Surface water quality in Costa Rica: new initiatives and challenges

Costa Rica has developed a valuable reputation for sustainable development and tourism as a relatively prosperous, stable, and secure tropical nation with bountiful nature and attractive beaches (Figueres 2008; Fletcher et al. 2020). However, despite its reputation as a leader in environmental policies and management, Costa Rica has severely contaminated surface waters. Principal causes of this surface water contamination are the lack of proper treatment for wastewater, an overreliance on septic tanks in increasingly congested urban areas, and the use of agrochemicals (Ballestero & Reyes 2006; Bower 2014; Hidalgo et al. 2019; MINAE & AyA 2020; Guillén Guardia 2023).

To address deteriorating surface water quality, Costa Rica initiated a new National Wastewater and Sanitation Policy (PNARS is its Spanish acronym) with an ambitious goal of 100% coverage of sewerage systems with treatment in urban areas by 2035, and 100% national coverage of adequate sanitation by 2045 (AyA et al. 2016). Achieving these goals requires planning, funding, coordinated support from multiple agencies, political will, and popular support. Current progress toward achieving these goals has shown numerous challenges including excessive cost overruns, disputes over treatment plant locations, and the long time between project initiation and completion (Taboada 2021; ARESEP 2023).

Costa Rica is a middle-income nation that has been considered to be environmentally friendly and a leader in environmental management (Bower 2014). With a land area of 51,100 km² and 2023 population of over 5,200,000, Costa Rica is one of the most densely populated nations in South and Central America. Over 80% of the population lives in urban areas, and over 50% live in the Greater Metropolitan Area (GAM) (Bower 2014; Guillen-Montero et al. 2021; US Central Intelligence Agency 2024). As an upper middle-income nation, Costa Rica enjoys relatively low levels of poverty, high levels of human development and nutrition, and a diverse economy (Figueres 2008; FAO 2015; Fletcher et al. 2020; World Bank 2023). Costa Rica's social services include a high coverage of chlorinated water supply to households, and a high percentage of households with sanitary waste disposal (Hidalgo et al. 2019; Mora & Portuguez 2021; World Bank 2024). The percentage of Costa Rican households with access to sanitation, which has averaged more than 92%, is similar to the average percentage of OECD member countries (Chacón & Schiel 2022).

The groundwater resources in Costa Rica represent a small fraction (1.4%) of total water extraction in Costa Rica (Herrera Murillo 2017). Aquifers provide a valuable source of freshwater in the GAM, because of the relatively high water quality, and in the northern Pacific zone where water is relatively scarce. As of 2010, there was insufficient baseline knowledge of aquifer water quantity and quality (Bower 2014; Herrera Murillo 2017).

Costa Rica is also noted for its high levels of manufactured agrichemical application. Damages from pesticide application in banana production have been well documented (Ballestero & Reyes 2006). However, a review of pesticide use shows that the major export fruits, banana and pineapple, account for 19–27% of imported pesticides. Coffee uses less than 5% of imported pesticides. Indeed, the nine important crops listed by Ruepert (2011) account for only 35–52% of imported pesticides. This implies widespread use, across multiple crops. Much of this pesticide use occurs in upland vegetable production, which is of particular concern because upstream pollution impacts downstream waters. Meanwhile, Costa Rica uses significant synthetic fertilizers, including the largest amount of nitrogen per hectare of cultivated land in all of the Americas (Ruepert 2011; Castillo et al. 2012; Hidalgo et al. 2019; Pérez et al. 2022; Ritchie et al. 2022).

Pesticides, nitrates, and ammoniacal nitrogen are featured as important indicators of water quality in the 2021 National Plan for Surface Water Monitoring. However, other indicators of nutrient levels and hypoxia, such as total nitrogen, phosphorus, and chlorophyll, are not included as water quality indicators (Dirección de Agua 2021). It should be noted that the Angostura Reservoir on the Reventazón River is highly eutrophic, which is a sign of high levels of nutrient runoff (Umaña-Villalobos 2008; Hidalgo et al. 2019). The widespread use of agrichemicals is important because the policy challenges of reducing nonpoint-source pollution are often more difficult than treating wastewater (Hearne 2021).

Because of the abundance of rainfall across most of the nation, and Costa Rica's short rivers, the need to maintain surface water quality for downstream reuse has been minimal. Many of Costa Rica's rivers have been polluted for decades. The Tárcoles River, which flows from metropolitan San Jose to the Pacific, has been considered the most polluted river in Central America (Bower 2014; Soto-Cordoba et al. 2019). The poor water quality in this river has been given as one reason why offshore commercial fish catches have fallen (Alpízar & Rodríguez 2019; Hidalgo et al. 2019).

Costa Rica has both important commercial and recreational offshore fishing. Recreational fishing mostly serves international tourists (Chacón et al. 2010). Whitewater rafting is an important tourist activity in a number of Costa Rican rivers. The Pacuare River has been noted as one of the top destinations in the world (iExplore, undated). Both the Pacuare River and the Savegre rivers have been temporarily protected from hydroelectricity development from 2015 to 2040 (Presidencia de Costa Rica. 2015). There is minimal freshwater recreation in the Arenal Reservoir, including fishing and windsurfing. There is also artisanal fishing in this large reservoir. But some reservoirs behind hydroelectric dams, such as the Angostura Reservoir, are highly polluted (Lobo & Álvarez 2016). Most Costa Rican lakes and reservoirs host neither recreational nor artisanal fishing (PREPAC 2005).

Costa Rica maintains its reputation of being an attractive, safe, and welcoming destination for international tourism (Braun et al. 2015). From 1995 to 2019, tourism visits and expenditures increased gradually. During this period, tourist expenditures averaged 7.1% of the national Gross Domestic Product (GDP) (Worlddata.info undated). Much of this tourism is associated with nature-based activities. However, freshwater recreation has not been a major attraction. Poor water quality has made bathing in a number of Costa Rica's beach destinations risky to human health (Mora et al. 2019). Thus, there are economic incentives for efforts to improve surface water quality.

Costa Rica's polluted surface water defies its reputation as an environmentally friendly nation that successfully markets its concern for nature to international tourists (Courvisanos & Jain 2006; Braun et al. 2015). Indeed, it has been estimated that in 2002, Costa Rica invested 0.06% of its GDP as payment for its environmental services program, mostly to conserve forest land, which was twice as much as its investment in water supply and sanitation (WSS) services. Costa Rica has 98% coverage of basic sanitation and wastewater disposal and household water supply. These figures are high for the region (Mora & Portuguez 2016; World Bank 2024), yet it has low levels of wastewater treatment. Although Costa Rica is a regional leader in sanitation coverage, only 14% of its population uses treated sewerage systems (TSSs), this is among the lowest in Latin America in terms of conventional treatment. Much of the nation relies upon septic tanks; however, with increased urbanization and population density, and poor construction and maintenance, many of these septic tanks are inadequate (Ballestero & Reyes 2006; Hidalgo et al. 2019; Mora & Portuguez 2016; Mora & Portuguez 2021).

As part of its United Nations' (UN) Agenda 2030 commitments, Costa Rica adopted its 17 Sustainable Development Goals (SDGs) in 2017. In terms of water quality, these goals include improving surface water quality, minimizing chemical discharges, halving the quantity of untreated wastewater, and increased recycling (MIDEPLAN. 2020; OECD 2022; Objetivos de Desarrollo Sostenible: Costa Rica 2023).

Previous literature on Costa Rican water quality include book chapters, journal articles, and government reports. Ballestero & Reyes (2006) present an overview of water quality issues in Central America with a case study on Costa Rica. The authors suggest that Costa Rica has legislation and regulations that could protect its water quality, but these regulations are not enforced. Hidalgo et al. (2019) provides a beneficial diagnostic of water quality in Costa Rica, a review of water management institutions, and a number of case studies of water quality challenges in selected watersheds. The authors emphasize the need for environmental awareness and a revised Water Law. Another set of reports, written by various Costa Rican authors, and published under the State of the Nation program, have addressed challenges in water management, WSS provision, and water quality (Angulo 2015, 2021; Herrera Murillo 2017). A similar review of WSS services was presented by Chacón & Schiel (2022). Some refereed journal articles have featured WSS and water quality issues in Costa Rica. Soto-Córdoba et al. (2019) reviewed wastewater disposal in rural areas of Cartago province and concluded that the potential for future water pollution was dangerous. Bower (2014) reviewed the WSS sector and featured a presentation of surface and groundwater contamination. Shahady & Boniface (2018) reviewed water quality in Costa Rica and discussed community management of water quality. These authors suggest that the legal framework for water quality protection requires community cooperation.

This review builds upon existing literature, government reports, and news articles and expands the understanding of Costa Rican water quality management by addressing recent initiatives and progress toward the objectives of recent policies. It also discusses the incentives for improved water quality and sewerage treatment. This paper focuses on Costa Rica but serves as a case study for other developing nations. In general, TSSs do not present the political popularity of water supply systems and are frequently neglected (Smith & Walker 2019). Many nations face increased urbanization with overreliance on septic systems, poor sewerage and treatment infrastructure, agrichemical use, and overlapping agencies and authorities. This generalized interest in water quality is important because as populations gain income, there is increased demand for environmental quality and acceptance of efforts to improve water quality and attain the UN's SDGs (Choi et al. 2015; World Health Organization 2024). Thus, this review will be of interest to water managers, researchers, and policy makers from many nations. This review will proceed with a quick overview of Costa Rican water management institutions. New initiatives to address water quality will be discussed along with progress in reaching recent goals. The paper will conclude with policy recommendations.

Despite the ambition of the PNARS policy goal, Costa Rica has maintained its divided institutional framework for water resources management. There are a variety of laws dictating water management and a variety of involved agencies. The National Water Law of 1942 stipulates that all water is a national asset. The Constitution was amended in 2020 in order to declare that potable water is a human right and water management should prioritize human consumption. The equitable use of water was reinforced in the National Water Policy of 2009 (MINAE 2009). A number of executive decrees have established the nation's regulatory authority over wastewater. These include the following: Decree No. 33601-MINAE-S, 2007, which states that all wastewater should be treated before discharge; Decree 39887-S-MINAE, 2016, which establishes requirements for wastewater treatment facilities; Decree 33903-MINAE-S, 2007, which establishes protocols for water quality monitoring and classifying surface water for different uses; Decree No. 32133-S, 2004, which mandates public finance and implementation of wastewater treatment; and Decree 34431-MINAE-S, 2008, which establishes payment for all wastewater discharges into public waters. These regulations do not specify the quality of water discharged from TSSs, nor the quality of water to be maintained in surface water bodies (Ballestero & Reyes 2006; AyA et al. 2016; Chacón & Schiel 2022; Villareal & Wilson 2022).

Absent from the review of pertinent regulations in the PNARS are regulations of the most common form of disposal in Costa Rica, septic tank systems. Rules concerning septic tank design, construction, and flows are specified in Decree 42075-S-MINAE (2020). Although this regulation does not prohibit septic tank system construction and use in urban areas, it does restrict use where sewerage systems are in place and where authorities prohibit them (AyA et al. 2016; Presidencia de Costa Rica 2020).

The PNARS lists the roles of a number of pertinent agencies (see Table 1). The Ministry of Energy and the Environment (MINAE) is in charge of maintaining water resources, its Water Directorate grants water-use and discharge permits. The Health Ministry (MS) regulates potable water quality, wastewater discharges, and the location of wastewater treatment plants. And the Public Services' Regulatory Authority (ARESEP) regulates WSS providers.

The Costa Rican Institute for Aqueducts and Sewerage (AyA) is the agency in charge of financing and developing potable WSS systems. It operates much of the nation's water supply systems, especially in the San Jose metropolitan area. However, many other regional, municipal, and community organizations (known as ASADAS) have developed and operated their own water supply systems, which AyA supervises. As of 2017, AyA supplies water to 49% of the nation's populace. As the three lead agencies in wastewater transport, treatment, and regulation, MINAE, AyA, and MS are the coauthors of the 2016 National Policy on Sanitation and Wastewater. Table 1 presents an overview of agencies involved in the WSS sector (Ballestero & Reyes 2006; AyA et al. 2016; Herrera Murillo 2017; Chacón & Schiel 2022).

The agencies involved in WSS in Costa Rica include national (AyA), regional (The Heredia Public Services Company (ESPH)), municipal, and community service providers. A variety of institutions have been successful in providing improved potable water service and basic sanitation. Economic theory enlightens the contrast between the high level of coverage of basic WSS services and the low level of coverage of wastewater treatment. Potable water supply and waste removal services can be considered to be private goods. Because these services can be excluded from those who do not pay, it is feasible for WSS providers to support their activities through user fees. However, water quality in downstream rivers is very much a public good, being non-excludable and non-rival in consumption. Thus, there is no direct incentive to pay for these services. Indeed, the beneficiaries of a wastewater treatment plant (WWTP) are not the populace being served by the sewerage system. It is downstream water users that benefit from water quality. However, it is common for WSS providers to require customers to pay for both water supply and sewerage services with treatment.

It should be noted that the low percentage of residential sewerage wastewater treatment does not imply low levels of industrial wastewater treatment. The PNARS reviews industrial wastewater disposal, and shows that while 84% of residential wastewater enters rivers untreated, 55% of industrial effluent is untreated, while 36% is reused. One explanation of this is the unequal application of the fee for discharging wastewater in natural water bodies. Another explanation is the initiative of the Costa Rican Chamber of Industry. The Chamber has promoted reduced waste and cleaner production through incentives and ISO certification. One particularly important source of agroindustrial wastewater in tropical America is coffee processing. This has been a traditional source of industrial effluent in many countries and brought health concerns in Costa Rica. Eventually, the MS was ordered to protect water quality from coffee processing discharges. These efforts to reduce wastewater contamination from coffee processing are often complementary to processes promoted by certification programs that increase producer prices (Ballestero & Reyes 2006; AyA et al. 2016; Hidalgo et al. 2019; Muthamma & Shankarappa 2020).

A number of recent governmental initiatives have addressed surface water quality. Among the first of these initiatives is the fee charged for disposal of commercial and industrial effluent into natural water bodies. This fee is an economic instrument to provide incentives for polluters to reduce pollution or pay for the discharge. Since all industrial and commercial point-source discharges need to be permitted, these discharges can be taxed under a ‘polluter pays’ principle. The fee, as implemented, is for levels of Biochemical Oxygen Demand and suspended solids. Fee implementation has been challenging because of lack of monitoring staff and reliance on reports from polluting businesses, who have not universally reported. Also, as noted by Sánchez-Gutiérez & Villalobos (2020), the level of the fee is too low to compensate for the complete environmental damages. WSS providers such as AyA have not been required to pay this fee. The fee was initially implemented in 2008, and as of 2017, only 45% industrial wastewater is either reused or receives treatment. Thus, low fees and administrative difficulties have impeded the effectiveness of this program (Ortega 2006; Caffera 2011; AyA 2016; Sánchez-Gutiérez & Villalobos 2020).

Another major initiative is the San Jose Metropolitan Area Environmental Improvement Project (PMAAMSJ), which features an extensive grid of sewerage canals and the Los Tajos WWTP. Although the project is executed by AyA, it also serves sanitation services of ESPH and other WSS providers. Los Tajos is the largest WWTP in Central America and is expected to treat wastewater from the entire GAM. The project can serve over 1,000,000 residents, but has significant unused capacity due to the incomplete network and slow pace of household connections. In early 2023, it was treating 700 L/s of wastewater, although it has the capacity to treat four times that quantity. The project was initiated in 2006 and is scheduled for final completion in 2024. There have been significant delays and cost overruns. The WWTP currently performs preliminary and primary treatment, although more advanced, secondary, or biological treatment would be required in order to meet the norms of Decree 33601-MINAE-S (MINAE & AyA, 2020; Lara 2022; Mora & López 2023).

In 2016, the PNARS was released and appeared to have launched a major initiative (AyA et al. 2016). The policy paper clearly states that water quality has deteriorated due to lack of WWTPs and that compliance with the SDGs is at risk. The inconvenience of mixed institutional roles for a variety of agencies is noted. And the lack of institutional capacity in monitoring discharges and water quality is also accepted. The policy maintains the actual institutional structure of water management with the goal of strengthening the institutional and technical capacity of wastewater management. It imposed a goal of 100% coverage of densely populated areas with sewerage systems with WWTPs by 2035. This goal expands to 100% coverage in other priority areas by 2045. The plan also proposes new monitoring for septic tank systems (AyA et al. 2016).

The PNARS also presented an initial plan to finance this investment and promised a more detailed National Sanitation Investment Plan. The investment plan specified an initial governmental seed grant of 15% of estimated investment costs. The seed grant could be augmented periodically by the government, but most of the required investments would be financed through user fees. The PNARS also allowed for private sector investment and expertise through public–private partnerships in WWTPs.

The 2017 National Sanitation Investment Plan (PNIS) clarifies some of the PNARS, provides an algorithm for prioritizing investments, and specifies a framework for financing of PNARS infrastructure. The PNARS goal of 100% coverage of treated sewerage in densely populated areas, by 2035, was clarified to include municipal areas with populations greater than 100,000. These municipalities are all in the GAM. All but the cities of Alajuela, Cartago, and Heredia are included in the Los Tajos WWTP service area. The rest of the nation's urban areas should have sewerage systems by 2036, with treatment by 2045. Rural areas should have approved sanitation systems, either septic tanks or treated sewerage, by 2045 (AyA 2017a). The PNIS provides criteria for prioritizing WWTP investments, which include environmental impact, population served, economic impact, and sunk costs (AyA 2017a).

The financial plan detailed in the PNIS was previously mentioned in the PNARS. The PNARS's coverage goals are estimated to cost US $6.2 billion (in 2017). This investment implies a 290% increase over actual investments. However, the PNIS proposes an alternative prioritization of the following: (1) the remaining areas of the GAM still not covered by the PMAAMSJ, (2) coastal tourist areas, and (3) current sewerage systems without proper WWTPs. In total, this reduced initial goal was estimated to cost US $1.644 billion (AyA 2017a, 2021).

The PNARS of 2016 proposed additional initiatives include the following: geographic information systems mapping to identify areas not suitable for septic tanks; improved university curriculums in sanitation; and a national plan for monitoring surface water quality. The 2013 and 2021 National Plans for Monitoring Surface Water Quality establish fairly rigorous norms for measuring surface water quality and testing for numerous contaminants in 32 basins. This is a program of MINAE's Water Directorate. As of early 2023, complete monitoring of all surface water has not been implemented. Only a few, basin specific, water quality monitoring reports have been made available. A complementary plan for monitoring surface water quality, which was promised in 2013, has not been released. A few reports of aquifer-specific water quality have been available (Dirección de Agua, undated; Dirección de Agua, 2013; Zeledón, 2013).

A complementary initiative is the 2020 National Strategy for the Recuperation of Urban Watersheds (MINAE & Aya 2020). This initiative addresses the need to reduce solid waste disposal in rivers, the benefits of interurban biological corridors, and the need to improve urban river water quality. This document also addresses the challenges of household connections to sewerage systems. Sewerage pipes are generally located in a street, in the front of a house. Most plumbing systems would lead to a septic tank located at the back of a house. Thus, relocating the plumbing discharge from a residence often implies a costly rerouting of piping. Noteworthy in their absence are the following: any mention of flood drainage, floodplain maintenance, and floodplain recreation such as urban greenways.

Since 2000, the percentage of the Costa Rican populace using septic tanks has gradually increased, from 60 to 77%. Since the release of the PNARS in 2016, the percentage has remained relatively stable at 77%. This implies that the absolute use of septic tanks continues to rise, but not quickly. Perhaps, investors are being cautious before installing septic tanks in an area that would eventually be expected to be included in a sewerage system. Meanwhile, the percentage of the populace using TSSs has gradually risen (Angulo 2021). This rise of the percentage of population with treated wastewater corresponds to the expanded connections to the Los Tajos WWTP across the GAM. However, the PMAAMSJ and the Los Tajos WWTP have experienced significant delays and budget shortfalls (Porras 2020; Rodriguez 2020; Martinez 2022). As a result of the delays in meeting the PNARS goals, Costa Rica has been stagnant in meeting its SDGs (WHO & UNICEF 2021; OECD 2022; SDG Transformation Center, 2024).

A number of new WWTP and sewerage system projects have been initiated since the 2016 PNARS (see Table 2). As seen in Table 2, these new investments clearly feature tourist areas on both the Pacific and Caribbean coasts. None of these investments occur in the GAM. Many of these systems are financed by external loans guaranteed by the central government. It should be noted that the November 2021 estimated completion dates listed in Table 2 are, on average, 7.3 months later than the estimates shown in an earlier 2021 document. This delay corresponds to the COVID-19 pandemic of 2020–2021 (Angulo 2021; AyA 2021).

Investment in TSSs in coastal areas should address potential concerns over beach water quality (Mora et al. 2019). However, there have been disagreements between AyA, which is developing these projects, and coastal communities. It is obvious that the construction and operations costs of coastal sanitation systems would be reduced with a WWTP close to the beach near the center of population to reduce construction and operation costs. However, beach communities do not want WWTPs to reduce the value of beach views and beach real estate. The communities of Jacó and Golfito have both had newsworthy challenges to WWTP location decisions. This is especially concerning due to the ecological fragility of the Dulce Golf adjacent to Golfito. Construction has been delayed by these disagreements (Chacón 2019; Granados 2020; Taboada 2021).

As presented in Table 1, ARESEP audits WSS service providers. An ARESEP audit report of 76 of AyA's sanitation investments, for the years 2016–2021, criticizes the agency's performance (ARESEP 2023). These 76 projects include the major investments provided in Table 2 as well as a number of small projects affiliated with the sewerage system and canals of the PMAAMSJ, and a number of small pipe replacement and building projects. Among the findings of this audit are the following: the lack of a master plan for sanitation investments; excessive cost overruns due to poor planning and management and the long time between project initiation and completion; and the lack of insurance for investments. The audit suggests that the concentration of AyA's effort in urban areas has been detrimental to rural and coastal areas. And although ARESEP's expertise is financial review, the audit report suggests that the poor execution of sanitation investments implies high costs to users and negative impacts on health, tourism, and the economy.

Similarly, ARESEP audited the ESPH in 2020. One of the major conclusions was there persists a very low coverage of adequate sewerage infrastructure. ESPH serves 23,414 clients in the sewerage service (32% of drinking water users); of these, only 5,386 receive wastewater treatment service (following the national standards on this subject). ESPH does not collect the rest of the wastewater generated by 68% of the clients (ARESEP 2020).

The ambitious goals of the 2016 PNARS imply a large-scale investment in urban sewerage systems and treatment plants. This implies both the inconvenience of digging new pipes in city streets and the need to reroute household sewerage connections from septic tanks, which are often placed in the rear of the house, to the street sewerage pipes (MINAE & AyA 2020). These inconveniences could imply real household costs in addition to the system construction costs.

Given the current rate of progress toward the coverage goals of the 2016 PNARS, it is obvious that reaching these goals will be very difficult. The revised goals of the 2017 PNIS, which prioritize TSSs in cities with populations above 100,000 by 2036, are still achievable, with significant effort. The 2017 PNIS's clarification of urban areas and principle cites is a valuable contribution. However, there are many densely populated urban areas with populations less than 100,000 that would eventually need TSSs in order to meet the goal of adequate coverage. Constructing sewerage systems and treatment plants for these urban centers by 2045, while ensuring proper septic tank systems in rural areas by 2045, will also be a difficult goal to achieve (AyA et al. 2016; AyA 2017a).

In recent years, Costa Rica has taken initial steps in addressing its poor surface water quality. The initiative outlined in the 2016 PNARS should eliminate much of the untreated point-source pollution that has deteriorated Costa Rican surface water. The goals of the 2016 PNARS may prove to be too difficult to achieve within the 2035/2045 time frame. And the implementation of these goals may not be sufficient to ensure good quality surface water.

Achieving the PNARS goals is a means to a desired goal of improving surface water quality. These will entail significant costs including land acquisition for WWTPs and the corresponding local opposition to the negative amenities of WWTPs; capital investment and operations and maintenance costs to the system operators; transportation and inconvenience costs as sewerage systems are constructed on public roads; and household connections costs. Public understanding and acceptance of these costs will be important to successfully adopt TSSs, especially as many urban areas are required to switch from septic to treated sewerage.

As noted, the challenges that face Costa Rica in improving its surface water quality and meeting its SDGs are common across many nations. With increased urbanization, reliance on septic tanks and latrines becomes less feasible. And investments in TSSs are costly. However, as incomes grow, nations will invest more in water quality. The need to perceive downstream water quality, and treated sewerage, as a public good is common across circumstances. All nations need to address the water quality impacts on their industrial, residential, and agricultural sectors. It should be noted that legislation and regulations are insufficient to protect water quality. Implementation of policies through monitoring, enforcement, and investment is required. Policymakers and water managers from many nations would benefit from an understanding of the challenges presented in Costa Rica and the nation's experiences in addressing these challenges.

One strategy for gaining the populace's support is to promote clean surface water's benefits to the Costa Rican people. Costa Ricans are active consumers of their beaches and natural areas. Unfortunately, generations of Costa Ricans have learned that most lakes and rivers are unsuitable for swimming and fishing. Urban rivers are not considered to be attractive for floodplain recreation in parks and trails (MINAE & AyA 2020; Instituto Costarricense de Turismo 2022). The benefits of improved water quality can be promoted by providing a guarantee of water quality that will enable investment in freshwater recreation and a sense of security among recreators. Currently, the National Water Quality Mentoring Plan states that classification of water bodies results from monitoring. However, it is possible to impose an exogenous goal of making certain lakes and rivers swimmable and fishable. This would target comprehensive water quality efforts toward certain water bodies that are suitable for recreation. An obvious start would be Lake Arenal and the Pacuare and Savegre Rivers, which are already protected from hydroelectric dam construction. Other reservoirs and rivers could be designated for this status. Once this water quality goal is accepted, the demand for waterborne recreation in these water bodies would be expected to increase and attract investment.

The financial investment required by the ambitious goal of the 2016 PNARS is large. The 2016, PNARS suggests that user fees will cover the majority of these costs. Given the large initial capital construction cost, this reliance on user fees may be unrealistic. As noted, while cost recovery is very appropriate for most WSS services – because households receive excludable and rival benefits – TSSs provide improved downstream water quality, which benefits society as a whole. Thus, it would make sense to disaggregate expenditures and have the central government accept the cost of treatment plants and the main pipes to these plants. This disaggregation would make the central government responsible for the costs of the non-excludable and non-rivalled water quality benefits and users responsible for the WSS services that benefit households directly.

Costa Rica has maintained a fragmented institutional structure for water and water quality management as well as WSS services. This institutional structure has been criticized for deficiency in policies and capacities (Ballestero & Reyes 2006). However, it should be noted that the WSS services have been relatively good except for wastewater treatment. However, to increase coverage of treated sewerage services and improve surface water quality, further evolution of Costa Rica's water institutions may be beneficial. One example of this institutional evolution is the use of the Los Tajos WWTP to treat water from a variety of WSS providers.

Despite the massive effort to adopt treated sewage systems in order to meet the stated goals of the 2016 PNARS, much of rural Costa Rica will continue to rely on septic tank systems. Septic systems in Costa Rica have been noted for poor construction, causing groundwater contamination, and inadequate drainage (Ballestero & Reyes 2006; AyA 2017b; Hidalgo et al. 2019). Although septic systems are regulated by Decree 42075-S-MINAE (2020), the effectiveness of these systems has not been analyzed. Efforts to construct TSSs should be complemented by efforts to ensure that septic tank systems are adequate, with proper drainage and periodic emptying. One goal of the 2016 PNARS was the establishment of a complete geographic information systems mapping of Costa Rica's water resources. This effort should be completed and used to identify where septic systems threaten aquifers used for water supply systems (AyA et al. 2016).

Reducing point-source pollution generally involves the high costs of infrastructure development and treatment plants. However, nonpoint-source pollution is more elusive in terms of policy prescriptions. Costa Rican farmers use large amounts of agrichemicals because they have direct financial incentives to do this. One way to limit agrichemical use is to tax these chemicals and increase the costs of their application. This would limit their overuse and incentivize precision application to reduce runoff.

This research was supported by a Fulbright US Scholar Grant and the National Institute of Food and Agriculture, US Department of Agriculture, under Project No. ND01315. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author and do not necessarily reflect the view of the US Departments of State nor Agriculture, nor the Institute of International Education. These funding sources were not involved in study design, analysis, report writing, or the choice of publishing outlet.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.