We all know the challenges related to the determination of aquifer's specific yield. The results from pumping test from a single borehole, which is often the case, suffers from lack of representativity. The cost if drilling is also high in developing countries. If one have the time series of streamflow discharge data, two questions comes in my mind: (1) is there any relationships between the flow duration curve of a spring and the specific yield of the underlying or aquifer? (2) is it possible to estimate the Sy of this aquifer using the flow duration curve?
Perhaps some water quality tests to compare spring and aquifer waters may help show similarities or differences. When I get to computer, I will attach paper discussing end member analysis to separate aspects of streamflow into portions of rainfall-runoff, interflow and groundwater. Springs are a point of discharge, that may or may not be connected to a specific aquifer, which may be localized or widespread. In karst terrain, the underground flow and streams that feed localized springs of various flow magnitudes and intensities may not exhibit the general aquifer conditions.
Thank you William for your answer. I think you did not get me right. I wanted to know if there is any relationship between the flow duration curve of a spring and the specific yield of an underlying aquifer. We assume the spring and the aquifer are hydraulically connected.
In any aquifer system, a water balance must exist. This balance is expressed very simply by the following equation (Equation (1):In any aquifer system, a water balance must exist. This balance is expressed very simply by the following equation (Equation (1):
Recharge + Groundwater inflow = Draft + Groundwater outflow ± change in storage (1)
The recharge includes such items as natural recharge from rainfall or stream flow and excess irrigation. The Draft includes evapotranspiration; withdrawals for irrigation, industry, and town water supplies; and stock and domestic uses. The change in storage (∆V) (Equation (2)) is expressed as:
∆V = A × S × ∆h (2)
where A is the surface area of the water table, S is the storage coefficient or specific yield, and ∆h is the change in water level during the period of analysis.3.2. Groundwater through FlowThe groundwater flow in any section of aquifer is obtained by using transmissivity, the hydraulic gradient, and the area through which the water is moving. The groundwater flow through an aquifer is obtained from (Equation (3)):
Q = T × i × W(3)
where Q is the total groundwater flow through the section considered, T is the average transmissivity in that section, i is the hydraulic gradient (the slope of the potentiometric surface), and W is the width of the section being considered
Josue, this paper by Mare'chal and others in Journal of Hydrology (2006) may be useful:http://www.sciencedirect.com/science/article/pii/S0022169406001004. Also a number of ways to analyze spring flow data to determine various aquifer properties are summarized in this USGS publication about karst which can be downloaded at https://pubs.usgs.gov/tm/04d02/pdf/TM4-D2-chap3.pdf. Many of these techniques have applicability to springs located in other hydrogeological settings besides karst. Good luck!
Josue,
Sure there is a strong positive relationship between the specific yield and spring discharges. But taking the spring discharges alone, determination of Sy may be difficult since there may be many other ground water discharge components from the aquifer. The following paper might help. Also attached are few other papers that might be of help to you if you are working on springs.
http://www.tandfonline.com/doi/pdf/10.1080/02626669009492419
Article Springs in a headwater basin in the Deccan Trap country of t...
Article Groundwater resources assessment of the Koyna River Basin, India
Article On the origin and classification of springs in the Western G...
Article On harnessing the springs in the Western Ghats, Maharashtra.
A spring is one where the water table meets the land surface and the ground water discharge takes place with or without hydraulic pressure. Many of these springs originates through a fracture or fault zone. Now we have to understand the extent of this fracture or fault zone, its recharge area, how many aquifers the fracture or fault zone is cutting across and what is the Sy of these aquifers. Though in simple words it can be told that there is relationship between the spring discharge and the specific yield of the underlying aquifer, actually it is difficult because of the above mentioned complex nature of the springs.
Dear Jouse
I am also interested to know about the yield so once you reached to some conclusion can you please share it with me.
Yes theoretically there is a relation ship in between the two, but this difficult to be found because large scale aquifers a discharge can not be controlled. Briefly a specific yield is discharge- drawdown relationship which can be found by traditional methods of Theis and Jacob ...etc on the basis of Theis solution in confined and unconfined aquifers under the same conditions. Springs flow in unconfined aquifer represent emptying the excessive groundwater storage above the dead storage level. This water flow may be continue for the whole year. The amount of Q start from zero to reach a maximum and then returns to zero. But in confined aquifer it slightly varies. The GW flow of a spring occurs under the existing GW head of the aquifer.
In general in natural conditions it is too difficult developing actual relation between spring discharge and specific yield or storage coefficient moreover the definitions of the both term are different.
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