Information on groundwater contribution to surface waters is an important but often neglected aspect of water quality, especially in the case of rivers and streams. The contribution of underground water sources to rivers is often significant, both in terms of the quantity of water discharged as well as the flux of nutrients and/or pollutants delivered. In recent years, many catchment hydrology studies have shown, through the use of environmental tracers, that the contribution of groundwater discharge and associated fluxes to river flows is often more important than anticipated. The lack of information on these aspects has important implications in adopting water management policies, since information is needed about the dependency of surface water flows or wetlands on underground sources. The proper hydrological characterization of surface/ground water interactions requires the identification of areas of groundwater discharge, estimation of the magnitude of discharge, its origin and age, as well as the impact of groundwater contribution to the water quality of a river. Methods based in the use of environmental isotopes and other geochemical tracers offer great potential to obtain valuable information on these aspects. This CRP aims to review and test existing and new approaches, coupling mass balance calculations of both water and dissolved substances with environmental tracers to gain further information on the transport processes of water and pollutants.
To improve the capability and expertise of Member States in using environmental isotopes and other tracers to better assess the role of groundwater in water quality issues involving rivers and streams.
To assess the potential and limitations of these tracer techniques and methodologies for routine application in hydrological studies.
To develop thematic maps based on isotope and related information relevant to the evaluation and assessment of the quality of surface water.
To develop/review approaches for the study of surface/ground water interaction and integrate this information into conceptual models and estimates of fluxes between ground and surface waters.
The CRP provided good insights to the participating counterparts of the complexities of understanding ground and surface water interactions. The related publications by several of the participants will be useful to provide documentary evidence of the efficacy of isotope tracers to study ground water pollution impacts.
The complex interaction between surface and groundwater remains a challenge, in particular with land use practices, growing population, and increasing flux of nutrients from soil to ground water and streams. The case studies presented show some good common practices, but ultimately problems are site specific and governed by the geology, climes and external pressures of land use and population.