Shallow Groundwater Dynamics Controlled by Lisse and Re­verse Wieringermeer Effects

Abstract

This paper reviews research on the causes and effects of rap- id shallow groundwater dynamics in response to recharge events and their contribution to soil salinization in arid and semi-arid areas. It identifies some of the major research questions which should answered for a better understanding and consequently a successful management and sustainabil- ity of these valuable resources. First, we give an overview of shallow groundwater systems with an emphasis on the rapid and disproportionate response of shallow water tables to recharge events. In this context, we highlight the two major phenomena responsible for such behavior, namely the Lisse Effect (LE) and the Reverse Wieringermeer Effect (RWE). The LE occurs when water infiltration caused by intense rain seals the surface soil layer to airflow, trapping and compressing air under pressure in the unsaturated zone. The RWE, as was usu- ally defined, occurs wherever the capillary fringe is close to the ground surface. We believe that RWE also occurs in cases with a certain unsaturated zone over the capillary fringe and in response to sub-surface lateral inflow. This work also dis- cusses the causes and potential effects of rapid water table rise in Metouia Oasis, South Tunisia, where the occurrence of rapid water table rises and soil surface salt accumulation, are presented. In Metouia Oasis, a highly dynamic saline shal- low groundwater coupled with an arid climate characterized by high evaporation and low precipitation led to a soil salini- zation problem which is currently threatening the sustainable development of agriculture in the Oasis. Key