PROBLEMS - Hydrogeology: Objectives, Methods, Applications - page 324

Answer 2: The average recharge elevation of spring #12 is on the order of
1,800 m, that of spring #14 around 1,400 m.
Answer 3: Conclusion: the entire slope feeds the aquifer; the gradual
infi ltration as snow melts creates an entry signal that varies in space: it rises
from the landslide area to the Mercantour peaks as a function of time. In a
hydrodynamic model of the hillside aquifer, this signal would have to be
located as a function of time.
Problem #2—Hydrologic budget
In a hydrosystem fed only by precipitation, the conservative ion
concentration can quantify their reconcentration through evaporation.
This global input-output approach presents the advantage of requiring no
hypotheses with respect to soil moisture, or the fi eld capacity. However,
the ion selected must be conservative, and must originate solely from
precipitation (not from the geologic context or from anthropogenic inputs).
This method uses the fl ux conservation equation:
C p ·P = C s ·ER
C p & C s : concentration in the rain and at the exit (the spring),
P & ER: precipitation and effective rainfall.
This fl ux conservation equation enables the calculation of:
• the recharge coeffi cient R c = ER/P = C p /C s
• the effective rainfall ER = P · C p /C s
• actual evapotranspiration AET = P (1 - C p /C s )
Question: Apply this method to the calculation of the budget for fl ow from
a stalactite in the Nerja cave (Andalusia, Spain, after Liñán et al. , 1999), by
completing the table below (Table 2), the average annual rainfall being 490
mm.