Assessment of Global change impacts on groundwater resources in Souss- Massa basin

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1 Assessment of Global change impacts on groundwater resources in Souss- Massa basin Choukr-Allah Redouane 1, Hirich Abdelaziz 1 and Nrhira Abdessadek 2 1 Agronomic and Veterinary Medicine Hassan II Institute, Complex of Horticulture, Agadir, Morocco 2 Watershed Basin Agency (ABH) of Souss Massa Daraa, Agadir, Morocco Introduction With worldwide concerns about water scarcity, agriculture is under pressure to improve water management and explore available options to match supply and demand (FAO, 2004). Morocco is a nation heavily dependent on agriculture, which is responsible for 19% of the country s gross domestic product (GDP) (Addison et al., 2012). The agricultural production in Morocco as most of Mediterranean countries suffers from water scarcity enhanced by increasing demand and climate change impacts (Schilling et al., 2012). Nowadays Morocco has implemented several strategies to cope with water scarcity as the National Green Plan which is a big project launched by the government to improve the agricultural production and the farmer s livelihood. The development of the agricultural sector allowed to Souss Massa region to play an important role in the socio-economic development of the kingdom. However this situation is accompanied with a significant depletion of groundwater reserves (Choukr-Allah et al., 2012). Indeed, the increased demand for irrigation water and the reduction in renewable water resources aggravated by climate change and agricultural production intensification leading to water table lowering, groundwater salinization and pumping costs increase are currently the major constraints of the management of groundwater resources which are considered the main source to satisfy the water requirements (ABHSMD, 2008). This situation calls for a fast intervention by both public and private sector to find out an eventual solutions as well as an alternative water resource. Among the succeed stories of PPP initiatives in the Souss Massa region, the irrigation district of El Guerdane zone which is managed by a private operator and has been implemented to save the citrus orchards in this zone, and the desalination project for irrigation purposes which will be built in the Chtouka zone to supply irrigation water for greenhouses growers. The government has also encouraged farmers to convert their surface irrigation system to drip irrigation by providing subsidies which can reach 100% of overall investment related to drip irrigation equipment, and to be organized within agricultural water user associations (WUAs) to facilitate their access to irrigation water and extension services. The objective of this study is to assess the global change impacts on groundwater management by developing many scenarios combining cropping system, climate change, political interventions and irrigation strategies, practices and technologies. Overview of the Souss-Massa basin The Souss- Massa basin, located in south- western Morocco, is one of the country s most important hydrological catchments with an area of 27,000 km 2. Elevations in the catchment range from 0 m (Atlantic Ocean) to 4,168 m (Toubkal peak in the High Atlas Mountains) (Bouchaou et al., 2011). Situated between the Atlantic Ocean and the high Atlas and Anti-atlas mountains. The watershed of the study area is composed of 25% of plains and 75% of mountains. The main plains are: Souss plain (4500 km 2 ), Chtouka plain (1260 Km 2 ), Tiznit plain (1200 km 2 ) (ABHSMD, 2007a). The climate is semi-arid to arid; it varies from humid to cold in winter on the summits of the Western High Atlas Mountain to the pre-saharian to fresh in winter in the plain. The rainfall presents a large spatial and temporal variability from 300 to 600 mm in the High Atlas to approximately 200 mm/yr in the plain. The average of potential evaporation ranges from 1400 mm in the mountains and near the Atlantic coast to 2000 mm in the plain (Bouragba et al.,

2 2011) The rivers of the region, locally called Oued are Souss and Massa, which receive important inflow, in particular from the rainladen High Atlas Mountains in the North and the Anti Atlas Mountains in the South (Bouchaou et al., 2011). The hydrological regime of rivers is characterized by strong seasonal and interannual irregularity. The maximum inflow occurs during the months of January, February and March, with a minimum in August (ABHSMD, 2007b). Water balance and water demand in Souss-Massa basin A survey carried out by the agency of Hydraulic basin of Souss Massa (ABHSM), the office of agricultural development of Souss Massa (ORMVASM), the office of drinking water (ONEP) and associations of water users (AUEA). The obtained results indicated that the water withdrawal in the region was equal to 738 Mm 3 of which 5% is used for drinking and industrial water and 95% for irrigation (ABHSMD, 2005). The existing dams in the Souss Massa basin allowed a water storage of 800 Mm 3 /yr to irrigate more than ha, 12 Mm 3 for drinking water and 162 Mm 3 for the artificial recharge of aquifers (MEMEE, 2014). The reduction in piezometric level of water table of Souss and Chtouka aquifer due to over-pumping and drought exhibited by a decreasing of water deficit varies from 100 to 370 Mm 3 /yr for Souss aquifer and 60 Mm 3 for Chtouka aquifer (ABHSMD, 2007d). Figure 3 shows the water balance for both aquifers. Figure 1: Water balance of Souss and Chtouka Aquifers Water quality monitoring The Hydraulic Basin of Souss Massa Drâa Agency (ABHSMD) has implemented a monitoring network of groundwater quality since The meausurements are carried out once per year (ABHSMD, 2007c). The monitored parameters are: Electrical Conductivity (EC), ph, N+, K+, Ca 2+, Mg 2+, Cl-, HCO3-, SO42-, NH4+, NO2-, NO3-, PO43-, Organic Matter (OM), Fecal coliforms and total coliforms. In general the groundwater quality in the Chtouka aquifer degrades from north to south. This

3 degradation is linked to agricultural activity within the perimeters of Massa and Tassila and movement of groundwater at shallow depth in the shale. According to Tagma et al., 2009) the aquifer in Chtouka-Massa region is the most severely contaminated; 36% of wells exceed the regulatory threshold of potability of 50 mg/l nitrate. In the Souss region, it is relatively less affected; 7% of wells crossed 50 mg/l with an average composition of 22 mg/l. The irrigated areas seem to be the most affected by nitrate pollution as result of the excess of nitrogen fertilizers application. Due to groundwater overexploitation the coastal area of the Souss-Massa basin tend to be affected by salinization problem led by the sea water intrusion. According to surveys carried out by the ABHSMD agency in the Souss-Mass basin the saline groundwater is located in Issen and the south Agadir coastal zone in Souss aquifer, Sidi Bibi, Massa, Belfâa and Aït Milk in the Chtouka aquifer, Tiznit aquifer, Ifni basin, the coastal zone of Tamraght basin and at the center of Tamri aquifer (ABHSMD, 2007c) Water management gaps and predicted scenarios Despite all efforts carried out by the water management authorities at technical or political level as the generalization of drip irrigation, developpement of new alternative water resources (treated wastewater), extension services and the aquifer contract, the water balance in the Souss- Massa continues to be negative as result of the increased agricultural activities especially cultivating large water consumer crops as banana and forage crops. As water became scarcer, the various strategies diverged. Disinterest in farming (resilience or abandonment of crop land) or the modification of cropping patterns (reduction of irrigated surface area and changes in production systems) occurred and alternative water resources were sought, leading to massive over-scaled investment in a race to pump water from the aquifer, or to shifting land tenure. The scenario to be achieved by the ABHSMD Integrated Water Resources Management and Development Plan (IWRM-DP) is based on restoring the balance between the supply and demand, mainly by increasing water availabilities, whether from underground, surface or nonconventional sources. This strategy confirms that on the one hand the same conceptual framework is sustained despite the problems encountered and the failure of previous IWRM-DP strategy to restore the balance, and on the other hand, that emphasis is being placed on the offer without really controlling the demand. In order to assess the global change impacts on groundwater in the Souss-Massa basin we have developed several scenarios taking in consideration all the stressors and their implications as well as the main interactions between them. Climate change seems to be one of the most important stressors exhibited by reduction in rainfall and increasing temperature resulted in reduction in the aquifer recharge and increase of water evaporation. Climate change scenarios A1b, A2 and B1 are generated using MarkSim DSSAT weather file generator. Change in the agricultural production trends following the market conditions and water availability is considered one of the stressors and at the same time implication, stressor because the increase in agricultural activitie leads to more water extraction and implication because it depends to water availability. The Cropping system scenarios are corresponding to change in production pattern especially adopting the soilless system and new crops and varieties. The political interventions and strategies which the government has implemented and willing to setup as the Public Private Partnership projects (the project of using desalination for irrigation in Chtouka zone, modern irrigation district in El Guerdane zone, aquifer contract) in order to reduce the global change impacts are also developed as political scenarios. Scenarios related to irrigation strategies especially at field scale which are conversion of surface to drip irrigation, using weather stations network in irrigation scheduling, reusing wastewater and installing water meters in pumping stations were taken in consideration in this assessment. The figure 2 show the groundwater management model

4 Figure 2: Groundwater management model Models are useful tools used to simulate and predict the effect of factors on receptors and they can give a quite clear vision about the current or future situation.the ModFlow model is used to simulate those changes and generate many outputs as the water table piezometric level, drawdown, water table depth, recharge, concentration etc. in order to predict the impacts of all scenarios on quantitative and qualitative parameters of the aquifers. Conclusion Groundwater resources management in the Souss-Massa basin requires several basic conditions. Among these are clear communications between all the actors involved in managing the basin's water resources. The water authorities have to do more efforts to make aware the water users about the serious water problem in the region before moving to political and practical solutions by enhancing the extension services and technical assistance. As 95% of water is used for irrigation, more works should be done on water saving at field scale by improving irrigation techniques and methods and adopting less water consumer crops. Regulations could play an important role to limit the overexploitation of groundwater by the implementation of aquifer contract. Looking for new alternative water resources as desalination and treated wastewater reuse could be also a judicious choice to restore the negative groundwater balance and to save water for future generation. The worst scenario (no action) predict the disappearance of the aquifer in the 20 or 30 coming years which calls for an urgent actions and strategies by all the actors because if water is our right is also the right of our children. Acknowledgements This work has been supported by the European Communities 7 th Framework Programme Funding under Grant agreement no ENV Globaqua References ABHSMD. Stratégie de préservation des ressources en eau souterraine dans le bassin du Souss Massa- Plan d'action ), 61. ABHSMD. Volume 1: Contexte général du PDAIRE. Etude de Révision du Plan Directeur d Aménagement Intégré des Ressources en Eau (PDAIRE) des bassins du Souss Massa (2007a), 1. ABHSMD. Volume 2: Ressources en eau de surface. Etude de Révision du Plan Directeur d Aménagement Intégré des Ressources en Eau (PDAIRE) des bassins du Souss Massa (2007b), 2. ABHSMD. Volume 6: Qualité de l eau et charge polluante. Etude de Révision du Plan Directeur d Aménagement Intégré des Ressources en Eau (PDAIRE) des bassins du Souss Massa (2007c), 6. ABHSMD. Volume 8: Utilisation des ressources en eau. Etude de Révision du Plan Directeur d Aménagement Intégré des Ressources en Eau (PDAIRE) des bassins du Souss Massa (2007d), 8. ABHSMD. Situalyion hydrologique du bassin hydraulique de Souss Massa. 2008).

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