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.
Total 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.
In Costa Rica, 2020 projections for water demand for all uses are estimated to reach , equivalent to 35% of the total water resources available. The key challenge is to properly manage the 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 over-exploitation from domestic, industrial, and agricultural demand. by matthew.t
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 makes 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-borne 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 loss 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.
Dispute with Nicaragua over the San Juan River
Dating back two hundred years, there have been disputes over the management and usage of the San Juan River forming the border between Nicaragua and Costa Rica. The San Juan River has long been viewed, for both countries, as offering the promise for a canal route across Central America. This was the case when the Panama Canal site was chosen rather than the San Juan River as the ultimate ship navigation route across the Americas. The conflict between Nicaragua and Costa Rica continues. The Nicaraguan government announced in August 2009 that it will begin construction at the end of September 2009 to reroute the San Juan River, which runs along the country's border with Costa Rica.
The head of the committee for development of the San Juan River in Nicaragua said that the $1 million project is intended to "recover the 1,700 m3 p/sec of water that was lost after Costa Rica rerouted it toward its Colorado River between 1945 and 1950." Costa Rica responded, issuing a statement that said a ruling by an international court "forcefully denies Nicaragua's wish to dredge a new route on the San Juan River." In July 2009 the United Nations’ International Court of Justice unanimously reaffirmed Nicaragua's sovereignty over the river and upheld the ban that does not allow Costa Rican police and military forces to use the river. Nicaragua's exclusive sovereignty over the San Juan River was established in 1858 with the Cañas-Jerez treaty.
According to the 151-year-old Cañas-Jerez treaty, the San Juan River is fully Nicaraguan property; however, Costa Rica can use the river freely for transport, without any restrictions from its neighbouring country. Costa Rica says Nicaragua is reneging on its obligations by requiring visas and forcing Costa Rican boats to stop for military inspection on the northern bank. All passengers are made to pay a $5 fee and every boat must fly the Nicaraguan flag. Nicaragua also banned commercial fishing by Costa Rican fisherman in retribution of Costa Rica initiating the ICJ suit in 2005.
Water resource base With an average width of 120 km, Costa Rica receives about 170 km3 from rain and about 75 km3 finds its way into the rivers and lakes of Costa Rica and yet another 37 km3 ends up in underground aquifers. The remaining water is lost through evaporation and evapotranspiration. Costa Rica is divided into three major slopes or basins. The Atlantic side is the wet and rainy side and rarely experiences a deficit of water throughout the year. The Atlantic sloping side incorporates the Northern slope that drains into the San Juan River bordering Nicaragua and also towards the Caribbean Sea. The sub-basins within this slope contribute 5.8 km3 annually to Lake Nicaragua and more than half of the water that flows into the San Juan River or around 23.2 km3 The Pacific slope is more dry with a shared decline in average flow during the dry season. In total, there are 34 principal drainage basins in Costa Rica with 17 having a major sloping contour and range in size from 207 km2 to 5,084 km2.
Groundwater and Surface water resources
Groundwater is the primary water source in Costa Rica where it accounts for nearly 90% of Costa Rica's agricultural, industrial, and domestic water demands with the exception of hydroelectric generation. Volcanic activity has formed highly permeable subterranean layers within the fragmented igneous lava. This phenomenon coupled with high rainfall has created the formation of aquifers in the central and northern part of Costa Rica's Central Valley, where more than half of the population lives. These aquifers are called the Upper and Lower Colima and are separated by a layer that acts as a semi-permeable aquitard, which allows the descending and ascending vertical transfer of water.
It has been estimated that the Lower Colima extends for approximately 230 km2 and that the Upper Colima spreads over approximately 170 km2. The Upper Colima aquifer is recharged from the Barva and La Libertad aquifers by vertical percolation. The Upper Colima also receives a large part of its recharge from rain infiltration in those areas where there are no overlying smaller aquifers. The Lower Colima is recharged from the Upper Colima by vertical percolation and from surface water where the Upper Colima is absent.
The average recharge of the aquifer system was calculated in 1990 at 8200 L/s. The depth of the water table level varies, depending on the surface topographical irregularities; but, generally it ranges between 50 and 100 m. The direction of the underground flow is from north-east to south-west in both aquifers. Surface water is represented by approximately 13 major rivers, with many adjoining tributaries that range in length from . Costa Rica's major reservoir is Lake Arenal.
Water quality While drinking water is good in many parts of the country, there are still many concerns about the quality of water in streams and lakes. It has been estimated that surface water pollution is a threefold problem. Untreated effluents from urban wastewater (only 3% of wastewaters receive treatment) account for 20% of the problem, 40% from solid waste and industrial effluents (heavy metals are the primary culprit), and 40% from the agricultural sector. In the agriculture sector alone, 70% of pollution comes from debris of coffee plantations. Water basins that are receiving large quantities of contaminated runoff include the Grande de Tárcoles and Large Terraba rivers.
+Key characteristics of the major climatic regions Region Land area (km2) Rainfall by depth (mm/year) Rainfall by volume (km3/year) Surface run off (km3/year) Infiltration (km3/year) Evapotranspiration (km3/year) Chorotega 9,552.4 2,006 19.2 5.7 3.5 10.3 Huetar Norte 9,001.5 3,527 31.8 14.9 9.6 7.5 Huetar Atlántico 9,688.5 3,933 38.1 17.6 9.3 11.1 Pacífico Central 4,722.9 2,801 13.2 5.2 2.2 4.9 Central 8,543.2 3,461 29.6 13 7 8.6 Brunca 9,294.5 3,809 35.4 18.6 5.6 12.2 Total 50,803 19,537 167.2 75.1 37.3 54.7 Source: FAO
Water resources management by sector
Drinking water and usage In general, water quality is acceptable for drinking in the urban areas as well as many rural areas. The Government of Costa Rica understands tourism to be the primary driver of the national economy, and more attention has been paid to improve the potable water systems throughout the country. Costa Rica has the highest demand of water, both in total and per capita measures. Per capita water usage is about 1860 L p/day amounting to 5% of total available groundwater and surfacewater. Remaining Central American countries use on average of 3% of total supplies.
About 60% of the Costa Rican population lives in urban areas. Considerable focus has been targeted to expand water services to cities over the last decade. Approximately 99% of the urban populations are connected to water services, which is higher than the 90% average for the rest of Latin America. Connection to the public water supply in rural areas of Costa Rica is about 92% representing about 1.56 million inhabitants.
Urban (61% of the population) Rural (39% of the population) TotalWater Broad definition 100% 92% 97% House connections 99% 81% 92%Sanitation Broad definition 89% 97% 92%Sewerage 48% 1% 30%
Irrigation Agriculture accounts for 6.5% of Costa Rica's GDP and 14% of the workforce. Costa Rica irrigates around 21% of its land under cultivation relying primarily on surface water.
The irrigation sector is managed by The National Irrigation and Drainage Service (SENARA).
Two striving irrigation districts of note that are different in size, and means of execution are: 1) Arenal-Tempisque Irrigation District (DRAT) which is a much larger district than the latter and grows staple crops; 2) and the Irrigation and Drainage of Small Areas (PARD) is smaller but benefits more families than DRAT and focuses on higher value crops.
Arenal-Tempisque Irrigation District (DRAT):