Integrated Management, Circular Economy and Reclaimed Water: Keys to Restoring the Long-Term Water Balance in La Marina Alta (Alicante, Spain)

Abstract

This research is focused on water governance problems in La Marina Alta District, in the province of Alicante (southeastern Spain). The district has a public management body, Consorcio de Abastecimiento y Saneamiento de Aguas de los Municipios de La Marina Alta (CASAMA), which has been inoperative since its creation in 1987. Although La Marina Alta has sufficient water resources in situations of hydrological normality, they are significantly affected by the impacts of climate change, insufficient water treatment technology and the absence of storage and regulation infrastructure. As a consequence, periods of scarcity and overexploitation of aquifers, together with high-demand situations, have generated scenarios of a lack of drinking water with reputational damage and uncertainty for the future of agricultural operations. Thus, the aim of this work is to propose the adoption of integrated water resource management strategies that will increase the resilience of this sub-basin in La Marina Alta. To this end, the contribution of new non-conventional resources to the water pool, combined with an efficient network of infrastructure, and all this supported by effective governance structures, would be essential to achieve a sustainable balance between demand and supply, preserving the environmental values of the territory.

1. Introduction and Area of Study

Water is a limited strategic resource whose sustainable management is a fundamental pillar for guaranteeing water security, environmental preservation and socioeconomic development. In Spain, water availability is affected by climate change, the overexploitation of aquifers and pollution of water resources, especially in the Mediterranean arc [1]. Water is important in all areas of life, from health to the economy, and the future of societies depends on it, despite its availability being taken for granted and wasted every day [2]. Thus, the lack of water has been a limiting factor for the growth and economic development of certain territories, such as the Spanish southeast [3], where this work is focused.

Spain faces significant challenges in relation to water resource management, given its scarcity and the unequal distribution of resources [4]. It is the leading country of water reuse in Europe, ranking fifth worldwide in terms of reuse capacity. Nevertheless, a sign of the potential to improve circularity in water management is the fact that Spain treats approximately 95% of its wastewater, but barely 7% to 13% of treated wastewater is reused [5].

In the context of persistent water stress, the Júcar River Basin, where the sub-basin to be analyzed is located, has shown significant progress in wastewater treatment and reuse. However, there are still districts in this basin that are not using the capacity to reuse their water, causing uncertainty and even concern in certain stress conditions. This is the case of the district (and sub-basin) of La Marina Alta, in the province of Alicante (Spain).

The way in which society manages water resources is essential for addressing climate change. In line with the proposals of the Ellen MacArthur Foundation [6], the energy transition to renewable sources can address 55% of the reduction in global greenhouse gas emissions, but to achieve the United Nations (UN) climate goals, it is imperative to address the remaining 45%, which would result from the way we produce, consume or work the land, as well as the way we treat natural resources, especially in economic activities where water plays a crucial role. This would be the case of La Marina Alta, which has a total area of 759 km², being the district with the largest number of kilometers of coastline in Alicante province (31% of the total). It is a territory where economic growth on the coast has been mainly due to the boom in tourism and urban development, which has caused an increase in pressure on water resources and led to an increasing incidence of the so-called socioeconomic drought in recent decades. This situation has resulted in transitory scenarios with insufficient water supply resources, as occurred during the summer of 2024 in some coastal municipalities of La Marina Alta [7].

From the demographic point of view, the district has experienced a notable increase in recent decades, especially with the arrival of tourists and workers seeking a place to live for long periods [8]. The new population model has conditioned the planning of endowment infrastructures and the natural resource management model, leading to a substantial increase in the demand for water resources that has altered the water balance of the district. The urban development model, associated with residential tourism, developed with the arrival of migrants seeking the Mediterranean lifestyle, and has been characterized by the dispersion of urbanization, with high water demands to satisfy the provision of swimming pools, gardens and other facilities.

The district also has a wide mosaic of land dedicated to agriculture, with its most outstanding products being vine in Vall del Pop and Teulada, and other crops in Rectoría [9]. From the agronomic point of view [10], La Marina Alta accounts for 9.5% of the provincial useful agricultural area, 11.7% of the production and 8.8% of the economic value of agriculture in the province of Alicante, accounting for around 13,150 hectares of active cultivation in the district, with dry farming representing 51% and irrigated farming 49%. The municipalities that make up this district draw a territory formed by the traces of the cultivation terraces adapted to the steep terrain of the mountain on its way to the sea, where they continue to soften the slopes. In the mountains, there are representative crops like cherry and olive groves, with vineyards of muscatel grapes and winemaking in the transition areas to the lower areas and near the sea, where citrus fruits such as oranges and tangerines predominate. Also noteworthy is the Pego rice and quality rice crops grown in the natural park of La Marjal Pego-Oliva [10].

Despite having, a priori, sufficient water to meet the demands, all available resources may be insufficient, especially at certain times. Since the mid-20th century, two events have altered the balance of the system water pool: on the one hand, the increase in water demands as a result of the construction and tourism boom, and, on the other hand, the impacts of climate change, materialized in the form of increasingly recurrent and intense periods of severe drought, as registered in 1976, 1985–1987, 1994–1996, 1999–2000, 2007 and 2016–2018 in the Júcar River Basin [11].

An historic water war took place during the first half of the 1980s, when the possibility of transferring water between the Bullent River and the Guadalest Reservoir was raised. At that time, the residents of Pego and Oliva, seeing how the La Marjal de Pego-Oliva Park was in danger, decided to launch social mobilizations to preserve their water ecosystems in front of the needs arising from the rise in tourism on the coast. It was a conflict with a strong identity-based character, in which the populations of the inland municipalities, primarily agricultural, felt themselves objects, not subjects, of decisions, seeing their traditional economies and ways of life threatened. In the late 1990s, water crises also occurred in the region, with overexploitation of aquifers and supply problems, particularly in coastal municipalities. This period of low rainfall encouraged Jávea, where water was reaching homes with high levels of salinity and turbidity, to plan the Xàbia desalination plant. In 2015, a water crisis again occurred in the region, with restrictions for more than 24,000 residents of La Marina Alta, in addition to losses due to leaks (reaching 70% in some municipalities at that time).

The district, even suffering periods of severe drought, such as the last experienced between 2021 and 2024, has one of the highest levels of precipitation in the province of Alicante, with an average of over 900 mm in the last decade (2014–2024). If the time frame of these last hydrological years is analyzed, there was a significant drop in average annual rainfall, from 1135 mm in 2021–2022 to 233 mm in 2023–2024. This decrease in rainfall, together with the high potential evapotranspiration in the area, has accelerated the aridity of the territory [12].

On the one hand, the overexploitation of aquifers, with the consequent increase in the salinity index, and the absence of infrastructures and technologies that make it possible to take advantage of the available resources, have resulted in an intense water deficit [13]. On the other hand, the district has no infrastructure to store surface water. Then, most of the runoff is lost directly to the sea due to the lack of retention and accumulation systems. Storage, in reservoirs or in the aquifers themselves, and the reuse of reclaimed water to ensure greater availability in periods of drought are major challenges facing the region [14]. These future infrastructures would also have a dual function: to minimize the impact of floods and to serve as a reservoir for subsequent uses established by regulations, such as agricultural, urban or recreational uses.

With a view to the management of water resources, the district has a public management body called Consorcio de Abastecimiento y Saneamiento de Aguas de los Municipios de La Marina Alta (in English, Supply and Sanitation Water Consortium of La Marina Alta; hereinafter CASAMA, in its Spanish acronym), which has failed since its inception in 1987. The reasons have been diverse, since it has not managed to implement the necessary and sometimes planned infrastructures, nor has it managed to align all the municipalities of the district in shared water objectives, so it has not responded to the challenges and threats posed by the district itself. For these reasons, as an alternative to CASAMA, other supralocal management bodies have been set up, such as the Teulada–Benitatxell Water Consortium, whose objective is the water supply between both towns; or the Mancomunidad del Pozo Lucifer, an entity grouped by the municipalities of Calpe, Murla and Vall de Laguar, which was born with the purpose of jointly managing the use of the aquifer known as Pozo Lucifer, located in Vall de Laguar and which has been proven to be a success story.

Over the last few decades, water management in La Marina Alta has faced significant challenges due to institutional fragmentation and the lack of integration of the municipalities in a system of shared governance [15], and CASAMA was not able to solve it. On the contrary, during the eighties in the twentieth century, in the neighboring district of La Marina Baja, the Water Consortium of La Marina Baja (CAMB) was set up after the supply crisis suffered by Benidorm, when the drought led to the depletion of water in the reservoirs and dried up or salinized the wells [16].

Moreover, the legal framework plays a transcendental role in the management of natural resources. Water management in Spain is based on the Water Law [17], whereas Law 10/2001 of the National Hydrological Plan [18] focuses on the construction of infrastructures and reuse. At the European level, Regulation 2020/741 of the European Parliament and of the Council regulates the reuse of reclaimed water [19]. In all cases, the legal framework is a powerful incentive to promote the reuse of reclaimed water, in line with the principles of the circular economy, which is a strong instrument for the sustainability of agriculture, avoiding the overexploitation of aquifers and restoring the deteriorated water balance, providing security of supply. At the institutional level, steps have been taken to address these water challenges, such as the Provincial Water Pact in Alicante [20], which represented an important exercise in the search for consensus in the comprehensive management of water resources. This agreement, promoted by the Provincial Council of Alicante (Diputación de Alicante, in Spanish), was based on the recognition of the existence of a structural water deficit in the province and established strategies to address this imbalance, by facing challenges such as the overexploitation of aquifers, desalination, the problem of the Tajo–Segura transfer and the need to address the interconnection of basins. This pact proposed extending the successful water management model of La Marina Baja to other areas of the province, including La Marina Alta, where the problem does not lie in the absence of water resources, but in the absence of efficient governance.

The hypothesis put forward in this work is how climate adaptation strategies and the principles of a circular water economy could contribute to balance water supply and demand in this area, whose current research debates are explored in the next section.

Based on the previous lines, the main objectives of this study are: to provide a diagnostic for the current water situation of La Marina Alta and the challenges it faces in the climate change context; to propose alternatives to prevent crisis situations; and to assess the benefits of the implementation of a more effective model of water governance.

2. Methods and Theoretical Framework: Integrated Resources Management and the Use of Reclaimed Water to Improve Water Governance

IWRM proposes water management models with the aim of improving the quality of life of people and the development of economic activities, making them compatible with the preservation of environmental values [21]. Approaches that incorporate IWRM together with the circular economy and the role of institutions in governance are proposed to address the problems of the balance between supply and demand in water-stressed territories to deal with the challenges associated with climate change, minimizing environmental impacts and guaranteeing strategic sovereignty. The circular water economy makes it possible to recover resources and reduce dependency, thus maintaining the value of resources for longer in use, as water reuse can serve as a reliable source in specific situations, in particular under conditions of water scarcity [22], which has an impact on greater resilience to meet the challenges exacerbated by climate change.

At the regulatory scale, the 1985 former Water Law already set as a fundamental objective the satisfaction of water demands, rationalizing its use in harmony with the environment and other natural resources [23], an objective that is also present in the European standard [24]. Public agencies also play an important role, as they are responsible for making the satisfaction of demands compatible with environmental sustainability. Failure in this task could lead to uncontrolled water use and use of water with detrimental effects on the environment [25]. The existing regulatory framework, determined by the Júcar River Basin Hydrological Plan [26], and the rest of the national and European regulations on water [17,18,19,24], promotes the implementation of sustainable management models, encouraging territories to move towards integrated planning, where institutional collaboration, the use of new technologies and the participation of all stakeholders take on special relevance.

The methodology proposed for this study has as its main element the bibliographic and documentary review of the literature published in official reports and/or scientific publications on water management in contexts of water crisis, as well as the analysis of current legislation on water, at regional, national and European levels. Interviews were also conducted with the technical managers of the main WWTPs in the district in order to analyze the current water treatment processes: Aguas de Calpe manager (Aguas de Calpe is a joint venture created by Calpe City Council and Serhico, S.A., to manage municipal services that are part of the integrated water cycle, including water supply, sewage treatment and wastewater treatment in the municipality of Calpe), Moraira WWTP manager, Dénia-Ondara-Pedreguer WWTP manager and Xàbia WWTP manager. The selection criteria for these interviews (all the technical managers of the main WWTPs, that were currently in service in the study area), and the scope (the evaluation of the volume of water treated, the existing infrastructures, the actors involved in the water cycle and potential measures to improve) are based on the research purpose of ensuring meaningful contributions. The interactions were conducted throughout the month of September 2024, lasting one morning each, and qualitative data from these sources are provided in Section 4 of this work.

The results of some analyses conducted in the Turia River Basin or Segura River Basin [27,28] show that there are clear benefits for both farmers and WWTP managers by implementing circular economy in water cycling in response to uncertainty derived from climate change: additional nutrients and regularity in their water supply benefit farmers, whereas pumping the treated water into the sea is avoided. Nevertheless, authors point out that more coordination is needed among the different stakeholders and some questions have gone unanswered, such as the illegal connection of waste pipes with traditional irrigation or the payment of pumping costs for reuse [27].

Other water-scarce regions have adopted the use of non-conventional water resources to tackle the water poverty issue [29,30], where authors noted that no individual measures or actions could effectively tackle the problem, and they recommend transformative approaches to provide pathways towards achieving a circular economy in the water; to this end, an important component required is the appropriate policy framework as a catalyst in change, and a more polycentric approach is needed to establish stronger linkages to the water–energy–food nexus, which represents fundamental opportunities for transitioning. Polycentric governance emphasizes the capacity of decentralized entities to take leadership in areas where nation-states have fallen short, and CASAMA, at a district scale, could exploit this window of opportunity.

It should be recalled, however, that the implementation of a circular economy involves combined efforts from organizations and individuals in key stakeholders’ major sectors of water and wastewater management to overcome infrastructural, constructional, and technological barriers [31], issues raised in the following sections.

3. The Paradox of Abundant and Insufficient Water Resources

As has been pointed out, climate change is exacerbating extreme phenomena, with a significant impact on ecosystems and natural resource management. In this district, as in the rest of the Mediterranean arc, periods of drought are increasingly recurrent and influence the availability of resources. It is useful to establish the difference between the total volume of water in a territory and the available water resources. On the one hand, we have the total the total available volume of water, which includes groundwater, surface water and non-conventional sources resulting from desalination and purification. On the other hand, these available water resources, circumstantially, are lower for reasons such as the salinity and contamination of the aquifers; the location of much of the groundwater resources inland of the district while demand is concentrated on the coast; or the absence of infrastructure for transporting and storing surface water (such as ponds and reservoirs), or for their adequate final treatment in purification and desalination plants (complementary technologies, such as reverse osmosis or tertiary treatments, which would make it possible to overcome the high levels of conductivity caused by saline intrusion in sewage networks). All this leads to a very low reuse of treated water and an erroneous perception of the real availability of water.

La Marina Alta has several sources of water potentially available in years of hydrological normality (Figure 1). On the one hand, in 2014, according to CASAMA’s own records [32] (whose figures that have remained practically unchanged at present), conventional resources accounted for 92% of the resource availability, including groundwater (206.04 hm³) and surface water (137.5 hm³), while non-conventional resources encompass a minority share, 12.34 hm³ from desalinated water and 19.3 hm³ from purified water.

On the other hand, analyzing the maximum water allocations in the studied sub-basin, according to the Hydrological Plan in force [26], at the beginning of the planning period of 2022–2027, we obtain the distribution from

Table 1. Water allocation in La Marina Alta according to resource origin in 2022. Source: own elaboration from CHJ [26].

Usage	Code	Name of Demand Unit	Surface Water (hm3/year)	Groundwater (hm3/year)	Reclaimed (hm3/year)	Desalinated (hm3/year)
Urban	U7005	Alfaro–Segaria, Ondara–Dénia and other water supplies.	0	8.4	0	0
Urban	U7010	Dénia supply	7.8	6	0	0
Urban	U7015	Supplies of Mediodía, Gorgos and others	0	0.6	0	0
Urban	U7020	Supplies of the Teulada–Benitatxell Municipal Water Consortium for Drinking Water Supply	0	4.3	0	0
Urban	U7025	Benissa–Senija User Community Supplies	0	2.5	0.3	0
Urban	U7030	Water supplies of the Vall del Pop Irrigation and Users’ Community	0	1.3	0	0
Urban	U7035	Supplies of the Community of Calpe, Murla and Vall de Laguar-Pozo Lucifer	0.2	6.9	0	0
Urban	U7040	Rest of supplies in La Marina Alta	0.2	1.4	0	0
Urban	U7045	Jávea water supply	0	3.4	0	3.6
Agricultural	A7005	Irrigable area of Oliva, Pego and Gallinera basin.	14.4	20.7	0	0
Agricultural	A7010	Irrigable area of the Girona River and Alberca Ravine	5.1	16.5	0.3	0
Agricultural	A7015	Groundwater irrigation of the Alberca–Gorgos Inter-river Basin	0	3.2	0	0
Agricultural	A7020	Irrigable area of the Gorgos River	1	3.6	0	0
Agricultural	A7025	Rest of irrigated land in La Marina Alta area	0	0.8	0	0
Agricultural	A7030	Irrigation of the Pla de Xàbia	0	0.9	0	0
Industrial	I7005	La Marina Alta system industries	0	1	0	0
Recreational	O7005	Oliva Nova Golf Club	0	0.5	0	0
Recreational	O7010	La Sella Golf	0	0	0.6	0
Recreational	O7015	Pego Golf Sector	0	0	0.6	0
Total maximum allocations planned			28.7	82	1.8	3.6

, in which 71% of the allocated resource is of groundwater origin, 25% surface, 3% from desalination and the remaining 1% from wastewater treatment:

In relation to rainfall, the district of La Marina Alta registers a more than significant pluviometric regime inland, reaching much higher humidity rates than those of the rest of the province of Alicante, a province that is mostly characterized by semi-arid conditions. According to historical data, the average annual rainfall in La Marina Alta is approximately 739.8 mm for the period 1980/81–2017/18, with the highest values concentrated in the autumn months, highlighting October and November with 101.2 mm and 104.0 mm, respectively [26]. It should be noted, however, that in recent years (up to 2024), there has been a significant decrease in precipitation in the area (Figure 2).

The potential surface water resource is scarce due to the lack of ponds or reservoirs, and practically all of it ends up in the watercourses and ravines transporting towards the sea. Furthermore, this imbalance is accentuated in periods of drought, such as the 2023–2024 hydrological year, which has been the driest on record, with a rainfall deficit of 56%; thus, in March 2024, the Water Basin Authority of Júcar River declared an exceptional, extraordinary drought due to the continued absence of precipitation in a large part of the basin. This situation occurs when water shortage compromises the satisfaction of the demand for all uses. In the case of La Marina Alta, there were situations of groundwater deficit in Oliva–Pego, Ondara–Dénia and Mediodía, which added to the structural deficit, accentuated by the summer period, the arrival of tourists and the scarcity of rainfall [34].

As shown before, there are municipalities that rely almost entirely on groundwater for their water supply, which has subjected the aquifers to intense overexploitation, causing high-conductivity scenarios due to marine intrusion [35]. Figure 3 shows the saline dome effect caused by the intense extraction activity through wells, which alters the balance between fresh water in the aquifer and salt water, given the proximity to the sea. As a result of water extraction rates above its own natural recharge capacity and the difference in density between freshwater and saltwater, this saltwater (being denser) tends to settle below the freshwater. Assuming that there is no mixing between saltwater and freshwater and that both fluids are in hydrostatic equilibrium, this equilibrium is altered when the overexploitation of the aquifer’s freshwater occurs. This is when saltwater penetrates inland and contaminates the aquifer’s freshwater [36]. Progressive salinization reduces the quality of the water and jeopardizes urban supply and other uses, such as agriculture. Therefore, the possibility of artificially recharging these aquifers with reclaimed water becomes important, which would improve the health of the groundwater and have a positive environmental impact on the district.

Regarding non-conventional resources, they come from wastewater treatment and desalination plants distributed throughout the municipalities of the district. In the case of the treatment plants, except for the Dénia and Moraira WWTPs, the rest do not have advanced tertiary treatments, so their contribution to the water pool system is negligible, and most of this water also ends up in the sea through outfalls.

The main source is, therefore, groundwater, with enormous diversity of catchments scattered throughout the district, from wells to springs. The aquifers supply both the inland municipalities of the district, with prevalence of the agricultural sector, and the coastal ones, focused on satisfying the demand coming from the strong tourist activity. This dependence compromises the quality of their water, as coastal aquifers experience marine intrusion and decalcification of clays, typical of the district, which produces an increase in turbidity.

The main aquifers include the following, quality map of which is shown in Figure 4:

• The Mediodía aquifer, which geographically spans Vall de Laguar to Ràfol d’Almúnia and currently presents salinity problems due to marine intrusion, especially in areas near the coast;
• The Almudaina–Segaria aquifer, located in Vall d’Ebo municipality, is in good piezometric conditions, although with risks of contamination due to turbidity during periods of heavy rainfall; it is mainly used for irrigation and urban supply;
• The Parcent aquifer, in Benigembla municipality, has experienced a progressive decrease in piezometric levels since 2015 due to overexploitation;
• Finally, the Albuerca–Mustalla aquifer, located in Vall de Gallinera municipality, is currently in a critical situation in some areas, with sustainability problems in the medium-term.

The recharge deficit is a generalized phenomenon in all of them, since the recent periods of drought have meant that the average annual rainfall in the region has been insufficient to counteract the extraction of water. In short, the aquifers of La Marina Alta represent a vital resource to support the development of activities in the district, but their current situation is very vulnerable, so their sustainability depends on the implementation of urgent measures. It is necessary to restore the balance between the reduction in abstractions and artificial recharge, which can be achieved with the integration of technologies that allow for the generation of quality treated water and efficiency in the urban water cycle, basic measures to guarantee the water supply in this strategic district [12].

In relation to surface water (Figure 5), the natural course of the water flows through river sub-basins associated with small rivers and ravines, in the absence of lamination infrastructures or reservoirs. The only one is the Isbert Reservoir, which was planned at the end of the 19th century as a solution to irrigate the Rectoría and Dénia plains, but it had filtration problems, and the waterproofing projects were never carried out [37]. Among the main sub-basins in the district, we can find the Bullent or Vedat River, which is associated with the ecosystem of La Marjal Pego–Oliva, a natural site of great environmental value. The Girona River is the most important course of La Marina Alta and on which both agricultural irrigation and aquifer recharge depend to a large extent. The Racons or Molinell River, located to the north of the district, is a sub-basin shared with the province of Valencia. Finally, the Gorgos or Jalón River, in the eastern area, which flows into Jávea, is also of great importance for irrigation and local aquifers and other basins linked to ravines or watercourses, such as the Gallinera Ravine.

Desalination plays a fundamental role in the district for guaranteeing urban supply. A distinction must be made between brackish water desalination plants and the seawater desalination plant of Xàbia (located in the municipality of Jávea), which stands out for its capacity, approximately 9.5 hm³/year. This plant, however, does not operate at full capacity due to the lack of infrastructure to distribute the water to other parts of the district. The brackish water desalination plants are located in Dénia (Racons and Beniardá), Calpe, Teulada, Poble Nou de Benitatxell, Els Poblets, Ondara, El Verger and Beniarbeig. As in the case of Jávea, one of the problems facing the district is the lack of transport and distribution networks, for which no financing formulas have been found, nor public–private investment, partly due to the lack of institutional leadership of CASAMA. In this context, the use of reclaimed water accompanied by adequate management of conventional renewable resources can lead the system to a situation of self-sustainable equilibrium over time [38].

According to data from the Public Entity for Wastewater Treatment of the Valencian Region (EPSAR) [39], the Valencian Region is one of the Spanish autonomous communities that reused most of its treated wastewater in 2023: 251.42 hm³ reused out of 446.86 hm³ treated per year (56%). In particular, the province of Alicante has the highest percentage among the three provinces, accounting for 72.44% of reused water with respect to treated water. However, since 2014, when 266.9 hm³ was reused, until 2023, the progress has been nonexistent. La Marina Alta treats 15.1 hm³ per year of the 131.96 hm³ per year treated in the province of Alicante as a whole. Additionally, 70.87% of the total treated water in La Marina Alta ends up in the sea, 22.86% in public waterways, 1.49% is infiltrated, 1.82% is reused for the agricultural sector, 2.87% is reused for recreational use (La Sella golf course in Dénia), and urban uses barely represent 0.08%. An example of the underuse of treated water resources is illustrated by the case of the municipality of Teulada–Moraira, which discharges almost all of the 547,000 m³ treated annually to the sea [39].

Regarding the quality of the effluent water treated in the 58 plants that exist in the district, most (44) meet the standards established in Council Directive 91/271/EEC [40], Regulation (EU) 2020/741 [19] and RD 1620/2007 [41], which establish minimum requirements for quality, monitoring and risk management for the safe use of treated water, especially in agricultural irrigation, thus contributing to a circular water economy. However, the salinity index is critical in La Marina Alta as there are 28 plants that present values that do not adapt their water for use in agricultural irrigation. The main problem lies in marine intrusion, both in the abovementioned aquifers and in the sewage networks. This problem is particularly relevant in coastal tourist towns, such as Dénia, Teulada–Moraira, Xàbia and Calpe. In these municipalities, the absence of advanced membrane water treatment systems (reverse osmosis) makes their subsequent use unfeasible as they do not comply with the regulations in force. In the interior of the district, although there are lower levels of salinity than in the coastal municipalities, there are fewer treatment plants, and the absence of transport networks complicates its use in agriculture. There is a paradigmatic example of the problem generated by the absence of technology, in this case reverse osmosis. This is the case of the Dénia–Ondara–Pedreguer WWTP, a treatment plant that has a tertiary ultraviolet disinfection system, which allows for part of the treated effluent to be used to irrigate the La Sella golf course, but when high levels of conductivity are present, the water cannot be used and ends up in the sea.

Another example is the case of the Moraira WWTP, which has a tertiary system with membranes, but the absence of distribution networks prevents the water from being used for urban uses, such as street washing or cleaning urban furniture. Furthermore, the lack of a reverse osmosis system to alleviate the problem resulting from salinity in the sewage networks makes it impossible to use it for the irrigation of parks and gardens or agriculture. In the first phase, the implementation of tanker trucks would allow for the water to be transported for different urban uses. The rest of the municipalities in the district have neither tertiary treatment nor systems to solve the problem of salinity, which limits its reuse.

If we analyze the 2014 demand for water resources, the needs for urban supply amount to 29,464,300 m³/year, focusing on the municipalities with the largest population and tourist development, which are those located on the coast, such as Dénia or Jávea, which in total demand 6,167,738 m³/year and 7,764,000 m³/year, respectively [32]. Inland municipalities, with a smaller population, have lower needs for supply. An example is the municipality of Vall d’Ebo, with a demand of 35,200 m³/year in 2014.

To conclude the characterization of water resources and their availability, it should be noted that the district is very vulnerable to the climate change scenario that involves the worsening of extreme phenomena, not only with a greater incidence of droughts, but also greater exposure to the effects of torrential rains as a result of the additional contributions of heat and moisture from the atmosphere in the Mediterranean area, as is the case for this district of southeastern Spain and that can lead to organized, adverse and long-lasting storms [42]. According to the Water Basin Authority estimations, runoff in the La Marina Alta sub-basin will decrease by 32% by 2033 under the pessimistic climate change scenario RCP 8.5, leading to a structural water resource deficit of 11.5 m³/year, whose origin would be in the groundwater-supplying system [43]. In this sense, the district of La Marina Alta not only suffers from insufficient infrastructure to manage water resources, but there are no infrastructures, such as dams, dykes, channeling of ravines in urban sections or flood control elements. Thus, it is a priority to address the implementation of these hydraulic infrastructures to prevent or mitigate the effects of flooding, which leaves the riverside populations in a situation of extreme vulnerability to the danger of flooding due to its torrential rainfall regime and the significant levels of runoff throughout the northern half of the province, particularly in the interior of La Marina Alta, both to provide security in cases of extreme events, and to make good use of these surface water resources, as well as to accumulate potential reclaimed water, as potential synergies between strategies for managing both drought and flood events. Among the different actions that are considered a priority is the Isbert dam, which is not in operation and only serves to retain water and then infiltrate it into the aquifer it feeds, called Pozo Lucifer. It was built in the 1930s and is located on the Girona River, but has a high infiltration rate due to the karst nature of the terrain. In the proposal for the provincial plan for the construction of recharge dams developed by technicians of the Provincial Council of Alicante [44], it was established that this infrastructure not only complied with the hydrological and geological criteria established for artificial recharge avoiding the overexploitation of aquifers, but also, by increasing its capacity and improving its waterproofing, it could play a decisive role for safety in the event of floods, protecting the riverside urban areas and acting, at the same time, as a reservoir in drought scenarios for supply and agricultural irrigation. Replicating the successful case of La Marina Baja [16], the dual use of recharge dams for aquifer replenishment to use resources during dry periods and flood mitigation during intense rainfall events would offer integrated and resilient solutions to La Marina Alta.

4. Circular Economy and Reclaimed Water: Proposals for the Long-Term Water Balance in La Marina Alta

The starting point for this work is to consider the importance of efficient water management in the district of La Marina Alta to preserve the ecosystems and the cultural landscape, to guarantee uses and provide security in the quantity and quality of supply for the supply and development of activities related to agriculture and tourism. It has been shown how, despite the area having sufficient resources, in critical periods, some municipalities do not manage to satisfy the needs derived from the supply to a growing population, concentrated in the coast, the demands of the main economic activities that have been developed (tourism and agriculture) and the environmental requirements, as is the case of La Marjal Pego–Oliva. Thus, according to the latest data registered by the Provincial Council of Alicante in 2014, the district had an excess of water, accounting for 370 hm³ potentially available in front of the demand associated with economic sectors, supply and environmental needs of just over 80 hm³ [32]. These figures show an apparent surplus of 290 hm³, but an example on the contrary is what happened in August 2024, when the supply of drinking water was compromised in the coastal municipalities and the Montgó natural park had difficulties in maintaining good ecosystem status, making it necessary to declare an emergency [45].

It is in this context, proposals from circular economy can play a key role in responding to the water challenges of La Marina Alta district, as they can help to optimize the available resources, improve the resilience of the system in the face of extreme events caused by climate change and reduce the environmental impacts of social and economic activity [46].

In conjunction with more efficient governance, explained in Section 5, the use of reclaimed water is proposed as the main element to recover the water balance in the district, incorporating the highest possible percentage of reclaimed water. This requires simultaneous operations at different levels, by improving the urban water cycle in relation to transport and distribution networks, implementing advanced technology for water treatment and considering the construction of reservoirs, dams and ponds to accumulate reclaimed water and subsequently put it to use. In relation to the necessary storage elements, although they may present problems derived from water evaporation, causing an increase in the concentration of salts in periods of high temperatures, the incorporation of renewable energy sources by means of the installation of floating photovoltaic plants should be considered in order to address the problem, as well as to meet the energy needs of pumping.

Following the map of groundwater quality in the district (Figure 4), which shows how groundwater in the coastal and middle zones present poor or regular quality, the proposal to implement circular economy of water in the municipalities of the coastal strip could environmentally recover the coastal aquifers, allowing them to be subsequently a guarantee of supply in scenarios of shortage or drought. It is also on the coast where most of the demand and the largest amount of basic water treatment infrastructures are concentrated. The main WWTPs of the coast are Calpe, Dénia–Ondara–Pedreguer, Jávea and Moraira, where more than 70% of the population of the district resides, are long-stay residents and receive thousands of tourists. These represent a strategic opportunity for the promotion of circularity in water management in a territory with marked water irregularity, but first it is essential to adapt the WWTPs of the proposed municipalities.

The most suitable option to adapt the plants is the use of membrane bioreactors (MBRs), as they are a technology that combines the biological degradation process by activated sludge with direct solid–liquid separation thanks to the membrane [47]. Although this technology has some disadvantages, such as energy costs or membrane replacement due to contamination, it is the most suitable in situations where conductivity indices are high. In addition, the combination of MBR as pretreatment reduces the organic load before RO (reverse osmosis), thus reducing the wear of the osmosis membranes and optimizing operating costs. This option outperforms elementary tertiary treatments (such as sand filtration or UV disinfection), which do not effectively address salinity.

As stated, the proposal of the analysis focuses on acting in the main WWTPs of the district, which embody 11.7 hm³ of treated water, where a negligible amount is reused nowadays. The Calpe WWTP treated 2.5 hm³ in 2023, with secondary and tertiary treatments with disinfection [39]. At present, due to its high conductivity, it is not reused, since the tertiary treatment to be implemented should include a stage with MBR. This technology makes it possible to obtain a higher quality of water, to which subsequent reverse osmosis treatment should be added. The reclaimed water, with this appropriate treatment, could be used for the irrigation of parks, gardens, street washing and other urban uses.

The Moraira WWTP treated 541,941 m³ in 2023, with secondary treatment and tertiary treatment with micro/ultrafiltration, disinfection and chlorination [39]. The ultrafiltration stage produces a high-quality treated effluent, but only 1% is reused, with the rest of the treated water ending up in the sea. This type of effluent is ideal for reuse; however, the presence of high conductivity, together with the absence of distribution networks, makes it unfeasible. Hence, reverse osmosis technology is proposed for this WWTP in order to alleviate salinity problems.

The Dénia–Ondara–Pedreguer WWTP treated 6.6 hm³ in 2023 via secondary treatment and advanced tertiary treatment, with disinfection, chlorination and UV radiation [39]. The effluent is discharged to the sea, except for 435,300 cubic meters that are destined for La Sella golf course. To increase reclaimed water, firstly, it is critical to improve the sewage network to minimize marine intrusion; secondly, tertiary MBR treatment should be installed for the treatment of the effluent flow that would be destined for reuse. In 2023, the percentage of reused water was 6.6% of treated water, which opens a strategic window of opportunity to meet agricultural needs, in addition to other environmental uses.

The Xàbia WWTP treated 2 hm³ in 2023, with secondary and tertiary treatments with disinfection and chlorination [39]. This is a municipality that also has problems with the sewerage network and with the sanitation network, for which the adoption of MBR is proposed, as in previous cases. Nowadays, through the submarine outfall located in the bay of Jávea, 100% of the treated water ends up in the sea. The modernization of the water treatment systems would make it possible, with the implementation of a distribution network, to take the water to reservoirs that are currently in disuse for urban, agricultural or recreational uses, and the recharge of aquifers.

In addition to these measures, a series of actions are proposed for the urban water cycle, based on improving the sewerage network and the primary distribution network to improve efficiency and avoid losses. In this way, the salinization of the water reaching the treatment plants would be considerably reduced and a lower conductivity would allow for the supply of drinking water in months with greater climatic stress. It is also proposed to develop a distribution network of treated water through a double urban network. This network would allow the channeling of treated water for urban uses, such as street washing, parks and gardens, public fountains, agricultural, recreational and industrial uses. This solution, moreover, is currently a legal requirement according to RD 1085/2024 [48] and obliges municipalities with more than 50,000 inhabitants or equivalent functional areas (as is the case here, especially in the summer season) to have water circularity plans for urban uses.

The proposal to reuse reclaimed water in the most important WWTPs entails the indirect recharge of the most affected aquifers and even the possibility of direct artificial recharge. In this sense, a volume of artificial recharge of more than 800 cubic hectometers per year in Spain could be realistically estimated, which constitutes a strategic opportunity for territories with shortages, severe risk of drought, overexploitation of aquifers or contaminated soils [49].

The digitization of the urban water cycle is a major challenge facing the municipalities of the district. Some municipalities suffer from losses and low levels of efficiency in their water management. It is therefore necessary to implement technologies that allow for the detention and correction of leaks in order to optimize and maximize the available water, as the use of new technologies, the implementation of Smart cities and the use of big data can also be useful tools to prevent water losses [50]. In this vein, education and awareness are essential in the responsible use of water. Consequently, information campaigns for tourists and training in educational centers, promoted by CASAMA, would contribute to understanding the value of the resource and making better use of it.

In parallel, it is vital to improve the distribution and transport networks of reclaimed water also for uses linked to agricultural and recreational demands. At present there is a golf course, La Sella, that regularly uses water from the Dénia WWTP, but there are other golf courses, such as Xàbia (in Jávea) or Ifach (in Benissa), that could also benefit from reclaimed water, as well as parks and gardens in the coastal municipalities and natural areas, such as La Marjal Pego–Oliva.

5. The Institutional Role of the Consortium in the Potential Integrated Water Resources Management in La Marina Alta

CASAMA was constituted on 31 March 1987, with the impulse and promotion of the Provincial Council of Alicante in an attempt to jointly solve the problems of water supply that were beginning to arise, mainly in the municipalities of the coast, as a result of the boom in tourism, construction and the increase in the associated demand. In this consortium, the municipalities could join on a voluntary basis and without financial contributions, but by ceding, theoretically, on a compulsory basis, their water flows, which has never happened. The lack of financing has prevented the implementation of the strategic infrastructures detailed in the previous sections. All this resulted in inactivity and a weak application of circular economy principles in the region [51].

This inoperability and the absence of strategic investments, probably due to the lack of collaborative culture in the district, together with progress in the municipalization or internalization of water management, were aggravated by the conflicts over the use of resources during recent periods of scarcity. The lack of joint responses led many municipalities to choose to prioritize the search for solutions individually (or together with a few nearby municipalities), and, in some cases, to consider leaving the CASAMA, as was the case of Dénia [52]. The lack of agreement between the municipalities on ceding their resources to the organization to manage them jointly, as established in its statutes [32], and the lack of commitment reflected in an attitude of “every man for himself”, has produced increasingly recurrent conjunctures of water insecurity [53]. Despite these circumstances, the consortium constitutes a first-rate tool to face the water challenges of the district with 18 municipalities integrated until now, representing 177,709 inhabitants of the 201,840 inhabitants in the district [12].

The recent periods of drought (2021–2024) have caused a crisis scenario in La Marina Alta, opening a profound debate on the future of water management in the district. The Water Basin Authority of Júcar River declared an exceptional situation of extraordinary drought due to the continued absence of rainfall in a large part of the basin [54], which led to urgent investments in water infrastructure being undertaken to ensure the supply of drinking water, especially after the summer of 2024, when the tourist reputation of the district was at risk.

Numerous national and international media echoed this water crisis, where it could be read “in Spain, on the Costa Blanca, people queue for bottled water” [55]. In August 2024, there were cuts in the supply of drinking water in some municipalities for several weeks, as was the case of Poble Nou de Benitatxell and Teulada–Moraira. The seriousness of the situation led administrations and experts to get to work with the aim of preventing and responding to future crisis scenarios. In line with what, in the Provincial Water Pact [20], was pointed out, the need to articulate an efficient governance model in La Marina Alta, based on the integrated management of resources (incorporating reclaimed water), which contemplates all uses, restores water balance, avoids overexploitation of aquifers and guarantees water for supply, economic activities and environmental needs.

The climatic alterations in this Mediterranean region are evident: the periods of drought have been accentuated by the evolution of global warming in the last 150 years, the increase in days per year with extreme heat has skyrocketed since the late twentieth century, while the days with extreme cold have decreased significantly, showing a significant thermal shift [42]. This change is also associated with the warming of the sea, with such terrible consequences as we have seen in the Mediterranean recently with phenomena such as the Valencia floods in October 2024 [56]. On the one hand, the alteration of the air masses that circulate over the continent has been evidenced, such that, in Europe, especially in the center and south of the continent, a historical succession of unprecedented heat waves and floods has been experienced in recent years [57]. Scenarios that have a special incidence on available water, whose absence has an undoubted negative impact on ecosystems and the economy, being at the core of sustainable development and fundamental for socioeconomic development, food and energy production, ecosystems and for human survival itself [58]. On the other hand, increasingly recurrent droughts are causing loss of vegetation and abandonment of crops, triggering two phenomena: erosion of the territory and salinization. In this sense, and in order to respond to the present challenges, territories such as La Marina Alta need an inclusive, integrated governance model, with the involvement and commitment of all stakeholders, especially civil society [59], which allows for offering a look beyond the current problems, providing resilience to the territory against extreme climate phenomena, while implementing communication, training and education strategies in the educational centers themselves and through awareness campaigns by the administrations.

The challenge posed in this research work is to propose the incorporation in CASAMA of all the municipalities of the district, establishing higher levels of institutional collaboration and involving, as a novelty, the users, mainly the tourism sector and farmers, in the decision-making process. These stakeholders are called upon to play a vital active role in the water balance of the area, together with the institutions and the consortium itself, a regulatory body that acts as a manager between the available resources, identified demands and potential exchanges [38]. Therefore, an IWRM model based on the circular economy of water and the principles of institutional economics is proposed [16]. In this new scenario of shared management and decision-making, the role of the municipalities is key, given the preferential nature that the local administration gives to urban drinking water supply, qualified in Spanish legislation as a public service of local competence [60]; likewise, intermunicipal water consortiums are called to become a leading player in the new system for the supply of water to towns [16]. Within the consortium, it is possible to promote cooperation among all the agents involved and to make use of one of the main characteristics of consortia, namely their flexibility, by allowing other types of institutions or organizations, beyond the public administrations themselves, to participate in them, which makes them an effective tool. As Emilio Pérez pointed out [61], the consortium is presented as an ideal formula for the joint management of groundwater, allowing for collaboration between different administrations and users in the planning and execution of measures for its sustainable use. This clarifies some of the characteristics and virtues of polycentric governance, in which the participation of users in the creation and application of rules is basic for effective and sustainable governance of common resources [62]. For these reasons, CASAMA must assume a coordinating role between administrations, private investment and users, which is essential to guarantee supply under water stress scenarios [63] and provide a well-articulated financial response to conflict resolution, with inclusive and participatory management of the stakeholders involved, as conceptualized in Figure 6.

Along with the role of the institutions and management bodies, it is important to highlight the importance of the rules and the application of water legislation to provide certainty to the consortium members and open scenarios where strategic projects and investments could be implemented. At this point, the use contracts are also central, specifically for the water from the Xàbia desalination plant with some near municipalities in the district, such as Teulada–Moraira or Poble Nou de Benitatxell, as well as for reclaimed water. The contracts provide not only legal certainty, but also economic viability for the treatment infrastructures and the necessary distribution networks. All this, together with the necessary modernization of the urban water cycle in the municipalities, are measures that constitute the basis on which to build a model of IWRM, the one to be promoted by the consortium, based on participation, shared decisions, rules, incentives and collaboration [64].

There are several investments that have been contemplated by CASAMA in recent years and that must be undertaken. These are infrastructures to connect the desalination plant of Xàbia and Poble Nou Benitatxell (through the so-called Camí Vell de Teulada), which would allow for greater use of the resources coming from the desalination plant, taking advantage of the maximum production capacity of the plant and, at the same time, reducing the dependence on aquifers. This connection would make possible the transfer of water from the desalination plant to the Teulada–Benitatxell Water Consortium, providing a water backbone for the south of the district. Another key planned infrastructure is the interconnection of the wells of Senija de Gata de Gorgos, Canor de Benissa and the Senija well of the Teulada–Benitatxell Water Consortium, which involves various pipelines and the construction of a reservoir to interconnect the water transfer between the municipalities and jointly manage the three wells in situations of drought. The construction of reservoirs in the middle zone of the district, together with the extension and improvement of transport and distribution networks from the coast, would make it possible to pump reclaimed water and have reserves for use in situations of drought or occasional shortages. As a result, the use contracts should play a fundamental role, providing economic stability and certainty in investments, contributing to a more efficient integrated management of the available water resources, providing water supply security in times of shortage. This type of contract, regulated by Spanish water legislation, can establish volumes, economic compensation and planning of future investments to ensure sustainable uses.

Table 2. Analysis of the proposed solutions. Source: own elaboration.

Scope	Type of Measure	Components of the Measure	Opportunities and Benefits	Weaknesses and Barriers	Financing and Participants Involved	Source of Energy
Governance	Modification of CASAMA’s statutes	Incorporation of users (neighborhood associations, irrigators and third sector) as members of CASAMA together with the consortium municipalities, the Valencian Regional Government and the Provincial Council of Alicante.	Dialogue, transparency, inclusive management and shared decisions.	Historical conflicts between the inland and the coast or between agricultural/environmental activities and tourism. Institutional fragmentation and lack of integration of municipalities. Risk of politicization.	Without any additional costs. Technicians from the municipalities and administrations composing the consortium. Stakeholders.	-
	Modification of CASAMA’s statutes	Creation of the urban water cycle observatory.	Analysis of resources and consumption (tracking indicators). Awareness campaigns, training and elaboration of consumer guides. Alignment with strategic plans such as the Spanish Circular Economy Strategy.	Poor culture of institutional collaboration and historical conflicts among users. Lack of financing. Need for investment in expensive technology. Risk of politicization.	Monetary contributions of administrations composing the consortium. Public–private partnership.	-
	Modification of CASAMA’s statutes	Creation of the water technical committee of the district.	Technical advice, reporting, collaboration between administrations, universities and companies, elaboration of plans (including cost-benefit analysis): drought, infrastructure and storage.	Historical conflicts between the inland and the coast or between agricultural/environmental activities and tourism. Lack of commitment on the part of the consortium member municipalities.	Without any additional costs. Technicians from the municipalities and administrations constituting the consortium.	-
	Modification of CASAMA’s statutes	Integration of existing associations of municipalities and other supralocal management bodies within CASAMA.	Interoperability of management bodies.	Institutional fragmentation and lack of integration of municipalities. Lack of trust in CASAMA.	Without any additional costs. Technicians from the municipalities and administrations constituting the consortium.	-
	Compliance with CASAMA’s statutes	Assignment of municipal flows to CASAMA.	Rational and efficient use of water resources at district level.	Institutional fragmentation and lack of integration of municipalities. Lack of trust in CASAMA.	Without any additional costs. Technicians from the municipalities and administrations constituting the consortium.	-
	Modification of CASAMA’s statutes	Minimum public tariffs for agricultural, recreational and water supply uses.	Feasibility of public–private investments and legal certainty.	Institutional fragmentation and lack of integration of municipalities. Lack of trust in CASAMA. Its implementation would have an initial social rejection.	Without any additional costs. Technicians from the municipalities and administrations constituting the consortium.	-
	Modification of CASAMA’s statutes	Contracts of use.	Establish volumes, economic compensation and viability of infrastructure investments with public–private partnerships.	Institutional fragmentation and lack of integration of municipalities. Distrust in CASAMA. To be approached with individual projects.	Without any additional costs. Technicians from the municipalities and administrations constituting the consortium.	-
	Modification of CASAMA’s statutes	Collaboration with universities and start-ups.	Knowledge transfer.	Seeking incentives.	Without any additional costs. Technicians from the municipalities and administrations constituting the consortium. Public–private partnership.	-
Technology and infrastructure	MBR	Implementation of tertiary treatment at Calpe WWTP, Xàbia WWTP, Dénia–Ondara–Pedreguer WWTP and Moraira WWTP to reach 11.7 hm3 of reclaimed water.	Product water in accordance with European framework legislation, advanced treatment and increased flow of reclaimed water, with sludge reduction.	High energy consumption and cost.	European funds. Spanish Ministry of Ecological Transition, Valencian Regional Government and Provincial Council of Alicante.	Cogeneration with biogas, photovoltaic, gasification and pyrolysis.
	RO	Implementation of ROs at Calpe WWTP, Xàbia WWTP, Dénia–Ondara–Pedreguer WWTP and Moraira WWTP.	Decrease in conductivity and possibility of agricultural, urban industrial and recreational uses.	High energy consumption and cost.	European funds. Spanish Ministry of Ecological Transition, Valencian Regional Government and Provincial Council of Alicante.	Cogeneración con biogás Fotovoltaica Gasificación y pirólisis.
	Urban water cycle digitalization and environmental health	Artificial intelligence, big data processing, digital twins and Internet of things	Demand forecasting and leak detection, weather forecasting, pattern identification, incident and conductivity monitoring or simulation of hazard scenarios (such as drought).	Impact on municipal tariffs, depending on the percentage of public subsidy.	Municipal revenues. European funds. Spanish Ministry of Ecological Transition, Valencian Regional Government and Provincial Council of Alicante.	-
	Sanitation and sewerage networks	Modernization of the urban drainage system, sewerage network and sanitation services. Especially in coastal municipalities where saline intrusion is a challenge.	Prevention and reduction of environmental and public health impacts by reducing discharge. Control of marine intrusion and increased potential reclaimed water resources.	Nuisances to neighbors during building processes.	European funds. Spanish Ministry of Ecological Transition, Valencian Regional Government and Provincial Council of Alicante.	-
	Desalination	Expansion of the desalination plant in Xàbia and new desalination plants: Calpe, Teulada–Benitatxell and Dénia.	More efficient use, increased resources during periods of high demand and guarantee of supply in scenarios of shortage or drought.	High energy consumption and cost.	European funds. Spanish Ministry of Ecological Transition, Valencian Regional Government and Provincial Council of Alicante.	Photovoltaic.
	Water purification	New filtration plants in: Vall de Laguar, Vall de Gallinera, Gata de Gorgos, Alcalali and Tormos.	Improved water quality and suitability for supply, agricultural use or discharge into the inland public water domain. Minimized downstream processes. Environmental benefits in ecosystems or aquifers and public health.	Excessive turbidity of the resources in some catchments due to decalcifying clays.	European funds. Spanish Ministry of Ecological Transition, Valencian Regional Government and Provincial Council of Alicante.	Photovoltaic.
	Transport and distribution networks	Some of the main required actions would be the connection of the Xàbia desalination plant to Poble Nou Benitatxell (through the so-called Camí Vell de Teulada); connection of WWTPs to new urban reservoirs; connection of the Dénia–Ondara–Pedreguer WWTP to the Pego aquifer; interconnection of the wells of Senija de Gata de Gorgos, Canor de Benissa and the Senija well; Vall del Pop pipeline.	Full exploitation of the potential capacity offered by the Xàbia desalination plant; reduction in aquifer resources; reuse of reclaimed water for urban, agricultural and recreational uses; environmental recovery of natural park of La Marjal Pego–Oliva.	High investment cost.	European funds. Spanish Ministry of Ecological Transition, Valencian Regional Government and Provincial Council of Alicante.	Pumping with photovoltaic energy.
	Storage and regulation infrastructures	Repair of Isbert Reservoir, together with the construction of new storage reservoirs, linked to the waterways of the district.	Full exploitation of the high-rainfall regime; flood mitigation during intense rainfall events; integrated and resilient solution to drought periods; dual use of recharge dams for aquifer replenishment and efficiency of investments.	Investment and operation cost.	European funds. Spanish Ministry of Ecological Transition, Valencian Regional Government and Provincial Council of Alicante.	Pumping with photovoltaic energy by installing floating photovoltaic panels on storage infrastructures.
	Aquifer recharge	Reclaimed water would entail the indirect recharge of the most affected aquifers and even the possibility of direct artificial recharge.	Improved water quality and availability; water reserve in case of drought; environmental, social and economic benefits.	High energy consumption and cost.	European funds. Spanish Ministry of Ecological Transition, Valencian Regional Government and Provincial Council of Alicante.	Pumping with photovoltaic energy.

illustrates the summary of the proposed measures according to the theoretical framework presented in Section 2 on how IWRM can be combined with the circular economy and the roles of institutions in a polycentric governance scheme at La Marina Alta.

Proposals such as the creation of the water technical committee of the district or the urban water cycle observatory are aimed to improve participation and inclusive policies through shared decision-making in accordance with the principles of polycentric governance of shared assets [64] in order to establish rules and regulations for joint operation, improve control and supervision of the use of the resource and implement mechanisms that allow for the resolution of local conflicts, a feature historically considered in the district [65].

The main barrier to the implementation of infrastructure and technology-related measures is the lack of financing. Some plant renovations are projected to begin in 2025 by the Public Entity for Wastewater Treatment of the Valencian Region, but there is still a long way to go. This could be solved with commitment, opening the sector to private participation and applying for public funding from specific European financing programs, such as the EU Innovation Fund, the EU LIFE program, the European Regional Development Fund, the NextGenerationEU or the Recovery and Resilience Mechanism. Nevertheless, for major projects, an obligation to undertake a cost–benefit analysis in line with the methodology described in legislation in force is included, which should be the subject of future research work, detailed at the scale of each project.

6. Conclusions

As has been shown, the district of La Marina Alta has sufficient water resources to meet the potential demands in times of hydrological normality, but faces the eventual problem of scarcity, mainly due to ineffective institutional structures. This paradox is amplified in conditions of severe drought, which inevitably leads to supply shortages in municipalities.

Therefore, an IWRM model is proposed based on the use of conventional water resources, water from aquifers and surface water, combined with the effective incorporation of reclaimed water from the four main wastewater treatment plants on the coast: Calpe, Dénia–Ondara–Pedreguer, Xàbia and Moraira. In this sense, the implementation of infrastructures to accumulate surface water would allow for a more efficient use of the same, while serving to mitigate the effects of floods and preserving agricultural wealth and populations. The reservoirs would serve also to guarantee supply in scenarios of high demand, such as summer periods, when irrigation needs are combined with the increase in water demand associated with tourism development in the coastal area. Infrastructures such as the Isbert dam or lamination and regulation ponds, together with possible reservoirs strategically located in the middle zone of the district, would play a key role in efficiency and water guarantee.

It is also necessary to reestablish the hydrological balance of the aquifers that are the primary basis of water use in the district and, in particular, of those groundwater bodies subject to overexploitation or that have been affected by the processes of marine intrusion. The artificial recharge of aquifers is a technique that allows for water to be intentionally introduced into groundwater; once stored, it can be subsequently extracted for use in supply, irrigation, curbing marine intrusion, reducing pollution or regenerating ecosystems.

In terms of the urban water cycle, it is necessary to undertake certain fundamental actions, such as digitalization and sensorization, to improve efficiency and avoid losses and leaks. In addition, it is necessary to modernize transport and distribution networks, and sanitation and sewerage networks, and to incorporate advanced treatment technologies such as membrane bioreactors and reverse osmosis systems in order to minimize conductivity and allow for water to be used in a circular economy scheme.

In short, in this model of IWRM in La Marina Alta that is proposed, the role of the institutional economy and effective governance is fundamental under the leadership of the CASAMA, as a management and meeting body between users, such as irrigation communities, local authorities, other administrations, companies specializing in water management and operating standards. Over the past few years, inland residents, where the district has greater and better groundwater resources, have felt like the object of decisions, rather than the subject of them. This has led to crises such the 1980s water war aforementioned and the recent problems with the extraction of the aquifers in La Marjal Pego–Oliva. Dialogue and shared decision-making are needed to minimize potential conflicts between coastal and inland residents or agricultural versus urban users, and seek solutions to the important challenges facing this territory; not only when an extreme situation occurs, but well in advance to manage natural resources more efficiently. The first half of the year 2025 was rainy and, probably, the supply for the next two years is ensured in the district; however, everyone knows that drought will be back soon, and then society must be ready to act. In that sense, this diagnosis can be set as an example for other territories with problems of effective governance.

Finally, further research is needed to complete data gaps or conduct detailed cost–benefit analysis, but circumstances are right for the circular water economy to become a strategic pillar to strengthen the resilience of the territory against the impacts of climate change, provide water security to supply and, at the same time, improve soil quality and preserve biodiversity and ecosystems of the cultural landscape of La Marina Alta.