Gestão Adaptativa das Águas Subterrâneas no aquífero de Benalup
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The Benalup aquifer in the Barbate River basin (MAS 062.14) is affected by the productive model of the region: livestock and agriculture that for years have been overexploiting the aquifer affecting its quality and quantity. The University of Cádiz, through the RNM-373 Geosciences group and the REMABAR project, has proposed alternatives for management based on the knowledge generated regarding the aquifer and its social and geographical environment. In order to generate proposals and manage the conflict between the use and the state of the body of water, the aquifer state and s and investigated the relationship between pressures and impacts, being relevant the existence of unauthorized catchments.
This project presents an innovative methodology on an environmental, social and economic scale in the context of climate change applicable to the SUDOE region
The Geosciences group of the University of Cádiz (UCA) led by Santiago García López is responsible for the project formed by 12 researchers The group was founded in 2009 participating to this day in 83 projects, 35 journal publications, 6 patents and other various activities.
At present, the Group’s activity is diverse and comprises the following areas:
- Dynamics of extinctions in marine environments.
- Groundwater: systems modelling and water resources assessment.
- Functioning of karst aquifers: hydrodynamics and hydrochemistry.
- Diagnosis and evaluation of groundwater contamination.
- Genesis, uses and contamination of soils.
- Integrated biostratigraphy.
- Storage and capture of CO2.
- Paleoclimatic and paleoecological reconstructions.
- Carbonation of alkaline solid waste.
The Benalup aquifer is located in the “La Janda” region of the Barbate watershed. The productive model of the regionlargely supports agricultural and livestock activity. The surface water comes from the reserves of Barbate, Celemín and Almodóvar. However, groundwater is obtained from the Barbate and Benalup aquifers that are subject to a high degree of exploitation and lack a regulatory entity, resulting in an uncontrolled situation of overexploitation of the aquifer. In the case of Benalup, you can find multiple unauthorized and unregistered farms, adding to this factor, the use of the land, the state of the water bodies is reduced both in quality and quantity.
To resolve the conflict between the state of these bodies of water, the uses and the environment, this “REMABAR” project is being developed.
The project has the following tasks:
Data collection by consulting cartographic databases, hydrogeological data, information and documents prior to the project, as well as data from the existing monitoring network. This information combined with GIS gives the possibility to manage and analyze to obtain significant information for the project.
The levels and qualitative status of the aquifer are then monitored. This campaign allows to define the recharge and discharge zone, the direction of the flow, the relationship between the river and the aquifer and the influence of the exploitations. Thus, the 1993 data were taken as a reference to study the evolution of the aquifer. The Benalup aquifer has a free / semi-confined aquifer behavior, the aquifer is mainly constituted by Myocene biocalcarenites with calcareous fossiliferous remains. The permeable formations of quaternary wind sands that form the upper part of the aquifer contribute greatly to the infiltration of rain (20-30%). The aquifer interpretation describes a conceptual model in which there is no connection between the aquifer and nearby rivers. In this context, the importance of the return of irrigation water and its influence on the state of the aquifer should be highlighted. On a hydrochemical scale, facies are mostly calcium bicarbonates, given the abundance of limestone in the region).
A geophysical campaign (ERT) provided knowledge regarding the geometry of the aquifer, allowing to discern the productive levels. Of the three formations that constitute the aquifer, the lower one is the most productive, being formed by calcareous rocks (biocalcarenites) The upper level formed by a mixture between sands and silts of the Quaternary presents lower porosity.
To characterize the properties of the aquifer, the porosity, permeability, transmissivity and storage coefficient of the materials were evaluated.
Through satellite images through the NDMI (Normalizad Difference Moisture Index) identified those plots that in the dry season and without previous rains, were wet, attributable to irrigation. With the official bases of land authorized for irrigation of the Junta de Andalucía (SIGPAC) and the identified plots, it was possible to discriminate between those authorized irrigations and those that did not have the permit.
Finally, dialogues were held with users to transmit knowledge and transmit the state of the aquifer to its users, round table sessions and information sessions were held where different agents involved in the use and management of water congregated. Likewise, a survey campaign was carried out to understand the vision of the users and their knowledge related to exploited water bodies and climate change.
Thus, the study of the Benalup aquifer has allowed the identification of multiple aspects to be taken into account for groundwater management (Vélez-Nicolás, 2020).
- Geometry and storage volume of the aquifer.
- The recharge and unloading areas.
- The hydraulic disconnection of the aquifer from the main hydrographic network.
- Define the 3 hydraulically differentiated aquifer sectors that constitute the aquifer and the direction of flow.
- The chemical characteristics of water.
- Approach to the possibility of carrying out actions of artificial recharge of the aquifer in order to achieve a joint management of surface water-groundwater and improve the qualitative status of the aquifer.
The use of surface water as a complement to supply the population is considered, a factor that will contribute to improving the quantitative status of the aquifer.
The work carried out within the framework of the REMABAR project is a step for the local water resource to improve quality and quantity.
With the evidence of the water need in the territory, it is expected that new policies focused on self-regulation by users will be necessary.
To contribute to the good practice and management of users, it is necessary to promote the study and generation of knowledge related to the aquifer system.
Political and economic regulations together with the necessary knowledge provide three pillars to recover and maintain the good state of the local water resource
The Department of Earth Sciences of the University of Cádiz has launched with the support of the Biodiversity Foundation, of the Ministry for the Ecological Transition, the REMABAR project has been framed in the research and transfer work of the University of Cádiz, aimed at improving knowledge and awareness in aspects related to water and adaptation to climate change. (MITECO, 2019)
The study area is located on the Atlantic coast of Andalusia, in the province of Cádiz. The Benalup aquifer is part of the Barbate River basin in the watershed of the Guadalete-Barbate.
Figure 1 Location of the Barbate River basin. Retrieved from: Vélez Nicolás, 2020
Great advances have been made in the framework of the management and protection of groundwater throughout the twentieth century. Even so, there are many problems that the authorities and those responsible for water resources must address. (Simpson, 2020).
At the beginning of the twentieth century, there is a growing trend in the exploitation of groundwater and unauthorized construction of wells (silent revolution) (Stephano et al, 2015). The main user was agriculture, a strategic sector, which generated jobs and food that have an impact on the economy. The lack of understanding of the rational use of water resources, together with the possibility of obtaining water near the fields without the need to transport it, led to the drilling of multiple wells without authorization or control by the hydraulic authorities, hindering the correct management of the resource that led to impacts of quality and quantity of the local water resource (Vélez-Nicolás, 2020).
Stephano et al. (2015) state that in the face of this situation, users begin to associate to protect their activities, avoid sanctions and acquire recognition as water users. It is stated that the subsequent trend is the application of technological solutions in: i) Modernizing irrigation; (ii) Finding new sources of supply; (iii) Apply methods of managed aquifer recharge. All actions in order to improve the quality and quantity of water bodies.
In the case of Benalup, management falls to the regional water authority and the community of water users. On the one hand, the Junta de Andalucía, the body responsible for ensuring the state of the body of water and its management, is overwhelmed and does not have the capacity to exercise its powers effectively. Thus, it is considered that the community of irrigators of Benalup, with greater capacity to exercise at the local level and the necessary knowledge should assume the management of the resource. In this sense, in Spain, the Water Law promotes the creation of user communities for groundwater to manage the problems exposed (Vélez-Nicolás, 2020).
Evidence of benefits from implementation
This project provides knowledge from scientific studies and communication with users. Hydrogeological knowledge related to the volume and geometry of the aquifer, flow direction, compartmentalization of the aquifer and information to understand the quantitative and qualitative state are highlighted.
The innovative aspect of management highlights the need for a community of users responsible for water bodies, both underground and surface and that has the ability to transfer knowledge to users. In this sense, it is necessary to have knowledge of the operation of the hydrogeological system, its particularities and affections that will grant the possibility of exercising effective control of the exploitation of the resource and generating participation policies. A local body capable of meeting the demands and making sustainable decisions around the water resource, according to the regional hydrological authority.
REPLICATION POTENTIAL IN SUDOE REGION
The methodology used in the study is applicable to all areas, especially arid regions with scarcity of resources, with water management problems at an environmental, social or economic scale. From generating knowledge and understanding of the case, involving the users themselves established in the Community, the proposed solutions are more suitable to face any conflict regarding the state of the water bodies themselves and in satisfaction of demand.
Key points of the innovative method
- Mechanisms of dialogue and pedagogy at the local level with users
- Social acceptance
- Use of decision support technologies, modeling and simulation around the aquifer system.
- Generate knowledge and transfer it to users to improve resource management in an arid and scarcity area.
The innovative practice was suggested by Sergi Compte of Catalan Water Partnership (CWP).
- Universidad de Cádiz (s/f). Geociencias – Universidad de Cádiz – Presentación. https://rnm373.uca.es
- Ministerio para la transición ecológica y el reto demográfico. (2019). REMABAR. Análisis de estrategias para mejorar el estado de los acuíferos bajo un contexto de cambio climático. https://fundacion-biodiversidad.es/es/cambio-climatico-y-calidad-ambiental/proyectos-convocatoria-ayudas/analisis-estrategias-mejora-acuiferos
- Junta de Andalucia, Consejería de medio ambiente y ordenación del territorio (2015). PLAN HIDROLÓGICO.
- Vélez-Nicolás, M., García-López, S., Ruiz-Ortiz, V., & Sánchez-Bellón, Á. (2020). Towards a sustainable and adaptive groundwater management: Lessons from the Benalup Aquifer (Southern Spain). Sustainability (Switzerland), 12(12).
- Simpson, H.C.; de Loe, R.C. Challenges and opportunities from a paradigm shift in groundwater governance. Hydrogeology Journal 2020, 28, 467–476.
- de Stefano, L., Fornés, J. M., López-Geta, J. A., & Villarroya, F. (2015). Groundwater use in Spain: an overview in light of the EU Water Framework Directive. International Journal of Water Resources Development, 31(4), 640–656.
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