Ranking suitable sites for irrigation with reclaimed water in the Nabeul-Hammamet region (Tunisia) using GIS and AHP-multicriteria decision analysis

https://doi.org/10.1016/j.resconrec.2012.05.006Get rights and content

Abstract

The present study describes an innovative methodology to rank suitable sites for irrigation with TWW using fuzzy-AHP based on GIS where the Nabeul-Hammamet aquifer catchment (Tunisia) is selected as the target area. The model is relatively simple and is extendable worldwide. Several influential parameters are identified considering simultaneously technical, social, economical and environmental aspects. They are grouped in five main criteria, namely land suitability for irrigation, resources conflicts, cost effectiveness, social acceptance and environmental impact. Each criterion is subdivided into several sub-criteria. A pair-wise matrix is used to compare these criteria and sub-criteria and to rank them according to their relative importance for site evaluation. Using GIS, geographical layers are obtained for the sub-criteria, leading to mapping and ranking the suitable sites for TWW irrigation.

The results show that the total suitable area covers 11,426 ha which represents 31% of the total Nabeul-Hammamet aquifer watershed. This constitutes quite a large zone that can absorb the entire volume of available treated wastewater, thereby increasing the region's agricultural production. The best sites to receive the surplus amount of TWW, produced by the treatment plants of the region, are located near these plants and inside agricultural lands. In addition, all these sites are located around the districts already irrigated by TWW, which underlines the role these districts may play in encouraging neighbouring farmers to change their attitude towards TWW and to accept it as an alternative resource for irrigation.

Highlights

► A new methodology is given to rank suitable sites for treated wastewater irrigation. ► Fuzzy-AHP based on GIS and easy-to-get spatial data, is the technique used. ► A Tunisian site is selected but the methodology is easily extendable worldwide. ► 31% of the total area is suitable and able to absorb all the wastewater produced. ► Best sites are located around the area already irrigated by treated wastewater.

Introduction

Tunisia, as well as several countries around the world, is facing the problem of water scarcity due to its arid and semi-arid climate, where the estimated available freshwater is only about 450 m3/citizen/year, which is relatively low compared to the international standards (1000 m3) (Louati et al., 2000). To tackle water penury and to fulfil growing population needs as well as agricultural, industrial and touristic sectors demand, Tunisia has made a remarkable investment in hydraulic resources mobilization. Thus, the available freshwater is mostly mobilized and is managed through various structures such as dams, channels, wells, hill dams and hill reservoirs and cisterns to harvest rainwater from houses roofs. In addition, water harvesting structures built on runoff watercourses and in the foothills areas (locally called jessours and tabias) are set up to meet olive trees and cereals water demand despite their location at Sahara limits (Ben Mechlia and Ouessar, 2004, Ben Mechlia et al., 2009).

Growing attention within the last 30 years has been paid to the treated wastewater (TWW) use, which has been considered as an important part of Tunisia's overall water resources balance (Bahri, 2002). Currently the Tunisian wastewater treatment office (ONAS) is running 106 urban wastewater treatment plants (WWTP) producing an annual total volume of 238 Mm3 (ONAS, 2009). This volume can irrigate up to 30,000 ha of cultivated lands, however only 9555 ha have been allocated (ONAS, 2009). Some irrigated districts failed in the start-up or in the long-term viability because of an inappropriate site selection.

In Tunisia, the irrigated land with TWW is commonly selected as the nearest agricultural area to the WWTP (CRDA, 2008). However, more criteria should be included to ensure a sound site selection where technical, economical, social and environmental characteristics interconnect. For instance, it is important to consider the negative impact of the practice on the environment (Ayni et al., 2011, Belaid et al., 2011, Drechsel et al., 2010) in addition to the farmers’ reticence, still considering treated wastewater as sewage (World Bank, 2010).

Considering the necessity of TWW use and its importance as a fast-growing practice (the allocated area is projected to reach 44,000 ha by 2021 (ONAS, 2009)), the establishment of a methodology to locate the best sites becomes a need. This methodology would be applied each time a WWTP's outflow is projected for use whatever the region. Thus, a better benefit of this non-conventional water is ensured along with the increasing availability of the national water and the reduction of the negative impact on environment.

On the other hand and according to a search made in scopus database, there is no scientific work published on site selection for TWW irrigation. However, site selection has been applied for many other applications such as aquifer recharge (Pedrero et al., 2011), solid waste disposal (Nouri et al., 2011), airport site selection (Ding et al., 2011), gas stations (Aslani and Alesheikh, 2011), water harvesting ponds (Al-Adamat et al., 2003), etc. Site selection techniques lead to the identification of the suitable sites and generate their suitability map through the integration of Multi-Criteria Decision Analysis (MCDA) into a Geographical Information System (GIS). MCDA combines technically feasible, economically viable, socially acceptable and environmental friendly criteria with respect to their importance to suitability. These criteria are then analysed using GIS and treated spatially to generate sites suitability maps.

Several MCDA techniques have been used in many fields for site selection and land allocation such as ELECTRE, PROMETHEE, AHP, TOPSIS, AIM, etc. (Behzadian et al., 2010, Conté et al., 2008, Gilliams et al., 2005, Reyhani-Khoram et al., 2007, Zhong-Wu et al., 2006). However, only few of them are integrated into GIS (Al-Adamat et al., 2010, Anane et al., 2008, Kallali et al., 2007, Marinoni, 2004), where Analytic Hierarchy Process (AHP) is the most applied (Anane et al., 2007, Tegou et al., 2010, Wang et al., 2009). AHP was established by Thomas Lorie Saaty in the 1970s (Saaty, 1980) and used to determine the priority for different decision alternatives via pair-wise comparisons with respect to common criteria.

The present study aims to establish an innovative methodology to map and rank suitable sites for irrigation with treated wastewater. It integrates a single-objective AHP method into a GIS model to select the most suitable sites for irrigation according to the available volume of TWW. The methodology uses easy-to-get data from Tunisian official institutions and available satellite images. The Nabeul-Hammamet aquifer watershed is selected as a study site to check the feasibility of the methodology.

Section snippets

Characterization of the study area

The study area corresponds to the Nabeul-Hammamet aquifer watershed. It is located at ‘Cap Bon’ peninsula at the North Eastern part of Tunisia and belongs to Nabeul District (Fig. 1). It covers 365 km2 of surface area, with a length of 34 km and a width ranging from 6 to 16 km. The climate is semi-arid with 400 mm as annual average precipitation at Nabeul city, and 19 °C as average temperature. The altitude varies between 0 m and 500 m. Geologically, the region is Pliocene and Quaternary, mainly

Suitable areas identification

The total suitable area for irrigation by TWW, obtained from the multiplication of the constraints, occupies 11,426 ha which corresponds to 31% of the total watershed area (Table 7). This constitutes quite a large area that can absorb all the amount of treated wastewater and contributes to increase the agricultural production of the region. The total suitable area is made by enclaves ranging from less than 1 ha to more than 1000 ha, sketched out mainly by the most restrictive constraints, namely

Conclusions and perspectives

In the present work, a single-objective AHP integrated with a GIS was carried out to identify and rank potential sites for irrigation with treated wastewater in the Nabeul-Hammamet aquifer watershed. Many criteria were selected, taking into account technical, environmental, social and economical aspects.

Constraints analysis shows that 31% of the Nabeul-Hammamet aquifer watershed is suitable for irrigation by TWW, which exceeds the required land for the reuse of the total SE3 and SE4 outflow.

Acknowledgements

We would like to thank the “Commissariat Regional de Development Agricole de Nabeul” and the “Groupement de Developpement Agricole” of Messaadi and Souhil for providing the needed data and information.

References (45)

  • V.F. Uricchio et al.

    A fuzzy knowledge-based decision support system for groundwater pollution risk evaluation

    Journal of Environmental Management

    (2004)
  • G. Wang et al.

    Landfill site selection using spatial information technologies and AHP: a case study in Beijing, China

    Journal of Environmental Management

    (2009)
  • M. Anane et al.

    Soil aquifer treatment areas in Tunisia: Jerba Island

  • M. Anane et al.

    Ranking suitable sites for SAT in Jerba island (Tunisia) using GIS, Remote Sensing and AHP-multicriteria decision analysis

    International Journal of Water

    (2008)
  • G.L. Asawa

    Irrigation and water resources engineering

    (2008)
  • M. Aslani et al.

    Site selection for small gas stations using GIS

    Scientific Research and Essays

    (2011)
  • F.E. Ayni et al.

    Impact of treated wastewater reuse on agriculture and aquifer recharge in a Coastal Area: Korba case study

    Water Resources Management

    (2011)
  • A. Bahri

    Water reuse in Tunisia: stakes and prospects. Vers une maîtrise des impacts environnementaux de l’irrigation

  • N. Belaid et al.

    Effects of treated wastewater irrigation on soil salinity and sodicity in Sfax (Tunisia): a case study

    Revue des Sciences de l’Eau

    (2011)
  • N. Ben Mechlia et al.

    Water harvesting systems in Tunisia

  • N. Ben Mechlia et al.

    Assessment of supplemental irrigation and water harvesting potential: methodologies and case studies from Tunisia

    (2009)
  • G. Conté et al.

    Multicriteria analysis for water and wastewater management in small rural areas

    Sustainable Water Management (Zer0-M)

    (2008)
  • Cited by (82)

    • Spatial multicriteria approach to support water resources management with multiple sources in semi-arid areas in Brazil

      2021, Journal of Environmental Management
      Citation Excerpt :

      The costs of the systems (e.g., operation and maintenance) were not considered in this study because of a lack of data. Sub-criteria were also established for each group of criteria to allow a hierarchical structure to be defined, similar to studies by Anane et al. (2012) and Gdoura et al. (2015). The CTEC is composed of sub-criteria that affect the operation and maintenance of the irrigation system.

    • Identification of water reuse potential in Metropolitan Regions using the Analytic Hierarchy Process

      2020, Environmental and Sustainability Indicators
      Citation Excerpt :

      In addition, several authors have been applying MCDA-GIS coupled approaches, especially because of its versatility and capacity to integrate different elements into complex multi-dimensional planning processes (Torrieri, 2017). Among the MCDA, the Analytic Hierarchy Process (AHP) seems to be the most applied, mainly because of its simplicity and good understandability (Paul et al., 2020; Campolina et al., 2017; Malinowski, 2006); wide applicability in different knowledge areas (Huang, 2017); and easy interoperability with systems such as Geographic Information Systems (GIS) (Alami Merrouni et al., 2018; Alves et al., 2017; Anane et al., 2012; Gdoura et al., 2015). A common problem to various environmental applications, including for water reuse, is site selection, evaluation and/or ranking.

    • Land suitability projections for traditional sub-alpine cropping in the Australian Alps and Chilean Dry Andes. A combined biophysical and irrigation potential perspective

      2020, Applied Geography
      Citation Excerpt :

      As expected, agricultural adaptation requires the identification of intricate synergies and trade-offs related to agricultural expansion, land use change processes and the supportive role of water storage and transfer capacity in these sub-alpine environments (Cornwell, Sposito, & Faggian, 2017; Howden et al., 2007). LSA has been applied to predict environmental gaps, later interpreted as land suitability indexes, dictated by biophysical parameters such as soil, landscape and climate factors, as well as other distance and areal metrics (e.g. Anane, Bouziri, Limam, & Jellali, 2012; Cengiz & Akbulak, 2009; Chen, Khan & Paydar, 2010; Yalew, van Griensven, Mul, & van der Zaag, 2016). Moreover, General Circulation Models (GCM) and Representative Concentration Pathways (RCP) (Taylor, Stouffer, & Meehl, 2012; Van Vuuren et al., 2011) have recently been included as inputs to LSA for projecting land suitability into the future (Sposito, Benke, Pelizaro & Wyatt, 2010; Sposito, Faggian, Romeijn & Downey, 2013).

    • Comparison of AHP and FAHP methods in determining suitable areas for drinking water harvesting in Birjand aquifer. Iran

      2020, Groundwater for Sustainable Development
      Citation Excerpt :

      First, they used FAHP to weight the alternatives under multiple attributes and thereafter, carried out a benefit/cost ratio analysis using both the FAHP score and the procurement cost of each alternative (Ertugrul and Karakasoglu, 2006). Anane et al. (2012) ranked suitable sites for irrigation with TWW using fuzzy-AHP based on GIS, where the Nabeul-Hammamet aquifer catchment (Tunisia) was selected as the target area. They believe that the model is relatively simple and is extendable worldwide.

    View all citing articles on Scopus
    View full text