Regulatory Challenges for the Use of Reclaimed Water in Mexico : A Case Study in Baja California

In Mexico, water planning is based on the National Water Law, the core of which is Integrated Water Resources Management (IWRM). The municipality provides wastewater treatment and reuse, and an integrated approach is mandatory for these processes. However, a traditional (non-integrated) management regime has prevailed in water legislation, resulting in pollution and the inefficient use of water. The objectives of this research were to analyze the Mexican legal framework and international guidelines in the use of reclaimed water for agricultural irrigation and environmental discharges, and to evaluate challenges facing reclaimed water in the Maneadero Valley, Baja California, as a case study. Results show that wastewater reuse was implemented in the absence of integrative planning and assessment of the potential impacts on the environment and public health. In addition, gaps between decisions linked to the legal attributes of the relevant institutions were identified. Defined roles across the three levels of authority, transparent and congruent funding, coherent water-quality requirements and the strengthening of stakeholder participation are needed to adopt integrated water resource management for reclaimed water use. The alignment of common goals on public health, environmental protection and agricultural development between authorities and the different sectors is crucial to bridge these challenges.


Introduction
In the last 80 years, the use of reclaimed municipal water (RW) has become a viable option worldwide to obtain environmental benefits and to achieve supply-demand balances [1].The main use of RW is in agriculture and has the advantage of providing minerals and nutrients that can be used by plants [2].However, some problems resulting from irrigation with RW are an increase in sodium adsorption ratio (SAR) and the possible presence of fecal coliforms [3].Aquifer recharge with RW through soil-aquifer treatment is also becoming important at the global scale to overcome groundwater exploitation and quality deterioration [4].However, pathogens and organic and inorganic pollutants may be present in RW, and thus may eventually contaminate groundwater [1].Since 1989, the World Health Organization (WHO) has developed guidelines for the safe use of wastewater and, on this basis, each country has established its own regulatory framework.In Mexico, wastewater discharges to the environment are regulated by federal legislation NOM-001-SEMARNAT-1996 and wastewater to be reused in public services by NOM-003-SEMARNAT-1997.The National Water Commission (Comisión Nacional del Agua: CONAGUA) established the requirements for aquifer recharge with RW through the NOM-014-CONAGUA-2003.For public health protection, water quality for human use and consumption must comply with NOM-127-SSA1-1994, NOM-230-SSA1-2002 and NOM-179-SSA1-1998 established by the Secretary of Health.
Mexico has developed a decentralized policy framework for managing water resources.CONAGUA is the federal agency under the mandate of the Secretary of the Environment and Natural Resources (Secretaría de Medio Ambiente y Recursos Naturales: SEMARNAT) responsible for managing water resources and its main functions are the development of national water policy and providing subsidized financing.CONAGUA's responsibilities are decentralized through stakeholders such as the state water commissions, the 13 watershed organizations, the watershed councils, the water utilities and other government and non-governmental bodies.Water management legally incorporates Integrated Water Resources Management (IWRM).This approach is defined as an empirical process, which promotes stakeholder participation in coordinating the development and management of water, land and related resources, in order to maximize the resultant economic and social welfare in an equitable manner without compromising the sustainability of vital ecosystems [5].Wastewater treatment and its reuse must be considered within the water cycle management and, thus, as part of the holistic IWRM procedures toward a more effective safety control.However, wastewater treatment and reuse within sanitation services has been little analyzed in terms of integrated water management.Sanitation is not even defined in the water legislation and it is uncertain whether RW reuse is implicit in this sub-sector.In addition, institutional fragmentation still hinders the clear allocation of each institution's role in this subject [6].
Mexico's strategy for managing water resources is based on the Planning Law, the National Democratic Planning System and the National Water Law (Ley de Aguas Nacionales: LAN), which mandate IWRM as established in Article 15 of the LAN.Every six-year period, the National Water Plan and Regional Water Programs, including specific and emerging plans, are drawn up based on the National Development Plan.These legal documents define specific policies and goals linked to developed scenarios for improving water productivity, increasing water quality, promoting sustainability in water management, and creating a culture of paying fees.Scenarios are plausible descriptions of likely and unlikely alternative futures, and are a representation of how the future may unfold [7].Thus, scenarios are the key information for management decisions and should be the primary mechanisms for generating solutions and assessing potential risks and opportunities from water issues.CONAGUA has employed scenarios since 1970; however, these have been developed without transparency and excluding the input from the academic sector [8].Additionally, water planning is based on a traditional management system supply-oriented for the optimization of project portfolio investments, with limited social participation and restricted to each Mexican Basin Council [9].Traditional planning practices have led to an inefficient use of water resources and pollution because their only focus is usually dominated by advocacy groups of common economic and political interests [10].Thus, water resources management has not engaged IWRM principles in a participatory and future-oriented way, constraining the development of public policies.
Across diverse contexts common challenges occur, whether in developed or developing countries or if water is scarce or plenty, such as unclear allocation of responsibilities, questionable resource distribution and poor stakeholder's participation.These obstacles often contribute to inefficient water resource management [11,12].The successful use of RW requires efficient legislation, financial analysis, stakeholder participation and, overall, integrated management.
In Mexico, less than 50% of wastewater is treated and no wastewater treatment facility is financially self-sufficient, leading to inconsistent water quality and unregulated RW reuse [13].Because the use of RW was consolidated without enough knowledge about the impacts of RW on groundwater quality and public health, the Maneadero Valley in Baja California is used as a case study to examine the legal and institutional barriers faced by RW discharges into the environment and its reuse in agriculture.Similar studies have not been reported before in Mexico.This investigation addresses the challenges and opportunities of using RW to achieve socio-economic and environmental benefits through a holistic approach, both in Mexico and other regions experiencing a similar situation.
Case Study: The Use of Reclaimed Water (RW) in the Maneadero Valley, Baja California Maneadero Valley is located 15 km south of Ensenada, at 31 • 41 N and 116 • 30 W and comprises a 130 km 2 coastal aquifer, which is the main water supply for the cities of Ensenada and Maneadero and on which the Valley agriculture depends.According to official data, the aquifer over-abstraction is estimated at 5.4 million cubic meters per year (Mm 3 y −1 ) [14] and is significantly affected by seawater intrusion and anthropogenic pollution [15].In consequence, salinity has caused severe deterioration of groundwater quality for agriculture and domestic water supply, resulting in several wells being abandoned in the last 10 years.To reduce stress on water supplies and prevent seawater intrusion, in 2003 the Integrated Water Management Plan (Plan de Manejo Integrado: PMI) for the Maneadero aquifer was drawn up by CONAGUA.Although this PMI was never made official by publication in the Official Gazette of the Federation (Diario Oficial de la Federación: DOF), it suggested the use of RW from the wastewater treatment plant "El Naranjo" (WWTPN) and recommended the construction of infrastructure for agricultural irrigation and artificial aquifer recharge.However, it was not until 2014 that agricultural irrigation with RW was initiated on 100 ha of flowers.Currently, the WWTPN provides ca.140 L/s of RW to irrigate approximately 140-150 ha of flowers, and in addition approximately 168 L/s are discharged into the Las Ánimas and San Carlos creeks [16].Figure 1 details the location of the study area and the RW discharges sites.

Methods
The approach of this research included reviewing Mexican legal framework governing wastewater and reuse at federal, regional and local levels.The documents were compiled from the Congress of the Union official web site [17] and from the government web page called "Gobierno en un solo punto" [18].
The regulations were associated to its respective institutional authority, considering the legal hierarchy of the three levels of Mexican government, on the basis of their relevant competences with four types of water destinations: (1) RW and wastewater discharges into natural receiving bodies; (2) artificial aquifer recharge with RW; (3) incidental recharge as a result of RW and wastewater infiltrations to the aquifer; and (4) RW and groundwater uses for agricultural irrigation and domestic use.These water destination types were linked at a local level in the Maneadero Valley and the relevant events on the use of RW were investigated to analyze the implemented actions in compliance with the Mexican water regulations and with international guidelines.
No written evidence is available for the implementation of RW use in Maneadero.Thus, most information was obtained by officials from the three key competent institutions in the context of the RW usage in the study area: CONAGUA, the State Commission of Public Services of Ensenada (Comisión Estatal de Servicios Públicos de Ensenada: CESPE) and the Technical Committee for Groundwater (Comité Técnico de Aguas Subterráneas: COTAS) of Maneadero.

Hierarchy of the Mexican Legal Framework Relating to the Use of RW
Seventeen legal instruments and five management instruments were hierarchized into three levels and summarized in Figure 2 focusing on articles associated with: wastewater, RW, groundwater and seawater, as well as on water usage for domestic purposes, agricultural irrigation, artificial recharge, and discharge into receiving (natural) bodies of land and water.Additionally, the PMI (2003), the Integral Water Program of Ensenada (Programa Integral del Agua de Ensenada: PIAE, 2008) and the Integral Water Program of Ensenada Municipality (Programa Integral del Agua del Municipio de Ensenada: PIAME, 2010) were considered because certain recommendations regarding the infrastructure for the use of RW were implemented.
The legal framework for managing water resources emanates from the Mexican Constitution.This contains two articles for managing water resources.The first, Article 27, refers to the types of water bodies and the conditions for water to be considered under a state government or to transfer titles of these water resources to private property.The second, Article 115, assigns responsibility to local governments for drinking water supply, sewerage, and sanitation services, as well as operating and maintaining water infrastructure.Legal and management instruments further develop this framework, specifying the competencies of the relevant authorities.The legal instruments express the enforceable obligations such as the federal laws; while the management instruments are the tools that enable decision makers to make rational and informed choices to specific situations.Examples include plans and programs referenced to legal compliance.
The institutional structuring indicated in Figure 2 was associated to the respective legal and management instrument in compliance with their legal attributes.Table 1 describes the enforceable obligations of the relevant authorities established in the laws and regulations of the 1st and 2nd hierarchical level in these matters.
Regarding the management instruments, the Sectorial Program for the Environment and Natural Resources stipulates that for 2013-2018 there is a need to monitor and ensure the compliance of wastewater and RW discharges; while the National Water Program (Programa Nacional Hídrico: PNH) for 2014-2018 emphasizes the duty to take actions for artificial aquifer recharge.The Regional Hydrological Program "Vision 2030" designates the need to use RW from the WWTPN, so that by 2030 the balance of the aquifer is established.The State Development Plan of Baja California for 2014-2019 recommends the use of color-coded purple pipelines-the official color used to designate reclaimed water-for RW distribution and the Municipal Development Plan of Ensenada for 2017-2019 encourages the proper management of RW usage.In general, the PMI (2003), the PIAE (2008) and the PIAME (2010) mentioned the opportunity to use RW for aquifer recharge and indicated that CESPE together with academic entities, such as the Autonomous University of Baja California (Universidad Autónoma de Baja California: UABC) and the Ensenada Center for Scientific Research and Higher Education (Centro de Investigación Científica y de Educación Superior de Ensenada: CICESE), should perform the following tasks: (1) hydrogeological and water balance studies; (2) the legal framework analysis regarding the treatment, disposal and reuse of wastewater; (3) pilot projects for the aquifer recharge with RW; (4) regulations for the efficient use of RW; and (5) developing scenarios to address the adverse effects of climate change and population on water demands.Table 1.Legal attributes of the relevant authorities in the water sector associated with wastewater and its reuse.

Government 1st
Setting policies and water abstraction and pollution charge rates.
Approving the budget to the water sector.
Authorizing multi-year investment programs.
CONAGUA a , by means of its delegated institutions 1st Leading and coordinating the use of RW.
Issuing permits for wastewater and RW discharges and for reuse in aquifer recharge and irrigation.
Collecting the user's declaration of RW quality quarterly, as well as the fees for water abstraction and wastewater and RW discharges.Guarantee that the objectives around the use of RW align with the Planning Law. 2nd Coordinating with municipalities to improve sanitation service provision and formulating development plans.
Setting the tariffs charged by water and sanitation providers.Guarantee the consolidation of a list of wastewater and RW discharges.
SEMARNAT b , through CONANP c and PROFEPA d 1st Monitoring and assessing wastewater and RW discharges into receiving natural bodies in compliance with the respective Mexican regulations.Applying sanctions when infiltrations of the (un)treated effluents pollutes water bodies.Conducting environmental impact studies, including an inventory of (un)controlled discharges.Taking actions to design regulations of cultivation practices with water use in agriculture.

2nd
Managing and protecting wetlands included in Ramsar List of Wetlands of intentional importance, such as the Punta Banda estuary in Manedero and the streams that flow into the estuary.

Secretary of the Navy 1st
Preventing and controlling marine pollution from discharges alongside regulations by CONAGUA.

Agrarian Attorney 1st
Guarantee that public lands consolidate an internal regulation, specifying the distributions, fees, and transfer of entitlements for water resources usage in agriculture and domestic purposes.

Secretary of Health 1st
Monitoring and certification of groundwater quality.

CESPE f 2nd
Providing water and sanitations services.Updating data of wastewater and RW discharges.
Preventing and controlling pollution into receiving bodies from sewage systems, as well as to determine the susceptibly of wastewater to be reutilized.

SPABC g 2nd
Preventing and controlling discharges into the receiving natural bodies.

SEDAGRO h 2nd
Promoting the efficient use of groundwater.
Establishing methods for RW usage in agricultural irrigation and, in this regard.

International and National Regulations of RW Usage in Agricultural Irrigation and Aquifer Recharge
The international criteria for the use of RW represent a useful guide to improve the complex Mexican water policies and agricultural practices.The main guidelines for RW use are published by the WHO [3], the Food and Agriculture Organization (FAO) of the United Nations [19] and the United States Environmental Protection Agency (USEPA) [20].The international water legal systems are generally based on the USEPA's classification according to use conditions, and on the effluent quality recommended by both the WHO and the FAO as shown in Table 2.These quality parameters are used with some modifications by many countries including Mexico in adopting regulations for the use of RW in agriculture and aquifer recharge, as well as for discharge purposes indicated in Table 2.
The main concerns of the international guidelines are public health (including protection of workers and consumers of agricultural products), environmental protection, and food security.Based on these three criteria, the implementation component considered for the RW management in agricultural irrigation and aquifer recharge was summarized in five phases and described in Table 3.     Exchange of specific information between authorities and public representatives through workshops, public meetings, newspapers, radio, school programs, letters, conferences, etc. Notification of RW uses signage using recognized terminology and advisory language.

Monitoring assessment
Validation, operational monitoring and verification of the procedures and the communication systems with all relevant stakeholders in compliance with the formulated strategies, plans and actions.

Conceptual and Legal Model of the Water Cycle in the Maneadero Valley
Different natural and social components are intertwined in the Maneadero Valley, involving the four types of water destination linked to the Mexican water legal framework.The flow dynamics of water types is represented in a conceptual model in Figure 3 and associated with the water legislation shown in Table 4.  4. The features of the water cycle in Maneadero Valley and the associated water legal framework are summarized as follows: For decades, due to the lack of infrastructure for sewage collection, the Maneadero urban area has been using latrines, which have polluted the aquifer (o).Only in the past 8 years have sewers and wastewater treatment plants been built in Maneadero, although still only few households have connected to the new infrastructure.The regulation NOM-014-CONAGUA-2003 defines the concept of incidental recharge as the groundwater recharge (infiltration) that occurs as a result of human activities unrelated to a recharge project, for example, irrigation operations and water diversion in unlined canals of diverse origin.Therefore, incidental aquifer recharge may occur from agricultural irrigation (n), latrines (o) and from the RW discharges (l, m), and is not subject to this Mexican regulation.
The Maneadero WWTP (Figure 1) treats approximately 7 L/s of sewage from the Maneadero urban area (c) while El Naranjo WWTP treats between 316 L/s and 441 L/s from the city of Ensenada (a, b), which are subsequently combined with RW from the WWTP el Gallo (Figure 1) (d).Sources of sewage include residential areas, the commercial sector and, in a lower proportion, industries.Once treated, the RW flows through a purple pipeline and discharges into three receiving areas: agriculture valley (g) public land adjacent to the San Carlos creek (h) and directly into the Las Ánimas creek (i).The Pacific Ocean and the Punta Banda estuary are considered receiving water bodies of RW from the WWTPN (e, j) and from the treated effluent discharged into the creeks (k), respectively.
Groundwater in Maneadero not only supplies agriculture in the valley (p) but also the urban areas of Maneadero and Ensenada (q), and so groundwater quality must comply with the Mexican regulations for human use and consumption: NOM-127-SSA1-1994, NOM-230-SSA1-2002 and NOM-179-SSA1-1998.In addition, the NOM-001-SEMARNAT-1996 applies to all flows d, f, g, h, i, and the NOM-003-SEMARNAT-1997 addresses the direct and indirect contact of humans with wastewater, as well as the compliance with respect to both natural and artificial reservoirs for irrigation stipulated in the NOM-001-SEMARNAT-1996.
The management instruments establish the government guidelines (at federal, state and municipal levels) and operate by hydrological regions during their administrative period.In such a case, the use of RW for agriculture and for discharge purposes into receiving natural bodies in Maneadero should be in compliance with the respective management instruments, in accordance with the jurisdiction and competence of the legal instruments.

Implementation of RW Usage in the Maneadero Valley
The main events related to the use of RW in the Maneadero Valley are described in Figure 4.In December 1959, the State of Baja California Government and the Maneadero farmers "Ejido Nacionalista Rodolfo Sánchez Taboada" signed a formal agreement to return sewage to Maneadero free of charge in an exchange of groundwater from the Valley to supply the city of Ensenada.In consequence, an open channel was built in 1959-1962 [34] to send untreated sewage to Maneadero for agriculture irrigation.However, the channel was severely damaged during a storm in 1985 and was never repaired.It took 55 years for the government to finally comply with the aforementioned agreement in order to respond to the water shortage in the valley.
In 2000, an agreement between UABC and CESPE was signed to continuously analyze RW quality from the WWTPN.The results showed that more than 90% of the RW samples complied with the Mexican regulations [35].These outcomes facilitated decision-makers in deciding to use RW for agricultural irrigation in abandoned lands and attempt to stop the progress of seawater intrusion.
In 2004 SEDAGRO applied a census to farmers in Maneadero to evaluate their acceptance of RW for irrigation, showing that 80% of farmers were in favor of such a measure.A year later CESPE scheduled the pipeline installation connecting the WWTPN to Maneadero, but it was not executed until 2008.In 2007, the UABC and the COTAS (Maneadero) signed an agreement to analyze groundwater quality for a year, primarily in areas envisaged for agricultural irrigation and for aquifer recharge with RW.Most of the results from this survey published by Daesslé et al. [36] identified an increase in total dissolved solids (TDS) and reported the prevalence of water pollution with nitrates.Bacteriological results were below permissible limits and the study suggested conducting specific studies on groundwater quality.
In 2008, the State Government of Baja California built a 20 km pipeline to connect the WWTPN with a holding tank of 2000 m 3 at a cost of about 3.5 million U.S. dollars [37].The aim was to supply approximately 80 L/s of RW for crop irrigation [34].The RW was scheduled to be provided with a cost to farmers; however, due to the lack of agreement among the farmers, the pipeline and the holding tank were never used.In 2014, representatives of CONAGUA, CESPE, SEDAGRO and the UABC as well as stakeholders of common land met and agreed to supply 120 L/s of RW to Maneadero free of charge for crop irrigation of 200 ha of flowers and fodder.CONAGUA would act as the entity responsible for managing the project and the CESPE as the executor of funds.
Finally, in 2014, the initial purple pipeline was repaired and a 4 km long secondary pipeline was installed at a cost of approximately $38,000 U.S. dollars to transport RW to holding tanks located in the agricultural fields, for floriculture (such as sunflowers) and fodder (alfalfa) irrigation.In addition, two pipelines were built to discharge the treated effluent into the creeks (Figure 1).Currently two thirds of the total volume of RW from the WWTPN is supplied to Maneadero for agricultural irrigation and creek discharge [16].

Discussion
Policies and regulations are the main driving forces guiding integrated water management.Within the scope of RW, the Mexican legalization provides a framework for wastewater treatment and reuse (Figure 2).Legal and management instruments associated to RW usage have been issued for beneficial purposes such as agricultural irrigation and aquifer recharge, but there is a wide range of challenges facing successful implementation of RW projects at national and local levels.Based on what the legal and management instruments state, and what the actual proceedings were in our case study, this investigation identifies four main challenges to ensure environmental, institutional and socio-economic benefits of RW use in this and other sites.

Institutional Coordination and Fragmentation Capacity
The local government (i.e., CESPE, private and/or municipally-owned companies) is responsible for providing wastewater and its reuse; while environmental and public health regulations are undertaken by SEMARNAT, the state and local water commissions of CONAGUA and the Secretary of Health (Table 1).The allocation of the legal and management instruments in the conceptual model of the Maneadero Valley in Figure 3 allows for "institutional mapping" of water policies on RW.It is observed that the institutional arrangement is intermingled (Table 4).In theory, regulations that govern the use of RW interact between the different water agencies at the national, regional and local levels.However, communication and coordination between the federation, state and municipality is rarely achievable [38].In this regard, RW discharges and agriculture irrigation with the treated effluent in the Maneadero Valley were authorized by CONAGUA without previous environmental impact studies on the potential effects of RW fluxes to the Punta Banda estuary and the infiltration into the aquifer derived from RW discharges and agricultural irrigation.As for groundwater quality for human use and consumption, according to CESPE, the parameters established in the NOM-127-SSA1-1994 are not routinely measured in the Valley.Moreover, TDS were double the maximum allowed by this regulation.So far, the co-responsibility in environmental policy between SEMARNAT and CONAGUA has been non-existent, and the role of the health sector (Secretary of Health) is excluded.In addition, the gap existing between the water policies and environmental policies has led to unclear roles of the relevant authorities on wastewater and reuse in the Maneadero Valley.The several shared responsibilities (Table 1) have created gaps in identifying who does what in water policy making.Encouraging coordination and building institutional fragmentation capacity and clarifying the role and responsibilities among government's institutions are critical steps towards bridging three-level governance gaps in water policy.Efforts in regulating the behavior of the authorities and its interactions could overcome these gaps, as well as strategic and congruent institutional funding, which brings us to the second challenge identified.

Transparent and Congruent Funding
The federal government provides most of the resources for water finance in Mexico.The state's authorities of the 2nd hierarchical level coordinate together with the local government of the 3rd level for covering infrastructure investments, and then negotiate with CONAGUA at the 1st administrative level the inclusion of projects in the federal program for approving sanitation funding.The approved programs aimed at water supply and sanitation include as a condition the payment of water-related taxes and tariffs from public sources (i.e., water extraction, pollution charges and (un)treated wastewater discharges).Revenues from these charges are collected by CONAGUA and integrated in the federal budget, and only ca.38% of the proceeds are transferred to local authorities to meet mainly the construction, operation and maintenance costs of WWTP [39].However, the budgetary allocation in this regard is usually insufficient or unstable.The federal government also raises funds from commercial loans, bonds and donations, but its expenses in the water sector are unknown [39].Many countries of Eastern Europe and Central Asia also face the situation where financing is insufficient for capital investments and even to maintain the existing assets at their low operational level, affecting the sanitation services provision [40].This raises two key questions: how the allocation of funding within the sanitation subsector takes place, and what is financed within such allocation.
While transparent and congruent allocation of public funds bridges the aforementioned funding gaps, several countries have increased funds from sources other than government funding to support sanitation facilities at municipal scale.Strategies employed for financial resource mobilization include: reducing costs while generating savings through improved operating efficiencies (e.g., Great Cairo), selecting specific water quality standards according to local circumstances, market-based repayable finance (through equity financing, such as the Brazilian water and waste management company (SABESP) and/or bond financing, such as in the United Kingdom), direct investments by water users (e.g., Sub-Saharan Africa), and many others [40].These options could be applied for achieving long-term investment in wastewater treatment and reuse by identifying the environmental and socio-economic benefits of RW, where larger investments are needed.Ultimately, strategic financial planning is essential for the mobilization of external financing and successful maintenance and expansion of water services and facilities.However, any country facing a sectorial fragmentation of water-related roles across multi-level governance (Gap 1) undermines the effectiveness of such a strategic financial approach.
In Mexico, tariffs for wastewater and RW discharges are established in the Federal Duties Law and vary according to the body of water into which discharges are made; while at a regional level the Income Law of Baja California for 2017 establishes a fee of ca.0.20 U.S. dollars per cubic meter of RW used.In the 1959 agreement (Figure 4) the state government agreed to return the sewage to Maneadero free of charge and, currently, there is a verbal agreement between the local farmers and CESPE to supply RW free of charge.However, there is no written agreement between water authorities and farmers, and to date the length of such a commitment remains unclear.In addition, CESPE monitors RW quality but routinely fails to meet the requirements.This is because the low budget for the maintenance of the WWTPN hinders the improvement of RW quality controls; thus, the RW quality is not guaranteed [16].This impedes expansion of the irrigated surface in the Maneadero Valley, so most of the RW is discharged directly into the creeks in Maneadero.Creating a local fund from the farmer's tariffs paid to service providers (utilities, water pumping, irrigation districts), through the financial management of the water utilities (e.g., CESPE) in coordination with the federal and state offices of CONAGUA, and/or creating investment trusteeships among agriculture users could bear the costs for the operation and maintenance of the WWTPN, as well as for RW quality monitoring plans.In fact, this policy's principle called water-pays-for-water is established in the water legal framework, but it has never been applied.
Planning documents published by the Federal Official Gazette (Figure 2) include the investment objectives, strategies, priorities and actions related to sanitation services.However, these documents focus on the use of federal budgetary resources and do not set targets across all sector actors.As for RW, the content of the scale implementation for reuse, as well as policy, regulation and the possibility to be used for specific purposes other than agricultural irrigation is rather limited.Expenditures in policy and regulation only represent 15% of the total Mexican water sector finances; thus, [39] strengthening funding in these topics towards the use of RW are urgently needed.Cost-effectiveness assessments for reuse and a contingent fund for adaptation to climate change and for abatement of external drivers such as technical, social, geopolitical and environmental (e.g., pollution derived from reuse) are not even considered.Efforts in these matters remain inadequate and neglected [41].The measures oriented to use RW for agricultural irrigation and aquifer recharge established in the PMI (2003), PIAE (2008) and the PIAME (2010) resulted in expenditure plans rather than integrated management plans.The federation never published these documents, despite describing relevant aspects such as the strategies and budgets associated with the use of RW in Maneadero.Ironically, none of the competent authorities currently refers to these manuscripts as the baseline of the implemented activities.

Coherent Water Quality Requirements
The international guidelines for the use of RW deal with the quality of irrigation water to protect public health in economic and environmentally sustainable ways through a clear management procedure (Table 3).The Mexican regulations for the use of RW are comparable with international guidelines (Table 2).The quality of RW from the WWTPN is analyzed by CESPE in compliance with the NOM-001-SEMARNAT-1996 and the NOM-003-SEMARNAT-1997, and analyses are handed to CONAGUA in accordance with the Federal Duties Law.
The NOM-001-SEMARNAT-1996 restricts the irrigation of vegetables, fruits and root crops eaten raw with RW; thus, it is unfeasible to supply the total volume of the treated effluent for agricultural irrigation in the Valley, mostly dedicated to horticulture for export.This situation provides fewer economic options to evaluate financial returns of other available crops, and Maneadero farmers decline to invest in high quality wastewater treatment.In other parts of Mexico, such as the Mezquital Valley [42], farmers use raw wastewater for eatable crops (non-export), despite the health risks and the aforementioned legal restrictions [42,43].As for direct aquifer recharge, RW must meet the quality regulations established in the NOM-127-SSA1-1994 for drinking water.Nonetheless, water in most coastal and urban aquifers already fails to comply with this drinking water regulation.For example, water in the Maneadero aquifer deteriorated through urban wastewater infiltration and the leaching of garbage and urban solid waste prior to reclaimed water use [15].The soil-aquifer treatment method [4] would represent a feasible alternative to further improve the RW quality and prevent potential risks to public health and the environment.In Maneadero, Gilabert-Alarcón et al. [15] reported the limited soil capacity to retain important elements derived from RW such as sodium, boron and bromide, which were found to remain in groundwater and, eventually, could affect the environment, public health and crop productivity.Infiltration during irrigation with RW represents a significant component in the water balance and water quality.Hence, direct recharge and irrigation projects with RW and/or raw sewage should be considered in compliance with coherent regulations for the protection of public health and the receiving natural bodies.

Strengthening Stakeholder's Participation and Public Awareness
Water planning must be based on the IWRM philosophy established on Article 15 of the LAN.Stakeholder participation is considered a major role in IWRM.CONAGUA's user associations, the watershed councils and the COTAS, are responsible for promoting social welfare and providing training to the water users in exploited aquifers, for participating in the integrated management of river basin and aquifers, as well as in developing policies and programs related to the aquifers.However, these institutions are only recognized as civil society counseling bodies and their participatory role in decision-making is excluded.The weak lawful representation of water users associations limits their participation in water planning processes with the local authority.
Coordination and participation between levels of government and researchers also plays a significant role in reporting and disseminating validated scientific information for decision-making.In this regard, academia has contributed significantly in assessing groundwater and RW quality, and participating in efforts toward proper water management.Mendoza-Espinosa et al. [35] characterized the treated sewage quality from the WWTPN and concluded that the treated effluent complied with the Mexican regulations.However, the authors suggested the inclusion of other analytical parameters recognized by the international guidelines such as residual Cl 2 , organic pollutants and the presence of virus-like pathogens, as well as the performance of a strict and regular monitoring of RW to prevent risks to public health and the environment.Daesslé et al. [36,44] found a significant deterioration of groundwater quality caused by the presence of nitrates, with concentrations four times the limit for drinking water of 10 mg/L.Yet agricultural irrigation with RW was implemented in response to the urgent need for water supply and the pressure of farmers on the state and local government 54 years later after it was initially considered.Only recommendations regarding the construction of infrastructure established in the PMI (2003) and the findings regarding the quality of RW were considered.So far, no regulation of cultivation practices with RW has been implemented as required by law (Table 1).Thus, these actions did not emerge as the result of an integrative and prospective planning based on hydrogeological, chemical, environmental and public health studies.In addition, the use of RW for agricultural irrigation was solely consulted and agreed upon with farmers, excluding the opinion of the local community.
Coordination and consultation mechanisms between government agencies and stakeholders cross multiple scales are critical steps in IWRM to overcome the gaps for effective implementation of water management programs.In the case of Maneadero, the technical and specialized information from local researchers appears superficially considered.In addition, public knowledge about RW use is ignored, as well as the general procedure provided by international guidelines as integrated reference to facilitate wastewater reuse.Agriculture users as well as other civil society organizations should be considered in supervising the compliance with regulations concerning the use of RW; thus, efforts to inform and educate farmers are needed and for this a facilitator may be required to address conflicting views (e.g., Leach and Pelkey [45]).

Conclusions
The present investigation highlights the regulations and relevant institutions associated with the use of RW, and identifies the main challenges to achieving integrated water management in this matter in Mexico.Wastewater treatment and reuse are included in the water utility operations in Mexico and, according to the LAN, its planning must incorporate IWRM.Wastewater treatment and reuse, including wastewater and RW discharges, are regulated by various legal and management instruments.Yet the content of implementation, policy and regulation of RW use is rather limited.In addition, water management instruments are generally built from scratch by new presidential administrations every six years, which prevents the continuity of plans and programs with consequent useless expenditure in efforts and capital, as well as deterioration of water and sanitation services.
The responsible use of RW for agricultural irrigation and aquifer infiltration results in many environmental and economic benefits such as saving crop production, reducing stress on water supplies and preventing seawater intrusion.However, the sectorial fragmentation of roles and responsibilities between the three-level authorities (Gap 1) result in insufficient or unstable financing and financial "losses" (Gap 2).This in turn hinders the development of coherent technical regulations (Gap 3), which could be improved overall by strengthening stakeholder participation and public awareness (Gap 4).These barriers hamper sustainable RW utilization in agriculture practices and strategies for WWTP rehabilitation to guarantee RW quality, and thus lead to negative effects on the environment and public health with elevated economic costs associated with these impacts.These challenges are still faced by Mexico, as shown in Maneadero, where decision-making is strongly based on political interests and social pressure.The alignment of common goals on public health, environmental protection and agricultural development between local authorities and different sectors are needed to bridge these challenges.
International guidelines recommend the analytical and operational procedure of IRWM to achieve the proper use of wastewater and reuse, considering five essential elements: (1) health and environmental diagnosis, including the development of effective scenarios to reduce adverse effects of human activities and climate change; (2) economic feasibility; (3) social impact and public perception through the acceptance and validation of RW use of the different sectors; (4) institutional commitment in compliance with their legal attributes; and (5) validated assessment from interdisciplinary research.International general procedure allows flexibility in developing local guidelines in accordance with local agro-economic conditions for public health safety.However, its efficient application will depend on the trust, commitment and shared knowledge between local authorities and the different sectors.

Figure 1 .
Figure 1.Location of the reclaimed water (RW) discharges sites and ponds for RW storage for agricultural irrigation in the Maneadero Valley.

Figure 2 .
Figure 2. Hierarchical organization of the Mexican legal framework with the respective relevant institutions associated with the use of reclaimed water.

Figure 3 .
Figure 3. Conceptual model of the water cycle in the Maneadero Valley, where letters in italics refer to the different water types and their corresponding regulation in compliance with the respective Mexican instrument given in Table4.

Figure 4 .
Figure 4. Relevant events leading the use of RW in the Maneadero Valley.
Notes: a National Water Commission; b Secretary of Environment and Natural Resources; c National Commission of Natural Protected Areas; d Federal Attorney's Office for Environmental Protection; e State Water Commission of Baja California; f State Commission of Public Services of Ensenada; g Secretary of Environmental Protection of Baja California; h Ministry of Agricultural Development.

Table 2 .
International and national regulations for the use of RW in agriculture and aquifer recharge.
Risk management plan: (1) hazard characterization (potentially polluting activities, inventory of potential contamination sources leached into the subsoil, protection of public water supply wells, interaction matrix methodology for pollutant loads, and assessment of soil for losing filtration capacity over time); (2) flow diagram of the existing or proposed system; (3) control measures (wastewater treatment, health and hygiene promotion, crop restrictions, use of personal protective equipment); (4) supporting programs (e.g., training, hygienic practices, standard operating procedures, etc.); (5) management and communications procedures.Participatory appraisal.

Table 3 .
Cont.Institutional capacity and jurisdiction to ensure the efficacy of health and environment protection measures (e.g., ability to (1) ensure that sanitation is effective in reducing pathogens to the extent required; and (2) promote effective washing of RW-irrigated produce).Programs prioritization related to (1) public health and environmental concerns; (2) water supply and water quality; and (3) regional conflicts over water.Integration of environmental and social indicators associated with the goals (output indicators) and activities (management indicators).ImplementationNational and local priorities, hygiene education programs, ensuring community operation and maintenance, public awareness and information channels, and execution of the institutional coordination strategies.National and local database.

Table 4 .
Legal and management instruments associated to the water cycle of the Maneadero Valley in Figure3.