Assessing Methods and Effectiveness of Enhanced Aquifer Recharge on an Agricultural Landscape

Abstract

The security of groundwater quantity and quality is a major issue facing communities across the world as it is difficult to predict how climate change will shape the hydrology of many regions. In agricultural areas, particularly those with considerable irrigation of crops, maintaining groundwater quantity is paramount to the livelihoods of farmers, as well as those who consume their agricultural outputs. As such, practical methods to enhance groundwater recharge from precipitation are an attractive option. In this thesis, we studied two strategies for groundwater recharge enhancement – drywells and infiltration trenches – through both field experiments and numerical models. Field experiments were carried out by simulating rainfall events over a 3 meter by 3 meter area with various configurations of the groundwater recharge enhancement strategies deployed in the experiment area. Soil moisture measurements were collected before, during, and after experiments, and water samples were collected before and for several weeks after each experiment. These experiments showed that drywells and infiltration trenches can be implemented in a practical manner to accommodate moderate rainfall events (2.54 cm over 30 minutes) and infiltrate the precipitation deeper than under natural infiltration conditions. 1D and 2D numerical models were developed to simulate the conditions during and after each type of field experiment, and to extrapolate to other hydrogeologic situations where these strategies could be employed. These models showed that infiltration with drywells and trenches could reduce precipitation losses to evaporation and transpiration by 60% and 50%, respectively, by successfully infiltrating water deeper in the vadose zone. These findings suggest that both drywells and infiltration trenches are viable options for enhancing groundwater recharge in rural settings.