Water Management in Transboundary Rivers: Allocation and Governace, The case of Medjerda River Basin

Abstract

Decisions related to water resources management are shaped by a range of considerations from traditional economic factors and physical constraints to political considerations such as the need to manage political support within a single state or to navigate complex international relationships with riparian countries. Water resources all over the world face two main challenges overexploitation and over pollution due to population growth, climate change and the lack of advanced water governance approaches in many countries. These challenges become more serious in transboundary river basins and it may lead to conflict between the riparian countries. The Medjerda River is the only sustainable river in Tunisia with a total length of 460 km including 350 km in Tunisia before reaching the Mediterranean Sea at the Gulf of Tunis. With its tributaries, the river collects 80% of the Tunisia’s northern surface water, about one million cubic meters representing 37% of Tunisia’s surface water and 22% of water resources of the country (Zahar , Ghorbel, & Albergel, 2008). The MRB begins in eastern Algeria (near Souk Ahras) and extends into Tunisia where it extends from the North-west to the North-East with a total area of 23,175 km2, of which 7,700 km2 in Algeria. This watershed produces more than 1.000 million m3 of surface water per year, which is used to irrigate an area of 33.173 ha. The main objective of this research is to assess the sustainability of the current transboundary water management strategies at the Medjerda River Basin (MRB) and to propose a transboundary water management strategy that can help to sustain water resources at the MRB. The research work in this thesis uses a mixed research design applying both quantitative and qualitative methods through collecting data and interviewing different stakeholders. Then, water governance and allocation strategies have been assessed and water budget has been estimated using the Water Evaluation and Planning (WEAP) system based with the reference, climate sequence and high population growth scenarios. The reference scenario is based on the key assumption with the unit of domestic, irrigation and the Domestic variation. The climate changes scenario is based on the Water year Method in the period 2020 to 2050 and for the high population growth is based in the increasing of the rate 2.2% to 5% in the period 2020 to 2050. The results showed that, for groundwater the volume is varied between 1002.3 Mm3 to 1020 Mm3 for the climate change scenario and to 944.89 Mm3 for reference sceanrio in the period of 2020 to 2050. The monthly outflow and inflow for the reference scenario appear to be higher than the one of the monthly outflow and inflow for climate change scenario. For the surface water, there is an increase in river flow with a minimum of about 13.55 Mm3 in 2020, the mean of about 213 Mm3 and Maximum of about 480 Mm3 in 2025 for climate scenario. The flow requirement scenario will present an average flow of 352.51 Mm3 with a very low flow of 13.55 Mm3. For the years of Climate and high population growth of scenarios, water demand varies from the 218 Mm3 to 509 Mm3 and for the reference scenario varies from the 218 Mm3 to 395 Mm3 for horizon 2020 to 2050 period. This leads to conclude that water demand remains satisfied for consumption, especially during prolonged periods of drought, in the case of climate change and for the Unmet demand. The volume of water that will be used in horizon 2020-2050 varies between 4 Mm3 to 3 Mm3 for the reference scenarios and 4 Mm3 to 0 m3 for high population growth and climate change scenarios. The demand sites are satisfied for some of them in both countries according to the reference scenarios because it is almost 0 Mm3 ( e.g. Industry sector, Tourism sector and Collective uses sector). The demand sites are not satisfied for other sites in each city because it is higher than 1 Mm3 (e.g. Agriculture sector, domestic sector). This means water shortage will be an issues in MRB in the future. To conclude, it can, therefore, be considered that the demand for water in MRB is satisfied from 2020 to 2050 for the different consumption centres according to all scenarios.