I need to determine if water that accumulates in an is groundwater seepage from the water table being raised by rain or if it's rainwater not soaking into the soil. I know that this can be done with radio-isotope signatures, but I don't have access to that kind of equipment currently. Does anyone have any suggestions as to an alternative method for determining what the source of the water is?
Maybe you measure the conductivity to discriminate groundwater from rainwater. In some regions the conductivity of rainwater is much lower than groundwater. But this depends from the solubility of the bedrock. E. g. the conductivity in areas wirh limestone is higher than in areas areas wirh granite.
Agree, conductivity may be low cost and simplest method. Also pH in rainfall may be very acidic, and low alkalinity, so as such, it may change quickly as infiltrated into the soil or in mixing with groundwater. Authors Garrett and others have used differences in chemical signatures to separate water in rain, streamflow and groundwater. Rainfall not appreciably entering soil would be runoff, so it may have higher sediment if soil is exposed, and increased coliform load, but also exhibit some of the properties of rainfall such as comparatively to groundwater, low pH and alkalinity, as well low conductivity. As suggested, there are some geological differences in substrate solubility to Consider.
I agree. Do you have the skill and equipment to measure the cations present in the water? Can your chemistry department help you? There are published groundwater quality analyses for most streams that can be used to compare with your samples. You can carry out the analyses of both rainwater and other samples from the groundwater yourself. Groundwater will carry salts from both the bedrock and from agricultural sources as well as pesticides and fertilizers.
Stuart.
I have articles about this topic in researchgate with name “Assessing The Earth Dams' Effect On The Groundwater Of Its Location Case Study: Kord-Oliya Dam”. I coupled two softer GMS with SEEP 3D. The case study is modeled in 3d mode.
To estimate the groundwater recharge from rainfall using a groundwater level fluctuation record, you can follow these steps:
This kind of analysis can help in understanding the impact of rainfall on groundwater levels in a specific region and can be used for planning and managing water resources. Remember to consider the specific geographical and geological conditions in the area of interest.