APPLICATION OF A SOLUTE TRANSPORT MODEL UNDER VARIABLE VELOCITY CONDITIONS IN A CONDUIT FLOW AQUIFER - OLALDE KARST SYSTEM, BASQUE COUNTRY,SPAIN

A model based on numerical solutions, which allows for solving the dis persion equation under variable recharge and velocity conditions, is d eveloped to simulate solute transport in conduit flow aquifers during flow recession periods. ks an example, the evolution of a tracer in th e little known karst conduit that links the sinking stream of Oma vall ey to the Olalde spring is investigated in the karstic region of Santa Eufemia-Erenozar (Basque Country, Spain). The model, with different h ypothetical structures, allows for obtaining series of tracer breakthr ough curves, which are fitted to experimental data using an optimizati on algorithm. These results, although they can be used to simulate the tracer evolution between the two points considered, do not allow for determining the internal structure and spatial disposition of contribu tions in the aquifer.