Old water contribution to streamflow: Insight from a linear Boussinesq model
Article first published online: 6 JUN 2012
©2012. American Geophysical Union. All Rights Reserved.
Water Resources Research
Volume 48, Issue 6, June 2012
How to Cite
2012), Old water contribution to streamflow: Insight from a linear Boussinesq model, Water Resour. Res., 48, W06601, doi:10.1029/2011WR011606.(
- Issue published online: 6 JUN 2012
- Article first published online: 6 JUN 2012
- Manuscript Accepted: 22 APR 2012
- Manuscript Revised: 23 MAR 2012
- Manuscript Received: 8 NOV 2011
- old water contribution;
- rainfall-runoff modeling;
- streamflow generation
 Old water contribution to streamflow is studied by the means of a simple groundwater model. The principal aim is not to develop a tool for applications but rather to understand some of the dynamics of old and new water after a rainfall event by using a simple model with a minimum set of variables. Event water is traced by solute transport analysis. Adopting a simple rainfall pulse of finite duration, the method identifies two key dimensionless parameters ruling the old water contribution to streamflow: a dimensionless rainfall time δ, ratio between the rain duration and the characteristic response time of the aquifer, and the ratio ρ between rainfall volume and the water volume present in the aquifer at the beginning of rainfall. It was found that the ρ parameter is crucial in the old water contribution to a rainfall event; less so are the temporal dynamics of rainfall, expressed through δ. For typical values of ρ it is expected that old water contributes more than 50% of the total streamflow. These findings suggest that the groundwater dynamics may have a strong influence on the way that the hillslope responds to the rainfall input, and hence the partition between new (precipitation) and old (pre-event) waters.