In many studies, groundwater recharge has been estimated by recession curve displacement method which is based on storm events but, in some cases, we need to estimate groundwater recharge annually and so by having daily streamflow data, how are we able to use a method like recession curve displacement technique to calculate recharge on a yearly scale?
Annual recession in the observed flow can give an indication of some of the lumped properties of the aquifers in a catchment (but this can be limited by the catchment characteristics). Once you have an understanding of the properites of the aquifer, you can then use this to estimate the recharge. One approach is using baseflow filters. However, while these can give an estimate of the aquifer properties, and subsequenctly the recharge, they are limited in that they are looking only at the total streamflow and making a prediction based on the underlying assumptions of the filter. If the assumptions are invalid, then the recharge estimate may have a large (and probably unacceptable) uncertainty.
The use of tracers (e.g. isotopic concentrations) can help, but these are also limited by the accuacy of the measurements and the difference in concentration between different sources.
Basically, an method that makes an indirect estimate of a value can be problematic, and care needs to be taken that the method is applicable.
As you know recession behavior is highly non-linear and perhaps the first step is to define the system. Is there riparian vegetation in the valley? What about irrigation activity? Is there pumping in the valley? See papers by Morel Seytoux & Illangasekere in irrigated areas where a linear system approach has been taken in that case.
- Badges
- Science topic
- Similar topics
- Geoscience
- Asia
- India