CHOOSING APPROPRIATE TECHNIQUES FOR QUANTIFYING GROUNDWATER RECHARGE

Presentation of techniques and background for estimating recharge of groundwaters. Water fluxes related to the degree of connection between rivers and aquifers. Techniques based on surface-water studies are resumed (seepage meter, tracer techniques, base flow discharge and numerical modelling). Techniques based on unsaturated-zone studies are detailed. Zero flux plane concept is developed. Sensitivity of drainage calculated using the chloride mass-balance approach is discussed. Techniques based on saturated-zone studies. Comparison of range of recharge rates and spatial and temporal scales of the various techniques for quantifying recharge. Application of multiple techniques and vulnerability to contamination.