents infiltrate subterranean supplies.〔 Additionally, the government and water management institutions are facing a water conveyance infrastructure that is in decline; therefore, non-revenue water losses within the system are increasing. Modernization projects are underway led by the Environmental Ministry in Costa Rica with the assistance of multi-lateral development banks where the aim is to address this infrastructure challenge as well as to help mend a fragmented system of water management institutions.〔 ==Water management challenges== In Costa Rica, 2020 projections for water demand for all uses are estimated to reach 39 km3, equivalent to 35% of the total water resources available.〔 The key challenge is to properly manage the exponential growth in demand from 5% to 35% of available water resources. Urban development continues to increase the pressure on water resources and the use of water and groundwater in particular is becoming increasingly more complex due to rapid urbanization and overexploitation from domestic, industrial, and agricultural demand.〔 Unsustainable land use practices are threatening to degrade watersheds and are adding to the growing complexities of managing groundwater. Additionally, the volcanic aquifers consist mainly of interstratifications of gaps and fissures which allow for high permeability and infiltration. In many cases, these make the aquifers highly vulnerable to human contamination from the cities in which they support. The heterogeneity of these aquifers make them complicated to study and manage. Consequently, growing signs of conflict and competition for water use between sector needs are being observed in some regions.〔 Another considerable challenge in Costa Rica is the lack of a monitoring and maintenance for potable water and the problem has precipitated a higher incidence of water-born illnesses. In response, the Health Ministry created a system of vigilant monitoring of the quality of water, illnesses, population migration, environmental sanitation, vulnerability of the aquifers, lakes, and rivers. The Health Ministry also analyzes and approves environmental impact studies as they pertain to the drinking water supply, regulates the quality of water being delivered to citizens.〔 The state of the water conveyance infrastructure is not good and large amounts of water are lost or not accounted for. Water losses from the delivery and conveyance systems is referred to as non-revenue water and losses are estimated at 50%. This problem exists because of deficiencies in the physical structures, use of outdated technologies, and inadequate maintenance.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Water resources management in Costa Rica」の詳細全文を読む スポンサード リンク
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