Issue 3

In this study, the effects of seepage flow in the swash zone on beach profile evolution under the wave action are examined numerically. The seepage flow is induced artificially by a porous drain pipe buried beneath swash zone parallel to the coastline. The system includes minimal environmental impact compared with the hard protection methods. A higher order Boussinesq model for breaking and non-breaking waves is extended in the swash zone and is coupled with a porous flow model, in order to take into account the influence of infiltration-exfiltration processes in the sediment transport. This influence is introduced in a simple and well-proven sediment transport formula by using a new modified Shields parameter, which is derived after the modification of the shear stress and the immerged sediment weight. In order to incorporate the suspended sediment transport rate, the depth-integrated transport equation for suspended sediment is solved. Model results are compared with experimental data. The agreement between numerical simulations and experiment is quite satisfactory. It is concluded that the beach drainage method is efficient for shore protection from erosion.

In order to design a network of drainage canals, it is essential to consider the excess water from the agricultural land (overland flow) and to evaluate the characteristics of flow routing, such as the flow depths and discharges in the system of tertiary and main drainage canals of various order. In this paper models based on the Saint-Venant equations are presented, simulating the flow routing in a system of drainage canals. In these models, the lateral inflow towards tertiary drainage canals is the overland flow from adjacent fields. The Saint-Venant equations in their complete form (dynamic model) or in simplified forms, such as the diffusion wave equations (diffusion model) and the kinematic wave equations (kinematic model) are numerically solved by using the MacCormack explicit computational scheme which is a two-step predictor-corrector scheme, conditionally stable and convergent. In modeling flow through the system of drainage canals, emphasis was given to the simulation of flow at the junction points of two or more canals by applying the characteristic equations (negative and positive equations) in addition to the mass and energy conservation principles. Applications of the models for the simulation of flow within the system of drainage canals, subject to lateral inflow owing to overland flow, were also conducted in order to study the effect of various parameters of the drainage canals, on the hydrographs’ formation and also on the accuracy of the diffusion and kinematic equations in predicting flow in a drainage network.

The present paper reviews the wastewater reuse regulations, practices and applications of countries around the Mediterranean Region, particularly focusing on reuse practices for municipal and industrial uses. Water scarcity and water need is established in Mediterranean countries using international indexes for a cross-border comparison of water availability specifically for fresh water supply for municipal and industrial applications. Wastewater reuse criteria based on necessary, application specific, treatment output quality are presented. Data for each individual country is reviewed, and the regulations governing each country around reuse and applications are summarized, focusing, when appropriate, on the production and use of reclaimed wastewater for municipal and industrial applications. Also a critical overview of the guidelines and regulations governing these countries is presented. After considering multiple parameters associated with adoption of municipal and industrial wastewater reuse, such as water supply and scarcity, country and regional parameters, as well as possible applications, we note that adoption is accelerated in countries that have stronger economies and higher water needs. This development is fueled by favorable guidelines and regulations; conversely it is hindered by prohibitive guidelines and regulations. Wastewater reuse for municipal and industrial applications so far remains a whimsical game of culture, perception, religion, available technology and politics. An increasing trend in wastewater treatment plant construction and planning is seen in almost all the countries of the Mediterranean region. In addition, reuse water standards are in the process of being developed in a way that will clearly take into account the local conditions while reasonably safeguarding the public health. Wastewater reuse for municipal and industrial applications in Mediterranean countries remains at the beginning stages of adoption and the potential for improvement is open.

In Tunisian semi-arid regions, where water is a rare commodity and the large dams cannot be justified considering the very limited water contributions and the very high evapotranspiration, innovative techniques of harvesting water have been adopted. Tunisia has initiated a policy of small dam construction aiming to combine land and water management with socioeconomic development. They also target erosion control and protection of downstream infrastructure. Integrated rural development is achieved through the provision of a scarce but vital renewable resource. Using the results of multi-disciplinary research carried out in a network of 25 hill lakes implemented in a semi-arid area, the present article shows the role of small dams in the mobilization and management of water and soil resources. The issues involved in integrated development around hill reservoirs are closely linked to the sustainability of water. The agricultural development must be adapted to the life expectancy of the dam and the availability of water in dry periods. The recharge of the groundwater in the aquifers improves the potential for development. However, the impact of the stored water on health must be studied. The environmental impact of the lake structures is linked to the quality of the water and the maintenance of its supply.