Numerical and experimental analyses of the use of double vertical barrier walls for groundwater protection

Leachate reduction and pollution control strategies for landfills in hilly areas based on site condition analysis and numerical simulation

Landfill is an important means of municipal solid waste treatment. Previous studies have shown that the combination of "cut-off wall and pumping well" technology is an effective measure to deal with the leachate emission reduction and pollution control of landfill, and has been widely used in plain areas. However, for landfills in hilly areas with complex terrain and geological conditions, there is still a lack of clear and referable ideas and operational strategies for leachate emission reduction and pollution control. In this study, we proposed strategies for determining the position and depth of cut-off walls and pumping wells and reasonable combinations of the cut-off wall depth and pumping quantity for leachate reduction and pollution prevention of landfills in hilly areas. The determination of leachate reduction and pollution control strategy need to be achieved in two stages, qualitative and quantitative: (1) In the qualitative stage, the natural conditions (Weathering degree, groundwater flow characteristics, topography condition, hydrometeor condition, and aquifer thickness) and engineering conditions (Operation status, landfill location, and excavation status) of the study area are analysed in detail, and then the depth range and location of the cut-off wall and pumping well are determined. (2) In the quantitative stage, we need to quantify the combination of the cut-off wall depth and pumping quantity by using profile particle tracing and pollutant transport modelling. A reasonable cut-off wall depth needs to control the leakage of pollutants inside the wall, and a reasonable pumping quantity needs to ensure that the depth of the pollutant distribution is equivalent to the depth of the separation line, which separates the water flow towards the pumping well and the water flow downstream. (3) The effectiveness of the leachate reduction and prevention strategies proposed in this study was verified through an example of a landfill in Northeast China. This study provides a reference and operation method for leachate emission reduction and pollution control of landfills in hilly areas.

Spatial and Temporal Effects of Irrigation Canals Rehabilitation on the Land and Crop Yields, a Case Study: The Nile Delta, Egypt

Shortage of surface water is considered an international problem that has even extended to countries that have rivers, in particular countries sharing the same river basins and downstream countries, such as Egypt. This issue requires intensive management of available water resources. Irrigation Canals Rehabilitation (ICR) has become essential to protect surface water in irrigation canals from losses due to seepage. Egypt is one of the countries that has started using this technique. This paper aims to evaluate the impact of ICR using concrete on the land and on crop yields. The SEEP/W model is used in the current study to estimate changes in the groundwater table and moisture in the root zone. Three cases studies have been simulated and compared including unlined, lined, and lined canals with a drainage pipe. The methodology is applied to three canals in the Nile Delta: Sero, Dafan, and New-Aslogy. The results demonstrate that ICR has decreased the losses from canals which resulted in lowering the groundwater, where the case of lining gave a higher reduction than the case of lining with a drainage pipe. In addition, the water table underneath the embankment was lowered. Decreasing the groundwater table could help to protect the land from logging and increase crop yields, but it may reduce the recharging of groundwater aquifers. Such a study is highly recommended in arid regions to decrease water losses where many countries are suffering from water shortage.